Merge tag 'trace-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:
"The major changes in this tracing update includes:

- Removal of non-DYNAMIC_FTRACE from 32bit x86

- Removal of mcount support from x86

- Emulating a call from int3 on x86_64, fixes live kernel patching

- Consolidated Tracing Error logs file

Minor updates:

- Removal of klp_check_compiler_support()

- kdb ftrace dumping output changes

- Accessing and creating ftrace instances from inside the kernel

- Clean up of #define if macro

- Introduction of TRACE_EVENT_NOP() to disable trace events based on
config options

And other minor fixes and clean ups"

* tag 'trace-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (44 commits)
x86: Hide the int3_emulate_call/jmp functions from UML
livepatch: Remove klp_check_compiler_support()
ftrace/x86: Remove mcount support
ftrace/x86_32: Remove support for non DYNAMIC_FTRACE
tracing: Simplify "if" macro code
tracing: Fix documentation about disabling options using trace_options
tracing: Replace kzalloc with kcalloc
tracing: Fix partial reading of trace event's id file
tracing: Allow RCU to run between postponed startup tests
tracing: Fix white space issues in parse_pred() function
tracing: Eliminate const char[] auto variables
ring-buffer: Fix mispelling of Calculate
tracing: probeevent: Fix to make the type of $comm string
tracing: probeevent: Do not accumulate on ret variable
tracing: uprobes: Re-enable $comm support for uprobe events
ftrace/x86_64: Emulate call function while updating in breakpoint handler
x86_64: Allow breakpoints to emulate call instructions
x86_64: Add gap to int3 to allow for call emulation
tracing: kdb: Allow ftdump to skip all but the last few entries
tracing: Add trace_total_entries() / trace_total_entries_cpu()
...

Documentation/trace/ftrace.rst

···
 	tracers from tracing simply echo "nop" into
 	current_tracer.
 
+Error conditions
+----------------
+
+  For most ftrace commands, failure modes are obvious and communicated
+  using standard return codes.
+
+  For other more involved commands, extended error information may be
+  available via the tracing/error_log file.  For the commands that
+  support it, reading the tracing/error_log file after an error will
+  display more detailed information about what went wrong, if
+  information is available.  The tracing/error_log file is a circular
+  error log displaying a small number (currently, 8) of ftrace errors
+  for the last (8) failed commands.
+
+  The extended error information and usage takes the form shown in
+  this example::
+
+    # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
+    echo: write error: Invalid argument
+
+    # cat /sys/kernel/debug/tracing/error_log
+    [ 5348.887237] location: error: Couldn't yyy: zzz
+      Command: xxx
+               ^
+    [ 7517.023364] location: error: Bad rrr: sss
+      Command: ppp qqq
+                   ^
+
+  To clear the error log, echo the empty string into it::
+
+    # echo > /sys/kernel/debug/tracing/error_log
 
 Examples of using the tracer
 ----------------------------

Documentation/trace/histogram.rst

···
 
   For some error conditions encountered when invoking a hist trigger
   command, extended error information is available via the
-  corresponding event's 'hist' file.  Reading the hist file after an
-  error will display more detailed information about what went wrong,
-  if information is available.  This extended error information will
-  be available until the next hist trigger command for that event.
-
-  If available for a given error condition, the extended error
-  information and usage takes the following form::
-
-    # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
-    echo: write error: Invalid argument
-
-    # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
-    ERROR: Couldn't yyy: zzz
-      Last command: xxx
+  tracing/error_log file.  See Error Conditions in
+  :file:`Documentation/trace/ftrace.rst` for details.
 
 6.2 'hist' trigger examples
 ---------------------------

arch/nds32/kernel/ftrace.c

···
 #ifndef CONFIG_DYNAMIC_FTRACE
 extern void (*ftrace_trace_function)(unsigned long, unsigned long,
 				     struct ftrace_ops*, struct pt_regs*);
-extern int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace);
 extern void ftrace_graph_caller(void);
 
 noinline void __naked ftrace_stub(unsigned long ip, unsigned long parent_ip,

arch/parisc/kernel/ftrace.c

···
 				unsigned long org_sp_gr3)
 {
 	extern ftrace_func_t ftrace_trace_function;  /* depends on CONFIG_DYNAMIC_FTRACE */
-	extern int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace);
 
 	if (ftrace_trace_function != ftrace_stub) {
 		/* struct ftrace_ops *op, struct pt_regs *regs); */

arch/powerpc/include/asm/livepatch.h

···
 #include <linux/sched/task_stack.h>
 
 #ifdef CONFIG_LIVEPATCH
-static inline int klp_check_compiler_support(void)
-{
-	return 0;
-}
-
 static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 {
 	regs->nip = ip;

arch/s390/include/asm/livepatch.h

···
 
 #include <asm/ptrace.h>
 
-static inline int klp_check_compiler_support(void)
-{
-	return 0;
-}
-
 static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 {
 	regs->psw.addr = ip;

arch/x86/Kconfig

···
 	select SWIOTLB
 	select ARCH_HAS_SYSCALL_WRAPPER
 
+config FORCE_DYNAMIC_FTRACE
+	def_bool y
+	depends on X86_32
+	depends on FUNCTION_TRACER
+	select DYNAMIC_FTRACE
+	help
+	 We keep the static function tracing (!DYNAMIC_FTRACE) around
+	 in order to test the non static function tracing in the
+	 generic code, as other architectures still use it. But we
+	 only need to keep it around for x86_64. No need to keep it
+	 for x86_32. For x86_32, force DYNAMIC_FTRACE. 
 #
 # Arch settings
 #

arch/x86/entry/entry_64.S

···
  * @paranoid == 2 is special: the stub will never switch stacks.  This is for
  * #DF: if the thread stack is somehow unusable, we'll still get a useful OOPS.
  */
-.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 ist_offset=0
+.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 ist_offset=0 create_gap=0
 ENTRY(\sym)
 	UNWIND_HINT_IRET_REGS offset=\has_error_code*8
 
···
 	.if \paranoid == 1
 	testb	$3, CS-ORIG_RAX(%rsp)		/* If coming from userspace, switch stacks */
 	jnz	.Lfrom_usermode_switch_stack_\@
+	.endif
+
+	.if \create_gap == 1
+	/*
+	 * If coming from kernel space, create a 6-word gap to allow the
+	 * int3 handler to emulate a call instruction.
+	 */
+	testb	$3, CS-ORIG_RAX(%rsp)
+	jnz	.Lfrom_usermode_no_gap_\@
+	.rept	6
+	pushq	5*8(%rsp)
+	.endr
+	UNWIND_HINT_IRET_REGS offset=8
+.Lfrom_usermode_no_gap_\@:
 	.endif
 
 	.if \paranoid
···
 #endif /* CONFIG_HYPERV */
 
 idtentry debug			do_debug		has_error_code=0	paranoid=1 shift_ist=IST_INDEX_DB ist_offset=DB_STACK_OFFSET
-idtentry int3			do_int3			has_error_code=0
+idtentry int3			do_int3			has_error_code=0	create_gap=1
 idtentry stack_segment		do_stack_segment	has_error_code=1
 
 #ifdef CONFIG_XEN_PV

arch/x86/include/asm/ftrace.h

···
 #define _ASM_X86_FTRACE_H
 
 #ifdef CONFIG_FUNCTION_TRACER
-#ifdef CC_USING_FENTRY
-# define MCOUNT_ADDR		((unsigned long)(__fentry__))
-#else
-# define MCOUNT_ADDR		((unsigned long)(mcount))
-# define HAVE_FUNCTION_GRAPH_FP_TEST
+#ifndef CC_USING_FENTRY
+# error Compiler does not support fentry?
 #endif
+# define MCOUNT_ADDR		((unsigned long)(__fentry__))
 #define MCOUNT_INSN_SIZE	5 /* sizeof mcount call */
 
 #ifdef CONFIG_DYNAMIC_FTRACE

arch/x86/include/asm/livepatch.h

···
 #include <asm/setup.h>
 #include <linux/ftrace.h>
 
-static inline int klp_check_compiler_support(void)
-{
-#ifndef CC_USING_FENTRY
-	return 1;
-#endif
-	return 0;
-}
-
 static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 {
 	regs->ip = ip;

arch/x86/include/asm/text-patching.h

···
 extern __ro_after_init struct mm_struct *poking_mm;
 extern __ro_after_init unsigned long poking_addr;
 
+#ifndef CONFIG_UML_X86
+static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
+{
+	regs->ip = ip;
+}
+
+#define INT3_INSN_SIZE 1
+#define CALL_INSN_SIZE 5
+
+#ifdef CONFIG_X86_64
+static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
+{
+	/*
+	 * The int3 handler in entry_64.S adds a gap between the
+	 * stack where the break point happened, and the saving of
+	 * pt_regs. We can extend the original stack because of
+	 * this gap. See the idtentry macro's create_gap option.
+	 */
+	regs->sp -= sizeof(unsigned long);
+	*(unsigned long *)regs->sp = val;
+}
+
+static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func)
+{
+	int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
+	int3_emulate_jmp(regs, func);
+}
+#endif /* CONFIG_X86_64 */
+#endif /* !CONFIG_UML_X86 */
+
 #endif /* _ASM_X86_TEXT_PATCHING_H */

arch/x86/kernel/ftrace.c

···
 #include <asm/kprobes.h>
 #include <asm/ftrace.h>
 #include <asm/nops.h>
+#include <asm/text-patching.h>
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 
···
 }
 
 static unsigned long ftrace_update_func;
+static unsigned long ftrace_update_func_call;
 
 static int update_ftrace_func(unsigned long ip, void *new)
 {
···
 	unsigned long ip = (unsigned long)(&ftrace_call);
 	unsigned char *new;
 	int ret;
+
+	ftrace_update_func_call = (unsigned long)func;
 
 	new = ftrace_call_replace(ip, (unsigned long)func);
 	ret = update_ftrace_func(ip, new);
···
 	if (WARN_ON_ONCE(!regs))
 		return 0;
 
-	ip = regs->ip - 1;
-	if (!ftrace_location(ip) && !is_ftrace_caller(ip))
-		return 0;
+	ip = regs->ip - INT3_INSN_SIZE;
 
-	regs->ip += MCOUNT_INSN_SIZE - 1;
+#ifdef CONFIG_X86_64
+	if (ftrace_location(ip)) {
+		int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);
+		return 1;
+	} else if (is_ftrace_caller(ip)) {
+		if (!ftrace_update_func_call) {
+			int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
+			return 1;
+		}
+		int3_emulate_call(regs, ftrace_update_func_call);
+		return 1;
+	}
+#else
+	if (ftrace_location(ip) || is_ftrace_caller(ip)) {
+		int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
+		return 1;
+	}
+#endif
 
-	return 1;
+	return 0;
 }
 NOKPROBE_SYMBOL(ftrace_int3_handler);
 
···
 
 	func = ftrace_ops_get_func(ops);
 
+	ftrace_update_func_call = (unsigned long)func;
+
 	/* Do a safe modify in case the trampoline is executing */
 	new = ftrace_call_replace(ip, (unsigned long)func);
 	ret = update_ftrace_func(ip, new);
···
 {
 	unsigned char *new;
 
+	ftrace_update_func_call = 0UL;
 	new = ftrace_jmp_replace(ip, (unsigned long)func);
 
 	return update_ftrace_func(ip, new);

arch/x86/kernel/ftrace_32.S

···
 #include <asm/ftrace.h>
 #include <asm/nospec-branch.h>
 
-#ifdef CC_USING_FENTRY
 # define function_hook	__fentry__
 EXPORT_SYMBOL(__fentry__)
-#else
-# define function_hook	mcount
-EXPORT_SYMBOL(mcount)
-#endif
 
-#ifdef CONFIG_DYNAMIC_FTRACE
-
-/* mcount uses a frame pointer even if CONFIG_FRAME_POINTER is not set */
-#if !defined(CC_USING_FENTRY) || defined(CONFIG_FRAME_POINTER)
-# define USING_FRAME_POINTER
-#endif
-
-#ifdef USING_FRAME_POINTER
+#ifdef CONFIG_FRAME_POINTER
 # define MCOUNT_FRAME			1	/* using frame = true  */
 #else
 # define MCOUNT_FRAME			0	/* using frame = false */
···
 
 ENTRY(ftrace_caller)
 
-#ifdef USING_FRAME_POINTER
-# ifdef CC_USING_FENTRY
+#ifdef CONFIG_FRAME_POINTER
 	/*
 	 * Frame pointers are of ip followed by bp.
 	 * Since fentry is an immediate jump, we are left with
···
 	pushl	%ebp
 	movl	%esp, %ebp
 	pushl	2*4(%esp)			/* function ip */
-# endif
+
 	/* For mcount, the function ip is directly above */
 	pushl	%ebp
 	movl	%esp, %ebp
···
 	pushl	%edx
 	pushl	$0				/* Pass NULL as regs pointer */
 
-#ifdef USING_FRAME_POINTER
+#ifdef CONFIG_FRAME_POINTER
 	/* Load parent ebp into edx */
 	movl	4*4(%esp), %edx
 #else
···
 	popl	%edx
 	popl	%ecx
 	popl	%eax
-#ifdef USING_FRAME_POINTER
+#ifdef CONFIG_FRAME_POINTER
 	popl	%ebp
-# ifdef CC_USING_FENTRY
 	addl	$4,%esp				/* skip function ip */
 	popl	%ebp				/* this is the orig bp */
 	addl	$4, %esp			/* skip parent ip */
-# endif
 #endif
 .Lftrace_ret:
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
···
 
 	movl	12*4(%esp), %eax		/* Load ip (1st parameter) */
 	subl	$MCOUNT_INSN_SIZE, %eax		/* Adjust ip */
-#ifdef CC_USING_FENTRY
 	movl	15*4(%esp), %edx		/* Load parent ip (2nd parameter) */
-#else
-	movl	0x4(%ebp), %edx			/* Load parent ip (2nd parameter) */
-#endif
 	movl	function_trace_op, %ecx		/* Save ftrace_pos in 3rd parameter */
 	pushl	%esp				/* Save pt_regs as 4th parameter */
 
···
 	lea	3*4(%esp), %esp			/* Skip orig_ax, ip and cs */
 
 	jmp	.Lftrace_ret
-#else /* ! CONFIG_DYNAMIC_FTRACE */
-
-ENTRY(function_hook)
-	cmpl	$__PAGE_OFFSET, %esp
-	jb	ftrace_stub			/* Paging not enabled yet? */
-
-	cmpl	$ftrace_stub, ftrace_trace_function
-	jnz	.Ltrace
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-	cmpl	$ftrace_stub, ftrace_graph_return
-	jnz	ftrace_graph_caller
-
-	cmpl	$ftrace_graph_entry_stub, ftrace_graph_entry
-	jnz	ftrace_graph_caller
-#endif
-.globl ftrace_stub
-ftrace_stub:
-	ret
-
-	/* taken from glibc */
-.Ltrace:
-	pushl	%eax
-	pushl	%ecx
-	pushl	%edx
-	movl	0xc(%esp), %eax
-	movl	0x4(%ebp), %edx
-	subl	$MCOUNT_INSN_SIZE, %eax
-
-	movl	ftrace_trace_function, %ecx
-	CALL_NOSPEC %ecx
-
-	popl	%edx
-	popl	%ecx
-	popl	%eax
-	jmp	ftrace_stub
-END(function_hook)
-#endif /* CONFIG_DYNAMIC_FTRACE */
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 ENTRY(ftrace_graph_caller)
···
 	pushl	%edx
 	movl	3*4(%esp), %eax
 	/* Even with frame pointers, fentry doesn't have one here */
-#ifdef CC_USING_FENTRY
 	lea	4*4(%esp), %edx
 	movl	$0, %ecx
-#else
-	lea	0x4(%ebp), %edx
-	movl	(%ebp), %ecx
-#endif
 	subl	$MCOUNT_INSN_SIZE, %eax
 	call	prepare_ftrace_return
 	popl	%edx
···
 return_to_handler:
 	pushl	%eax
 	pushl	%edx
-#ifdef CC_USING_FENTRY
 	movl	$0, %eax
-#else
-	movl	%ebp, %eax
-#endif
 	call	ftrace_return_to_handler
 	movl	%eax, %ecx
 	popl	%edx

arch/x86/kernel/ftrace_64.S

···
 	.code64
 	.section .entry.text, "ax"
 
-#ifdef CC_USING_FENTRY
 # define function_hook	__fentry__
 EXPORT_SYMBOL(__fentry__)
-#else
-# define function_hook	mcount
-EXPORT_SYMBOL(mcount)
-#endif
 
 #ifdef CONFIG_FRAME_POINTER
-# ifdef CC_USING_FENTRY
 /* Save parent and function stack frames (rip and rbp) */
 #  define MCOUNT_FRAME_SIZE	(8+16*2)
-# else
-/* Save just function stack frame (rip and rbp) */
-#  define MCOUNT_FRAME_SIZE	(8+16)
-# endif
 #else
 /* No need to save a stack frame */
 # define MCOUNT_FRAME_SIZE	0
···
 	 * fentry is called before the stack frame is set up, where as mcount
 	 * is called afterward.
 	 */
-#ifdef CC_USING_FENTRY
+
 	/* Save the parent pointer (skip orig rbp and our return address) */
 	pushq \added+8*2(%rsp)
 	pushq %rbp
 	movq %rsp, %rbp
 	/* Save the return address (now skip orig rbp, rbp and parent) */
 	pushq \added+8*3(%rsp)
-#else
-	/* Can't assume that rip is before this (unless added was zero) */
-	pushq \added+8(%rsp)
-#endif
 	pushq %rbp
 	movq %rsp, %rbp
 #endif /* CONFIG_FRAME_POINTER */
···
 	movq %rdx, RBP(%rsp)
 
 	/* Copy the parent address into %rsi (second parameter) */
-#ifdef CC_USING_FENTRY
 	movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi
-#else
-	/* %rdx contains original %rbp */
-	movq 8(%rdx), %rsi
-#endif
 
 	 /* Move RIP to its proper location */
 	movq MCOUNT_REG_SIZE+\added(%rsp), %rdi
···
 	/* Saves rbp into %rdx and fills first parameter  */
 	save_mcount_regs
 
-#ifdef CC_USING_FENTRY
 	leaq MCOUNT_REG_SIZE+8(%rsp), %rsi
 	movq $0, %rdx	/* No framepointers needed */
-#else
-	/* Save address of the return address of traced function */
-	leaq 8(%rdx), %rsi
-	/* ftrace does sanity checks against frame pointers */
-	movq (%rdx), %rdx
-#endif
 	call	prepare_ftrace_return
 
 	restore_mcount_regs

include/linux/compiler.h

···
  * "Define 'is'", Bill Clinton
  * "Define 'if'", Steven Rostedt
  */
-#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
-#define __trace_if(cond) \
-	if (__builtin_constant_p(!!(cond)) ? !!(cond) :			\
-	({								\
-		int ______r;						\
-		static struct ftrace_branch_data			\
-			__aligned(4)					\
-			__section("_ftrace_branch")			\
-			______f = {					\
-				.func = __func__,			\
-				.file = __FILE__,			\
-				.line = __LINE__,			\
-			};						\
-		______r = !!(cond);					\
-		______r ? ______f.miss_hit[1]++ : ______f.miss_hit[0]++;\
-		______r;						\
-	}))
+#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
+
+#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
+
+#define __trace_if_value(cond) ({			\
+	static struct ftrace_branch_data		\
+		__aligned(4)				\
+		__section("_ftrace_branch")		\
+		__if_trace = {				\
+			.func = __func__,		\
+			.file = __FILE__,		\
+			.line = __LINE__,		\
+		};					\
+	(cond) ?					\
+		(__if_trace.miss_hit[1]++,1) :		\
+		(__if_trace.miss_hit[0]++,0);		\
+})
+
 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 
 #else

include/linux/ftrace.h

···
 typedef void (*trace_func_graph_ret_t)(struct ftrace_graph_ret *); /* return */
 typedef int (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */
 
+extern int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace);
+
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
 struct fgraph_ops {

include/linux/tracepoint.h

···
 
 #define TRACE_EVENT_PERF_PERM(event, expr...)
 
+#define DECLARE_EVENT_NOP(name, proto, args)				\
+	static inline void trace_##name(proto)				\
+	{ }								\
+	static inline bool trace_##name##_enabled(void)			\
+	{								\
+		return false;						\
+	}
+
+#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)	\
+	DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
+
+#define DECLARE_EVENT_CLASS_NOP(name, proto, args, tstruct, assign, print)
+#define DEFINE_EVENT_NOP(template, name, proto, args)			\
+	DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
+
 #endif /* ifdef TRACE_EVENT (see note above) */

include/trace/define_trace.h

···
 		assign, print, reg, unreg)			\
 	DEFINE_TRACE_FN(name, reg, unreg)
 
+#undef TRACE_EVENT_NOP
+#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)
+
+#undef DEFINE_EVENT_NOP
+#define DEFINE_EVENT_NOP(template, name, proto, args)
+
 #undef DEFINE_EVENT
 #define DEFINE_EVENT(template, name, proto, args) \
 	DEFINE_TRACE(name)
···
 #undef TRACE_EVENT_FN
 #undef TRACE_EVENT_FN_COND
 #undef TRACE_EVENT_CONDITION
+#undef TRACE_EVENT_NOP
+#undef DEFINE_EVENT_NOP
 #undef DECLARE_EVENT_CLASS
 #undef DEFINE_EVENT
 #undef DEFINE_EVENT_FN

include/trace/events/rcu.h

···
 
 #include <linux/tracepoint.h>
 
+#ifdef CONFIG_RCU_TRACE
+#define TRACE_EVENT_RCU TRACE_EVENT
+#else
+#define TRACE_EVENT_RCU TRACE_EVENT_NOP
+#endif
+
 /*
  * Tracepoint for start/end markers used for utilization calculations.
  * By convention, the string is of the following forms:
···
 	TP_printk("%s", __entry->s)
 );
 
-#ifdef CONFIG_RCU_TRACE
-
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
 
 /*
···
  *	"end": End a grace period.
  *	"cpuend": CPU first notices a grace-period end.
  */
-TRACE_EVENT(rcu_grace_period,
+TRACE_EVENT_RCU(rcu_grace_period,
 
 	TP_PROTO(const char *rcuname, unsigned long gp_seq, const char *gpevent),
 
···
  * "Cleanup": Clean up rcu_node structure after previous GP.
  * "CleanupMore": Clean up, and another GP is needed.
  */
-TRACE_EVENT(rcu_future_grace_period,
+TRACE_EVENT_RCU(rcu_future_grace_period,
 
 	TP_PROTO(const char *rcuname, unsigned long gp_seq,
 		 unsigned long gp_seq_req, u8 level, int grplo, int grphi,
···
  * rcu_node structure, and the mask of CPUs that will be waited for.
  * All but the type of RCU are extracted from the rcu_node structure.
  */
-TRACE_EVENT(rcu_grace_period_init,
+TRACE_EVENT_RCU(rcu_grace_period_init,
 
 	TP_PROTO(const char *rcuname, unsigned long gp_seq, u8 level,
 		 int grplo, int grphi, unsigned long qsmask),
···
  *	"endwake": Woke piggybackers up.
  *	"done": Someone else did the expedited grace period for us.
  */
-TRACE_EVENT(rcu_exp_grace_period,
+TRACE_EVENT_RCU(rcu_exp_grace_period,
 
 	TP_PROTO(const char *rcuname, unsigned long gpseq, const char *gpevent),
 
···
  *	"nxtlvl": Advance to next level of rcu_node funnel
  *	"wait": Wait for someone else to do expedited GP
  */
-TRACE_EVENT(rcu_exp_funnel_lock,
+TRACE_EVENT_RCU(rcu_exp_funnel_lock,
 
 	TP_PROTO(const char *rcuname, u8 level, int grplo, int grphi,
 		 const char *gpevent),
···
  *	"WaitQueue": Enqueue partially done, timed wait for it to complete.
  *	"WokeQueue": Partial enqueue now complete.
  */
-TRACE_EVENT(rcu_nocb_wake,
+TRACE_EVENT_RCU(rcu_nocb_wake,
 
 	TP_PROTO(const char *rcuname, int cpu, const char *reason),
 
···
  * include SRCU), the grace-period number that the task is blocking
  * (the current or the next), and the task's PID.
  */
-TRACE_EVENT(rcu_preempt_task,
+TRACE_EVENT_RCU(rcu_preempt_task,
 
 	TP_PROTO(const char *rcuname, int pid, unsigned long gp_seq),
 
···
  * read-side critical section exiting that critical section.  Track the
  * type of RCU (which one day might include SRCU) and the task's PID.
  */
-TRACE_EVENT(rcu_unlock_preempted_task,
+TRACE_EVENT_RCU(rcu_unlock_preempted_task,
 
 	TP_PROTO(const char *rcuname, unsigned long gp_seq, int pid),
 
···
  * whether there are any blocked tasks blocking the current grace period.
  * All but the type of RCU are extracted from the rcu_node structure.
  */
-TRACE_EVENT(rcu_quiescent_state_report,
+TRACE_EVENT_RCU(rcu_quiescent_state_report,
 
 	TP_PROTO(const char *rcuname, unsigned long gp_seq,
 		 unsigned long mask, unsigned long qsmask,
···
  * state, which can be "dti" for dyntick-idle mode or "kick" when kicking
  * a CPU that has been in dyntick-idle mode for too long.
  */
-TRACE_EVENT(rcu_fqs,
+TRACE_EVENT_RCU(rcu_fqs,
 
 	TP_PROTO(const char *rcuname, unsigned long gp_seq, int cpu, const char *qsevent),
 
···
  * events use two separate counters, and that the "++=" and "--=" events
  * for irq/NMI will change the counter by two, otherwise by one.
  */
-TRACE_EVENT(rcu_dyntick,
+TRACE_EVENT_RCU(rcu_dyntick,
 
 	TP_PROTO(const char *polarity, long oldnesting, long newnesting, atomic_t dynticks),
 
···
  * number of lazy callbacks queued, and the fourth element is the
  * total number of callbacks queued.
  */
-TRACE_EVENT(rcu_callback,
+TRACE_EVENT_RCU(rcu_callback,
 
 	TP_PROTO(const char *rcuname, struct rcu_head *rhp, long qlen_lazy,
 		 long qlen),
···
  * the fourth argument is the number of lazy callbacks queued, and the
  * fifth argument is the total number of callbacks queued.
  */
-TRACE_EVENT(rcu_kfree_callback,
+TRACE_EVENT_RCU(rcu_kfree_callback,
 
 	TP_PROTO(const char *rcuname, struct rcu_head *rhp, unsigned long offset,
 		 long qlen_lazy, long qlen),
···
  * the total number of callbacks queued, and the fourth argument is
  * the current RCU-callback batch limit.
  */
-TRACE_EVENT(rcu_batch_start,
+TRACE_EVENT_RCU(rcu_batch_start,
 
 	TP_PROTO(const char *rcuname, long qlen_lazy, long qlen, long blimit),
 
···
  * The first argument is the type of RCU, and the second argument is
  * a pointer to the RCU callback itself.
  */
-TRACE_EVENT(rcu_invoke_callback,
+TRACE_EVENT_RCU(rcu_invoke_callback,
 
 	TP_PROTO(const char *rcuname, struct rcu_head *rhp),
 
···
  * is the offset of the callback within the enclosing RCU-protected
  * data structure.
  */
-TRACE_EVENT(rcu_invoke_kfree_callback,
+TRACE_EVENT_RCU(rcu_invoke_kfree_callback,
 
 	TP_PROTO(const char *rcuname, struct rcu_head *rhp, unsigned long offset),
 
···
  * and the sixth argument (risk) is the return value from
  * rcu_is_callbacks_kthread().
  */
-TRACE_EVENT(rcu_batch_end,
+TRACE_EVENT_RCU(rcu_batch_end,
 
 	TP_PROTO(const char *rcuname, int callbacks_invoked,
 		 char cb, char nr, char iit, char risk),
···
  * callback address can be NULL.
  */
 #define RCUTORTURENAME_LEN 8
-TRACE_EVENT(rcu_torture_read,
+TRACE_EVENT_RCU(rcu_torture_read,
 
 	TP_PROTO(const char *rcutorturename, struct rcu_head *rhp,
 		 unsigned long secs, unsigned long c_old, unsigned long c),
···
  * The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument
  * is the count of remaining callbacks, and "done" is the piggybacking count.
  */
-TRACE_EVENT(rcu_barrier,
+TRACE_EVENT_RCU(rcu_barrier,
 
 	TP_PROTO(const char *rcuname, const char *s, int cpu, int cnt, unsigned long done),
 
···
 		  __entry->rcuname, __entry->s, __entry->cpu, __entry->cnt,
 		  __entry->done)
 );
-
-#else /* #ifdef CONFIG_RCU_TRACE */
-
-#define trace_rcu_grace_period(rcuname, gp_seq, gpevent) do { } while (0)
-#define trace_rcu_future_grace_period(rcuname, gp_seq, gp_seq_req, \
-				      level, grplo, grphi, event) \
-				      do { } while (0)
-#define trace_rcu_grace_period_init(rcuname, gp_seq, level, grplo, grphi, \
-				    qsmask) do { } while (0)
-#define trace_rcu_exp_grace_period(rcuname, gqseq, gpevent) \
-	do { } while (0)
-#define trace_rcu_exp_funnel_lock(rcuname, level, grplo, grphi, gpevent) \
-	do { } while (0)
-#define trace_rcu_nocb_wake(rcuname, cpu, reason) do { } while (0)
-#define trace_rcu_preempt_task(rcuname, pid, gp_seq) do { } while (0)
-#define trace_rcu_unlock_preempted_task(rcuname, gp_seq, pid) do { } while (0)
-#define trace_rcu_quiescent_state_report(rcuname, gp_seq, mask, qsmask, level, \
-					 grplo, grphi, gp_tasks) do { } \
-	while (0)
-#define trace_rcu_fqs(rcuname, gp_seq, cpu, qsevent) do { } while (0)
-#define trace_rcu_dyntick(polarity, oldnesting, newnesting, dyntick) do { } while (0)
-#define trace_rcu_callback(rcuname, rhp, qlen_lazy, qlen) do { } while (0)
-#define trace_rcu_kfree_callback(rcuname, rhp, offset, qlen_lazy, qlen) \
-	do { } while (0)
-#define trace_rcu_batch_start(rcuname, qlen_lazy, qlen, blimit) \
-	do { } while (0)
-#define trace_rcu_invoke_callback(rcuname, rhp) do { } while (0)
-#define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0)
-#define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \
-	do { } while (0)
-#define trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
-	do { } while (0)
-#define trace_rcu_barrier(name, s, cpu, cnt, done) do { } while (0)
-
-#endif /* #else #ifdef CONFIG_RCU_TRACE */
 
 #endif /* _TRACE_RCU_H */
 

include/trace/events/sched.h

···
 DEFINE_EVENT(sched_process_template, sched_process_free,
 	     TP_PROTO(struct task_struct *p),
 	     TP_ARGS(p));
-	     
 
 /*
  * Tracepoint for a task exiting:
···
 		  __entry->pid, __entry->old_pid)
 );
 
+
+#ifdef CONFIG_SCHEDSTATS
+#define DEFINE_EVENT_SCHEDSTAT DEFINE_EVENT
+#define DECLARE_EVENT_CLASS_SCHEDSTAT DECLARE_EVENT_CLASS
+#else
+#define DEFINE_EVENT_SCHEDSTAT DEFINE_EVENT_NOP
+#define DECLARE_EVENT_CLASS_SCHEDSTAT DECLARE_EVENT_CLASS_NOP
+#endif
+
 /*
  * XXX the below sched_stat tracepoints only apply to SCHED_OTHER/BATCH/IDLE
  *     adding sched_stat support to SCHED_FIFO/RR would be welcome.
  */
-DECLARE_EVENT_CLASS(sched_stat_template,
+DECLARE_EVENT_CLASS_SCHEDSTAT(sched_stat_template,
 
 	TP_PROTO(struct task_struct *tsk, u64 delay),
 
···
 			(unsigned long long)__entry->delay)
 );
 
-
 /*
  * Tracepoint for accounting wait time (time the task is runnable
  * but not actually running due to scheduler contention).
  */
-DEFINE_EVENT(sched_stat_template, sched_stat_wait,
+DEFINE_EVENT_SCHEDSTAT(sched_stat_template, sched_stat_wait,
 	     TP_PROTO(struct task_struct *tsk, u64 delay),
 	     TP_ARGS(tsk, delay));
 
···
  * Tracepoint for accounting sleep time (time the task is not runnable,
  * including iowait, see below).
  */
-DEFINE_EVENT(sched_stat_template, sched_stat_sleep,
+DEFINE_EVENT_SCHEDSTAT(sched_stat_template, sched_stat_sleep,
 	     TP_PROTO(struct task_struct *tsk, u64 delay),
 	     TP_ARGS(tsk, delay));
 
···
  * Tracepoint for accounting iowait time (time the task is not runnable
  * due to waiting on IO to complete).
  */
-DEFINE_EVENT(sched_stat_template, sched_stat_iowait,
+DEFINE_EVENT_SCHEDSTAT(sched_stat_template, sched_stat_iowait,
 	     TP_PROTO(struct task_struct *tsk, u64 delay),
 	     TP_ARGS(tsk, delay));
 
 /*
  * Tracepoint for accounting blocked time (time the task is in uninterruptible).
  */
-DEFINE_EVENT(sched_stat_template, sched_stat_blocked,
+DEFINE_EVENT_SCHEDSTAT(sched_stat_template, sched_stat_blocked,
 	     TP_PROTO(struct task_struct *tsk, u64 delay),
 	     TP_ARGS(tsk, delay));
 

kernel/livepatch/core.c

···
 
 static int __init klp_init(void)
 {
-	int ret;
-
-	ret = klp_check_compiler_support();
-	if (ret) {
-		pr_info("Your compiler is too old; turning off.\n");
-		return -EINVAL;
-	}
-
 	klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
 	if (!klp_root_kobj)
 		return -ENOMEM;

kernel/rcu/rcu.h

···
 #define __LINUX_RCU_H
 
 #include <trace/events/rcu.h>
-#ifdef CONFIG_RCU_TRACE
-#define RCU_TRACE(stmt) stmt
-#else /* #ifdef CONFIG_RCU_TRACE */
-#define RCU_TRACE(stmt)
-#endif /* #else #ifdef CONFIG_RCU_TRACE */
 
 /* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
 #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
···
 
 	rcu_lock_acquire(&rcu_callback_map);
 	if (__is_kfree_rcu_offset(offset)) {
-		RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);)
+		trace_rcu_invoke_kfree_callback(rn, head, offset);
 		kfree((void *)head - offset);
 		rcu_lock_release(&rcu_callback_map);
 		return true;
 	} else {
-		RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
+		trace_rcu_invoke_callback(rn, head);
 		f = head->func;
 		WRITE_ONCE(head->func, (rcu_callback_t)0L);
 		f(head);

kernel/rcu/tree.c

···
  */
 int rcutree_dying_cpu(unsigned int cpu)
 {
-	RCU_TRACE(bool blkd;)
-	RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(&rcu_data);)
-	RCU_TRACE(struct rcu_node *rnp = rdp->mynode;)
+	bool blkd;
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+	struct rcu_node *rnp = rdp->mynode;
 
 	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
 		return 0;
 
-	RCU_TRACE(blkd = !!(rnp->qsmask & rdp->grpmask);)
+	blkd = !!(rnp->qsmask & rdp->grpmask);
 	trace_rcu_grace_period(rcu_state.name, rnp->gp_seq,
 			       blkd ? TPS("cpuofl") : TPS("cpuofl-bgp"));
 	return 0;

kernel/trace/ftrace.c

···
 #define INIT_OPS_HASH(opsname)	\
 	.func_hash		= &opsname.local_hash,			\
 	.local_hash.regex_lock	= __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
-#define ASSIGN_OPS_HASH(opsname, val) \
-	.func_hash		= val, \
-	.local_hash.regex_lock	= __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
 #else
 #define INIT_OPS_HASH(opsname)
-#define ASSIGN_OPS_HASH(opsname, val)
 #endif
 
 enum {
···
 static bool module_exists(const char *module)
 {
 	/* All modules have the symbol __this_module */
-	const char this_mod[] = "__this_module";
+	static const char this_mod[] = "__this_module";
 	char modname[MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 2];
 	unsigned long val;
 	int n;
···
 	preempt_disable_notrace();
 
 	do_for_each_ftrace_op(op, ftrace_ops_list) {
+		/* Stub functions don't need to be called nor tested */
+		if (op->flags & FTRACE_OPS_FL_STUB)
+			continue;
 		/*
 		 * Check the following for each ops before calling their func:
 		 *  if RCU flag is set, then rcu_is_watching() must be true

kernel/trace/ring_buffer.c

···
 	cnt = data->cnt + (nested ? 27 : 0);
 
 	/* Multiply cnt by ~e, to make some unique increment */
-	size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
+	size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
 
 	len = size + sizeof(struct rb_item);
 

kernel/trace/ring_buffer_benchmark.c

···
 			hit--; /* make it non zero */
 		}
 
-		/* Caculate the average time in nanosecs */
+		/* Calculate the average time in nanosecs */
 		avg = NSEC_PER_MSEC / (hit + missed);
 		trace_printk("%ld ns per entry\n", avg);
 	}

kernel/trace/trace.c

···
 	pr_info("Running postponed tracer tests:\n");
 
 	list_for_each_entry_safe(p, n, &postponed_selftests, list) {
+		/* This loop can take minutes when sanitizers are enabled, so
+		 * lets make sure we allow RCU processing.
+		 */
+		cond_resched();
 		ret = run_tracer_selftest(p->type);
 		/* If the test fails, then warn and remove from available_tracers */
 		if (ret < 0) {
···
 	if (global_trace.trace_buffer.buffer)
 		tracing_start_cmdline_record();
 }
+EXPORT_SYMBOL_GPL(trace_printk_init_buffers);
 
 void trace_printk_start_comm(void)
 {
···
 	va_end(ap);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(trace_array_printk);
 
 __printf(3, 4)
 int trace_array_printk_buf(struct ring_buffer *buffer,
···
 }
 
 static void
+get_total_entries_cpu(struct trace_buffer *buf, unsigned long *total,
+		      unsigned long *entries, int cpu)
+{
+	unsigned long count;
+
+	count = ring_buffer_entries_cpu(buf->buffer, cpu);
+	/*
+	 * If this buffer has skipped entries, then we hold all
+	 * entries for the trace and we need to ignore the
+	 * ones before the time stamp.
+	 */
+	if (per_cpu_ptr(buf->data, cpu)->skipped_entries) {
+		count -= per_cpu_ptr(buf->data, cpu)->skipped_entries;
+		/* total is the same as the entries */
+		*total = count;
+	} else
+		*total = count +
+			ring_buffer_overrun_cpu(buf->buffer, cpu);
+	*entries = count;
+}
+
+static void
 get_total_entries(struct trace_buffer *buf,
 		  unsigned long *total, unsigned long *entries)
 {
-	unsigned long count;
+	unsigned long t, e;
 	int cpu;
 
 	*total = 0;
 	*entries = 0;
 
 	for_each_tracing_cpu(cpu) {
-		count = ring_buffer_entries_cpu(buf->buffer, cpu);
-		/*
-		 * If this buffer has skipped entries, then we hold all
-		 * entries for the trace and we need to ignore the
-		 * ones before the time stamp.
-		 */
-		if (per_cpu_ptr(buf->data, cpu)->skipped_entries) {
-			count -= per_cpu_ptr(buf->data, cpu)->skipped_entries;
-			/* total is the same as the entries */
-			*total += count;
-		} else
-			*total += count +
-				ring_buffer_overrun_cpu(buf->buffer, cpu);
-		*entries += count;
+		get_total_entries_cpu(buf, &t, &e, cpu);
+		*total += t;
+		*entries += e;
 	}
+}
+
+unsigned long trace_total_entries_cpu(struct trace_array *tr, int cpu)
+{
+	unsigned long total, entries;
+
+	if (!tr)
+		tr = &global_trace;
+
+	get_total_entries_cpu(&tr->trace_buffer, &total, &entries, cpu);
+
+	return entries;
+}
+
+unsigned long trace_total_entries(struct trace_array *tr)
+{
+	unsigned long total, entries;
+
+	if (!tr)
+		tr = &global_trace;
+
+	get_total_entries(&tr->trace_buffer, &total, &entries);
+
+	return entries;
 }
 
 static void print_lat_help_header(struct seq_file *m)
···
 				       unsigned int flags)
 {
 	bool tgid = flags & TRACE_ITER_RECORD_TGID;
-	const char tgid_space[] = "          ";
-	const char space[] = "  ";
+	const char *space = "          ";
+	int prec = tgid ? 10 : 2;
 
 	print_event_info(buf, m);
 
-	seq_printf(m, "#                          %s  _-----=> irqs-off\n",
-		   tgid ? tgid_space : space);
-	seq_printf(m, "#                          %s / _----=> need-resched\n",
-		   tgid ? tgid_space : space);
-	seq_printf(m, "#                          %s| / _---=> hardirq/softirq\n",
-		   tgid ? tgid_space : space);
-	seq_printf(m, "#                          %s|| / _--=> preempt-depth\n",
-		   tgid ? tgid_space : space);
-	seq_printf(m, "#                          %s||| /     delay\n",
-		   tgid ? tgid_space : space);
-	seq_printf(m, "#           TASK-PID %sCPU#  ||||    TIMESTAMP  FUNCTION\n",
-		   tgid ? "   TGID   " : space);
-	seq_printf(m, "#              | |   %s  |   ||||       |         |\n",
-		   tgid ? "     |    " : space);
+	seq_printf(m, "#                          %.*s  _-----=> irqs-off\n", prec, space);
+	seq_printf(m, "#                          %.*s / _----=> need-resched\n", prec, space);
+	seq_printf(m, "#                          %.*s| / _---=> hardirq/softirq\n", prec, space);
+	seq_printf(m, "#                          %.*s|| / _--=> preempt-depth\n", prec, space);
+	seq_printf(m, "#                          %.*s||| /     delay\n", prec, space);
+	seq_printf(m, "#           TASK-PID %.*sCPU#  ||||    TIMESTAMP  FUNCTION\n", prec, "   TGID   ");
+	seq_printf(m, "#              | |   %.*s  |   ||||       |         |\n", prec, "     |    ");
 }
 
 void
···
 	"  trace_pipe\t\t- A consuming read to see the contents of the buffer\n"
 	"  current_tracer\t- function and latency tracers\n"
 	"  available_tracers\t- list of configured tracers for current_tracer\n"
+	"  error_log\t- error log for failed commands (that support it)\n"
 	"  buffer_size_kb\t- view and modify size of per cpu buffer\n"
 	"  buffer_total_size_kb  - view total size of all cpu buffers\n\n"
 	"  trace_clock\t\t-change the clock used to order events\n"
···
 	"  instances\t\t- Make sub-buffers with: mkdir instances/foo\n"
 	"\t\t\t  Remove sub-buffer with rmdir\n"
 	"  trace_options\t\t- Set format or modify how tracing happens\n"
-	"\t\t\t  Disable an option by adding a suffix 'no' to the\n"
+	"\t\t\t  Disable an option by prefixing 'no' to the\n"
 	"\t\t\t  option name\n"
 	"  saved_cmdlines_size\t- echo command number in here to store comm-pid list\n"
 #ifdef CONFIG_DYNAMIC_FTRACE
···
 	struct ring_buffer *buffer;
 	struct print_entry *entry;
 	unsigned long irq_flags;
-	const char faulted[] = "<faulted>";
 	ssize_t written;
 	int size;
 	int len;
 
 /* Used in tracing_mark_raw_write() as well */
-#define FAULTED_SIZE (sizeof(faulted) - 1) /* '\0' is already accounted for */
+#define FAULTED_STR "<faulted>"
+#define FAULTED_SIZE (sizeof(FAULTED_STR) - 1) /* '\0' is already accounted for */
 
 	if (tracing_disabled)
 		return -EINVAL;
···
 
 	len = __copy_from_user_inatomic(&entry->buf, ubuf, cnt);
 	if (len) {
-		memcpy(&entry->buf, faulted, FAULTED_SIZE);
+		memcpy(&entry->buf, FAULTED_STR, FAULTED_SIZE);
 		cnt = FAULTED_SIZE;
 		written = -EFAULT;
 	} else
···
 	struct ring_buffer_event *event;
 	struct ring_buffer *buffer;
 	struct raw_data_entry *entry;
-	const char faulted[] = "<faulted>";
 	unsigned long irq_flags;
 	ssize_t written;
 	int size;
···
 	len = __copy_from_user_inatomic(&entry->id, ubuf, cnt);
 	if (len) {
 		entry->id = -1;
-		memcpy(&entry->buf, faulted, FAULTED_SIZE);
+		memcpy(&entry->buf, FAULTED_STR, FAULTED_SIZE);
 		written = -EFAULT;
 	} else
 		written = cnt;
···
 };
 
 #endif /* CONFIG_TRACER_SNAPSHOT */
+
+#define TRACING_LOG_ERRS_MAX	8
+#define TRACING_LOG_LOC_MAX	128
+
+#define CMD_PREFIX "  Command: "
+
+struct err_info {
+	const char	**errs;	/* ptr to loc-specific array of err strings */
+	u8		type;	/* index into errs -> specific err string */
+	u8		pos;	/* MAX_FILTER_STR_VAL = 256 */
+	u64		ts;
+};
+
+struct tracing_log_err {
+	struct list_head	list;
+	struct err_info		info;
+	char			loc[TRACING_LOG_LOC_MAX]; /* err location */
+	char			cmd[MAX_FILTER_STR_VAL]; /* what caused err */
+};
+
+static DEFINE_MUTEX(tracing_err_log_lock);
+
+struct tracing_log_err *get_tracing_log_err(struct trace_array *tr)
+{
+	struct tracing_log_err *err;
+
+	if (tr->n_err_log_entries < TRACING_LOG_ERRS_MAX) {
+		err = kzalloc(sizeof(*err), GFP_KERNEL);
+		if (!err)
+			err = ERR_PTR(-ENOMEM);
+		tr->n_err_log_entries++;
+
+		return err;
+	}
+
+	err = list_first_entry(&tr->err_log, struct tracing_log_err, list);
+	list_del(&err->list);
+
+	return err;
+}
+
+/**
+ * err_pos - find the position of a string within a command for error careting
+ * @cmd: The tracing command that caused the error
+ * @str: The string to position the caret at within @cmd
+ *
+ * Finds the position of the first occurence of @str within @cmd.  The
+ * return value can be passed to tracing_log_err() for caret placement
+ * within @cmd.
+ *
+ * Returns the index within @cmd of the first occurence of @str or 0
+ * if @str was not found.
+ */
+unsigned int err_pos(char *cmd, const char *str)
+{
+	char *found;
+
+	if (WARN_ON(!strlen(cmd)))
+		return 0;
+
+	found = strstr(cmd, str);
+	if (found)
+		return found - cmd;
+
+	return 0;
+}
+
+/**
+ * tracing_log_err - write an error to the tracing error log
+ * @tr: The associated trace array for the error (NULL for top level array)
+ * @loc: A string describing where the error occurred
+ * @cmd: The tracing command that caused the error
+ * @errs: The array of loc-specific static error strings
+ * @type: The index into errs[], which produces the specific static err string
+ * @pos: The position the caret should be placed in the cmd
+ *
+ * Writes an error into tracing/error_log of the form:
+ *
+ * <loc>: error: <text>
+ *   Command: <cmd>
+ *              ^
+ *
+ * tracing/error_log is a small log file containing the last
+ * TRACING_LOG_ERRS_MAX errors (8).  Memory for errors isn't allocated
+ * unless there has been a tracing error, and the error log can be
+ * cleared and have its memory freed by writing the empty string in
+ * truncation mode to it i.e. echo > tracing/error_log.
+ *
+ * NOTE: the @errs array along with the @type param are used to
+ * produce a static error string - this string is not copied and saved
+ * when the error is logged - only a pointer to it is saved.  See
+ * existing callers for examples of how static strings are typically
+ * defined for use with tracing_log_err().
+ */
+void tracing_log_err(struct trace_array *tr,
+		     const char *loc, const char *cmd,
+		     const char **errs, u8 type, u8 pos)
+{
+	struct tracing_log_err *err;
+
+	if (!tr)
+		tr = &global_trace;
+
+	mutex_lock(&tracing_err_log_lock);
+	err = get_tracing_log_err(tr);
+	if (PTR_ERR(err) == -ENOMEM) {
+		mutex_unlock(&tracing_err_log_lock);
+		return;
+	}
+
+	snprintf(err->loc, TRACING_LOG_LOC_MAX, "%s: error: ", loc);
+	snprintf(err->cmd, MAX_FILTER_STR_VAL,"\n" CMD_PREFIX "%s\n", cmd);
+
+	err->info.errs = errs;
+	err->info.type = type;
+	err->info.pos = pos;
+	err->info.ts = local_clock();
+
+	list_add_tail(&err->list, &tr->err_log);
+	mutex_unlock(&tracing_err_log_lock);
+}
+
+static void clear_tracing_err_log(struct trace_array *tr)
+{
+	struct tracing_log_err *err, *next;
+
+	mutex_lock(&tracing_err_log_lock);
+	list_for_each_entry_safe(err, next, &tr->err_log, list) {
+		list_del(&err->list);
+		kfree(err);
+	}
+
+	tr->n_err_log_entries = 0;
+	mutex_unlock(&tracing_err_log_lock);
+}
+
+static void *tracing_err_log_seq_start(struct seq_file *m, loff_t *pos)
+{
+	struct trace_array *tr = m->private;
+
+	mutex_lock(&tracing_err_log_lock);
+
+	return seq_list_start(&tr->err_log, *pos);
+}
+
+static void *tracing_err_log_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct trace_array *tr = m->private;
+
+	return seq_list_next(v, &tr->err_log, pos);
+}
+
+static void tracing_err_log_seq_stop(struct seq_file *m, void *v)
+{
+	mutex_unlock(&tracing_err_log_lock);
+}
+
+static void tracing_err_log_show_pos(struct seq_file *m, u8 pos)
+{
+	u8 i;
+
+	for (i = 0; i < sizeof(CMD_PREFIX) - 1; i++)
+		seq_putc(m, ' ');
+	for (i = 0; i < pos; i++)
+		seq_putc(m, ' ');
+	seq_puts(m, "^\n");
+}
+
+static int tracing_err_log_seq_show(struct seq_file *m, void *v)
+{
+	struct tracing_log_err *err = v;
+
+	if (err) {
+		const char *err_text = err->info.errs[err->info.type];
+		u64 sec = err->info.ts;
+		u32 nsec;
+
+		nsec = do_div(sec, NSEC_PER_SEC);
+		seq_printf(m, "[%5llu.%06u] %s%s", sec, nsec / 1000,
+			   err->loc, err_text);
+		seq_printf(m, "%s", err->cmd);
+		tracing_err_log_show_pos(m, err->info.pos);
+	}
+
+	return 0;
+}
+
+static const struct seq_operations tracing_err_log_seq_ops = {
+	.start  = tracing_err_log_seq_start,
+	.next   = tracing_err_log_seq_next,
+	.stop   = tracing_err_log_seq_stop,
+	.show   = tracing_err_log_seq_show
+};
+
+static int tracing_err_log_open(struct inode *inode, struct file *file)
+{
+	struct trace_array *tr = inode->i_private;
+	int ret = 0;
+
+	if (trace_array_get(tr) < 0)
+		return -ENODEV;
+
+	/* If this file was opened for write, then erase contents */
+	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC))
+		clear_tracing_err_log(tr);
+
+	if (file->f_mode & FMODE_READ) {
+		ret = seq_open(file, &tracing_err_log_seq_ops);
+		if (!ret) {
+			struct seq_file *m = file->private_data;
+			m->private = tr;
+		} else {
+			trace_array_put(tr);
+		}
+	}
+	return ret;
+}
+
+static ssize_t tracing_err_log_write(struct file *file,
+				     const char __user *buffer,
+				     size_t count, loff_t *ppos)
+{
+	return count;
+}
+
+static const struct file_operations tracing_err_log_fops = {
+	.open           = tracing_err_log_open,
+	.write		= tracing_err_log_write,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release	= tracing_release_generic_tr,
+};
 
 static int tracing_buffers_open(struct inode *inode, struct file *filp)
 {
···
 	mutex_unlock(&trace_types_lock);
 }
 
-static int instance_mkdir(const char *name)
+struct trace_array *trace_array_create(const char *name)
 {
 	struct trace_array *tr;
 	int ret;
···
 	INIT_LIST_HEAD(&tr->systems);
 	INIT_LIST_HEAD(&tr->events);
 	INIT_LIST_HEAD(&tr->hist_vars);
+	INIT_LIST_HEAD(&tr->err_log);
 
 	if (allocate_trace_buffers(tr, trace_buf_size) < 0)
 		goto out_free_tr;
···
 	mutex_unlock(&trace_types_lock);
 	mutex_unlock(&event_mutex);
 
-	return 0;
+	return tr;
 
  out_free_tr:
 	free_trace_buffers(tr);
···
 	mutex_unlock(&trace_types_lock);
 	mutex_unlock(&event_mutex);
 
-	return ret;
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(trace_array_create);
 
+static int instance_mkdir(const char *name)
+{
+	return PTR_ERR_OR_ZERO(trace_array_create(name));
 }
 
-static int instance_rmdir(const char *name)
+static int __remove_instance(struct trace_array *tr)
 {
-	struct trace_array *tr;
-	int found = 0;
-	int ret;
 	int i;
 
-	mutex_lock(&event_mutex);
-	mutex_lock(&trace_types_lock);
-
-	ret = -ENODEV;
-	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
-		if (tr->name && strcmp(tr->name, name) == 0) {
-			found = 1;
-			break;
-		}
-	}
-	if (!found)
-		goto out_unlock;
-
-	ret = -EBUSY;
 	if (tr->ref || (tr->current_trace && tr->current_trace->ref))
-		goto out_unlock;
+		return -EBUSY;
 
 	list_del(&tr->list);
 
···
 	free_cpumask_var(tr->tracing_cpumask);
 	kfree(tr->name);
 	kfree(tr);
+	tr = NULL;
 
-	ret = 0;
+	return 0;
+}
 
- out_unlock:
+int trace_array_destroy(struct trace_array *tr)
+{
+	int ret;
+
+	if (!tr)
+		return -EINVAL;
+
+	mutex_lock(&event_mutex);
+	mutex_lock(&trace_types_lock);
+
+	ret = __remove_instance(tr);
+
+	mutex_unlock(&trace_types_lock);
+	mutex_unlock(&event_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(trace_array_destroy);
+
+static int instance_rmdir(const char *name)
+{
+	struct trace_array *tr;
+	int ret;
+
+	mutex_lock(&event_mutex);
+	mutex_lock(&trace_types_lock);
+
+	ret = -ENODEV;
+	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+		if (tr->name && strcmp(tr->name, name) == 0) {
+			ret = __remove_instance(tr);
+			break;
+		}
+	}
+
 	mutex_unlock(&trace_types_lock);
 	mutex_unlock(&event_mutex);
 
···
 	trace_create_file("snapshot", 0644, d_tracer,
 			  tr, &snapshot_fops);
 #endif
+
+	trace_create_file("error_log", 0644, d_tracer,
+			  tr, &tracing_err_log_fops);
 
 	for_each_tracing_cpu(cpu)
 		tracing_init_tracefs_percpu(tr, cpu);
···
 	INIT_LIST_HEAD(&global_trace.systems);
 	INIT_LIST_HEAD(&global_trace.events);
 	INIT_LIST_HEAD(&global_trace.hist_vars);
+	INIT_LIST_HEAD(&global_trace.err_log);
 	list_add(&global_trace.list, &ftrace_trace_arrays);
 
 	apply_trace_boot_options();

kernel/trace/trace.h

···
 	int			nr_topts;
 	bool			clear_trace;
 	int			buffer_percent;
+	unsigned int		n_err_log_entries;
 	struct tracer		*current_trace;
 	unsigned int		trace_flags;
 	unsigned char		trace_flags_index[TRACE_FLAGS_MAX_SIZE];
 	unsigned int		flags;
 	raw_spinlock_t		start_lock;
+	struct list_head	err_log;
 	struct dentry		*dir;
 	struct dentry		*options;
 	struct dentry		*percpu_dir;
···
 void trace_init_global_iter(struct trace_iterator *iter);
 
 void tracing_iter_reset(struct trace_iterator *iter, int cpu);
+
+unsigned long trace_total_entries_cpu(struct trace_array *tr, int cpu);
+unsigned long trace_total_entries(struct trace_array *tr);
 
 void trace_function(struct trace_array *tr,
 		    unsigned long ip,
···
 extern void print_subsystem_event_filter(struct event_subsystem *system,
 					 struct trace_seq *s);
 extern int filter_assign_type(const char *type);
-extern int create_event_filter(struct trace_event_call *call,
+extern int create_event_filter(struct trace_array *tr,
+			       struct trace_event_call *call,
 			       char *filter_str, bool set_str,
 			       struct event_filter **filterp);
 extern void free_event_filter(struct event_filter *filter);
···
 extern ssize_t trace_parse_run_command(struct file *file,
 		const char __user *buffer, size_t count, loff_t *ppos,
 		int (*createfn)(int, char**));
+
+extern unsigned int err_pos(char *cmd, const char *str);
+extern void tracing_log_err(struct trace_array *tr,
+			    const char *loc, const char *cmd,
+			    const char **errs, u8 type, u8 pos);
 
 /*
  * Normal trace_printk() and friends allocates special buffers

kernel/trace/trace_events.c

···
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(ftrace_set_clr_event);
 
 /**
  * trace_set_clr_event - enable or disable an event
···
 	int id = (long)event_file_data(filp);
 	char buf[32];
 	int len;
-
-	if (*ppos)
-		return 0;
 
 	if (unlikely(!id))
 		return -ENODEV;

kernel/trace/trace_events_filter.c

···
 	C(INVALID_FILTER,	"Meaningless filter expression"),	\
 	C(IP_FIELD_ONLY,	"Only 'ip' field is supported for function trace"), \
 	C(INVALID_VALUE,	"Invalid value (did you forget quotes)?"), \
-	C(NO_FILTER,		"No filter found"),
+	C(ERRNO,		"Error"),				\
+	C(NO_FILTER,		"No filter found")
 
 #undef C
 #define C(a, b)		FILT_ERR_##a
···
 #undef C
 #define C(a, b)		b
 
-static char *err_text[] = { ERRORS };
+static const char *err_text[] = { ERRORS };
 
 /* Called after a '!' character but "!=" and "!~" are not "not"s */
 static bool is_not(const char *str)
···
 	filter->filter_string = NULL;
 }
 
-static void append_filter_err(struct filter_parse_error *pe,
+static void append_filter_err(struct trace_array *tr,
+			      struct filter_parse_error *pe,
 			      struct event_filter *filter)
 {
 	struct trace_seq *s;
···
 	if (pe->lasterr > 0) {
 		trace_seq_printf(s, "\n%*s", pos, "^");
 		trace_seq_printf(s, "\nparse_error: %s\n", err_text[pe->lasterr]);
+		tracing_log_err(tr, "event filter parse error",
+				filter->filter_string, err_text,
+				pe->lasterr, pe->lasterr_pos);
 	} else {
 		trace_seq_printf(s, "\nError: (%d)\n", pe->lasterr);
+		tracing_log_err(tr, "event filter parse error",
+				filter->filter_string, err_text,
+				FILT_ERR_ERRNO, 0);
 	}
 	trace_seq_putc(s, 0);
 	buf = kmemdup_nul(s->buffer, s->seq.len, GFP_KERNEL);
···
 		 * (perf doesn't use it) and grab everything.
 		 */
 		if (strcmp(field->name, "ip") != 0) {
-			 parse_error(pe, FILT_ERR_IP_FIELD_ONLY, pos + i);
-			 goto err_free;
-		 }
-		 pred->fn = filter_pred_none;
+			parse_error(pe, FILT_ERR_IP_FIELD_ONLY, pos + i);
+			goto err_free;
+		}
+		pred->fn = filter_pred_none;
 
-		 /*
-		  * Quotes are not required, but if they exist then we need
-		  * to read them till we hit a matching one.
-		  */
-		 if (str[i] == '\'' || str[i] == '"')
-			 q = str[i];
-		 else
-			 q = 0;
+		/*
+		 * Quotes are not required, but if they exist then we need
+		 * to read them till we hit a matching one.
+		 */
+		if (str[i] == '\'' || str[i] == '"')
+			q = str[i];
+		else
+			q = 0;
 
-		 for (i++; str[i]; i++) {
-			 if (q && str[i] == q)
-				 break;
-			 if (!q && (str[i] == ')' || str[i] == '&' ||
-				    str[i] == '|'))
-				 break;
-		 }
-		 /* Skip quotes */
-		 if (q)
-			 s++;
+		for (i++; str[i]; i++) {
+			if (q && str[i] == q)
+				break;
+			if (!q && (str[i] == ')' || str[i] == '&' ||
+				   str[i] == '|'))
+				break;
+		}
+		/* Skip quotes */
+		if (q)
+			s++;
 		len = i - s;
 		if (len >= MAX_FILTER_STR_VAL) {
 			parse_error(pe, FILT_ERR_OPERAND_TOO_LONG, pos + i);
···
 		if (err) {
 			filter_disable(file);
 			parse_error(pe, FILT_ERR_BAD_SUBSYS_FILTER, 0);
-			append_filter_err(pe, filter);
+			append_filter_err(tr, pe, filter);
 		} else
 			event_set_filtered_flag(file);
 
···
  * information if @set_str is %true and the caller is responsible for
  * freeing it.
  */
-static int create_filter(struct trace_event_call *call,
+static int create_filter(struct trace_array *tr,
+			 struct trace_event_call *call,
 			 char *filter_string, bool set_str,
 			 struct event_filter **filterp)
 {
···
 
 	err = process_preds(call, filter_string, *filterp, pe);
 	if (err && set_str)
-		append_filter_err(pe, *filterp);
+		append_filter_err(tr, pe, *filterp);
 	create_filter_finish(pe);
 
 	return err;
 }
 
-int create_event_filter(struct trace_event_call *call,
+int create_event_filter(struct trace_array *tr,
+			struct trace_event_call *call,
 			char *filter_str, bool set_str,
 			struct event_filter **filterp)
 {
-	return create_filter(call, filter_str, set_str, filterp);
+	return create_filter(tr, call, filter_str, set_str, filterp);
 }
 
 /**
···
 			kfree((*filterp)->filter_string);
 			(*filterp)->filter_string = NULL;
 		} else {
-			append_filter_err(pe, *filterp);
+			append_filter_err(tr, pe, *filterp);
 		}
 	}
 	create_filter_finish(pe);
···
 		return 0;
 	}
 
-	err = create_filter(call, filter_string, true, &filter);
+	err = create_filter(file->tr, call, filter_string, true, &filter);
 
 	/*
 	 * Always swap the call filter with the new filter
···
 	if (event->filter)
 		goto out_unlock;
 
-	err = create_filter(call, filter_str, false, &filter);
+	err = create_filter(NULL, call, filter_str, false, &filter);
 	if (err)
 		goto free_filter;
 
···
 		struct test_filter_data_t *d = &test_filter_data[i];
 		int err;
 
-		err = create_filter(&event_ftrace_test_filter, d->filter,
-				    false, &filter);
+		err = create_filter(NULL, &event_ftrace_test_filter,
+				    d->filter, false, &filter);
 		if (err) {
 			printk(KERN_INFO
 			       "Failed to get filter for '%s', err %d\n",

kernel/trace/trace_events_hist.c

···
 
 #define STR_VAR_LEN_MAX		32 /* must be multiple of sizeof(u64) */
 
+#define ERRORS								\
+	C(NONE,			"No error"),				\
+	C(DUPLICATE_VAR,	"Variable already defined"),		\
+	C(VAR_NOT_UNIQUE,	"Variable name not unique, need to use fully qualified name (subsys.event.var) for variable"), \
+	C(TOO_MANY_VARS,	"Too many variables defined"),		\
+	C(MALFORMED_ASSIGNMENT,	"Malformed assignment"),		\
+	C(NAMED_MISMATCH,	"Named hist trigger doesn't match existing named trigger (includes variables)"), \
+	C(TRIGGER_EEXIST,	"Hist trigger already exists"),		\
+	C(TRIGGER_ENOENT_CLEAR,	"Can't clear or continue a nonexistent hist trigger"), \
+	C(SET_CLOCK_FAIL,	"Couldn't set trace_clock"),		\
+	C(BAD_FIELD_MODIFIER,	"Invalid field modifier"),		\
+	C(TOO_MANY_SUBEXPR,	"Too many subexpressions (3 max)"),	\
+	C(TIMESTAMP_MISMATCH,	"Timestamp units in expression don't match"), \
+	C(TOO_MANY_FIELD_VARS,	"Too many field variables defined"),	\
+	C(EVENT_FILE_NOT_FOUND,	"Event file not found"),		\
+	C(HIST_NOT_FOUND,	"Matching event histogram not found"),	\
+	C(HIST_CREATE_FAIL,	"Couldn't create histogram for field"),	\
+	C(SYNTH_VAR_NOT_FOUND,	"Couldn't find synthetic variable"),	\
+	C(SYNTH_EVENT_NOT_FOUND,"Couldn't find synthetic event"),	\
+	C(SYNTH_TYPE_MISMATCH,	"Param type doesn't match synthetic event field type"), \
+	C(SYNTH_COUNT_MISMATCH,	"Param count doesn't match synthetic event field count"), \
+	C(FIELD_VAR_PARSE_FAIL,	"Couldn't parse field variable"),	\
+	C(VAR_CREATE_FIND_FAIL,	"Couldn't create or find variable"),	\
+	C(ONX_NOT_VAR,		"For onmax(x) or onchange(x), x must be a variable"), \
+	C(ONX_VAR_NOT_FOUND,	"Couldn't find onmax or onchange variable"), \
+	C(ONX_VAR_CREATE_FAIL,	"Couldn't create onmax or onchange variable"), \
+	C(FIELD_VAR_CREATE_FAIL,"Couldn't create field variable"),	\
+	C(TOO_MANY_PARAMS,	"Too many action params"),		\
+	C(PARAM_NOT_FOUND,	"Couldn't find param"),			\
+	C(INVALID_PARAM,	"Invalid action param"),		\
+	C(ACTION_NOT_FOUND,	"No action found"),			\
+	C(NO_SAVE_PARAMS,	"No params found for save()"),		\
+	C(TOO_MANY_SAVE_ACTIONS,"Can't have more than one save() action per hist"), \
+	C(ACTION_MISMATCH,	"Handler doesn't support action"),	\
+	C(NO_CLOSING_PAREN,	"No closing paren found"),		\
+	C(SUBSYS_NOT_FOUND,	"Missing subsystem"),			\
+	C(INVALID_SUBSYS_EVENT,	"Invalid subsystem or event name"),	\
+	C(INVALID_REF_KEY,	"Using variable references as keys not supported"), \
+	C(VAR_NOT_FOUND,	"Couldn't find variable"),		\
+	C(FIELD_NOT_FOUND,	"Couldn't find field"),
+
+#undef C
+#define C(a, b)		HIST_ERR_##a
+
+enum { ERRORS };
+
+#undef C
+#define C(a, b)		b
+
+static const char *err_text[] = { ERRORS };
+
 struct hist_field;
 
 typedef u64 (*hist_field_fn_t) (struct hist_field *field,
···
 	return data;
 }
 
-static char last_hist_cmd[MAX_FILTER_STR_VAL];
-static char hist_err_str[MAX_FILTER_STR_VAL];
+static char last_cmd[MAX_FILTER_STR_VAL];
+static char last_cmd_loc[MAX_FILTER_STR_VAL];
 
-static void last_cmd_set(char *str)
+static int errpos(char *str)
 {
+	return err_pos(last_cmd, str);
+}
+
+static void last_cmd_set(struct trace_event_file *file, char *str)
+{
+	const char *system = NULL, *name = NULL;
+	struct trace_event_call *call;
+
 	if (!str)
 		return;
 
-	strncpy(last_hist_cmd, str, MAX_FILTER_STR_VAL - 1);
+	strncpy(last_cmd, str, MAX_FILTER_STR_VAL - 1);
+
+	if (file) {
+		call = file->event_call;
+
+		system = call->class->system;
+		if (system) {
+			name = trace_event_name(call);
+			if (!name)
+				system = NULL;
+		}
+	}
+
+	if (system)
+		snprintf(last_cmd_loc, MAX_FILTER_STR_VAL, "hist:%s:%s", system, name);
 }
 
-static void hist_err(char *str, char *var)
+static void hist_err(struct trace_array *tr, u8 err_type, u8 err_pos)
 {
-	int maxlen = MAX_FILTER_STR_VAL - 1;
-
-	if (!str)
-		return;
-
-	if (strlen(hist_err_str))
-		return;
-
-	if (!var)
-		var = "";
-
-	if (strlen(hist_err_str) + strlen(str) + strlen(var) > maxlen)
-		return;
-
-	strcat(hist_err_str, str);
-	strcat(hist_err_str, var);
-}
-
-static void hist_err_event(char *str, char *system, char *event, char *var)
-{
-	char err[MAX_FILTER_STR_VAL];
-
-	if (system && var)
-		snprintf(err, MAX_FILTER_STR_VAL, "%s.%s.%s", system, event, var);
-	else if (system)
-		snprintf(err, MAX_FILTER_STR_VAL, "%s.%s", system, event);
-	else
-		strscpy(err, var, MAX_FILTER_STR_VAL);
-
-	hist_err(str, err);
+	tracing_log_err(tr, last_cmd_loc, last_cmd, err_text,
+			err_type, err_pos);
 }
 
 static void hist_err_clear(void)
 {
-	hist_err_str[0] = '\0';
-}
-
-static bool have_hist_err(void)
-{
-	if (strlen(hist_err_str))
-		return true;
-
-	return false;
+	last_cmd[0] = '\0';
+	last_cmd_loc[0] = '\0';
 }
 
 struct synth_trace_event {
···
 
 		if (find_var_field(var_hist_data, var_name)) {
 			if (found) {
-				hist_err_event("Variable name not unique, need to use fully qualified name (subsys.event.var) for variable: ", system, event_name, var_name);
+				hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE, errpos(var_name));
 				return NULL;
 			}
 
···
 			hist_field = find_file_var(file, var_name);
 			if (hist_field) {
 				if (found) {
-					hist_err_event("Variable name not unique, need to use fully qualified name (subsys.event.var) for variable: ", system, event_name, var_name);
+					hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE,
+						 errpos(var_name));
 					return ERR_PTR(-EINVAL);
 				}
 
···
 		attrs->n_actions++;
 		ret = 0;
 	}
-
 	return ret;
 }
 
-static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
+static int parse_assignment(struct trace_array *tr,
+			    char *str, struct hist_trigger_attrs *attrs)
 {
 	int ret = 0;
 
···
 		char *assignment;
 
 		if (attrs->n_assignments == TRACING_MAP_VARS_MAX) {
-			hist_err("Too many variables defined: ", str);
+			hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(str));
 			ret = -EINVAL;
 			goto out;
 		}
···
 	return ret;
 }
 
-static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
+static struct hist_trigger_attrs *
+parse_hist_trigger_attrs(struct trace_array *tr, char *trigger_str)
 {
 	struct hist_trigger_attrs *attrs;
 	int ret = 0;
···
 		char *str = strsep(&trigger_str, ":");
 
 		if (strchr(str, '=')) {
-			ret = parse_assignment(str, attrs);
+			ret = parse_assignment(tr, str, attrs);
 			if (ret)
 				goto free;
 		} else if (strcmp(str, "pause") == 0)
···
 					char *var_name)
 {
 	struct hist_field *var_field = NULL, *ref_field = NULL;
+	struct trace_array *tr = hist_data->event_file->tr;
 
 	if (!is_var_ref(var_name))
 		return NULL;
···
 					   system, event_name);
 
 	if (!ref_field)
-		hist_err_event("Couldn't find variable: $",
-			       system, event_name, var_name);
+		hist_err(tr, HIST_ERR_VAR_NOT_FOUND, errpos(var_name));
 
 	return ref_field;
 }
···
 {
 	struct ftrace_event_field *field = NULL;
 	char *field_name, *modifier, *str;
+	struct trace_array *tr = file->tr;
 
 	modifier = str = kstrdup(field_str, GFP_KERNEL);
 	if (!modifier)
···
 		else if (strcmp(modifier, "usecs") == 0)
 			*flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
 		else {
-			hist_err("Invalid field modifier: ", modifier);
+			hist_err(tr, HIST_ERR_BAD_FIELD_MODIFIER, errpos(modifier));
 			field = ERR_PTR(-EINVAL);
 			goto out;
 		}
···
 	else {
 		field = trace_find_event_field(file->event_call, field_name);
 		if (!field || !field->size) {
-			hist_err("Couldn't find field: ", field_name);
+			hist_err(tr, HIST_ERR_FIELD_NOT_FOUND, errpos(field_name));
 			field = ERR_PTR(-EINVAL);
 			goto out;
 		}
···
 
 	s = local_field_var_ref(hist_data, ref_system, ref_event, ref_var);
 	if (!s) {
-		hist_field = parse_var_ref(hist_data, ref_system, ref_event, ref_var);
+		hist_field = parse_var_ref(hist_data, ref_system,
+					   ref_event, ref_var);
 		if (hist_field) {
 			if (var_name) {
 				hist_field = create_alias(hist_data, hist_field, var_name);
···
 	/* we support only -(xxx) i.e. explicit parens required */
 
 	if (level > 3) {
-		hist_err("Too many subexpressions (3 max): ", str);
+		hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
 		ret = -EINVAL;
 		goto free;
 	}
···
 	return ERR_PTR(ret);
 }
 
-static int check_expr_operands(struct hist_field *operand1,
+static int check_expr_operands(struct trace_array *tr,
+			       struct hist_field *operand1,
 			       struct hist_field *operand2)
 {
 	unsigned long operand1_flags = operand1->flags;
···
 
 	if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
 	    (operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS)) {
-		hist_err("Timestamp units in expression don't match", NULL);
+		hist_err(tr, HIST_ERR_TIMESTAMP_MISMATCH, 0);
 		return -EINVAL;
 	}
 
···
 	char *sep, *operand1_str;
 
 	if (level > 3) {
-		hist_err("Too many subexpressions (3 max): ", str);
+		hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
 		return ERR_PTR(-EINVAL);
 	}
 
···
 		goto free;
 	}
 
-	ret = check_expr_operands(operand1, operand2);
+	ret = check_expr_operands(file->tr, operand1, operand2);
 	if (ret)
 		goto free;
 
···
 	int ret;
 
 	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX) {
-		hist_err_event("trace action: Too many field variables defined: ",
-			       subsys_name, event_name, field_name);
+		hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
 		return ERR_PTR(-EINVAL);
 	}
 
 	file = event_file(tr, subsys_name, event_name);
 
 	if (IS_ERR(file)) {
-		hist_err_event("trace action: Event file not found: ",
-			       subsys_name, event_name, field_name);
+		hist_err(tr, HIST_ERR_EVENT_FILE_NOT_FOUND, errpos(field_name));
 		ret = PTR_ERR(file);
 		return ERR_PTR(ret);
 	}
···
 	 */
 	hist_data = find_compatible_hist(target_hist_data, file);
 	if (!hist_data) {
-		hist_err_event("trace action: Matching event histogram not found: ",
-			       subsys_name, event_name, field_name);
+		hist_err(tr, HIST_ERR_HIST_NOT_FOUND, errpos(field_name));
 		return ERR_PTR(-EINVAL);
 	}
 
···
 		kfree(cmd);
 		kfree(var_hist->cmd);
 		kfree(var_hist);
-		hist_err_event("trace action: Couldn't create histogram for field: ",
-			       subsys_name, event_name, field_name);
+		hist_err(tr, HIST_ERR_HIST_CREATE_FAIL, errpos(field_name));
 		return ERR_PTR(ret);
 	}
 
···
 	if (IS_ERR_OR_NULL(event_var)) {
 		kfree(var_hist->cmd);
 		kfree(var_hist);
-		hist_err_event("trace action: Couldn't find synthetic variable: ",
-			       subsys_name, event_name, field_name);
+		hist_err(tr, HIST_ERR_SYNTH_VAR_NOT_FOUND, errpos(field_name));
 		return ERR_PTR(-EINVAL);
 	}
 
···
 {
 	struct hist_field *val = NULL, *var = NULL;
 	unsigned long flags = HIST_FIELD_FL_VAR;
+	struct trace_array *tr = file->tr;
 	struct field_var *field_var;
 	int ret = 0;
 
 	if (hist_data->n_field_vars >= SYNTH_FIELDS_MAX) {
-		hist_err("Too many field variables defined: ", field_name);
+		hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
 		ret = -EINVAL;
 		goto err;
 	}
 
 	val = parse_atom(hist_data, file, field_name, &flags, NULL);
 	if (IS_ERR(val)) {
-		hist_err("Couldn't parse field variable: ", field_name);
+		hist_err(tr, HIST_ERR_FIELD_VAR_PARSE_FAIL, errpos(field_name));
 		ret = PTR_ERR(val);
 		goto err;
 	}
 
 	var = create_var(hist_data, file, field_name, val->size, val->type);
 	if (IS_ERR(var)) {
-		hist_err("Couldn't create or find variable: ", field_name);
+		hist_err(tr, HIST_ERR_VAR_CREATE_FIND_FAIL, errpos(field_name));
 		kfree(val);
 		ret = PTR_ERR(var);
 		goto err;
···
 {
 	struct hist_field *var_field, *ref_field, *track_var = NULL;
 	struct trace_event_file *file = hist_data->event_file;
+	struct trace_array *tr = file->tr;
 	char *track_data_var_str;
 	int ret = 0;
 
 	track_data_var_str = data->track_data.var_str;
 	if (track_data_var_str[0] != '$') {
-		hist_err("For onmax(x) or onchange(x), x must be a variable: ", track_data_var_str);
+		hist_err(tr, HIST_ERR_ONX_NOT_VAR, errpos(track_data_var_str));
 		return -EINVAL;
 	}
 	track_data_var_str++;
 
 	var_field = find_target_event_var(hist_data, NULL, NULL, track_data_var_str);
 	if (!var_field) {
-		hist_err("Couldn't find onmax or onchange variable: ", track_data_var_str);
+		hist_err(tr, HIST_ERR_ONX_VAR_NOT_FOUND, errpos(track_data_var_str));
 		return -EINVAL;
 	}
 
···
 	if (data->handler == HANDLER_ONMAX)
 		track_var = create_var(hist_data, file, "__max", sizeof(u64), "u64");
 	if (IS_ERR(track_var)) {
-		hist_err("Couldn't create onmax variable: ", "__max");
+		hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
 		ret = PTR_ERR(track_var);
 		goto out;
 	}
···
 	if (data->handler == HANDLER_ONCHANGE)
 		track_var = create_var(hist_data, file, "__change", sizeof(u64), "u64");
 	if (IS_ERR(track_var)) {
-		hist_err("Couldn't create onchange variable: ", "__change");
+		hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
 		ret = PTR_ERR(track_var);
 		goto out;
 	}
···
 	return ret;
 }
 
-static int parse_action_params(char *params, struct action_data *data)
+static int parse_action_params(struct trace_array *tr, char *params,
+			       struct action_data *data)
 {
 	char *param, *saved_param;
 	bool first_param = true;
···
 
 	while (params) {
 		if (data->n_params >= SYNTH_FIELDS_MAX) {
-			hist_err("Too many action params", "");
+			hist_err(tr, HIST_ERR_TOO_MANY_PARAMS, 0);
 			goto out;
 		}
 
 		param = strsep(&params, ",");
 		if (!param) {
-			hist_err("No action param found", "");
+			hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, 0);
 			ret = -EINVAL;
 			goto out;
 		}
 
 		param = strstrip(param);
 		if (strlen(param) < 2) {
-			hist_err("Invalid action param: ", param);
+			hist_err(tr, HIST_ERR_INVALID_PARAM, errpos(param));
 			ret = -EINVAL;
 			goto out;
 		}
···
 	return ret;
 }
 
-static int action_parse(char *str, struct action_data *data,
+static int action_parse(struct trace_array *tr, char *str, struct action_data *data,
 			enum handler_id handler)
 {
 	char *action_name;
···
 
 	strsep(&str, ".");
 	if (!str) {
-		hist_err("action parsing: No action found", "");
+		hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
 		ret = -EINVAL;
 		goto out;
 	}
 
 	action_name = strsep(&str, "(");
 	if (!action_name || !str) {
-		hist_err("action parsing: No action found", "");
+		hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
 		ret = -EINVAL;
 		goto out;
 	}
···
 		char *params = strsep(&str, ")");
 
 		if (!params) {
-			hist_err("action parsing: No params found for %s", "save");
+			hist_err(tr, HIST_ERR_NO_SAVE_PARAMS, 0);
 			ret = -EINVAL;
 			goto out;
 		}
 
-		ret = parse_action_params(params, data);
+		ret = parse_action_params(tr, params, data);
 		if (ret)
 			goto out;
 
···
 		else if (handler == HANDLER_ONCHANGE)
 			data->track_data.check_val = check_track_val_changed;
 		else {
-			hist_err("action parsing: Handler doesn't support action: ", action_name);
+			hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
 			ret = -EINVAL;
 			goto out;
 		}
···
 		char *params = strsep(&str, ")");
 
 		if (!str) {
-			hist_err("action parsing: No closing paren found: %s", params);
+			hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(params));
 			ret = -EINVAL;
 			goto out;
 		}
···
 		else if (handler == HANDLER_ONCHANGE)
 			data->track_data.check_val = check_track_val_changed;
 		else {
-			hist_err("action parsing: Handler doesn't support action: ", action_name);
+			hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
 			ret = -EINVAL;
 			goto out;
 		}
···
 			data->use_trace_keyword = true;
 
 		if (params) {
-			ret = parse_action_params(params, data);
+			ret = parse_action_params(tr, params, data);
 			if (ret)
 				goto out;
 		}
···
 		goto free;
 	}
 
-	ret = action_parse(str, data, handler);
+	ret = action_parse(hist_data->event_file->tr, str, data, handler);
 	if (ret)
 		goto free;
  out:
···
 		      struct action_data *data,
 		      char *system, char *event, char *var)
 {
+	struct trace_array *tr = hist_data->event_file->tr;
 	struct hist_field *hist_field;
 
 	var++; /* skip '$' */
···
 	}
 
 	if (!hist_field)
-		hist_err_event("trace action: Couldn't find param: $", system, event, var);
+		hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, errpos(var));
 
 	return hist_field;
 }
···
 static int trace_action_create(struct hist_trigger_data *hist_data,
 			       struct action_data *data)
 {
+	struct trace_array *tr = hist_data->event_file->tr;
 	char *event_name, *param, *system = NULL;
 	struct hist_field *hist_field, *var_ref;
 	unsigned int i, var_ref_idx;
···
 
 	event = find_synth_event(synth_event_name);
 	if (!event) {
-		hist_err("trace action: Couldn't find synthetic event: ", synth_event_name);
+		hist_err(tr, HIST_ERR_SYNTH_EVENT_NOT_FOUND, errpos(synth_event_name));
 		return -EINVAL;
 	}
 
···
 			continue;
 		}
 
-		hist_err_event("trace action: Param type doesn't match synthetic event field type: ",
-			       system, event_name, param);
+		hist_err(tr, HIST_ERR_SYNTH_TYPE_MISMATCH, errpos(param));
 		kfree(p);
 		ret = -EINVAL;
 		goto err;
 	}
 
 	if (field_pos != event->n_fields) {
-		hist_err("trace action: Param count doesn't match synthetic event field count: ", event->name);
+		hist_err(tr, HIST_ERR_SYNTH_COUNT_MISMATCH, errpos(event->name));
 		ret = -EINVAL;
 		goto err;
 	}
···
 			 struct action_data *data)
 {
 	struct trace_event_file *file = hist_data->event_file;
+	struct trace_array *tr = file->tr;
 	struct track_data *track_data;
 	struct field_var *field_var;
 	unsigned int i;
···
 	if (data->action == ACTION_SAVE) {
 		if (hist_data->n_save_vars) {
 			ret = -EEXIST;
-			hist_err("save action: Can't have more than one save() action per hist", "");
+			hist_err(tr, HIST_ERR_TOO_MANY_SAVE_ACTIONS, 0);
 			goto out;
 		}
 
···
 
 			field_var = create_target_field_var(hist_data, NULL, NULL, param);
 			if (IS_ERR(field_var)) {
-				hist_err("save action: Couldn't create field variable: ", param);
+				hist_err(tr, HIST_ERR_FIELD_VAR_CREATE_FAIL,
+					 errpos(param));
 				ret = PTR_ERR(field_var);
 				kfree(param);
 				goto out;
···
 
 	match_event = strsep(&str, ")");
 	if (!match_event || !str) {
-		hist_err("onmatch: Missing closing paren: ", match_event);
+		hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(match_event));
 		goto free;
 	}
 
 	match_event_system = strsep(&match_event, ".");
 	if (!match_event) {
-		hist_err("onmatch: Missing subsystem for match event: ", match_event_system);
+		hist_err(tr, HIST_ERR_SUBSYS_NOT_FOUND, errpos(match_event_system));
 		goto free;
 	}
 
 	if (IS_ERR(event_file(tr, match_event_system, match_event))) {
-		hist_err_event("onmatch: Invalid subsystem or event name: ",
-			       match_event_system, match_event, NULL);
+		hist_err(tr, HIST_ERR_INVALID_SUBSYS_EVENT, errpos(match_event));
 		goto free;
 	}
 
···
 		goto free;
 	}
 
-	ret = action_parse(str, data, HANDLER_ONMATCH);
+	ret = action_parse(tr, str, data, HANDLER_ONMATCH);
 	if (ret)
 		goto free;
  out:
···
 			    struct trace_event_file *file,
 			    char *var_name, char *expr_str)
 {
+	struct trace_array *tr = hist_data->event_file->tr;
 	unsigned long flags = 0;
 
 	if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
 		return -EINVAL;
 
 	if (find_var(hist_data, file, var_name) && !hist_data->remove) {
-		hist_err("Variable already defined: ", var_name);
+		hist_err(tr, HIST_ERR_DUPLICATE_VAR, errpos(var_name));
 		return -EINVAL;
 	}
 
···
 			    struct trace_event_file *file,
 			    char *field_str)
 {
+	struct trace_array *tr = hist_data->event_file->tr;
 	struct hist_field *hist_field = NULL;
-
 	unsigned long flags = 0;
 	unsigned int key_size;
 	int ret = 0;
···
 		}
 
 		if (hist_field->flags & HIST_FIELD_FL_VAR_REF) {
-			hist_err("Using variable references as keys not supported: ", field_str);
+			hist_err(tr, HIST_ERR_INVALID_REF_KEY, errpos(field_str));
 			destroy_hist_field(hist_field, 0);
 			ret = -EINVAL;
 			goto out;
···
 
 static int parse_var_defs(struct hist_trigger_data *hist_data)
 {
+	struct trace_array *tr = hist_data->event_file->tr;
 	char *s, *str, *var_name, *field_str;
 	unsigned int i, j, n_vars = 0;
 	int ret = 0;
···
 
 			var_name = strsep(&field_str, "=");
 			if (!var_name || !field_str) {
-				hist_err("Malformed assignment: ", var_name);
+				hist_err(tr, HIST_ERR_MALFORMED_ASSIGNMENT,
+					 errpos(var_name));
 				ret = -EINVAL;
 				goto free;
 			}
 
 			if (n_vars == TRACING_MAP_VARS_MAX) {
-				hist_err("Too many variables defined: ", var_name);
+				hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(var_name));
 				ret = -EINVAL;
 				goto free;
 			}
···
 			hist_trigger_show(m, data, n++);
 	}
 
-	if (have_hist_err()) {
-		seq_printf(m, "\nERROR: %s\n", hist_err_str);
-		seq_printf(m, "  Last command: %s\n", last_hist_cmd);
-	}
-
  out_unlock:
 	mutex_unlock(&event_mutex);
 
···
 {
 	struct hist_trigger_data *hist_data = data->private_data;
 	struct event_trigger_data *test, *named_data = NULL;
+	struct trace_array *tr = file->tr;
 	int ret = 0;
 
 	if (hist_data->attrs->name) {
···
 		if (named_data) {
 			if (!hist_trigger_match(data, named_data, named_data,
 						true)) {
-				hist_err("Named hist trigger doesn't match existing named trigger (includes variables): ", hist_data->attrs->name);
+				hist_err(tr, HIST_ERR_NAMED_MISMATCH, errpos(hist_data->attrs->name));
 				ret = -EINVAL;
 				goto out;
 			}
···
 			else if (hist_data->attrs->clear)
 				hist_clear(test);
 			else {
-				hist_err("Hist trigger already exists", NULL);
+				hist_err(tr, HIST_ERR_TRIGGER_EEXIST, 0);
 				ret = -EEXIST;
 			}
 			goto out;
···
 	}
  new:
 	if (hist_data->attrs->cont || hist_data->attrs->clear) {
-		hist_err("Can't clear or continue a nonexistent hist trigger", NULL);
+		hist_err(tr, HIST_ERR_TRIGGER_ENOENT_CLEAR, 0);
 		ret = -ENOENT;
 		goto out;
 	}
···
 
 		ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
 		if (ret) {
-			hist_err("Couldn't set trace_clock: ", clock);
+			hist_err(tr, HIST_ERR_SET_CLOCK_FAIL, errpos(clock));
 			goto out;
 		}
 
···
 	lockdep_assert_held(&event_mutex);
 
 	if (glob && strlen(glob)) {
-		last_cmd_set(param);
 		hist_err_clear();
+		last_cmd_set(file, param);
 	}
 
 	if (!param)
···
 		trigger = strstrip(trigger);
 	}
 
-	attrs = parse_hist_trigger_attrs(trigger);
+	attrs = parse_hist_trigger_attrs(file->tr, trigger);
 	if (IS_ERR(attrs))
 		return PTR_ERR(attrs);
 

kernel/trace/trace_events_trigger.c

···
 		goto out;
 
 	/* The filter is for the 'trigger' event, not the triggered event */
-	ret = create_event_filter(file->event_call, filter_str, false, &filter);
+	ret = create_event_filter(file->tr, file->event_call,
+				  filter_str, false, &filter);
 	/*
 	 * If create_event_filter() fails, filter still needs to be freed.
 	 * Which the calling code will do with data->filter.

kernel/trace/trace_kdb.c

···
 #include "trace.h"
 #include "trace_output.h"
 
-static void ftrace_dump_buf(int skip_lines, long cpu_file)
+static struct trace_iterator iter;
+static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
+
+static void ftrace_dump_buf(int skip_entries, long cpu_file)
 {
-	/* use static because iter can be a bit big for the stack */
-	static struct trace_iterator iter;
-	static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
 	struct trace_array *tr;
 	unsigned int old_userobj;
 	int cnt = 0, cpu;
 
-	trace_init_global_iter(&iter);
-	iter.buffer_iter = buffer_iter;
 	tr = iter.tr;
-
-	for_each_tracing_cpu(cpu) {
-		atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
-	}
 
 	old_userobj = tr->trace_flags;
 
···
 	tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
 
 	kdb_printf("Dumping ftrace buffer:\n");
+	if (skip_entries)
+		kdb_printf("(skipping %d entries)\n", skip_entries);
 
 	/* reset all but tr, trace, and overruns */
 	memset(&iter.seq, 0,
···
 			kdb_printf("---------------------------------\n");
 		cnt++;
 
-		if (!skip_lines) {
+		if (!skip_entries) {
 			print_trace_line(&iter);
 			trace_printk_seq(&iter.seq);
 		} else {
-			skip_lines--;
+			skip_entries--;
 		}
 
 		if (KDB_FLAG(CMD_INTERRUPT))
···
 	tr->trace_flags = old_userobj;
 
 	for_each_tracing_cpu(cpu) {
-		atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
-	}
-
-	for_each_tracing_cpu(cpu) {
 		if (iter.buffer_iter[cpu]) {
 			ring_buffer_read_finish(iter.buffer_iter[cpu]);
 			iter.buffer_iter[cpu] = NULL;
···
  */
 static int kdb_ftdump(int argc, const char **argv)
 {
-	int skip_lines = 0;
+	int skip_entries = 0;
 	long cpu_file;
 	char *cp;
+	int cnt;
+	int cpu;
 
 	if (argc > 2)
 		return KDB_ARGCOUNT;
 
 	if (argc) {
-		skip_lines = simple_strtol(argv[1], &cp, 0);
+		skip_entries = simple_strtol(argv[1], &cp, 0);
 		if (*cp)
-			skip_lines = 0;
+			skip_entries = 0;
 	}
 
 	if (argc == 2) {
···
 	}
 
 	kdb_trap_printk++;
-	ftrace_dump_buf(skip_lines, cpu_file);
+
+	trace_init_global_iter(&iter);
+	iter.buffer_iter = buffer_iter;
+
+	for_each_tracing_cpu(cpu) {
+		atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
+	}
+
+	/* A negative skip_entries means skip all but the last entries */
+	if (skip_entries < 0) {
+		if (cpu_file == RING_BUFFER_ALL_CPUS)
+			cnt = trace_total_entries(NULL);
+		else
+			cnt = trace_total_entries_cpu(NULL, cpu_file);
+		skip_entries = max(cnt + skip_entries, 0);
+	}
+
+	ftrace_dump_buf(skip_entries, cpu_file);
+
+	for_each_tracing_cpu(cpu) {
+		atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
+	}
+
 	kdb_trap_printk--;
 
 	return 0;
···
 
 static __init int kdb_ftrace_register(void)
 {
-	kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
-			    "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
+	kdb_register_flags("ftdump", kdb_ftdump, "[skip_#entries] [cpu]",
+			    "Dump ftrace log; -skip dumps last #entries", 0,
+			    KDB_ENABLE_ALWAYS_SAFE);
 	return 0;
 }
 

kernel/trace/trace_kprobe.c

···
 	else
 		ret = register_kprobe(&tk->rp.kp);
 
-	if (ret == 0) {
+	if (ret == 0)
 		tk->tp.flags |= TP_FLAG_REGISTERED;
-	} else if (ret == -EILSEQ) {
-		pr_warn("Probing address(0x%p) is not an instruction boundary.\n",
-			tk->rp.kp.addr);
-		ret = -EINVAL;
-	}
 	return ret;
 }
 
···
 	 * Type of args:
 	 *  FETCHARG:TYPE : use TYPE instead of unsigned long.
 	 */
-	struct trace_kprobe *tk;
+	struct trace_kprobe *tk = NULL;
 	int i, len, ret = 0;
 	bool is_return = false;
 	char *symbol = NULL, *tmp = NULL;
···
 	if (argc < 2)
 		return -ECANCELED;
 
+	trace_probe_log_init("trace_kprobe", argc, argv);
+
 	event = strchr(&argv[0][1], ':');
 	if (event)
 		event++;
 
 	if (isdigit(argv[0][1])) {
 		if (!is_return) {
-			pr_info("Maxactive is not for kprobe");
-			return -EINVAL;
+			trace_probe_log_err(1, MAXACT_NO_KPROBE);
+			goto parse_error;
 		}
 		if (event)
 			len = event - &argv[0][1] - 1;
 		else
 			len = strlen(&argv[0][1]);
-		if (len > MAX_EVENT_NAME_LEN - 1)
-			return -E2BIG;
+		if (len > MAX_EVENT_NAME_LEN - 1) {
+			trace_probe_log_err(1, BAD_MAXACT);
+			goto parse_error;
+		}
 		memcpy(buf, &argv[0][1], len);
 		buf[len] = '\0';
 		ret = kstrtouint(buf, 0, &maxactive);
 		if (ret || !maxactive) {
-			pr_info("Invalid maxactive number\n");
-			return ret;
+			trace_probe_log_err(1, BAD_MAXACT);
+			goto parse_error;
 		}
 		/* kretprobes instances are iterated over via a list. The
 		 * maximum should stay reasonable.
 		 */
 		if (maxactive > KRETPROBE_MAXACTIVE_MAX) {
-			pr_info("Maxactive is too big (%d > %d).\n",
-				maxactive, KRETPROBE_MAXACTIVE_MAX);
-			return -E2BIG;
+			trace_probe_log_err(1, MAXACT_TOO_BIG);
+			goto parse_error;
 		}
 	}
 
 	/* try to parse an address. if that fails, try to read the
 	 * input as a symbol. */
 	if (kstrtoul(argv[1], 0, (unsigned long *)&addr)) {
+		trace_probe_log_set_index(1);
 		/* Check whether uprobe event specified */
-		if (strchr(argv[1], '/') && strchr(argv[1], ':'))
-			return -ECANCELED;
+		if (strchr(argv[1], '/') && strchr(argv[1], ':')) {
+			ret = -ECANCELED;
+			goto error;
+		}
 		/* a symbol specified */
 		symbol = kstrdup(argv[1], GFP_KERNEL);
 		if (!symbol)
···
 		/* TODO: support .init module functions */
 		ret = traceprobe_split_symbol_offset(symbol, &offset);
 		if (ret || offset < 0 || offset > UINT_MAX) {
-			pr_info("Failed to parse either an address or a symbol.\n");
-			goto out;
+			trace_probe_log_err(0, BAD_PROBE_ADDR);
+			goto parse_error;
 		}
 		if (kprobe_on_func_entry(NULL, symbol, offset))
 			flags |= TPARG_FL_FENTRY;
 		if (offset && is_return && !(flags & TPARG_FL_FENTRY)) {
-			pr_info("Given offset is not valid for return probe.\n");
-			ret = -EINVAL;
-			goto out;
+			trace_probe_log_err(0, BAD_RETPROBE);
+			goto parse_error;
 		}
 	}
-	argc -= 2; argv += 2;
 
+	trace_probe_log_set_index(0);
 	if (event) {
-		ret = traceprobe_parse_event_name(&event, &group, buf);
+		ret = traceprobe_parse_event_name(&event, &group, buf,
+						  event - argv[0]);
 		if (ret)
-			goto out;
+			goto parse_error;
 	} else {
 		/* Make a new event name */
 		if (symbol)
···
 
 	/* setup a probe */
 	tk = alloc_trace_kprobe(group, event, addr, symbol, offset, maxactive,
-			       argc, is_return);
+			       argc - 2, is_return);
 	if (IS_ERR(tk)) {
 		ret = PTR_ERR(tk);
-		/* This must return -ENOMEM otherwise there is a bug */
+		/* This must return -ENOMEM, else there is a bug */
 		WARN_ON_ONCE(ret != -ENOMEM);
-		goto out;
+		goto out;	/* We know tk is not allocated */
 	}
+	argc -= 2; argv += 2;
 
 	/* parse arguments */
 	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
···
 			goto error;
 		}
 
+		trace_probe_log_set_index(i + 2);
 		ret = traceprobe_parse_probe_arg(&tk->tp, i, tmp, flags);
 		kfree(tmp);
 		if (ret)
-			goto error;
+			goto error;	/* This can be -ENOMEM */
 	}
 
 	ret = register_trace_kprobe(tk);
-	if (ret)
+	if (ret) {
+		trace_probe_log_set_index(1);
+		if (ret == -EILSEQ)
+			trace_probe_log_err(0, BAD_INSN_BNDRY);
+		else if (ret == -ENOENT)
+			trace_probe_log_err(0, BAD_PROBE_ADDR);
+		else if (ret != -ENOMEM)
+			trace_probe_log_err(0, FAIL_REG_PROBE);
 		goto error;
+	}
+
 out:
+	trace_probe_log_clear();
 	kfree(symbol);
 	return ret;
 
+parse_error:
+	ret = -EINVAL;
 error:
 	free_trace_kprobe(tk);
 	goto out;

kernel/trace/trace_probe.c

···
 
 #include "trace_probe.h"
 
+#undef C
+#define C(a, b)		b
+
+static const char *trace_probe_err_text[] = { ERRORS };
+
 static const char *reserved_field_names[] = {
 	"common_type",
 	"common_flags",
···
 	return NULL;
 }
 
+static struct trace_probe_log trace_probe_log;
+
+void trace_probe_log_init(const char *subsystem, int argc, const char **argv)
+{
+	trace_probe_log.subsystem = subsystem;
+	trace_probe_log.argc = argc;
+	trace_probe_log.argv = argv;
+	trace_probe_log.index = 0;
+}
+
+void trace_probe_log_clear(void)
+{
+	memset(&trace_probe_log, 0, sizeof(trace_probe_log));
+}
+
+void trace_probe_log_set_index(int index)
+{
+	trace_probe_log.index = index;
+}
+
+void __trace_probe_log_err(int offset, int err_type)
+{
+	char *command, *p;
+	int i, len = 0, pos = 0;
+
+	if (!trace_probe_log.argv)
+		return;
+
+	/* Recalcurate the length and allocate buffer */
+	for (i = 0; i < trace_probe_log.argc; i++) {
+		if (i == trace_probe_log.index)
+			pos = len;
+		len += strlen(trace_probe_log.argv[i]) + 1;
+	}
+	command = kzalloc(len, GFP_KERNEL);
+	if (!command)
+		return;
+
+	/* And make a command string from argv array */
+	p = command;
+	for (i = 0; i < trace_probe_log.argc; i++) {
+		len = strlen(trace_probe_log.argv[i]);
+		strcpy(p, trace_probe_log.argv[i]);
+		p[len] = ' ';
+		p += len + 1;
+	}
+	*(p - 1) = '\0';
+
+	tracing_log_err(NULL, trace_probe_log.subsystem, command,
+			trace_probe_err_text, err_type, pos + offset);
+
+	kfree(command);
+}
+
 /* Split symbol and offset. */
 int traceprobe_split_symbol_offset(char *symbol, long *offset)
 {
···
 
 /* @buf must has MAX_EVENT_NAME_LEN size */
 int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
-				char *buf)
+				char *buf, int offset)
 {
 	const char *slash, *event = *pevent;
 	int len;
···
 	slash = strchr(event, '/');
 	if (slash) {
 		if (slash == event) {
-			pr_info("Group name is not specified\n");
+			trace_probe_log_err(offset, NO_GROUP_NAME);
 			return -EINVAL;
 		}
 		if (slash - event + 1 > MAX_EVENT_NAME_LEN) {
-			pr_info("Group name is too long\n");
-			return -E2BIG;
+			trace_probe_log_err(offset, GROUP_TOO_LONG);
+			return -EINVAL;
 		}
 		strlcpy(buf, event, slash - event + 1);
 		if (!is_good_name(buf)) {
-			pr_info("Group name must follow the same rules as C identifiers\n");
+			trace_probe_log_err(offset, BAD_GROUP_NAME);
 			return -EINVAL;
 		}
 		*pgroup = buf;
 		*pevent = slash + 1;
+		offset += slash - event + 1;
 		event = *pevent;
 	}
 	len = strlen(event);
 	if (len == 0) {
-		pr_info("Event name is not specified\n");
+		trace_probe_log_err(offset, NO_EVENT_NAME);
 		return -EINVAL;
 	} else if (len > MAX_EVENT_NAME_LEN) {
-		pr_info("Event name is too long\n");
-		return -E2BIG;
+		trace_probe_log_err(offset, EVENT_TOO_LONG);
+		return -EINVAL;
 	}
 	if (!is_good_name(event)) {
-		pr_info("Event name must follow the same rules as C identifiers\n");
+		trace_probe_log_err(offset, BAD_EVENT_NAME);
 		return -EINVAL;
 	}
 	return 0;
···
 #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
 
 static int parse_probe_vars(char *arg, const struct fetch_type *t,
-			    struct fetch_insn *code, unsigned int flags)
+			struct fetch_insn *code, unsigned int flags, int offs)
 {
 	unsigned long param;
 	int ret = 0;
 	int len;
 
 	if (strcmp(arg, "retval") == 0) {
-		if (flags & TPARG_FL_RETURN)
+		if (flags & TPARG_FL_RETURN) {
 			code->op = FETCH_OP_RETVAL;
-		else
+		} else {
+			trace_probe_log_err(offs, RETVAL_ON_PROBE);
 			ret = -EINVAL;
+		}
 	} else if ((len = str_has_prefix(arg, "stack"))) {
 		if (arg[len] == '\0') {
 			code->op = FETCH_OP_STACKP;
 		} else if (isdigit(arg[len])) {
 			ret = kstrtoul(arg + len, 10, &param);
-			if (ret || ((flags & TPARG_FL_KERNEL) &&
-				    param > PARAM_MAX_STACK))
+			if (ret) {
+				goto inval_var;
+			} else if ((flags & TPARG_FL_KERNEL) &&
+				    param > PARAM_MAX_STACK) {
+				trace_probe_log_err(offs, BAD_STACK_NUM);
 				ret = -EINVAL;
-			else {
+			} else {
 				code->op = FETCH_OP_STACK;
 				code->param = (unsigned int)param;
 			}
 		} else
-			ret = -EINVAL;
+			goto inval_var;
 	} else if (strcmp(arg, "comm") == 0) {
 		code->op = FETCH_OP_COMM;
 #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
 	} else if (((flags & TPARG_FL_MASK) ==
 		    (TPARG_FL_KERNEL | TPARG_FL_FENTRY)) &&
 		   (len = str_has_prefix(arg, "arg"))) {
-		if (!isdigit(arg[len]))
-			return -EINVAL;
 		ret = kstrtoul(arg + len, 10, &param);
-		if (ret || !param || param > PARAM_MAX_STACK)
+		if (ret) {
+			goto inval_var;
+		} else if (!param || param > PARAM_MAX_STACK) {
+			trace_probe_log_err(offs, BAD_ARG_NUM);
 			return -EINVAL;
+		}
 		code->op = FETCH_OP_ARG;
 		code->param = (unsigned int)param - 1;
 #endif
 	} else
-		ret = -EINVAL;
+		goto inval_var;
 
 	return ret;
+
+inval_var:
+	trace_probe_log_err(offs, BAD_VAR);
+	return -EINVAL;
 }
 
 /* Recursive argument parser */
 static int
 parse_probe_arg(char *arg, const struct fetch_type *type,
 		struct fetch_insn **pcode, struct fetch_insn *end,
-		unsigned int flags)
+		unsigned int flags, int offs)
 {
 	struct fetch_insn *code = *pcode;
 	unsigned long param;
···
 
 	switch (arg[0]) {
 	case '$':
-		ret = parse_probe_vars(arg + 1, type, code, flags);
+		ret = parse_probe_vars(arg + 1, type, code, flags, offs);
 		break;
 
 	case '%':	/* named register */
···
 			code->op = FETCH_OP_REG;
 			code->param = (unsigned int)ret;
 			ret = 0;
-		}
+		} else
+			trace_probe_log_err(offs, BAD_REG_NAME);
 		break;
 
 	case '@':	/* memory, file-offset or symbol */
 		if (isdigit(arg[1])) {
 			ret = kstrtoul(arg + 1, 0, &param);
-			if (ret)
+			if (ret) {
+				trace_probe_log_err(offs, BAD_MEM_ADDR);
 				break;
+			}
 			/* load address */
 			code->op = FETCH_OP_IMM;
 			code->immediate = param;
 		} else if (arg[1] == '+') {
 			/* kprobes don't support file offsets */
-			if (flags & TPARG_FL_KERNEL)
+			if (flags & TPARG_FL_KERNEL) {
+				trace_probe_log_err(offs, FILE_ON_KPROBE);
 				return -EINVAL;
-
+			}
 			ret = kstrtol(arg + 2, 0, &offset);
-			if (ret)
+			if (ret) {
+				trace_probe_log_err(offs, BAD_FILE_OFFS);
 				break;
+			}
 
 			code->op = FETCH_OP_FOFFS;
 			code->immediate = (unsigned long)offset;  // imm64?
 		} else {
 			/* uprobes don't support symbols */
-			if (!(flags & TPARG_FL_KERNEL))
+			if (!(flags & TPARG_FL_KERNEL)) {
+				trace_probe_log_err(offs, SYM_ON_UPROBE);
 				return -EINVAL;
-
+			}
 			/* Preserve symbol for updating */
 			code->op = FETCH_NOP_SYMBOL;
 			code->data = kstrdup(arg + 1, GFP_KERNEL);
 			if (!code->data)
 				return -ENOMEM;
-			if (++code == end)
-				return -E2BIG;
-
+			if (++code == end) {
+				trace_probe_log_err(offs, TOO_MANY_OPS);
+				return -EINVAL;
+			}
 			code->op = FETCH_OP_IMM;
 			code->immediate = 0;
 		}
 		/* These are fetching from memory */
-		if (++code == end)
-			return -E2BIG;
+		if (++code == end) {
+			trace_probe_log_err(offs, TOO_MANY_OPS);
+			return -EINVAL;
+		}
 		*pcode = code;
 		code->op = FETCH_OP_DEREF;
 		code->offset = offset;
···
 		/* fall through */
 	case '-':
 		tmp = strchr(arg, '(');
-		if (!tmp)
+		if (!tmp) {
+			trace_probe_log_err(offs, DEREF_NEED_BRACE);
 			return -EINVAL;
-
+		}
 		*tmp = '\0';
 		ret = kstrtol(arg, 0, &offset);
-		if (ret)
+		if (ret) {
+			trace_probe_log_err(offs, BAD_DEREF_OFFS);
 			break;
-
+		}
+		offs += (tmp + 1 - arg) + (arg[0] != '-' ? 1 : 0);
 		arg = tmp + 1;
 		tmp = strrchr(arg, ')');
-
-		if (tmp) {
+		if (!tmp) {
+			trace_probe_log_err(offs + strlen(arg),
+					    DEREF_OPEN_BRACE);
+			return -EINVAL;
+		} else {
 			const struct fetch_type *t2 = find_fetch_type(NULL);
 
 			*tmp = '\0';
-			ret = parse_probe_arg(arg, t2, &code, end, flags);
+			ret = parse_probe_arg(arg, t2, &code, end, flags, offs);
 			if (ret)
 				break;
-			if (code->op == FETCH_OP_COMM)
+			if (code->op == FETCH_OP_COMM) {
+				trace_probe_log_err(offs, COMM_CANT_DEREF);
 				return -EINVAL;
-			if (++code == end)
-				return -E2BIG;
+			}
+			if (++code == end) {
+				trace_probe_log_err(offs, TOO_MANY_OPS);
+				return -EINVAL;
+			}
 			*pcode = code;
 
 			code->op = FETCH_OP_DEREF;
···
 	}
 	if (!ret && code->op == FETCH_OP_NOP) {
 		/* Parsed, but do not find fetch method */
+		trace_probe_log_err(offs, BAD_FETCH_ARG);
 		ret = -EINVAL;
 	}
 	return ret;
···
 		return -EINVAL;
 	code++;
 	if (code->op != FETCH_OP_NOP)
-		return -E2BIG;
+		return -EINVAL;
 	*pcode = code;
 
 	code->op = FETCH_OP_MOD_BF;
···
 
 /* String length checking wrapper */
 static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
-		struct probe_arg *parg, unsigned int flags)
+		struct probe_arg *parg, unsigned int flags, int offset)
 {
 	struct fetch_insn *code, *scode, *tmp = NULL;
-	char *t, *t2;
+	char *t, *t2, *t3;
 	int ret, len;
 
-	if (strlen(arg) > MAX_ARGSTR_LEN) {
-		pr_info("Argument is too long.: %s\n",  arg);
-		return -ENOSPC;
+	len = strlen(arg);
+	if (len > MAX_ARGSTR_LEN) {
+		trace_probe_log_err(offset, ARG_TOO_LONG);
+		return -EINVAL;
+	} else if (len == 0) {
+		trace_probe_log_err(offset, NO_ARG_BODY);
+		return -EINVAL;
 	}
+
 	parg->comm = kstrdup(arg, GFP_KERNEL);
-	if (!parg->comm) {
-		pr_info("Failed to allocate memory for command '%s'.\n", arg);
+	if (!parg->comm)
 		return -ENOMEM;
-	}
+
 	t = strchr(arg, ':');
 	if (t) {
 		*t = '\0';
 		t2 = strchr(++t, '[');
 		if (t2) {
-			*t2 = '\0';
-			parg->count = simple_strtoul(t2 + 1, &t2, 0);
-			if (strcmp(t2, "]") || parg->count == 0)
+			*t2++ = '\0';
+			t3 = strchr(t2, ']');
+			if (!t3) {
+				offset += t2 + strlen(t2) - arg;
+				trace_probe_log_err(offset,
+						    ARRAY_NO_CLOSE);
 				return -EINVAL;
-			if (parg->count > MAX_ARRAY_LEN)
-				return -E2BIG;
+			} else if (t3[1] != '\0') {
+				trace_probe_log_err(offset + t3 + 1 - arg,
+						    BAD_ARRAY_SUFFIX);
+				return -EINVAL;
+			}
+			*t3 = '\0';
+			if (kstrtouint(t2, 0, &parg->count) || !parg->count) {
+				trace_probe_log_err(offset + t2 - arg,
+						    BAD_ARRAY_NUM);
+				return -EINVAL;
+			}
+			if (parg->count > MAX_ARRAY_LEN) {
+				trace_probe_log_err(offset + t2 - arg,
+						    ARRAY_TOO_BIG);
+				return -EINVAL;
+			}
 		}
 	}
-	/*
-	 * The default type of $comm should be "string", and it can't be
-	 * dereferenced.
-	 */
-	if (!t && strcmp(arg, "$comm") == 0)
+
+	/* Since $comm can not be dereferred, we can find $comm by strcmp */
+	if (strcmp(arg, "$comm") == 0) {
+		/* The type of $comm must be "string", and not an array. */
+		if (parg->count || (t && strcmp(t, "string")))
+			return -EINVAL;
 		parg->type = find_fetch_type("string");
-	else
+	} else
 		parg->type = find_fetch_type(t);
 	if (!parg->type) {
-		pr_info("Unsupported type: %s\n", t);
+		trace_probe_log_err(offset + (t ? (t - arg) : 0), BAD_TYPE);
 		return -EINVAL;
 	}
 	parg->offset = *size;
···
 			 parg->count);
 	}
 
-	code = tmp = kzalloc(sizeof(*code) * FETCH_INSN_MAX, GFP_KERNEL);
+	code = tmp = kcalloc(FETCH_INSN_MAX, sizeof(*code), GFP_KERNEL);
 	if (!code)
 		return -ENOMEM;
 	code[FETCH_INSN_MAX - 1].op = FETCH_OP_END;
 
 	ret = parse_probe_arg(arg, parg->type, &code, &code[FETCH_INSN_MAX - 1],
-			      flags);
+			      flags, offset);
 	if (ret)
 		goto fail;
 
···
 	if (!strcmp(parg->type->name, "string")) {
 		if (code->op != FETCH_OP_DEREF && code->op != FETCH_OP_IMM &&
 		    code->op != FETCH_OP_COMM) {
-			pr_info("string only accepts memory or address.\n");
+			trace_probe_log_err(offset + (t ? (t - arg) : 0),
+					    BAD_STRING);
 			ret = -EINVAL;
 			goto fail;
 		}
···
 			 */
 			code++;
 			if (code->op != FETCH_OP_NOP) {
-				ret = -E2BIG;
+				trace_probe_log_err(offset, TOO_MANY_OPS);
+				ret = -EINVAL;
 				goto fail;
 			}
 		}
···
 	} else {
 		code++;
 		if (code->op != FETCH_OP_NOP) {
-			ret = -E2BIG;
+			trace_probe_log_err(offset, TOO_MANY_OPS);
+			ret = -EINVAL;
 			goto fail;
 		}
 		code->op = FETCH_OP_ST_RAW;
···
 	/* Modify operation */
 	if (t != NULL) {
 		ret = __parse_bitfield_probe_arg(t, parg->type, &code);
-		if (ret)
+		if (ret) {
+			trace_probe_log_err(offset + t - arg, BAD_BITFIELD);
 			goto fail;
+		}
 	}
 	/* Loop(Array) operation */
 	if (parg->count) {
 		if (scode->op != FETCH_OP_ST_MEM &&
 		    scode->op != FETCH_OP_ST_STRING) {
-			pr_info("array only accepts memory or address\n");
+			trace_probe_log_err(offset + (t ? (t - arg) : 0),
+					    BAD_STRING);
 			ret = -EINVAL;
 			goto fail;
 		}
 		code++;
 		if (code->op != FETCH_OP_NOP) {
-			ret = -E2BIG;
+			trace_probe_log_err(offset, TOO_MANY_OPS);
+			ret = -EINVAL;
 			goto fail;
 		}
 		code->op = FETCH_OP_LP_ARRAY;
···
 	code->op = FETCH_OP_END;
 
 	/* Shrink down the code buffer */
-	parg->code = kzalloc(sizeof(*code) * (code - tmp + 1), GFP_KERNEL);
+	parg->code = kcalloc(code - tmp + 1, sizeof(*code), GFP_KERNEL);
 	if (!parg->code)
 		ret = -ENOMEM;
 	else
···
 {
 	struct probe_arg *parg = &tp->args[i];
 	char *body;
-	int ret;
 
 	/* Increment count for freeing args in error case */
 	tp->nr_args++;
 
 	body = strchr(arg, '=');
 	if (body) {
-		if (body - arg > MAX_ARG_NAME_LEN || body == arg)
+		if (body - arg > MAX_ARG_NAME_LEN) {
+			trace_probe_log_err(0, ARG_NAME_TOO_LONG);
 			return -EINVAL;
+		} else if (body == arg) {
+			trace_probe_log_err(0, NO_ARG_NAME);
+			return -EINVAL;
+		}
 		parg->name = kmemdup_nul(arg, body - arg, GFP_KERNEL);
 		body++;
 	} else {
···
 		return -ENOMEM;
 
 	if (!is_good_name(parg->name)) {
-		pr_info("Invalid argument[%d] name: %s\n",
-			i, parg->name);
+		trace_probe_log_err(0, BAD_ARG_NAME);
 		return -EINVAL;
 	}
-
 	if (traceprobe_conflict_field_name(parg->name, tp->args, i)) {
-		pr_info("Argument[%d]: '%s' conflicts with another field.\n",
-			i, parg->name);
+		trace_probe_log_err(0, USED_ARG_NAME);
 		return -EINVAL;
 	}
-
 	/* Parse fetch argument */
-	ret = traceprobe_parse_probe_arg_body(body, &tp->size, parg, flags);
-	if (ret)
-		pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
-	return ret;
+	return traceprobe_parse_probe_arg_body(body, &tp->size, parg, flags,
+					       body - arg);
 }
 
 void traceprobe_free_probe_arg(struct probe_arg *arg)

kernel/trace/trace_probe.h

···
 
 /* fetch + deref*N + store + mod + end <= 16, this allows N=12, enough */
 #define FETCH_INSN_MAX	16
+#define FETCH_TOKEN_COMM	(-ECOMM)
 
 /* Fetch type information table */
 struct fetch_type {
···
 extern void traceprobe_free_probe_arg(struct probe_arg *arg);
 
 extern int traceprobe_split_symbol_offset(char *symbol, long *offset);
-extern int traceprobe_parse_event_name(const char **pevent,
-				       const char **pgroup, char *buf);
+int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
+				char *buf, int offset);
 
 extern int traceprobe_set_print_fmt(struct trace_probe *tp, bool is_return);
 
···
 #endif
 extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 					size_t offset, struct trace_probe *tp);
+
+#undef ERRORS
+#define ERRORS	\
+	C(FILE_NOT_FOUND,	"Failed to find the given file"),	\
+	C(NO_REGULAR_FILE,	"Not a regular file"),			\
+	C(BAD_REFCNT,		"Invalid reference counter offset"),	\
+	C(REFCNT_OPEN_BRACE,	"Reference counter brace is not closed"), \
+	C(BAD_REFCNT_SUFFIX,	"Reference counter has wrong suffix"),	\
+	C(BAD_UPROBE_OFFS,	"Invalid uprobe offset"),		\
+	C(MAXACT_NO_KPROBE,	"Maxactive is not for kprobe"),		\
+	C(BAD_MAXACT,		"Invalid maxactive number"),		\
+	C(MAXACT_TOO_BIG,	"Maxactive is too big"),		\
+	C(BAD_PROBE_ADDR,	"Invalid probed address or symbol"),	\
+	C(BAD_RETPROBE,		"Retprobe address must be an function entry"), \
+	C(NO_GROUP_NAME,	"Group name is not specified"),		\
+	C(GROUP_TOO_LONG,	"Group name is too long"),		\
+	C(BAD_GROUP_NAME,	"Group name must follow the same rules as C identifiers"), \
+	C(NO_EVENT_NAME,	"Event name is not specified"),		\
+	C(EVENT_TOO_LONG,	"Event name is too long"),		\
+	C(BAD_EVENT_NAME,	"Event name must follow the same rules as C identifiers"), \
+	C(RETVAL_ON_PROBE,	"$retval is not available on probe"),	\
+	C(BAD_STACK_NUM,	"Invalid stack number"),		\
+	C(BAD_ARG_NUM,		"Invalid argument number"),		\
+	C(BAD_VAR,		"Invalid $-valiable specified"),	\
+	C(BAD_REG_NAME,		"Invalid register name"),		\
+	C(BAD_MEM_ADDR,		"Invalid memory address"),		\
+	C(FILE_ON_KPROBE,	"File offset is not available with kprobe"), \
+	C(BAD_FILE_OFFS,	"Invalid file offset value"),		\
+	C(SYM_ON_UPROBE,	"Symbol is not available with uprobe"),	\
+	C(TOO_MANY_OPS,		"Dereference is too much nested"), 	\
+	C(DEREF_NEED_BRACE,	"Dereference needs a brace"),		\
+	C(BAD_DEREF_OFFS,	"Invalid dereference offset"),		\
+	C(DEREF_OPEN_BRACE,	"Dereference brace is not closed"),	\
+	C(COMM_CANT_DEREF,	"$comm can not be dereferenced"),	\
+	C(BAD_FETCH_ARG,	"Invalid fetch argument"),		\
+	C(ARRAY_NO_CLOSE,	"Array is not closed"),			\
+	C(BAD_ARRAY_SUFFIX,	"Array has wrong suffix"),		\
+	C(BAD_ARRAY_NUM,	"Invalid array size"),			\
+	C(ARRAY_TOO_BIG,	"Array number is too big"),		\
+	C(BAD_TYPE,		"Unknown type is specified"),		\
+	C(BAD_STRING,		"String accepts only memory argument"),	\
+	C(BAD_BITFIELD,		"Invalid bitfield"),			\
+	C(ARG_NAME_TOO_LONG,	"Argument name is too long"),		\
+	C(NO_ARG_NAME,		"Argument name is not specified"),	\
+	C(BAD_ARG_NAME,		"Argument name must follow the same rules as C identifiers"), \
+	C(USED_ARG_NAME,	"This argument name is already used"),	\
+	C(ARG_TOO_LONG,		"Argument expression is too long"),	\
+	C(NO_ARG_BODY,		"No argument expression"),		\
+	C(BAD_INSN_BNDRY,	"Probe point is not an instruction boundary"),\
+	C(FAIL_REG_PROBE,	"Failed to register probe event"),
+
+#undef C
+#define C(a, b)		TP_ERR_##a
+
+/* Define TP_ERR_ */
+enum { ERRORS };
+
+/* Error text is defined in trace_probe.c */
+
+struct trace_probe_log {
+	const char	*subsystem;
+	const char	**argv;
+	int		argc;
+	int		index;
+};
+
+void trace_probe_log_init(const char *subsystem, int argc, const char **argv);
+void trace_probe_log_set_index(int index);
+void trace_probe_log_clear(void);
+void __trace_probe_log_err(int offset, int err);
+
+#define trace_probe_log_err(offs, err)	\
+	__trace_probe_log_err(offs, TP_ERR_##err)

kernel/trace/trace_probe_tmpl.h

···
 	/* 3rd stage: store value to buffer */
 	if (unlikely(!dest)) {
 		if (code->op == FETCH_OP_ST_STRING) {
-			ret += fetch_store_strlen(val + code->offset);
+			ret = fetch_store_strlen(val + code->offset);
 			code++;
 			goto array;
 		} else

kernel/trace/trace_selftest.c

···
 	/* check the trace buffer */
 	ret = trace_test_buffer(&tr->trace_buffer, &count);
 
-	trace->reset(tr);
+	/* Need to also simulate the tr->reset to remove this fgraph_ops */
+	tracing_stop_cmdline_record();
+	unregister_ftrace_graph(&fgraph_ops);
+
 	tracing_start();
 
 	if (!ret && !count) {

kernel/trace/trace_uprobe.c

···
 	if (unlikely(!maxlen))
 		return -ENOMEM;
 
-	ret = strncpy_from_user(dst, src, maxlen);
+	if (addr == FETCH_TOKEN_COMM)
+		ret = strlcpy(dst, current->comm, maxlen);
+	else
+		ret = strncpy_from_user(dst, src, maxlen);
 	if (ret >= 0) {
 		if (ret == maxlen)
 			dst[ret - 1] = '\0';
···
 	int len;
 	void __user *vaddr = (void __force __user *) addr;
 
-	len = strnlen_user(vaddr, MAX_STRING_SIZE);
+	if (addr == FETCH_TOKEN_COMM)
+		len = strlen(current->comm) + 1;
+	else
+		len = strnlen_user(vaddr, MAX_STRING_SIZE);
 
 	return (len > MAX_STRING_SIZE) ? 0 : len;
 }
···
 		break;
 	case FETCH_OP_IMM:
 		val = code->immediate;
+		break;
+	case FETCH_OP_COMM:
+		val = FETCH_TOKEN_COMM;
 		break;
 	case FETCH_OP_FOFFS:
 		val = translate_user_vaddr(code->immediate);
···
 		return -ECANCELED;
 	}
 
+	trace_probe_log_init("trace_uprobe", argc, argv);
+	trace_probe_log_set_index(1);	/* filename is the 2nd argument */
+
 	*arg++ = '\0';
 	ret = kern_path(filename, LOOKUP_FOLLOW, &path);
 	if (ret) {
+		trace_probe_log_err(0, FILE_NOT_FOUND);
 		kfree(filename);
+		trace_probe_log_clear();
 		return ret;
 	}
 	if (!d_is_reg(path.dentry)) {
+		trace_probe_log_err(0, NO_REGULAR_FILE);
 		ret = -EINVAL;
 		goto fail_address_parse;
 	}
···
 	rctr = strchr(arg, '(');
 	if (rctr) {
 		rctr_end = strchr(rctr, ')');
-		if (rctr > rctr_end || *(rctr_end + 1) != 0) {
+		if (!rctr_end) {
 			ret = -EINVAL;
-			pr_info("Invalid reference counter offset.\n");
+			rctr_end = rctr + strlen(rctr);
+			trace_probe_log_err(rctr_end - filename,
+					    REFCNT_OPEN_BRACE);
+			goto fail_address_parse;
+		} else if (rctr_end[1] != '\0') {
+			ret = -EINVAL;
+			trace_probe_log_err(rctr_end + 1 - filename,
+					    BAD_REFCNT_SUFFIX);
 			goto fail_address_parse;
 		}
 
···
 		*rctr_end = '\0';
 		ret = kstrtoul(rctr, 0, &ref_ctr_offset);
 		if (ret) {
-			pr_info("Invalid reference counter offset.\n");
+			trace_probe_log_err(rctr - filename, BAD_REFCNT);
 			goto fail_address_parse;
 		}
 	}
 
 	/* Parse uprobe offset. */
 	ret = kstrtoul(arg, 0, &offset);
-	if (ret)
+	if (ret) {
+		trace_probe_log_err(arg - filename, BAD_UPROBE_OFFS);
 		goto fail_address_parse;
-
-	argc -= 2;
-	argv += 2;
+	}
 
 	/* setup a probe */
+	trace_probe_log_set_index(0);
 	if (event) {
-		ret = traceprobe_parse_event_name(&event, &group, buf);
+		ret = traceprobe_parse_event_name(&event, &group, buf,
+						  event - argv[0]);
 		if (ret)
 			goto fail_address_parse;
 	} else {
···
 		kfree(tail);
 	}
 
+	argc -= 2;
+	argv += 2;
+
 	tu = alloc_trace_uprobe(group, event, argc, is_return);
 	if (IS_ERR(tu)) {
 		ret = PTR_ERR(tu);
···
 			goto error;
 		}
 
+		trace_probe_log_set_index(i + 2);
 		ret = traceprobe_parse_probe_arg(&tu->tp, i, tmp,
 					is_return ? TPARG_FL_RETURN : 0);
 		kfree(tmp);
···
 	}
 
 	ret = register_trace_uprobe(tu);
-	if (ret)
-		goto error;
-	return 0;
+	if (!ret)
+		goto out;
 
 error:
 	free_trace_uprobe(tu);
+out:
+	trace_probe_log_clear();
 	return ret;
 
 fail_address_parse:
+	trace_probe_log_clear();
 	path_put(&path);
 	kfree(filename);
-
-	pr_info("Failed to parse address or file.\n");
 
 	return ret;
 }

tools/testing/selftests/ftrace/test.d/ftrace/tracing-error-log.tc

···
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: ftrace - test tracing error log support
+
+fail() { #msg
+    echo $1
+    exit_fail
+}
+
+# event tracing is currently the only ftrace tracer that uses the
+# tracing error_log, hence this check
+if [ ! -f set_event ]; then
+    echo "event tracing is not supported"
+    exit_unsupported
+fi
+
+ftrace_errlog_check 'event filter parse error' '((sig >= 10 && sig < 15) || dsig ^== 17) && comm != bash' 'events/signal/signal_generate/filter'
+
+exit 0

tools/testing/selftests/ftrace/test.d/functions

···
 yield() {
     ping $LOCALHOST -c 1 || sleep .001 || usleep 1 || sleep 1
 }
+
+ftrace_errlog_check() { # err-prefix command-with-error-pos-by-^ command-file
+    pos=$(echo -n "${2%^*}" | wc -c) # error position
+    command=$(echo "$2" | tr -d ^)
+    echo "Test command: $command"
+    echo > error_log
+    (! echo "$command" > "$3" ) 2> /dev/null
+    grep "$1: error:" -A 3 error_log
+    N=$(tail -n 1 error_log | wc -c)
+    # "  Command: " and "^\n" => 13
+    test $(expr 13 + $pos) -eq $N
+}

tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc

···
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Kprobe event parser error log check
+
+[ -f kprobe_events ] || exit_unsupported # this is configurable
+
+[ -f error_log ] || exit_unsupported
+
+check_error() { # command-with-error-pos-by-^
+    ftrace_errlog_check 'trace_kprobe' "$1" 'kprobe_events'
+}
+
+if grep -q 'r\[maxactive\]' README; then
+check_error 'p^100 vfs_read'		# MAXACT_NO_KPROBE
+check_error 'r^1a111 vfs_read'		# BAD_MAXACT
+check_error 'r^100000 vfs_read'		# MAXACT_TOO_BIG
+fi
+
+check_error 'p ^non_exist_func'		# BAD_PROBE_ADDR (enoent)
+check_error 'p ^hoge-fuga'		# BAD_PROBE_ADDR (bad syntax)
+check_error 'p ^hoge+1000-1000'		# BAD_PROBE_ADDR (bad syntax)
+check_error 'r ^vfs_read+10'		# BAD_RETPROBE
+check_error 'p:^/bar vfs_read'		# NO_GROUP_NAME
+check_error 'p:^12345678901234567890123456789012345678901234567890123456789012345/bar vfs_read'	# GROUP_TOO_LONG
+
+check_error 'p:^foo.1/bar vfs_read'	# BAD_GROUP_NAME
+check_error 'p:foo/^ vfs_read'		# NO_EVENT_NAME
+check_error 'p:foo/^12345678901234567890123456789012345678901234567890123456789012345 vfs_read'	# EVENT_TOO_LONG
+check_error 'p:foo/^bar.1 vfs_read'	# BAD_EVENT_NAME
+
+check_error 'p vfs_read ^$retval'	# RETVAL_ON_PROBE
+check_error 'p vfs_read ^$stack10000'	# BAD_STACK_NUM
+
+if grep -q '$arg<N>' README; then
+check_error 'p vfs_read ^$arg10000'	# BAD_ARG_NUM
+fi
+
+check_error 'p vfs_read ^$none_var'	# BAD_VAR
+
+check_error 'p vfs_read ^%none_reg'	# BAD_REG_NAME
+check_error 'p vfs_read ^@12345678abcde'	# BAD_MEM_ADDR
+check_error 'p vfs_read ^@+10'		# FILE_ON_KPROBE
+
+check_error 'p vfs_read ^+0@0)'		# DEREF_NEED_BRACE
+check_error 'p vfs_read ^+0ab1(@0)'	# BAD_DEREF_OFFS
+check_error 'p vfs_read +0(+0(@0^)'	# DEREF_OPEN_BRACE
+
+if grep -A1 "fetcharg:" README | grep -q '\$comm' ; then
+check_error 'p vfs_read +0(^$comm)'	# COMM_CANT_DEREF
+fi
+
+check_error 'p vfs_read ^&1'		# BAD_FETCH_ARG
+
+
+# We've introduced this limitation with array support
+if grep -q ' <type>\\\[<array-size>\\\]' README; then
+check_error 'p vfs_read +0(^+0(+0(+0(+0(+0(+0(+0(+0(+0(+0(+0(+0(+0(@0))))))))))))))'	# TOO_MANY_OPS?
+check_error 'p vfs_read +0(@11):u8[10^'		# ARRAY_NO_CLOSE
+check_error 'p vfs_read +0(@11):u8[10]^a'	# BAD_ARRAY_SUFFIX
+check_error 'p vfs_read +0(@11):u8[^10a]'	# BAD_ARRAY_NUM
+check_error 'p vfs_read +0(@11):u8[^256]'	# ARRAY_TOO_BIG
+fi
+
+check_error 'p vfs_read @11:^unknown_type'	# BAD_TYPE
+check_error 'p vfs_read $stack0:^string'	# BAD_STRING
+check_error 'p vfs_read @11:^b10@a/16'		# BAD_BITFIELD
+
+check_error 'p vfs_read ^arg123456789012345678901234567890=@11'	# ARG_NAME_TOO_LOG
+check_error 'p vfs_read ^=@11'			# NO_ARG_NAME
+check_error 'p vfs_read ^var.1=@11'		# BAD_ARG_NAME
+check_error 'p vfs_read var1=@11 ^var1=@12'	# USED_ARG_NAME
+check_error 'p vfs_read ^+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(@1234))))))'	# ARG_TOO_LONG
+check_error 'p vfs_read arg1=^'			# NO_ARG_BODY
+
+# instruction boundary check is valid on x86 (at this moment)
+case $(uname -m) in
+  x86_64|i[3456]86)
+    echo 'p vfs_read' > kprobe_events
+    if grep -q FTRACE ../kprobes/list ; then
+	check_error 'p ^vfs_read+3'		# BAD_INSN_BNDRY (only if function-tracer is enabled)
+    fi
+    ;;
+esac
+
+exit 0

tools/testing/selftests/ftrace/test.d/kprobe/uprobe_syntax_errors.tc

···
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Uprobe event parser error log check
+
+[ -f uprobe_events ] || exit_unsupported # this is configurable
+
+[ -f error_log ] || exit_unsupported
+
+check_error() { # command-with-error-pos-by-^
+    ftrace_errlog_check 'trace_uprobe' "$1" 'uprobe_events'
+}
+
+check_error 'p ^/non_exist_file:100'	# FILE_NOT_FOUND
+check_error 'p ^/sys:100'		# NO_REGULAR_FILE
+check_error 'p /bin/sh:^10a'		# BAD_UPROBE_OFFS
+check_error 'p /bin/sh:10(^1a)'		# BAD_REFCNT
+check_error 'p /bin/sh:10(10^'		# REFCNT_OPEN_BRACE
+check_error 'p /bin/sh:10(10)^a'	# BAD_REFCNT_SUFFIX
+
+check_error 'p /bin/sh:10 ^@+ab'	# BAD_FILE_OFFS
+check_error 'p /bin/sh:10 ^@symbol'	# SYM_ON_UPROBE
+
+exit 0

tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-extended-error-support.tc

···
-#!/bin/sh
-# SPDX-License-Identifier: GPL-2.0
-# description: event trigger - test extended error support
-
-
-fail() { #msg
-    echo $1
-    exit_fail
-}
-
-if [ ! -f set_event ]; then
-    echo "event tracing is not supported"
-    exit_unsupported
-fi
-
-if [ ! -f synthetic_events ]; then
-    echo "synthetic event is not supported"
-    exit_unsupported
-fi
-
-echo "Test extended error support"
-echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' > events/sched/sched_wakeup/trigger
-! echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' >> events/sched/sched_wakeup/trigger 2> /dev/null
-if ! grep -q "ERROR:" events/sched/sched_wakeup/hist; then
-    fail "Failed to generate extended error in histogram"
-fi
-
-exit 0