Merge tag 'trace-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:
"This pull request has a lot of work done. The main thing is the
changes to the ftrace function callback infrastructure. It's
introducing a way to allow different functions to call directly
different trampolines instead of all calling the same "mcount" one.

The only user of this for now is the function graph tracer, which
always had a different trampoline, but the function tracer trampoline
was called and did basically nothing, and then the function graph
tracer trampoline was called. The difference now, is that the
function graph tracer trampoline can be called directly if a function
is only being traced by the function graph trampoline. If function
tracing is also happening on the same function, the old way is still
done.

The accounting for this takes up more memory when function graph
tracing is activated, as it needs to keep track of which functions it
uses. I have a new way that wont take as much memory, but it's not
ready yet for this merge window, and will have to wait for the next
one.

Another big change was the removal of the ftrace_start/stop() calls
that were used by the suspend/resume code that stopped function
tracing when entering into suspend and resume paths. The stop of
ftrace was done because there was some function that would crash the
system if one called smp_processor_id()! The stop/start was a big
hammer to solve the issue at the time, which was when ftrace was first
introduced into Linux. Now ftrace has better infrastructure to debug
such issues, and I found the problem function and labeled it with
"notrace" and function tracing can now safely be activated all the way
down into the guts of suspend and resume

Other changes include clean ups of uprobe code, clean up of the
trace_seq() code, and other various small fixes and clean ups to
ftrace and tracing"

* tag 'trace-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (57 commits)
ftrace: Add warning if tramp hash does not match nr_trampolines
ftrace: Fix trampoline hash update check on rec->flags
ring-buffer: Use rb_page_size() instead of open coded head_page size
ftrace: Rename ftrace_ops field from trampolines to nr_trampolines
tracing: Convert local function_graph functions to static
ftrace: Do not copy old hash when resetting
tracing: let user specify tracing_thresh after selecting function_graph
ring-buffer: Always run per-cpu ring buffer resize with schedule_work_on()
tracing: Remove function_trace_stop and HAVE_FUNCTION_TRACE_MCOUNT_TEST
s390/ftrace: remove check of obsolete variable function_trace_stop
arm64, ftrace: Remove check of obsolete variable function_trace_stop
Blackfin: ftrace: Remove check of obsolete variable function_trace_stop
metag: ftrace: Remove check of obsolete variable function_trace_stop
microblaze: ftrace: Remove check of obsolete variable function_trace_stop
MIPS: ftrace: Remove check of obsolete variable function_trace_stop
parisc: ftrace: Remove check of obsolete variable function_trace_stop
sh: ftrace: Remove check of obsolete variable function_trace_stop
sparc64,ftrace: Remove check of obsolete variable function_trace_stop
tile: ftrace: Remove check of obsolete variable function_trace_stop
ftrace: x86: Remove check of obsolete variable function_trace_stop
...

Documentation/kernel-parameters.txt

···
 			that can be changed at run time by the
 			set_graph_function file in the debugfs tracing directory.
 
+	ftrace_graph_notrace=[function-list]
+			[FTRACE] Do not trace from the functions specified in
+			function-list.  This list is a comma separated list of
+			functions that can be changed at run time by the
+			set_graph_notrace file in the debugfs tracing directory.
+
 	gamecon.map[2|3]=
 			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 			support via parallel port (up to 5 devices per port)

Documentation/trace/ftrace-design.txt

···
 EXPORT_SYMBOL(mcount);
 
 
-HAVE_FUNCTION_TRACE_MCOUNT_TEST
--------------------------------
-
-This is an optional optimization for the normal case when tracing is turned off
-in the system.  If you do not enable this Kconfig option, the common ftrace
-code will take care of doing the checking for you.
-
-To support this feature, you only need to check the function_trace_stop
-variable in the mcount function.  If it is non-zero, there is no tracing to be
-done at all, so you can return.
-
-This additional pseudo code would simply be:
-void mcount(void)
-{
-	/* save any bare state needed in order to do initial checking */
-
-+	if (function_trace_stop)
-+		return;
-
-	extern void (*ftrace_trace_function)(unsigned long, unsigned long);
-	if (ftrace_trace_function != ftrace_stub)
-...
-
-
 HAVE_FUNCTION_GRAPH_TRACER
 --------------------------
 
···
 
 void ftrace_caller(void)
 {
-	/* implement HAVE_FUNCTION_TRACE_MCOUNT_TEST if you desire */
-
 	/* save all state needed by the ABI (see paragraph above) */
 
 	unsigned long frompc = ...;

arch/arm64/kernel/entry-ftrace.S

···
  *     - ftrace_graph_caller to set up an exit hook
  */
 ENTRY(_mcount)
-#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
-	ldr	x0, =ftrace_trace_stop
-	ldr	x0, [x0]		// if ftrace_trace_stop
-	ret				//   return;
-#endif
 	mcount_enter
 
 	ldr	x0, =ftrace_trace_function

arch/blackfin/Kconfig

···
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_IDE
 	select HAVE_KERNEL_GZIP if RAMKERNEL
 	select HAVE_KERNEL_BZIP2 if RAMKERNEL

arch/blackfin/kernel/ftrace-entry.S

···
  * function will be waiting there.  mmmm pie.
  */
 ENTRY(_ftrace_caller)
-# ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
-	/* optional micro optimization: return if stopped */
-	p1.l = _function_trace_stop;
-	p1.h = _function_trace_stop;
-	r3 = [p1];
-	cc = r3 == 0;
-	if ! cc jump _ftrace_stub (bp);
-# endif
-
 	/* save first/second/third function arg and the return register */
 	[--sp] = r2;
 	[--sp] = r0;
···
 
 /* See documentation for _ftrace_caller */
 ENTRY(__mcount)
-# ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
-	/* optional micro optimization: return if stopped */
-	p1.l = _function_trace_stop;
-	p1.h = _function_trace_stop;
-	r3 = [p1];
-	cc = r3 == 0;
-	if ! cc jump _ftrace_stub (bp);
-# endif
-
 	/* save third function arg early so we can do testing below */
 	[--sp] = r2;
 

arch/metag/Kconfig

···
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_TRACER
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_LZO

arch/metag/kernel/ftrace_stub.S

···
 	.global _ftrace_caller
 	.type	_ftrace_caller,function
 _ftrace_caller:
-	MOVT    D0Re0,#HI(_function_trace_stop)
-	ADD	D0Re0,D0Re0,#LO(_function_trace_stop)
-	GETD	D0Re0,[D0Re0]
-	CMP	D0Re0,#0
-	BEQ	$Lcall_stub
-	MOV	PC,D0.4
-$Lcall_stub:
 	MSETL   [A0StP], D0Ar6, D0Ar4, D0Ar2, D0.4
 	MOV     D1Ar1, D0.4
 	MOV     D0Ar2, D1RtP
···
 	.global	_mcount_wrapper
 	.type	_mcount_wrapper,function
 _mcount_wrapper:
-	MOVT    D0Re0,#HI(_function_trace_stop)
-	ADD	D0Re0,D0Re0,#LO(_function_trace_stop)
-	GETD	D0Re0,[D0Re0]
-	CMP	D0Re0,#0
-	BEQ	$Lcall_mcount
-	MOV	PC,D0.4
-$Lcall_mcount:
 	MSETL   [A0StP], D0Ar6, D0Ar4, D0Ar2, D0.4
 	MOV     D1Ar1, D0.4
 	MOV     D0Ar2, D1RtP

arch/microblaze/Kconfig

···
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_GRAPH_TRACER
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_FUNCTION_TRACER
 	select HAVE_MEMBLOCK
 	select HAVE_MEMBLOCK_NODE_MAP

arch/microblaze/kernel/ftrace.c

···
 	unsigned long return_hooker = (unsigned long)
 				&return_to_handler;
 
+	if (unlikely(ftrace_graph_is_dead()))
+		return;
+
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
 

arch/microblaze/kernel/mcount.S

···
 #endif /* CONFIG_DYNAMIC_FTRACE */
 	SAVE_REGS
 	swi	r15, r1, 0;
-	/* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST begin of checking */
-	lwi	r5, r0, function_trace_stop;
-	bneid	r5, end;
-	nop;
-	/* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST end of checking */
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 #ifndef CONFIG_DYNAMIC_FTRACE
 	lwi	r5, r0, ftrace_graph_return;

arch/mips/Kconfig

···
 	select HAVE_BPF_JIT if !CPU_MICROMIPS
 	select ARCH_HAVE_CUSTOM_GPIO_H
 	select HAVE_FUNCTION_TRACER
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_C_RECORDMCOUNT

arch/mips/kernel/ftrace.c

···
 	    &return_to_handler;
 	int faulted, insns;
 
+	if (unlikely(ftrace_graph_is_dead()))
+		return;
+
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
 

arch/mips/kernel/mcount.S

···
 #endif
 
 	/* When tracing is activated, it calls ftrace_caller+8 (aka here) */
-	lw	t1, function_trace_stop
-	bnez	t1, ftrace_stub
-	 nop
-
 	MCOUNT_SAVE_REGS
 #ifdef KBUILD_MCOUNT_RA_ADDRESS
 	PTR_S	MCOUNT_RA_ADDRESS_REG, PT_R12(sp)
···
 #else	/* ! CONFIG_DYNAMIC_FTRACE */
 
 NESTED(_mcount, PT_SIZE, ra)
-	lw	t1, function_trace_stop
-	bnez	t1, ftrace_stub
-	 nop
 	PTR_LA	t1, ftrace_stub
 	PTR_L	t2, ftrace_trace_function /* Prepare t2 for (1) */
 	bne	t1, t2, static_trace

arch/parisc/Kconfig

···
 	select HAVE_OPROFILE
 	select HAVE_FUNCTION_TRACER if 64BIT
 	select HAVE_FUNCTION_GRAPH_TRACER if 64BIT
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST if 64BIT
 	select ARCH_WANT_FRAME_POINTERS
 	select RTC_CLASS
 	select RTC_DRV_GENERIC

arch/parisc/kernel/ftrace.c

···
 	unsigned long long calltime;
 	struct ftrace_graph_ent trace;
 
+	if (unlikely(ftrace_graph_is_dead()))
+		return;
+
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
 
···
 				unsigned long org_sp_gr3)
 {
 	extern ftrace_func_t ftrace_trace_function;
-
-	if (function_trace_stop)
-		return;
 
 	if (ftrace_trace_function != ftrace_stub) {
 		ftrace_trace_function(parent, self_addr);

arch/powerpc/kernel/ftrace.c

···
 	struct ftrace_graph_ent trace;
 	unsigned long return_hooker = (unsigned long)&return_to_handler;
 
+	if (unlikely(ftrace_graph_is_dead()))
+		return;
+
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
 

arch/s390/Kconfig

···
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_FUTEX_CMPXCHG if FUTEX
 	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_GZIP

arch/s390/kernel/mcount.S

···
 ENTRY(ftrace_caller)
 #endif
 	stm	%r2,%r5,16(%r15)
-	bras	%r1,2f
+	bras	%r1,1f
 0:	.long	ftrace_trace_function
-1:	.long	function_trace_stop
-2:	l	%r2,1b-0b(%r1)
-	icm	%r2,0xf,0(%r2)
-	jnz	3f
-	st	%r14,56(%r15)
+1:	st	%r14,56(%r15)
 	lr	%r0,%r15
 	ahi	%r15,-96
 	l	%r3,100(%r15)
···
 #endif
 	ahi	%r15,96
 	l	%r14,56(%r15)
-3:	lm	%r2,%r5,16(%r15)
+	lm	%r2,%r5,16(%r15)
 	br	%r14
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER

arch/s390/kernel/mcount64.S

···
 
 ENTRY(ftrace_caller)
 #endif
-	larl	%r1,function_trace_stop
-	icm	%r1,0xf,0(%r1)
-	bnzr	%r14
 	stmg	%r2,%r5,32(%r15)
 	stg	%r14,112(%r15)
 	lgr	%r1,%r15

arch/sh/Kconfig

···
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_DYNAMIC_FTRACE
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select HAVE_FUNCTION_GRAPH_TRACER

arch/sh/kernel/ftrace.c

···
 	struct ftrace_graph_ent trace;
 	unsigned long return_hooker = (unsigned long)&return_to_handler;
 
+	if (unlikely(ftrace_graph_is_dead()))
+		return;
+
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
 

arch/sh/lib/mcount.S

···
 	rts
 	 nop
 #else
-#ifndef CONFIG_DYNAMIC_FTRACE
-	mov.l	.Lfunction_trace_stop, r0
-	mov.l	@r0, r0
-	tst	r0, r0
-	bf	ftrace_stub
-#endif
-
 	MCOUNT_ENTER()
 
 #ifdef CONFIG_DYNAMIC_FTRACE
···
 
 	.globl ftrace_caller
 ftrace_caller:
-	mov.l	.Lfunction_trace_stop, r0
-	mov.l	@r0, r0
-	tst	r0, r0
-	bf	ftrace_stub
-
 	MCOUNT_ENTER()
 
 	.globl ftrace_call
···
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
 	.align 2
-.Lfunction_trace_stop:
-	.long	function_trace_stop
 
 /*
  * NOTE: From here on the locations of the .Lftrace_stub label and
···
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	.globl	ftrace_graph_caller
 ftrace_graph_caller:
-	mov.l	2f, r0
-	mov.l	@r0, r0
-	tst	r0, r0
-	bt	1f
-
-	mov.l	3f, r1
+	mov.l	2f, r1
 	jmp	@r1
 	 nop
 1:
···
 	MCOUNT_LEAVE()
 
 	.align 2
-2:	.long	function_trace_stop
-3:	.long	skip_trace
+2:	.long	skip_trace
 .Lprepare_ftrace_return:
 	.long	prepare_ftrace_return
 

arch/sparc/Kconfig

···
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_FP_TEST
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_KRETPROBES
 	select HAVE_KPROBES
 	select HAVE_RCU_TABLE_FREE if SMP

arch/sparc/lib/mcount.S

···
 #ifdef CONFIG_DYNAMIC_FTRACE
 	/* Do nothing, the retl/nop below is all we need.  */
 #else
-	sethi		%hi(function_trace_stop), %g1
-	lduw		[%g1 + %lo(function_trace_stop)], %g2
-	brnz,pn		%g2, 2f
-	 sethi		%hi(ftrace_trace_function), %g1
+	sethi		%hi(ftrace_trace_function), %g1
 	sethi		%hi(ftrace_stub), %g2
 	ldx		[%g1 + %lo(ftrace_trace_function)], %g1
 	or		%g2, %lo(ftrace_stub), %g2
···
 	.globl		ftrace_caller
 	.type		ftrace_caller,#function
 ftrace_caller:
-	sethi		%hi(function_trace_stop), %g1
 	mov		%i7, %g2
-	lduw		[%g1 + %lo(function_trace_stop)], %g1
-	brnz,pn		%g1, ftrace_stub
-	 mov		%fp, %g3
+	mov		%fp, %g3
 	save		%sp, -176, %sp
 	mov		%g2, %o1
 	mov		%g2, %l0

arch/tile/Kconfig

···
 	select SPARSE_IRQ
 	select GENERIC_IRQ_LEGACY_ALLOC_HWIRQ
 	select HAVE_FUNCTION_TRACER
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD

arch/tile/kernel/mcount_64.S

···
 
 	.align	64
 STD_ENTRY(ftrace_caller)
-	moveli	r11, hw2_last(function_trace_stop)
-	{ shl16insli	r11, r11, hw1(function_trace_stop); move r12, lr }
-	{ shl16insli	r11, r11, hw0(function_trace_stop); move lr, r10 }
-	ld	r11, r11
-	beqz	r11, 1f
-	jrp	r12
-
-1:
-	{ move	r10, lr; move	lr, r12 }
 	MCOUNT_SAVE_REGS
 
 	/* arg1: self return address */
···
 
 	.align	64
 STD_ENTRY(__mcount)
-	moveli	r11, hw2_last(function_trace_stop)
-	{ shl16insli	r11, r11, hw1(function_trace_stop); move r12, lr }
-	{ shl16insli	r11, r11, hw0(function_trace_stop); move lr, r10 }
-	ld	r11, r11
-	beqz	r11, 1f
-	jrp	r12
-
-1:
-	{ move	r10, lr; move	lr, r12 }
 	{
 	 moveli	r11, hw2_last(ftrace_trace_function)
 	 moveli	r13, hw2_last(ftrace_stub)

arch/x86/Kconfig

···
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_FP_TEST
-	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_SYSCALL_TRACEPOINTS
 	select SYSCTL_EXCEPTION_TRACE
 	select HAVE_KVM

arch/x86/include/asm/ftrace.h

···
 
 int ftrace_int3_handler(struct pt_regs *regs);
 
+#define FTRACE_GRAPH_TRAMP_ADDR FTRACE_GRAPH_ADDR
+
 #endif /*  CONFIG_DYNAMIC_FTRACE */
 #endif /* __ASSEMBLY__ */
 #endif /* CONFIG_FUNCTION_TRACER */

arch/x86/kernel/entry_32.S

···
 END(mcount)
 
 ENTRY(ftrace_caller)
-	cmpl $0, function_trace_stop
-	jne  ftrace_stub
-
 	pushl %eax
 	pushl %ecx
 	pushl %edx
···
 
 ENTRY(ftrace_regs_caller)
 	pushf	/* push flags before compare (in cs location) */
-	cmpl $0, function_trace_stop
-	jne ftrace_restore_flags
 
 	/*
 	 * i386 does not save SS and ESP when coming from kernel.
···
 	popf			/* Pop flags at end (no addl to corrupt flags) */
 	jmp ftrace_ret
 
-ftrace_restore_flags:
 	popf
 	jmp  ftrace_stub
 #else /* ! CONFIG_DYNAMIC_FTRACE */
···
 ENTRY(mcount)
 	cmpl $__PAGE_OFFSET, %esp
 	jb ftrace_stub		/* Paging not enabled yet? */
-
-	cmpl $0, function_trace_stop
-	jne  ftrace_stub
 
 	cmpl $ftrace_stub, ftrace_trace_function
 	jnz trace

arch/x86/kernel/ftrace.c

···
 	unsigned long return_hooker = (unsigned long)
 				&return_to_handler;
 
+	if (unlikely(ftrace_graph_is_dead()))
+		return;
+
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
 

arch/x86/kernel/mcount_64.S

···
 .endm
 
 ENTRY(ftrace_caller)
-	/* Check if tracing was disabled (quick check) */
-	cmpl $0, function_trace_stop
-	jne  ftrace_stub
-
 	ftrace_caller_setup
 	/* regs go into 4th parameter (but make it NULL) */
 	movq $0, %rcx
···
 ENTRY(ftrace_regs_caller)
 	/* Save the current flags before compare (in SS location)*/
 	pushfq
-
-	/* Check if tracing was disabled (quick check) */
-	cmpl $0, function_trace_stop
-	jne  ftrace_restore_flags
 
 	/* skip=8 to skip flags saved in SS */
 	ftrace_caller_setup 8
···
 	popfq
 
 	jmp ftrace_return
-ftrace_restore_flags:
+
 	popfq
 	jmp  ftrace_stub
 
···
 #else /* ! CONFIG_DYNAMIC_FTRACE */
 
 ENTRY(function_hook)
-	cmpl $0, function_trace_stop
-	jne  ftrace_stub
-
 	cmpq $ftrace_stub, ftrace_trace_function
 	jnz trace
 

arch/x86/kvm/mmutrace.h

···
 	__entry->unsync = sp->unsync;
 
 #define KVM_MMU_PAGE_PRINTK() ({				        \
-	const char *ret = p->buffer + p->len;				\
+	const char *ret = trace_seq_buffer_ptr(p);			\
 	static const char *access_str[] = {			        \
 		"---", "--x", "w--", "w-x", "-u-", "-ux", "wu-", "wux"  \
 	};							        \

arch/x86/power/cpu.c

···
  *		by __save_processor_state()
  *	@ctxt - structure to load the registers contents from
  */
-static void __restore_processor_state(struct saved_context *ctxt)
+static void notrace __restore_processor_state(struct saved_context *ctxt)
 {
 	if (ctxt->misc_enable_saved)
 		wrmsrl(MSR_IA32_MISC_ENABLE, ctxt->misc_enable);
···
 }
 
 /* Needed by apm.c */
-void restore_processor_state(void)
+void notrace restore_processor_state(void)
 {
 	__restore_processor_state(&saved_context);
 }

drivers/scsi/scsi_trace.c

···
 static const char *
 scsi_trace_rw6(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 	sector_t lba = 0, txlen = 0;
 
 	lba |= ((cdb[1] & 0x1F) << 16);
···
 static const char *
 scsi_trace_rw10(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 	sector_t lba = 0, txlen = 0;
 
 	lba |= (cdb[2] << 24);
···
 static const char *
 scsi_trace_rw12(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 	sector_t lba = 0, txlen = 0;
 
 	lba |= (cdb[2] << 24);
···
 static const char *
 scsi_trace_rw16(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 	sector_t lba = 0, txlen = 0;
 
 	lba |= ((u64)cdb[2] << 56);
···
 static const char *
 scsi_trace_rw32(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len, *cmd;
+	const char *ret = trace_seq_buffer_ptr(p), *cmd;
 	sector_t lba = 0, txlen = 0;
 	u32 ei_lbrt = 0;
 
···
 static const char *
 scsi_trace_unmap(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 	unsigned int regions = cdb[7] << 8 | cdb[8];
 
 	trace_seq_printf(p, "regions=%u", (regions - 8) / 16);
···
 static const char *
 scsi_trace_service_action_in(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len, *cmd;
+	const char *ret = trace_seq_buffer_ptr(p), *cmd;
 	sector_t lba = 0;
 	u32 alloc_len = 0;
 
···
 static const char *
 scsi_trace_misc(struct trace_seq *p, unsigned char *cdb, int len)
 {
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 
 	trace_seq_printf(p, "-");
 	trace_seq_putc(p, 0);

include/linux/ftrace.h

···
  * features, then it must call an indirect function that
  * does. Or at least does enough to prevent any unwelcomed side effects.
  */
-#if !defined(CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST) || \
-	!ARCH_SUPPORTS_FTRACE_OPS
+#if !ARCH_SUPPORTS_FTRACE_OPS
 # define FTRACE_FORCE_LIST_FUNC 1
 #else
 # define FTRACE_FORCE_LIST_FUNC 0
···
 	ftrace_func_t			func;
 	struct ftrace_ops		*next;
 	unsigned long			flags;
-	int __percpu			*disabled;
 	void				*private;
+	int __percpu			*disabled;
 #ifdef CONFIG_DYNAMIC_FTRACE
+	int				nr_trampolines;
 	struct ftrace_hash		*notrace_hash;
 	struct ftrace_hash		*filter_hash;
+	struct ftrace_hash		*tramp_hash;
 	struct mutex			regex_lock;
+	unsigned long			trampoline;
 #endif
 };
-
-extern int function_trace_stop;
 
 /*
  * Type of the current tracing.
···
 
 /* Current tracing type, default is FTRACE_TYPE_ENTER */
 extern enum ftrace_tracing_type_t ftrace_tracing_type;
-
-/**
- * ftrace_stop - stop function tracer.
- *
- * A quick way to stop the function tracer. Note this an on off switch,
- * it is not something that is recursive like preempt_disable.
- * This does not disable the calling of mcount, it only stops the
- * calling of functions from mcount.
- */
-static inline void ftrace_stop(void)
-{
-	function_trace_stop = 1;
-}
-
-/**
- * ftrace_start - start the function tracer.
- *
- * This function is the inverse of ftrace_stop. This does not enable
- * the function tracing if the function tracer is disabled. This only
- * sets the function tracer flag to continue calling the functions
- * from mcount.
- */
-static inline void ftrace_start(void)
-{
-	function_trace_stop = 0;
-}
 
 /*
  * The ftrace_ops must be a static and should also
···
 }
 static inline void clear_ftrace_function(void) { }
 static inline void ftrace_kill(void) { }
-static inline void ftrace_stop(void) { }
-static inline void ftrace_start(void) { }
 #endif /* CONFIG_FUNCTION_TRACER */
 
 #ifdef CONFIG_STACK_TRACER
···
  * from tracing that function.
  */
 enum {
-	FTRACE_FL_ENABLED	= (1UL << 29),
+	FTRACE_FL_ENABLED	= (1UL << 31),
 	FTRACE_FL_REGS		= (1UL << 30),
-	FTRACE_FL_REGS_EN	= (1UL << 31)
+	FTRACE_FL_REGS_EN	= (1UL << 29),
+	FTRACE_FL_TRAMP		= (1UL << 28),
+	FTRACE_FL_TRAMP_EN	= (1UL << 27),
 };
 
-#define FTRACE_FL_MASK		(0x7UL << 29)
-#define FTRACE_REF_MAX		((1UL << 29) - 1)
+#define FTRACE_REF_MAX_SHIFT	27
+#define FTRACE_FL_BITS		5
+#define FTRACE_FL_MASKED_BITS	((1UL << FTRACE_FL_BITS) - 1)
+#define FTRACE_FL_MASK		(FTRACE_FL_MASKED_BITS << FTRACE_REF_MAX_SHIFT)
+#define FTRACE_REF_MAX		((1UL << FTRACE_REF_MAX_SHIFT) - 1)
+
+#define ftrace_rec_count(rec)	((rec)->flags & ~FTRACE_FL_MASK)
 
 struct dyn_ftrace {
 	unsigned long		ip; /* address of mcount call-site */
···
 #define FTRACE_ADDR ((unsigned long)ftrace_caller)
 #endif
 
+#ifndef FTRACE_GRAPH_ADDR
+#define FTRACE_GRAPH_ADDR ((unsigned long)ftrace_graph_caller)
+#endif
+
 #ifndef FTRACE_REGS_ADDR
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 # define FTRACE_REGS_ADDR ((unsigned long)ftrace_regs_caller)
 #else
 # define FTRACE_REGS_ADDR FTRACE_ADDR
 #endif
+#endif
+
+/*
+ * If an arch would like functions that are only traced
+ * by the function graph tracer to jump directly to its own
+ * trampoline, then they can define FTRACE_GRAPH_TRAMP_ADDR
+ * to be that address to jump to.
+ */
+#ifndef FTRACE_GRAPH_TRAMP_ADDR
+#define FTRACE_GRAPH_TRAMP_ADDR ((unsigned long) 0)
 #endif
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
···
 extern int register_ftrace_graph(trace_func_graph_ret_t retfunc,
 				trace_func_graph_ent_t entryfunc);
 
+extern bool ftrace_graph_is_dead(void);
 extern void ftrace_graph_stop(void);
 
 /* The current handlers in use */

include/linux/trace_seq.h

···
 	s->full = 0;
 }
 
+/**
+ * trace_seq_buffer_ptr - return pointer to next location in buffer
+ * @s: trace sequence descriptor
+ *
+ * Returns the pointer to the buffer where the next write to
+ * the buffer will happen. This is useful to save the location
+ * that is about to be written to and then return the result
+ * of that write.
+ */
+static inline unsigned char *
+trace_seq_buffer_ptr(struct trace_seq *s)
+{
+	return s->buffer + s->len;
+}
+
 /*
  * Currently only defined when tracing is enabled.
  */
···
 extern int
 trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary);
 extern int trace_print_seq(struct seq_file *m, struct trace_seq *s);
-extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
-				 size_t cnt);
+extern int trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
+			     int cnt);
 extern int trace_seq_puts(struct trace_seq *s, const char *str);
 extern int trace_seq_putc(struct trace_seq *s, unsigned char c);
-extern int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len);
+extern int trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len);
 extern int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
-				size_t len);
-extern void *trace_seq_reserve(struct trace_seq *s, size_t len);
+				unsigned int len);
 extern int trace_seq_path(struct trace_seq *s, const struct path *path);
 
 extern int trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
···
 {
 	return 0;
 }
-static inline ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
-				 size_t cnt)
+static inline int trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
+				    int cnt)
 {
 	return 0;
 }
···
 	return 0;
 }
 static inline int
-trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len)
+trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
 {
 	return 0;
 }
 static inline int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
-				       size_t len)
+				       unsigned int len)
 {
 	return 0;
-}
-static inline void *trace_seq_reserve(struct trace_seq *s, size_t len)
-{
-	return NULL;
 }
 static inline int trace_seq_path(struct trace_seq *s, const struct path *path)
 {

kernel/power/hibernate.c

···
 	}
 
 	suspend_console();
-	ftrace_stop();
 	pm_restrict_gfp_mask();
 
 	error = dpm_suspend(PMSG_FREEZE);
···
 	if (error || !in_suspend)
 		pm_restore_gfp_mask();
 
-	ftrace_start();
 	resume_console();
 	dpm_complete(msg);
 
···
 
 	pm_prepare_console();
 	suspend_console();
-	ftrace_stop();
 	pm_restrict_gfp_mask();
 	error = dpm_suspend_start(PMSG_QUIESCE);
 	if (!error) {
···
 		dpm_resume_end(PMSG_RECOVER);
 	}
 	pm_restore_gfp_mask();
-	ftrace_start();
 	resume_console();
 	pm_restore_console();
 	return error;
···
 
 	entering_platform_hibernation = true;
 	suspend_console();
-	ftrace_stop();
 	error = dpm_suspend_start(PMSG_HIBERNATE);
 	if (error) {
 		if (hibernation_ops->recover)
···
  Resume_devices:
 	entering_platform_hibernation = false;
 	dpm_resume_end(PMSG_RESTORE);
-	ftrace_start();
 	resume_console();
 
  Close:

kernel/power/suspend.c

···
 		goto Platform_wake;
 	}
 
-	ftrace_stop();
 	error = disable_nonboot_cpus();
 	if (error || suspend_test(TEST_CPUS))
 		goto Enable_cpus;
···
 
  Enable_cpus:
 	enable_nonboot_cpus();
-	ftrace_start();
 
  Platform_wake:
 	if (need_suspend_ops(state) && suspend_ops->wake)

kernel/trace/Kconfig

···
 	help
 	  See Documentation/trace/ftrace-design.txt
 
-config HAVE_FUNCTION_TRACE_MCOUNT_TEST
-	bool
-	help
-	  See Documentation/trace/ftrace-design.txt
-
 config HAVE_DYNAMIC_FTRACE
 	bool
 	help

kernel/trace/Makefile

···
 
 obj-$(CONFIG_TRACING) += trace.o
 obj-$(CONFIG_TRACING) += trace_output.o
+obj-$(CONFIG_TRACING) += trace_seq.o
 obj-$(CONFIG_TRACING) += trace_stat.o
 obj-$(CONFIG_TRACING) += trace_printk.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o

kernel/trace/ftrace.c

···
 int ftrace_enabled __read_mostly;
 static int last_ftrace_enabled;
 
-/* Quick disabling of function tracer. */
-int function_trace_stop __read_mostly;
-
 /* Current function tracing op */
 struct ftrace_ops *function_trace_op __read_mostly = &ftrace_list_end;
 /* What to set function_trace_op to */
···
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 
+static struct ftrace_ops *removed_ops;
+
 #ifndef CONFIG_FTRACE_MCOUNT_RECORD
 # error Dynamic ftrace depends on MCOUNT_RECORD
 #endif
···
 	struct ftrace_hash *new_hash;
 	int size = src->count;
 	int bits = 0;
-	int ret;
 	int i;
-
-	/*
-	 * Remove the current set, update the hash and add
-	 * them back.
-	 */
-	ftrace_hash_rec_disable(ops, enable);
 
 	/*
 	 * If the new source is empty, just free dst and assign it
 	 * the empty_hash.
 	 */
 	if (!src->count) {
-		free_ftrace_hash_rcu(*dst);
-		rcu_assign_pointer(*dst, EMPTY_HASH);
-		/* still need to update the function records */
-		ret = 0;
-		goto out;
+		new_hash = EMPTY_HASH;
+		goto update;
 	}
 
 	/*
···
 	if (bits > FTRACE_HASH_MAX_BITS)
 		bits = FTRACE_HASH_MAX_BITS;
 
-	ret = -ENOMEM;
 	new_hash = alloc_ftrace_hash(bits);
 	if (!new_hash)
-		goto out;
+		return -ENOMEM;
 
 	size = 1 << src->size_bits;
 	for (i = 0; i < size; i++) {
···
 		}
 	}
 
+update:
+	/*
+	 * Remove the current set, update the hash and add
+	 * them back.
+	 */
+	ftrace_hash_rec_disable(ops, enable);
+
 	old_hash = *dst;
 	rcu_assign_pointer(*dst, new_hash);
 	free_ftrace_hash_rcu(old_hash);
 
-	ret = 0;
- out:
-	/*
-	 * Enable regardless of ret:
-	 *  On success, we enable the new hash.
-	 *  On failure, we re-enable the original hash.
-	 */
 	ftrace_hash_rec_enable(ops, enable);
 
-	return ret;
+	return 0;
 }
 
 /*
···
 	return (int)!!ret;
 }
 
+/* Test if ops registered to this rec needs regs */
+static bool test_rec_ops_needs_regs(struct dyn_ftrace *rec)
+{
+	struct ftrace_ops *ops;
+	bool keep_regs = false;
+
+	for (ops = ftrace_ops_list;
+	     ops != &ftrace_list_end; ops = ops->next) {
+		/* pass rec in as regs to have non-NULL val */
+		if (ftrace_ops_test(ops, rec->ip, rec)) {
+			if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
+				keep_regs = true;
+				break;
+			}
+		}
+	}
+
+	return  keep_regs;
+}
+
+static void ftrace_remove_tramp(struct ftrace_ops *ops,
+				struct dyn_ftrace *rec)
+{
+	struct ftrace_func_entry *entry;
+
+	entry = ftrace_lookup_ip(ops->tramp_hash, rec->ip);
+	if (!entry)
+		return;
+
+	/*
+	 * The tramp_hash entry will be removed at time
+	 * of update.
+	 */
+	ops->nr_trampolines--;
+	rec->flags &= ~FTRACE_FL_TRAMP;
+}
+
+static void ftrace_clear_tramps(struct dyn_ftrace *rec)
+{
+	struct ftrace_ops *op;
+
+	do_for_each_ftrace_op(op, ftrace_ops_list) {
+		if (op->nr_trampolines)
+			ftrace_remove_tramp(op, rec);
+	} while_for_each_ftrace_op(op);
+}
+
 static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
 				     int filter_hash,
 				     bool inc)
···
 
 		if (inc) {
 			rec->flags++;
-			if (FTRACE_WARN_ON((rec->flags & ~FTRACE_FL_MASK) == FTRACE_REF_MAX))
+			if (FTRACE_WARN_ON(ftrace_rec_count(rec) == FTRACE_REF_MAX))
 				return;
+
+			/*
+			 * If there's only a single callback registered to a
+			 * function, and the ops has a trampoline registered
+			 * for it, then we can call it directly.
+			 */
+			if (ftrace_rec_count(rec) == 1 && ops->trampoline) {
+				rec->flags |= FTRACE_FL_TRAMP;
+				ops->nr_trampolines++;
+			} else {
+				/*
+				 * If we are adding another function callback
+				 * to this function, and the previous had a
+				 * trampoline used, then we need to go back to
+				 * the default trampoline.
+				 */
+				rec->flags &= ~FTRACE_FL_TRAMP;
+
+				/* remove trampolines from any ops for this rec */
+				ftrace_clear_tramps(rec);
+			}
+
 			/*
 			 * If any ops wants regs saved for this function
 			 * then all ops will get saved regs.
···
 			if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
 				rec->flags |= FTRACE_FL_REGS;
 		} else {
-			if (FTRACE_WARN_ON((rec->flags & ~FTRACE_FL_MASK) == 0))
+			if (FTRACE_WARN_ON(ftrace_rec_count(rec) == 0))
 				return;
 			rec->flags--;
+
+			if (ops->trampoline && !ftrace_rec_count(rec))
+				ftrace_remove_tramp(ops, rec);
+
+			/*
+			 * If the rec had REGS enabled and the ops that is
+			 * being removed had REGS set, then see if there is
+			 * still any ops for this record that wants regs.
+			 * If not, we can stop recording them.
+			 */
+			if (ftrace_rec_count(rec) > 0 &&
+			    rec->flags & FTRACE_FL_REGS &&
+			    ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
+				if (!test_rec_ops_needs_regs(rec))
+					rec->flags &= ~FTRACE_FL_REGS;
+			}
+
+			/*
+			 * flags will be cleared in ftrace_check_record()
+			 * if rec count is zero.
+			 */
 		}
 		count++;
 		/* Shortcut, if we handled all records, we are done. */
···
 	 * If we are disabling calls, then disable all records that
 	 * are enabled.
 	 */
-	if (enable && (rec->flags & ~FTRACE_FL_MASK))
+	if (enable && ftrace_rec_count(rec))
 		flag = FTRACE_FL_ENABLED;
 
 	/*
-	 * If enabling and the REGS flag does not match the REGS_EN, then
-	 * do not ignore this record. Set flags to fail the compare against
-	 * ENABLED.
+	 * If enabling and the REGS flag does not match the REGS_EN, or
+	 * the TRAMP flag doesn't match the TRAMP_EN, then do not ignore
+	 * this record. Set flags to fail the compare against ENABLED.
 	 */
-	if (flag &&
-	    (!(rec->flags & FTRACE_FL_REGS) != !(rec->flags & FTRACE_FL_REGS_EN)))
-		flag |= FTRACE_FL_REGS;
+	if (flag) {
+		if (!(rec->flags & FTRACE_FL_REGS) != 
+		    !(rec->flags & FTRACE_FL_REGS_EN))
+			flag |= FTRACE_FL_REGS;
+
+		if (!(rec->flags & FTRACE_FL_TRAMP) != 
+		    !(rec->flags & FTRACE_FL_TRAMP_EN))
+			flag |= FTRACE_FL_TRAMP;
+	}
 
 	/* If the state of this record hasn't changed, then do nothing */
 	if ((rec->flags & FTRACE_FL_ENABLED) == flag)
···
 				else
 					rec->flags &= ~FTRACE_FL_REGS_EN;
 			}
+			if (flag & FTRACE_FL_TRAMP) {
+				if (rec->flags & FTRACE_FL_TRAMP)
+					rec->flags |= FTRACE_FL_TRAMP_EN;
+				else
+					rec->flags &= ~FTRACE_FL_TRAMP_EN;
+			}
 		}
 
 		/*
···
 		 * Otherwise,
 		 *   return UPDATE_MODIFY_CALL to tell the caller to convert
 		 *   from the save regs, to a non-save regs function or
-		 *   vice versa.
+		 *   vice versa, or from a trampoline call.
 		 */
 		if (flag & FTRACE_FL_ENABLED)
 			return FTRACE_UPDATE_MAKE_CALL;
···
 
 	if (update) {
 		/* If there's no more users, clear all flags */
-		if (!(rec->flags & ~FTRACE_FL_MASK))
+		if (!ftrace_rec_count(rec))
 			rec->flags = 0;
 		else
 			/* Just disable the record (keep REGS state) */
···
 	return ftrace_check_record(rec, enable, 0);
 }
 
+static struct ftrace_ops *
+ftrace_find_tramp_ops_curr(struct dyn_ftrace *rec)
+{
+	struct ftrace_ops *op;
+
+	/* Removed ops need to be tested first */
+	if (removed_ops && removed_ops->tramp_hash) {
+		if (ftrace_lookup_ip(removed_ops->tramp_hash, rec->ip))
+			return removed_ops;
+	}
+
+	do_for_each_ftrace_op(op, ftrace_ops_list) {
+		if (!op->tramp_hash)
+			continue;
+
+		if (ftrace_lookup_ip(op->tramp_hash, rec->ip))
+			return op;
+
+	} while_for_each_ftrace_op(op);
+
+	return NULL;
+}
+
+static struct ftrace_ops *
+ftrace_find_tramp_ops_new(struct dyn_ftrace *rec)
+{
+	struct ftrace_ops *op;
+
+	do_for_each_ftrace_op(op, ftrace_ops_list) {
+		/* pass rec in as regs to have non-NULL val */
+		if (ftrace_ops_test(op, rec->ip, rec))
+			return op;
+	} while_for_each_ftrace_op(op);
+
+	return NULL;
+}
+
 /**
  * ftrace_get_addr_new - Get the call address to set to
  * @rec:  The ftrace record descriptor
···
  */
 unsigned long ftrace_get_addr_new(struct dyn_ftrace *rec)
 {
+	struct ftrace_ops *ops;
+
+	/* Trampolines take precedence over regs */
+	if (rec->flags & FTRACE_FL_TRAMP) {
+		ops = ftrace_find_tramp_ops_new(rec);
+		if (FTRACE_WARN_ON(!ops || !ops->trampoline)) {
+			pr_warning("Bad trampoline accounting at: %p (%pS)\n",
+				    (void *)rec->ip, (void *)rec->ip);
+			/* Ftrace is shutting down, return anything */
+			return (unsigned long)FTRACE_ADDR;
+		}
+		return ops->trampoline;
+	}
+
 	if (rec->flags & FTRACE_FL_REGS)
 		return (unsigned long)FTRACE_REGS_ADDR;
 	else
···
  */
 unsigned long ftrace_get_addr_curr(struct dyn_ftrace *rec)
 {
+	struct ftrace_ops *ops;
+
+	/* Trampolines take precedence over regs */
+	if (rec->flags & FTRACE_FL_TRAMP_EN) {
+		ops = ftrace_find_tramp_ops_curr(rec);
+		if (FTRACE_WARN_ON(!ops)) {
+			pr_warning("Bad trampoline accounting at: %p (%pS)\n",
+				    (void *)rec->ip, (void *)rec->ip);
+			/* Ftrace is shutting down, return anything */
+			return (unsigned long)FTRACE_ADDR;
+		}
+		return ops->trampoline;
+	}
+
 	if (rec->flags & FTRACE_FL_REGS_EN)
 		return (unsigned long)FTRACE_REGS_ADDR;
 	else
···
 	ftrace_run_stop_machine(command);
 }
 
+static int ftrace_save_ops_tramp_hash(struct ftrace_ops *ops)
+{
+	struct ftrace_page *pg;
+	struct dyn_ftrace *rec;
+	int size, bits;
+	int ret;
+
+	size = ops->nr_trampolines;
+	bits = 0;
+	/*
+	 * Make the hash size about 1/2 the # found
+	 */
+	for (size /= 2; size; size >>= 1)
+		bits++;
+
+	ops->tramp_hash = alloc_ftrace_hash(bits);
+	/*
+	 * TODO: a failed allocation is going to screw up
+	 * the accounting of what needs to be modified
+	 * and not. For now, we kill ftrace if we fail
+	 * to allocate here. But there are ways around this,
+	 * but that will take a little more work.
+	 */
+	if (!ops->tramp_hash)
+		return -ENOMEM;
+
+	do_for_each_ftrace_rec(pg, rec) {
+		if (ftrace_rec_count(rec) == 1 &&
+		    ftrace_ops_test(ops, rec->ip, rec)) {
+
+			/*
+			 * If another ops adds to a rec, the rec will
+			 * lose its trampoline and never get it back
+			 * until all ops are off of it.
+			 */
+			if (!(rec->flags & FTRACE_FL_TRAMP))
+				continue;
+
+			/* This record had better have a trampoline */
+			if (FTRACE_WARN_ON(!(rec->flags & FTRACE_FL_TRAMP_EN)))
+				return -1;
+
+			ret = add_hash_entry(ops->tramp_hash, rec->ip);
+			if (ret < 0)
+				return ret;
+		}
+	} while_for_each_ftrace_rec();
+
+	/* The number of recs in the hash must match nr_trampolines */
+	FTRACE_WARN_ON(ops->tramp_hash->count != ops->nr_trampolines);
+
+	return 0;
+}
+
+static int ftrace_save_tramp_hashes(void)
+{
+	struct ftrace_ops *op;
+	int ret;
+
+	/*
+	 * Now that any trampoline is being used, we need to save the
+	 * hashes for the ops that have them. This allows the mapping
+	 * back from the record to the ops that has the trampoline to
+	 * know what code is being replaced. Modifying code must always
+	 * verify what it is changing.
+	 */
+	do_for_each_ftrace_op(op, ftrace_ops_list) {
+
+		/* The tramp_hash is recreated each time. */
+		free_ftrace_hash(op->tramp_hash);
+		op->tramp_hash = NULL;
+
+		if (op->nr_trampolines) {
+			ret = ftrace_save_ops_tramp_hash(op);
+			if (ret)
+				return ret;
+		}
+
+	} while_for_each_ftrace_op(op);
+
+	return 0;
+}
+
 static void ftrace_run_update_code(int command)
 {
 	int ret;
···
 	FTRACE_WARN_ON(ret);
 	if (ret)
 		return;
-	/*
-	 * Do not call function tracer while we update the code.
-	 * We are in stop machine.
-	 */
-	function_trace_stop++;
 
 	/*
 	 * By default we use stop_machine() to modify the code.
···
 	 */
 	arch_ftrace_update_code(command);
 
-	function_trace_stop--;
-
 	ret = ftrace_arch_code_modify_post_process();
+	FTRACE_WARN_ON(ret);
+
+	ret = ftrace_save_tramp_hashes();
 	FTRACE_WARN_ON(ret);
 }
 
 static ftrace_func_t saved_ftrace_func;
 static int ftrace_start_up;
-static int global_start_up;
 
 static void control_ops_free(struct ftrace_ops *ops)
 {
···
 
 	ftrace_hash_rec_disable(ops, 1);
 
-	if (!global_start_up)
-		ops->flags &= ~FTRACE_OPS_FL_ENABLED;
+	ops->flags &= ~FTRACE_OPS_FL_ENABLED;
 
 	command |= FTRACE_UPDATE_CALLS;
 
···
 		return 0;
 	}
 
+	/*
+	 * If the ops uses a trampoline, then it needs to be
+	 * tested first on update.
+	 */
+	removed_ops = ops;
+
 	ftrace_run_update_code(command);
+
+	removed_ops = NULL;
 
 	/*
 	 * Dynamic ops may be freed, we must make sure that all
···
 	return start_pg;
 
  free_pages:
-	while (start_pg) {
+	pg = start_pg;
+	while (pg) {
 		order = get_count_order(pg->size / ENTRIES_PER_PAGE);
 		free_pages((unsigned long)pg->records, order);
 		start_pg = pg->next;
···
 	 * off, we can short cut and just print out that all
 	 * functions are enabled.
 	 */
-	if (iter->flags & FTRACE_ITER_FILTER &&
-	    ftrace_hash_empty(ops->filter_hash)) {
+	if ((iter->flags & FTRACE_ITER_FILTER &&
+	     ftrace_hash_empty(ops->filter_hash)) ||
+	    (iter->flags & FTRACE_ITER_NOTRACE &&
+	     ftrace_hash_empty(ops->notrace_hash))) {
 		if (*pos > 0)
 			return t_hash_start(m, pos);
 		iter->flags |= FTRACE_ITER_PRINTALL;
···
 		return t_hash_show(m, iter);
 
 	if (iter->flags & FTRACE_ITER_PRINTALL) {
-		seq_printf(m, "#### all functions enabled ####\n");
+		if (iter->flags & FTRACE_ITER_NOTRACE)
+			seq_printf(m, "#### no functions disabled ####\n");
+		else
+			seq_printf(m, "#### all functions enabled ####\n");
 		return 0;
 	}
 
···
 		return 0;
 
 	seq_printf(m, "%ps", (void *)rec->ip);
-	if (iter->flags & FTRACE_ITER_ENABLED)
+	if (iter->flags & FTRACE_ITER_ENABLED) {
 		seq_printf(m, " (%ld)%s",
-			   rec->flags & ~FTRACE_FL_MASK,
-			   rec->flags & FTRACE_FL_REGS ? " R" : "");
+			   ftrace_rec_count(rec),
+			   rec->flags & FTRACE_FL_REGS ? " R" : "  ");
+		if (rec->flags & FTRACE_FL_TRAMP_EN) {
+			struct ftrace_ops *ops;
+
+			ops = ftrace_find_tramp_ops_curr(rec);
+			if (ops && ops->trampoline)
+				seq_printf(m, "\ttramp: %pS",
+					   (void *)ops->trampoline);
+			else
+				seq_printf(m, "\ttramp: ERROR!");
+		}
+	}	
+
 	seq_printf(m, "\n");
 
 	return 0;
···
 	}
 
 	return iter ? 0 : -ENOMEM;
-}
-
-static void ftrace_filter_reset(struct ftrace_hash *hash)
-{
-	mutex_lock(&ftrace_lock);
-	ftrace_hash_clear(hash);
-	mutex_unlock(&ftrace_lock);
 }
 
 /**
···
 		hash = ops->filter_hash;
 
 	if (file->f_mode & FMODE_WRITE) {
-		iter->hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);
+		const int size_bits = FTRACE_HASH_DEFAULT_BITS;
+
+		if (file->f_flags & O_TRUNC)
+			iter->hash = alloc_ftrace_hash(size_bits);
+		else
+			iter->hash = alloc_and_copy_ftrace_hash(size_bits, hash);
+
 		if (!iter->hash) {
 			trace_parser_put(&iter->parser);
 			kfree(iter);
···
 			goto out_unlock;
 		}
 	}
-
-	if ((file->f_mode & FMODE_WRITE) &&
-	    (file->f_flags & O_TRUNC))
-		ftrace_filter_reset(iter->hash);
 
 	if (file->f_mode & FMODE_READ) {
 		iter->pg = ftrace_pages_start;
···
 	else
 		orig_hash = &ops->notrace_hash;
 
-	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
+	if (reset)
+		hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
+	else
+		hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
+
 	if (!hash) {
 		ret = -ENOMEM;
 		goto out_regex_unlock;
 	}
 
-	if (reset)
-		ftrace_filter_reset(hash);
 	if (buf && !ftrace_match_records(hash, buf, len)) {
 		ret = -EINVAL;
 		goto out_regex_unlock;
···
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
+static char ftrace_graph_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
 static int ftrace_set_func(unsigned long *array, int *idx, int size, char *buffer);
 
 static int __init set_graph_function(char *str)
···
 }
 __setup("ftrace_graph_filter=", set_graph_function);
 
-static void __init set_ftrace_early_graph(char *buf)
+static int __init set_graph_notrace_function(char *str)
+{
+	strlcpy(ftrace_graph_notrace_buf, str, FTRACE_FILTER_SIZE);
+	return 1;
+}
+__setup("ftrace_graph_notrace=", set_graph_notrace_function);
+
+static void __init set_ftrace_early_graph(char *buf, int enable)
 {
 	int ret;
 	char *func;
+	unsigned long *table = ftrace_graph_funcs;
+	int *count = &ftrace_graph_count;
+
+	if (!enable) {
+		table = ftrace_graph_notrace_funcs;
+		count = &ftrace_graph_notrace_count;
+	}
 
 	while (buf) {
 		func = strsep(&buf, ",");
 		/* we allow only one expression at a time */
-		ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
-				      FTRACE_GRAPH_MAX_FUNCS, func);
+		ret = ftrace_set_func(table, count, FTRACE_GRAPH_MAX_FUNCS, func);
 		if (ret)
 			printk(KERN_DEBUG "ftrace: function %s not "
 					  "traceable\n", func);
···
 		ftrace_set_early_filter(&global_ops, ftrace_notrace_buf, 0);
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	if (ftrace_graph_buf[0])
-		set_ftrace_early_graph(ftrace_graph_buf);
+		set_ftrace_early_graph(ftrace_graph_buf, 1);
+	if (ftrace_graph_notrace_buf[0])
+		set_ftrace_early_graph(ftrace_graph_notrace_buf, 0);
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 }
 
···
 		return 0;
 
 	if (ptr == (unsigned long *)1) {
-		seq_printf(m, "#### all functions enabled ####\n");
+		struct ftrace_graph_data *fgd = m->private;
+
+		if (fgd->table == ftrace_graph_funcs)
+			seq_printf(m, "#### all functions enabled ####\n");
+		else
+			seq_printf(m, "#### no functions disabled ####\n");
 		return 0;
 	}
 
···
 	struct ftrace_ops *op;
 	int bit;
 
-	if (function_trace_stop)
-		return;
-
 	bit = trace_test_and_set_recursion(TRACE_LIST_START, TRACE_LIST_MAX);
 	if (bit < 0)
 		return;
···
 	preempt_disable_notrace();
 	do_for_each_ftrace_op(op, ftrace_ops_list) {
 		if (ftrace_ops_test(op, ip, regs)) {
-			if (WARN_ON(!op->func)) {
-				function_trace_stop = 1;
-				printk("op=%p %pS\n", op, op);
+			if (FTRACE_WARN_ON(!op->func)) {
+				pr_warn("op=%p %pS\n", op, op);
 				goto out;
 			}
 			op->func(ip, parent_ip, op, regs);
···
 	/* Function graph doesn't use the .func field of global_ops */
 	global_ops.flags |= FTRACE_OPS_FL_STUB;
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+	/* Optimize function graph calling (if implemented by arch) */
+	if (FTRACE_GRAPH_TRAMP_ADDR != 0)
+		global_ops.trampoline = FTRACE_GRAPH_TRAMP_ADDR;
+#endif
+
 	ret = ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);
 
 out:
···
 	__ftrace_graph_entry = ftrace_graph_entry_stub;
 	ftrace_shutdown(&global_ops, FTRACE_STOP_FUNC_RET);
 	global_ops.flags &= ~FTRACE_OPS_FL_STUB;
+#ifdef CONFIG_DYNAMIC_FTRACE
+	if (FTRACE_GRAPH_TRAMP_ADDR != 0)
+		global_ops.trampoline = 0;
+#endif
 	unregister_pm_notifier(&ftrace_suspend_notifier);
 	unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
 
···
 	barrier();
 
 	kfree(ret_stack);
-}
-
-void ftrace_graph_stop(void)
-{
-	ftrace_stop();
 }
 #endif

kernel/trace/ring_buffer.c

···
 			if (!cpu_buffer->nr_pages_to_update)
 				continue;
 
-			/* The update must run on the CPU that is being updated. */
-			preempt_disable();
-			if (cpu == smp_processor_id() || !cpu_online(cpu)) {
+			/* Can't run something on an offline CPU. */
+			if (!cpu_online(cpu)) {
 				rb_update_pages(cpu_buffer);
 				cpu_buffer->nr_pages_to_update = 0;
 			} else {
-				/*
-				 * Can not disable preemption for schedule_work_on()
-				 * on PREEMPT_RT.
-				 */
-				preempt_enable();
 				schedule_work_on(cpu,
 						&cpu_buffer->update_pages_work);
-				preempt_disable();
 			}
-			preempt_enable();
 		}
 
 		/* wait for all the updates to complete */
···
 
 		get_online_cpus();
 
-		preempt_disable();
-		/* The update must run on the CPU that is being updated. */
-		if (cpu_id == smp_processor_id() || !cpu_online(cpu_id))
+		/* Can't run something on an offline CPU. */
+		if (!cpu_online(cpu_id))
 			rb_update_pages(cpu_buffer);
 		else {
-			/*
-			 * Can not disable preemption for schedule_work_on()
-			 * on PREEMPT_RT.
-			 */
-			preempt_enable();
 			schedule_work_on(cpu_id,
 					 &cpu_buffer->update_pages_work);
 			wait_for_completion(&cpu_buffer->update_done);
-			preempt_disable();
 		}
-		preempt_enable();
 
 		cpu_buffer->nr_pages_to_update = 0;
 		put_online_cpus();
···
 	if (rb_per_cpu_empty(cpu_buffer))
 		return NULL;
 
-	if (iter->head >= local_read(&iter->head_page->page->commit)) {
+	if (iter->head >= rb_page_size(iter->head_page)) {
 		rb_inc_iter(iter);
 		goto again;
 	}

kernel/trace/trace.c

···
 	return ret;
 }
 
-ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
-{
-	int len;
-	int ret;
-
-	if (!cnt)
-		return 0;
-
-	if (s->len <= s->readpos)
-		return -EBUSY;
-
-	len = s->len - s->readpos;
-	if (cnt > len)
-		cnt = len;
-	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
-	if (ret == cnt)
-		return -EFAULT;
-
-	cnt -= ret;
-
-	s->readpos += cnt;
-	return cnt;
-}
-
 static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 {
 	int len;
···
 #endif
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	"  set_graph_function\t- Trace the nested calls of a function (function_graph)\n"
+	"  set_graph_notrace\t- Do not trace the nested calls of a function (function_graph)\n"
 	"  max_graph_depth\t- Trace a limited depth of nested calls (0 is unlimited)\n"
 #endif
 #ifdef CONFIG_TRACER_SNAPSHOT
···
 }
 
 static ssize_t
-tracing_max_lat_read(struct file *filp, char __user *ubuf,
-		     size_t cnt, loff_t *ppos)
+tracing_nsecs_read(unsigned long *ptr, char __user *ubuf,
+		   size_t cnt, loff_t *ppos)
 {
-	unsigned long *ptr = filp->private_data;
 	char buf[64];
 	int r;
 
···
 }
 
 static ssize_t
-tracing_max_lat_write(struct file *filp, const char __user *ubuf,
-		      size_t cnt, loff_t *ppos)
+tracing_nsecs_write(unsigned long *ptr, const char __user *ubuf,
+		    size_t cnt, loff_t *ppos)
 {
-	unsigned long *ptr = filp->private_data;
 	unsigned long val;
 	int ret;
 
···
 	*ptr = val * 1000;
 
 	return cnt;
+}
+
+static ssize_t
+tracing_thresh_read(struct file *filp, char __user *ubuf,
+		    size_t cnt, loff_t *ppos)
+{
+	return tracing_nsecs_read(&tracing_thresh, ubuf, cnt, ppos);
+}
+
+static ssize_t
+tracing_thresh_write(struct file *filp, const char __user *ubuf,
+		     size_t cnt, loff_t *ppos)
+{
+	struct trace_array *tr = filp->private_data;
+	int ret;
+
+	mutex_lock(&trace_types_lock);
+	ret = tracing_nsecs_write(&tracing_thresh, ubuf, cnt, ppos);
+	if (ret < 0)
+		goto out;
+
+	if (tr->current_trace->update_thresh) {
+		ret = tr->current_trace->update_thresh(tr);
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = cnt;
+out:
+	mutex_unlock(&trace_types_lock);
+
+	return ret;
+}
+
+static ssize_t
+tracing_max_lat_read(struct file *filp, char __user *ubuf,
+		     size_t cnt, loff_t *ppos)
+{
+	return tracing_nsecs_read(filp->private_data, ubuf, cnt, ppos);
+}
+
+static ssize_t
+tracing_max_lat_write(struct file *filp, const char __user *ubuf,
+		      size_t cnt, loff_t *ppos)
+{
+	return tracing_nsecs_write(filp->private_data, ubuf, cnt, ppos);
 }
 
 static int tracing_open_pipe(struct inode *inode, struct file *filp)
···
 
 #endif /* CONFIG_TRACER_SNAPSHOT */
 
+
+static const struct file_operations tracing_thresh_fops = {
+	.open		= tracing_open_generic,
+	.read		= tracing_thresh_read,
+	.write		= tracing_thresh_write,
+	.llseek		= generic_file_llseek,
+};
 
 static const struct file_operations tracing_max_lat_fops = {
 	.open		= tracing_open_generic,
···
 	if (!topts)
 		return;
 
-	for (cnt = 0; topts[cnt].opt; cnt++) {
-		if (topts[cnt].entry)
-			debugfs_remove(topts[cnt].entry);
-	}
+	for (cnt = 0; topts[cnt].opt; cnt++)
+		debugfs_remove(topts[cnt].entry);
 
 	kfree(topts);
 }
···
 	init_tracer_debugfs(&global_trace, d_tracer);
 
 	trace_create_file("tracing_thresh", 0644, d_tracer,
-			&tracing_thresh, &tracing_max_lat_fops);
+			&global_trace, &tracing_thresh_fops);
 
 	trace_create_file("README", 0444, d_tracer,
 			NULL, &tracing_readme_fops);

kernel/trace/trace.h

···
  * @reset: called when one switches to another tracer
  * @start: called when tracing is unpaused (echo 1 > tracing_enabled)
  * @stop: called when tracing is paused (echo 0 > tracing_enabled)
+ * @update_thresh: called when tracing_thresh is updated
  * @open: called when the trace file is opened
  * @pipe_open: called when the trace_pipe file is opened
  * @close: called when the trace file is released
···
 	void			(*reset)(struct trace_array *tr);
 	void			(*start)(struct trace_array *tr);
 	void			(*stop)(struct trace_array *tr);
+	int			(*update_thresh)(struct trace_array *tr);
 	void			(*open)(struct trace_iterator *iter);
 	void			(*pipe_open)(struct trace_iterator *iter);
 	void			(*close)(struct trace_iterator *iter);

kernel/trace/trace_events.c

···
  *
  */
 
+#define pr_fmt(fmt) fmt
+
 #include <linux/workqueue.h>
 #include <linux/spinlock.h>
 #include <linux/kthread.h>
···
 
 	dir->entry = debugfs_create_dir(name, parent);
 	if (!dir->entry) {
-		pr_warning("Failed to create system directory %s\n", name);
+		pr_warn("Failed to create system directory %s\n", name);
 		__put_system(system);
 		goto out_free;
 	}
···
 	if (!entry) {
 		kfree(system->filter);
 		system->filter = NULL;
-		pr_warning("Could not create debugfs '%s/filter' entry\n", name);
+		pr_warn("Could not create debugfs '%s/filter' entry\n", name);
 	}
 
 	trace_create_file("enable", 0644, dir->entry, dir,
···
  out_fail:
 	/* Only print this message if failed on memory allocation */
 	if (!dir || !system)
-		pr_warning("No memory to create event subsystem %s\n",
-			   name);
+		pr_warn("No memory to create event subsystem %s\n", name);
 	return NULL;
 }
 
···
 	name = ftrace_event_name(call);
 	file->dir = debugfs_create_dir(name, d_events);
 	if (!file->dir) {
-		pr_warning("Could not create debugfs '%s' directory\n",
-			   name);
+		pr_warn("Could not create debugfs '%s' directory\n", name);
 		return -1;
 	}
 
···
 	if (list_empty(head)) {
 		ret = call->class->define_fields(call);
 		if (ret < 0) {
-			pr_warning("Could not initialize trace point"
-				   " events/%s\n", name);
+			pr_warn("Could not initialize trace point events/%s\n",
+				name);
 			return -1;
 		}
 	}
···
 	if (call->class->raw_init) {
 		ret = call->class->raw_init(call);
 		if (ret < 0 && ret != -ENOSYS)
-			pr_warn("Could not initialize trace events/%s\n",
-				name);
+			pr_warn("Could not initialize trace events/%s\n", name);
 	}
 
 	return ret;
···
 	list_for_each_entry(call, &ftrace_events, list) {
 		ret = __trace_add_new_event(call, tr);
 		if (ret < 0)
-			pr_warning("Could not create directory for event %s\n",
-				   ftrace_event_name(call));
+			pr_warn("Could not create directory for event %s\n",
+				ftrace_event_name(call));
 	}
 }
 
···
 	list_for_each_entry(file, &tr->events, list) {
 		ret = event_create_dir(tr->event_dir, file);
 		if (ret < 0)
-			pr_warning("Could not create directory for event %s\n",
-				   ftrace_event_name(file->event_call));
+			pr_warn("Could not create directory for event %s\n",
+				ftrace_event_name(file->event_call));
 	}
 }
 
···
 
 		ret = __trace_early_add_new_event(call, tr);
 		if (ret < 0)
-			pr_warning("Could not create early event %s\n",
-				   ftrace_event_name(call));
+			pr_warn("Could not create early event %s\n",
+				ftrace_event_name(call));
 	}
 }
 
···
 	entry = debugfs_create_file("set_event", 0644, parent,
 				    tr, &ftrace_set_event_fops);
 	if (!entry) {
-		pr_warning("Could not create debugfs 'set_event' entry\n");
+		pr_warn("Could not create debugfs 'set_event' entry\n");
 		return -ENOMEM;
 	}
 
 	d_events = debugfs_create_dir("events", parent);
 	if (!d_events) {
-		pr_warning("Could not create debugfs 'events' directory\n");
+		pr_warn("Could not create debugfs 'events' directory\n");
 		return -ENOMEM;
 	}
 
···
 	entry = debugfs_create_file("available_events", 0444, d_tracer,
 				    tr, &ftrace_avail_fops);
 	if (!entry)
-		pr_warning("Could not create debugfs "
-			   "'available_events' entry\n");
+		pr_warn("Could not create debugfs 'available_events' entry\n");
 
 	if (trace_define_common_fields())
-		pr_warning("tracing: Failed to allocate common fields");
+		pr_warn("tracing: Failed to allocate common fields");
 
 	ret = early_event_add_tracer(d_tracer, tr);
 	if (ret)
···
 #ifdef CONFIG_MODULES
 	ret = register_module_notifier(&trace_module_nb);
 	if (ret)
-		pr_warning("Failed to register trace events module notifier\n");
+		pr_warn("Failed to register trace events module notifier\n");
 #endif
 	return 0;
 }
···
 		 * it and the self test should not be on.
 		 */
 		if (file->flags & FTRACE_EVENT_FL_ENABLED) {
-			pr_warning("Enabled event during self test!\n");
+			pr_warn("Enabled event during self test!\n");
 			WARN_ON_ONCE(1);
 			continue;
 		}
···
 
 		ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 1);
 		if (WARN_ON_ONCE(ret)) {
-			pr_warning("error enabling system %s\n",
-				   system->name);
+			pr_warn("error enabling system %s\n",
+				system->name);
 			continue;
 		}
 
···
 
 		ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 0);
 		if (WARN_ON_ONCE(ret)) {
-			pr_warning("error disabling system %s\n",
-				   system->name);
+			pr_warn("error disabling system %s\n",
+				system->name);
 			continue;
 		}
 
···
 
 	ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 1);
 	if (WARN_ON_ONCE(ret)) {
-		pr_warning("error enabling all events\n");
+		pr_warn("error enabling all events\n");
 		return;
 	}
 
···
 	/* reset sysname */
 	ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 0);
 	if (WARN_ON_ONCE(ret)) {
-		pr_warning("error disabling all events\n");
+		pr_warn("error disabling all events\n");
 		return;
 	}
 

kernel/trace/trace_functions_graph.c

···
 #include "trace.h"
 #include "trace_output.h"
 
+static bool kill_ftrace_graph;
+
+/**
+ * ftrace_graph_is_dead - returns true if ftrace_graph_stop() was called
+ *
+ * ftrace_graph_stop() is called when a severe error is detected in
+ * the function graph tracing. This function is called by the critical
+ * paths of function graph to keep those paths from doing any more harm.
+ */
+bool ftrace_graph_is_dead(void)
+{
+	return kill_ftrace_graph;
+}
+
+/**
+ * ftrace_graph_stop - set to permanently disable function graph tracincg
+ *
+ * In case of an error int function graph tracing, this is called
+ * to try to keep function graph tracing from causing any more harm.
+ * Usually this is pretty severe and this is called to try to at least
+ * get a warning out to the user.
+ */
+void ftrace_graph_stop(void)
+{
+	kill_ftrace_graph = true;
+}
+
 /* When set, irq functions will be ignored */
 static int ftrace_graph_skip_irqs;
 
···
 {
 	unsigned long long calltime;
 	int index;
+
+	if (unlikely(ftrace_graph_is_dead()))
+		return -EBUSY;
 
 	if (!current->ret_stack)
 		return -EBUSY;
···
 	return ret;
 }
 
-int trace_graph_thresh_entry(struct ftrace_graph_ent *trace)
+static int trace_graph_thresh_entry(struct ftrace_graph_ent *trace)
 {
 	if (tracing_thresh)
 		return 1;
···
 	smp_mb();
 }
 
-void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
+static void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
 {
 	if (tracing_thresh &&
 	    (trace->rettime - trace->calltime < tracing_thresh))
···
 {
 	tracing_stop_cmdline_record();
 	unregister_ftrace_graph();
+}
+
+static int graph_trace_update_thresh(struct trace_array *tr)
+{
+	graph_trace_reset(tr);
+	return graph_trace_init(tr);
 }
 
 static int max_bytes_for_cpu;
···
 	seq_printf(s, "               |   |   |   |\n");
 }
 
-void print_graph_headers(struct seq_file *s)
+static void print_graph_headers(struct seq_file *s)
 {
 	print_graph_headers_flags(s, tracer_flags.val);
 }
···
 
 static struct tracer graph_trace __tracer_data = {
 	.name		= "function_graph",
+	.update_thresh	= graph_trace_update_thresh,
 	.open		= graph_trace_open,
 	.pipe_open	= graph_trace_open,
 	.close		= graph_trace_close,

kernel/trace/trace_output.c

···
 
 static int next_event_type = __TRACE_LAST_TYPE + 1;
 
-int trace_print_seq(struct seq_file *m, struct trace_seq *s)
-{
-	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
-	int ret;
-
-	ret = seq_write(m, s->buffer, len);
-
-	/*
-	 * Only reset this buffer if we successfully wrote to the
-	 * seq_file buffer.
-	 */
-	if (!ret)
-		trace_seq_init(s);
-
-	return ret;
-}
-
 enum print_line_t trace_print_bputs_msg_only(struct trace_iterator *iter)
 {
 	struct trace_seq *s = &iter->seq;
···
 	return TRACE_TYPE_HANDLED;
 }
 
-/**
- * trace_seq_printf - sequence printing of trace information
- * @s: trace sequence descriptor
- * @fmt: printf format string
- *
- * It returns 0 if the trace oversizes the buffer's free
- * space, 1 otherwise.
- *
- * The tracer may use either sequence operations or its own
- * copy to user routines. To simplify formating of a trace
- * trace_seq_printf is used to store strings into a special
- * buffer (@s). Then the output may be either used by
- * the sequencer or pulled into another buffer.
- */
-int
-trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
-{
-	int len = (PAGE_SIZE - 1) - s->len;
-	va_list ap;
-	int ret;
-
-	if (s->full || !len)
-		return 0;
-
-	va_start(ap, fmt);
-	ret = vsnprintf(s->buffer + s->len, len, fmt, ap);
-	va_end(ap);
-
-	/* If we can't write it all, don't bother writing anything */
-	if (ret >= len) {
-		s->full = 1;
-		return 0;
-	}
-
-	s->len += ret;
-
-	return 1;
-}
-EXPORT_SYMBOL_GPL(trace_seq_printf);
-
-/**
- * trace_seq_bitmask - put a list of longs as a bitmask print output
- * @s:		trace sequence descriptor
- * @maskp:	points to an array of unsigned longs that represent a bitmask
- * @nmaskbits:	The number of bits that are valid in @maskp
- *
- * It returns 0 if the trace oversizes the buffer's free
- * space, 1 otherwise.
- *
- * Writes a ASCII representation of a bitmask string into @s.
- */
-int
-trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
-		  int nmaskbits)
-{
-	int len = (PAGE_SIZE - 1) - s->len;
-	int ret;
-
-	if (s->full || !len)
-		return 0;
-
-	ret = bitmap_scnprintf(s->buffer, len, maskp, nmaskbits);
-	s->len += ret;
-
-	return 1;
-}
-EXPORT_SYMBOL_GPL(trace_seq_bitmask);
-
-/**
- * trace_seq_vprintf - sequence printing of trace information
- * @s: trace sequence descriptor
- * @fmt: printf format string
- *
- * The tracer may use either sequence operations or its own
- * copy to user routines. To simplify formating of a trace
- * trace_seq_printf is used to store strings into a special
- * buffer (@s). Then the output may be either used by
- * the sequencer or pulled into another buffer.
- */
-int
-trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
-{
-	int len = (PAGE_SIZE - 1) - s->len;
-	int ret;
-
-	if (s->full || !len)
-		return 0;
-
-	ret = vsnprintf(s->buffer + s->len, len, fmt, args);
-
-	/* If we can't write it all, don't bother writing anything */
-	if (ret >= len) {
-		s->full = 1;
-		return 0;
-	}
-
-	s->len += ret;
-
-	return len;
-}
-EXPORT_SYMBOL_GPL(trace_seq_vprintf);
-
-int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
-{
-	int len = (PAGE_SIZE - 1) - s->len;
-	int ret;
-
-	if (s->full || !len)
-		return 0;
-
-	ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
-
-	/* If we can't write it all, don't bother writing anything */
-	if (ret >= len) {
-		s->full = 1;
-		return 0;
-	}
-
-	s->len += ret;
-
-	return len;
-}
-
-/**
- * trace_seq_puts - trace sequence printing of simple string
- * @s: trace sequence descriptor
- * @str: simple string to record
- *
- * The tracer may use either the sequence operations or its own
- * copy to user routines. This function records a simple string
- * into a special buffer (@s) for later retrieval by a sequencer
- * or other mechanism.
- */
-int trace_seq_puts(struct trace_seq *s, const char *str)
-{
-	int len = strlen(str);
-
-	if (s->full)
-		return 0;
-
-	if (len > ((PAGE_SIZE - 1) - s->len)) {
-		s->full = 1;
-		return 0;
-	}
-
-	memcpy(s->buffer + s->len, str, len);
-	s->len += len;
-
-	return len;
-}
-
-int trace_seq_putc(struct trace_seq *s, unsigned char c)
-{
-	if (s->full)
-		return 0;
-
-	if (s->len >= (PAGE_SIZE - 1)) {
-		s->full = 1;
-		return 0;
-	}
-
-	s->buffer[s->len++] = c;
-
-	return 1;
-}
-EXPORT_SYMBOL(trace_seq_putc);
-
-int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len)
-{
-	if (s->full)
-		return 0;
-
-	if (len > ((PAGE_SIZE - 1) - s->len)) {
-		s->full = 1;
-		return 0;
-	}
-
-	memcpy(s->buffer + s->len, mem, len);
-	s->len += len;
-
-	return len;
-}
-
-int trace_seq_putmem_hex(struct trace_seq *s, const void *mem, size_t len)
-{
-	unsigned char hex[HEX_CHARS];
-	const unsigned char *data = mem;
-	int i, j;
-
-	if (s->full)
-		return 0;
-
-#ifdef __BIG_ENDIAN
-	for (i = 0, j = 0; i < len; i++) {
-#else
-	for (i = len-1, j = 0; i >= 0; i--) {
-#endif
-		hex[j++] = hex_asc_hi(data[i]);
-		hex[j++] = hex_asc_lo(data[i]);
-	}
-	hex[j++] = ' ';
-
-	return trace_seq_putmem(s, hex, j);
-}
-
-void *trace_seq_reserve(struct trace_seq *s, size_t len)
-{
-	void *ret;
-
-	if (s->full)
-		return NULL;
-
-	if (len > ((PAGE_SIZE - 1) - s->len)) {
-		s->full = 1;
-		return NULL;
-	}
-
-	ret = s->buffer + s->len;
-	s->len += len;
-
-	return ret;
-}
-
-int trace_seq_path(struct trace_seq *s, const struct path *path)
-{
-	unsigned char *p;
-
-	if (s->full)
-		return 0;
-
-	if (s->len >= (PAGE_SIZE - 1)) {
-		s->full = 1;
-		return 0;
-	}
-
-	p = d_path(path, s->buffer + s->len, PAGE_SIZE - s->len);
-	if (!IS_ERR(p)) {
-		p = mangle_path(s->buffer + s->len, p, "\n");
-		if (p) {
-			s->len = p - s->buffer;
-			return 1;
-		}
-	} else {
-		s->buffer[s->len++] = '?';
-		return 1;
-	}
-
-	s->full = 1;
-	return 0;
-}
-
 const char *
 ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
 		       unsigned long flags,
···
 {
 	unsigned long mask;
 	const char *str;
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 	int i, first = 1;
 
 	for (i = 0;  flag_array[i].name && flags; i++) {
···
 			 const struct trace_print_flags *symbol_array)
 {
 	int i;
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 
 	for (i = 0;  symbol_array[i].name; i++) {
 
···
 		break;
 	}
 
-	if (ret == (const char *)(p->buffer + p->len))
+	if (ret == (const char *)(trace_seq_buffer_ptr(p)))
 		trace_seq_printf(p, "0x%lx", val);
 		
 	trace_seq_putc(p, 0);
···
 			 const struct trace_print_flags_u64 *symbol_array)
 {
 	int i;
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 
 	for (i = 0;  symbol_array[i].name; i++) {
 
···
 		break;
 	}
 
-	if (ret == (const char *)(p->buffer + p->len))
+	if (ret == (const char *)(trace_seq_buffer_ptr(p)))
 		trace_seq_printf(p, "0x%llx", val);
 
 	trace_seq_putc(p, 0);
···
 ftrace_print_bitmask_seq(struct trace_seq *p, void *bitmask_ptr,
 			 unsigned int bitmask_size)
 {
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 
 	trace_seq_bitmask(p, bitmask_ptr, bitmask_size * 8);
 	trace_seq_putc(p, 0);
···
 ftrace_print_hex_seq(struct trace_seq *p, const unsigned char *buf, int buf_len)
 {
 	int i;
-	const char *ret = p->buffer + p->len;
+	const char *ret = trace_seq_buffer_ptr(p);
 
 	for (i = 0; i < buf_len; i++)
 		trace_seq_printf(p, "%s%2.2x", i == 0 ? "" : " ", buf[i]);

kernel/trace/trace_output.h

···
 extern int __unregister_ftrace_event(struct trace_event *event);
 extern struct rw_semaphore trace_event_sem;
 
-#define MAX_MEMHEX_BYTES	8
-#define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)
-
 #define SEQ_PUT_FIELD_RET(s, x)				\
 do {							\
 	if (!trace_seq_putmem(s, &(x), sizeof(x)))	\
···
 
 #define SEQ_PUT_HEX_FIELD_RET(s, x)			\
 do {							\
-	BUILD_BUG_ON(sizeof(x) > MAX_MEMHEX_BYTES);	\
 	if (!trace_seq_putmem_hex(s, &(x), sizeof(x)))	\
 		return TRACE_TYPE_PARTIAL_LINE;		\
 } while (0)

kernel/trace/trace_seq.c

···
+/*
+ * trace_seq.c
+ *
+ * Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt <[e-mail]>
+ *
+ * The trace_seq is a handy tool that allows you to pass a descriptor around
+ * to a buffer that other functions can write to. It is similar to the
+ * seq_file functionality but has some differences.
+ *
+ * To use it, the trace_seq must be initialized with trace_seq_init().
+ * This will set up the counters within the descriptor. You can call
+ * trace_seq_init() more than once to reset the trace_seq to start
+ * from scratch.
+ * 
+ * The buffer size is currently PAGE_SIZE, although it may become dynamic
+ * in the future.
+ *
+ * A write to the buffer will either succed or fail. That is, unlike
+ * sprintf() there will not be a partial write (well it may write into
+ * the buffer but it wont update the pointers). This allows users to
+ * try to write something into the trace_seq buffer and if it fails
+ * they can flush it and try again.
+ *
+ */
+#include <linux/uaccess.h>
+#include <linux/seq_file.h>
+#include <linux/trace_seq.h>
+
+/* How much buffer is left on the trace_seq? */
+#define TRACE_SEQ_BUF_LEFT(s) ((PAGE_SIZE - 1) - (s)->len)
+
+/* How much buffer is written? */
+#define TRACE_SEQ_BUF_USED(s) min((s)->len, (unsigned int)(PAGE_SIZE - 1))
+
+/**
+ * trace_print_seq - move the contents of trace_seq into a seq_file
+ * @m: the seq_file descriptor that is the destination
+ * @s: the trace_seq descriptor that is the source.
+ *
+ * Returns 0 on success and non zero on error. If it succeeds to
+ * write to the seq_file it will reset the trace_seq, otherwise
+ * it does not modify the trace_seq to let the caller try again.
+ */
+int trace_print_seq(struct seq_file *m, struct trace_seq *s)
+{
+	unsigned int len = TRACE_SEQ_BUF_USED(s);
+	int ret;
+
+	ret = seq_write(m, s->buffer, len);
+
+	/*
+	 * Only reset this buffer if we successfully wrote to the
+	 * seq_file buffer. This lets the caller try again or
+	 * do something else with the contents.
+	 */
+	if (!ret)
+		trace_seq_init(s);
+
+	return ret;
+}
+
+/**
+ * trace_seq_printf - sequence printing of trace information
+ * @s: trace sequence descriptor
+ * @fmt: printf format string
+ *
+ * The tracer may use either sequence operations or its own
+ * copy to user routines. To simplify formating of a trace
+ * trace_seq_printf() is used to store strings into a special
+ * buffer (@s). Then the output may be either used by
+ * the sequencer or pulled into another buffer.
+ *
+ * Returns 1 if we successfully written all the contents to
+ *   the buffer.
+  * Returns 0 if we the length to write is bigger than the
+ *   reserved buffer space. In this case, nothing gets written.
+ */
+int trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
+{
+	unsigned int len = TRACE_SEQ_BUF_LEFT(s);
+	va_list ap;
+	int ret;
+
+	if (s->full || !len)
+		return 0;
+
+	va_start(ap, fmt);
+	ret = vsnprintf(s->buffer + s->len, len, fmt, ap);
+	va_end(ap);
+
+	/* If we can't write it all, don't bother writing anything */
+	if (ret >= len) {
+		s->full = 1;
+		return 0;
+	}
+
+	s->len += ret;
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(trace_seq_printf);
+
+/**
+ * trace_seq_bitmask - write a bitmask array in its ASCII representation
+ * @s:		trace sequence descriptor
+ * @maskp:	points to an array of unsigned longs that represent a bitmask
+ * @nmaskbits:	The number of bits that are valid in @maskp
+ *
+ * Writes a ASCII representation of a bitmask string into @s.
+ *
+ * Returns 1 if we successfully written all the contents to
+ *   the buffer.
+ * Returns 0 if we the length to write is bigger than the
+ *   reserved buffer space. In this case, nothing gets written.
+ */
+int trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
+		      int nmaskbits)
+{
+	unsigned int len = TRACE_SEQ_BUF_LEFT(s);
+	int ret;
+
+	if (s->full || !len)
+		return 0;
+
+	ret = bitmap_scnprintf(s->buffer, len, maskp, nmaskbits);
+	s->len += ret;
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(trace_seq_bitmask);
+
+/**
+ * trace_seq_vprintf - sequence printing of trace information
+ * @s: trace sequence descriptor
+ * @fmt: printf format string
+ *
+ * The tracer may use either sequence operations or its own
+ * copy to user routines. To simplify formating of a trace
+ * trace_seq_printf is used to store strings into a special
+ * buffer (@s). Then the output may be either used by
+ * the sequencer or pulled into another buffer.
+ *
+ * Returns how much it wrote to the buffer.
+ */
+int trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
+{
+	unsigned int len = TRACE_SEQ_BUF_LEFT(s);
+	int ret;
+
+	if (s->full || !len)
+		return 0;
+
+	ret = vsnprintf(s->buffer + s->len, len, fmt, args);
+
+	/* If we can't write it all, don't bother writing anything */
+	if (ret >= len) {
+		s->full = 1;
+		return 0;
+	}
+
+	s->len += ret;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(trace_seq_vprintf);
+
+/**
+ * trace_seq_bprintf - Write the printf string from binary arguments
+ * @s: trace sequence descriptor
+ * @fmt: The format string for the @binary arguments
+ * @binary: The binary arguments for @fmt.
+ *
+ * When recording in a fast path, a printf may be recorded with just
+ * saving the format and the arguments as they were passed to the
+ * function, instead of wasting cycles converting the arguments into
+ * ASCII characters. Instead, the arguments are saved in a 32 bit
+ * word array that is defined by the format string constraints.
+ *
+ * This function will take the format and the binary array and finish
+ * the conversion into the ASCII string within the buffer.
+ *
+ * Returns how much it wrote to the buffer.
+ */
+int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
+{
+	unsigned int len = TRACE_SEQ_BUF_LEFT(s);
+	int ret;
+
+	if (s->full || !len)
+		return 0;
+
+	ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
+
+	/* If we can't write it all, don't bother writing anything */
+	if (ret >= len) {
+		s->full = 1;
+		return 0;
+	}
+
+	s->len += ret;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(trace_seq_bprintf);
+
+/**
+ * trace_seq_puts - trace sequence printing of simple string
+ * @s: trace sequence descriptor
+ * @str: simple string to record
+ *
+ * The tracer may use either the sequence operations or its own
+ * copy to user routines. This function records a simple string
+ * into a special buffer (@s) for later retrieval by a sequencer
+ * or other mechanism.
+ *
+ * Returns how much it wrote to the buffer.
+ */
+int trace_seq_puts(struct trace_seq *s, const char *str)
+{
+	unsigned int len = strlen(str);
+
+	if (s->full)
+		return 0;
+
+	if (len > TRACE_SEQ_BUF_LEFT(s)) {
+		s->full = 1;
+		return 0;
+	}
+
+	memcpy(s->buffer + s->len, str, len);
+	s->len += len;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(trace_seq_puts);
+
+/**
+ * trace_seq_putc - trace sequence printing of simple character
+ * @s: trace sequence descriptor
+ * @c: simple character to record
+ *
+ * The tracer may use either the sequence operations or its own
+ * copy to user routines. This function records a simple charater
+ * into a special buffer (@s) for later retrieval by a sequencer
+ * or other mechanism.
+ *
+ * Returns how much it wrote to the buffer.
+ */
+int trace_seq_putc(struct trace_seq *s, unsigned char c)
+{
+	if (s->full)
+		return 0;
+
+	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
+		s->full = 1;
+		return 0;
+	}
+
+	s->buffer[s->len++] = c;
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(trace_seq_putc);
+
+/**
+ * trace_seq_putmem - write raw data into the trace_seq buffer
+ * @s: trace sequence descriptor
+ * @mem: The raw memory to copy into the buffer
+ * @len: The length of the raw memory to copy (in bytes)
+ *
+ * There may be cases where raw memory needs to be written into the
+ * buffer and a strcpy() would not work. Using this function allows
+ * for such cases.
+ *
+ * Returns how much it wrote to the buffer.
+ */
+int trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
+{
+	if (s->full)
+		return 0;
+
+	if (len > TRACE_SEQ_BUF_LEFT(s)) {
+		s->full = 1;
+		return 0;
+	}
+
+	memcpy(s->buffer + s->len, mem, len);
+	s->len += len;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(trace_seq_putmem);
+
+#define MAX_MEMHEX_BYTES	8U
+#define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)
+
+/**
+ * trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
+ * @s: trace sequence descriptor
+ * @mem: The raw memory to write its hex ASCII representation of
+ * @len: The length of the raw memory to copy (in bytes)
+ *
+ * This is similar to trace_seq_putmem() except instead of just copying the
+ * raw memory into the buffer it writes its ASCII representation of it
+ * in hex characters.
+ *
+ * Returns how much it wrote to the buffer.
+ */
+int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
+			 unsigned int len)
+{
+	unsigned char hex[HEX_CHARS];
+	const unsigned char *data = mem;
+	unsigned int start_len;
+	int i, j;
+	int cnt = 0;
+
+	if (s->full)
+		return 0;
+
+	while (len) {
+		start_len = min(len, HEX_CHARS - 1);
+#ifdef __BIG_ENDIAN
+		for (i = 0, j = 0; i < start_len; i++) {
+#else
+		for (i = start_len-1, j = 0; i >= 0; i--) {
+#endif
+			hex[j++] = hex_asc_hi(data[i]);
+			hex[j++] = hex_asc_lo(data[i]);
+		}
+		if (WARN_ON_ONCE(j == 0 || j/2 > len))
+			break;
+
+		/* j increments twice per loop */
+		len -= j / 2;
+		hex[j++] = ' ';
+
+		cnt += trace_seq_putmem(s, hex, j);
+	}
+	return cnt;
+}
+EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
+
+/**
+ * trace_seq_path - copy a path into the sequence buffer
+ * @s: trace sequence descriptor
+ * @path: path to write into the sequence buffer.
+ *
+ * Write a path name into the sequence buffer.
+ *
+ * Returns 1 if we successfully written all the contents to
+ *   the buffer.
+ * Returns 0 if we the length to write is bigger than the
+ *   reserved buffer space. In this case, nothing gets written.
+ */
+int trace_seq_path(struct trace_seq *s, const struct path *path)
+{
+	unsigned char *p;
+
+	if (s->full)
+		return 0;
+
+	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
+		s->full = 1;
+		return 0;
+	}
+
+	p = d_path(path, s->buffer + s->len, PAGE_SIZE - s->len);
+	if (!IS_ERR(p)) {
+		p = mangle_path(s->buffer + s->len, p, "\n");
+		if (p) {
+			s->len = p - s->buffer;
+			return 1;
+		}
+	} else {
+		s->buffer[s->len++] = '?';
+		return 1;
+	}
+
+	s->full = 1;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(trace_seq_path);
+
+/**
+ * trace_seq_to_user - copy the squence buffer to user space
+ * @s: trace sequence descriptor
+ * @ubuf: The userspace memory location to copy to
+ * @cnt: The amount to copy
+ *
+ * Copies the sequence buffer into the userspace memory pointed to
+ * by @ubuf. It starts from the last read position (@s->readpos)
+ * and writes up to @cnt characters or till it reaches the end of
+ * the content in the buffer (@s->len), which ever comes first.
+ *
+ * On success, it returns a positive number of the number of bytes
+ * it copied.
+ *
+ * On failure it returns -EBUSY if all of the content in the
+ * sequence has been already read, which includes nothing in the
+ * sequenc (@s->len == @s->readpos).
+ *
+ * Returns -EFAULT if the copy to userspace fails.
+ */
+int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
+{
+	int len;
+	int ret;
+
+	if (!cnt)
+		return 0;
+
+	if (s->len <= s->readpos)
+		return -EBUSY;
+
+	len = s->len - s->readpos;
+	if (cnt > len)
+		cnt = len;
+	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
+	if (ret == cnt)
+		return -EFAULT;
+
+	cnt -= ret;
+
+	s->readpos += cnt;
+	return cnt;
+}
+EXPORT_SYMBOL_GPL(trace_seq_to_user);

samples/trace_events/trace-events-sample.h

···
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->foo, foo, 10);
+		strlcpy(__entry->foo, foo, 10);
 		__entry->bar	= bar;
 	),