[S390] ftrace: add system call tracer support

System call tracer support for s390.

Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/Kconfig

···
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_FTRACE_MCOUNT_RECORD
+	select HAVE_FTRACE_SYSCALLS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_DEFAULT_NO_SPIN_MUTEXES

arch/s390/include/asm/syscall.h

···
 #ifndef _ASM_SYSCALL_H
 #define _ASM_SYSCALL_H	1
 
+#include <linux/sched.h>
 #include <asm/ptrace.h>
 
 static inline long syscall_get_nr(struct task_struct *task,

arch/s390/include/asm/thread_info.h

···
 #define TIF_SYSCALL_TRACE	8	/* syscall trace active */
 #define TIF_SYSCALL_AUDIT	9	/* syscall auditing active */
 #define TIF_SECCOMP		10	/* secure computing */
+#define TIF_SYSCALL_FTRACE	11	/* ftrace syscall instrumentation */
 #define TIF_USEDFPU		16	/* FPU was used by this task this quantum (SMP) */
 #define TIF_POLLING_NRFLAG	17	/* true if poll_idle() is polling 
 					   TIF_NEED_RESCHED */
···
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP		(1<<TIF_SECCOMP)
+#define _TIF_SYSCALL_FTRACE	(1<<TIF_SYSCALL_FTRACE)
 #define _TIF_USEDFPU		(1<<TIF_USEDFPU)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
 #define _TIF_31BIT		(1<<TIF_31BIT)

arch/s390/kernel/entry.S

···
 		 _TIF_MCCK_PENDING | _TIF_RESTART_SVC | _TIF_SINGLE_STEP )
 _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
 		 _TIF_MCCK_PENDING)
-_TIF_SYSCALL = (_TIF_SYSCALL_TRACE>>8 | _TIF_SYSCALL_AUDIT>>8 | _TIF_SECCOMP>>8)
+_TIF_SYSCALL = (_TIF_SYSCALL_TRACE>>8 | _TIF_SYSCALL_AUDIT>>8 | \
+		_TIF_SECCOMP>>8 | _TIF_SYSCALL_FTRACE>>8)
 
 STACK_SHIFT = PAGE_SHIFT + THREAD_ORDER
 STACK_SIZE  = 1 << STACK_SHIFT
···
 
 		.section .rodata, "a"
 #define SYSCALL(esa,esame,emu)	.long esa
+	.globl	sys_call_table
 sys_call_table:
 #include "syscalls.S"
 #undef SYSCALL

arch/s390/kernel/entry64.S

···
 		 _TIF_MCCK_PENDING | _TIF_RESTART_SVC | _TIF_SINGLE_STEP )
 _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
 		 _TIF_MCCK_PENDING)
-_TIF_SYSCALL = (_TIF_SYSCALL_TRACE>>8 | _TIF_SYSCALL_AUDIT>>8 | _TIF_SECCOMP>>8)
+_TIF_SYSCALL = (_TIF_SYSCALL_TRACE>>8 | _TIF_SYSCALL_AUDIT>>8 | \
+		_TIF_SECCOMP>>8 | _TIF_SYSCALL_FTRACE>>8)
 
 #define BASED(name) name-system_call(%r13)
 
···
 
 		.section .rodata, "a"
 #define SYSCALL(esa,esame,emu)	.long esame
+	.globl	sys_call_table
 sys_call_table:
 #include "syscalls.S"
 #undef SYSCALL

arch/s390/kernel/ftrace.c

···
 #include <linux/ftrace.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
+#include <trace/syscall.h>
 #include <asm/lowcore.h>
 
 #ifdef CONFIG_DYNAMIC_FTRACE
···
 	return parent;
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+#ifdef CONFIG_FTRACE_SYSCALLS
+
+extern unsigned long __start_syscalls_metadata[];
+extern unsigned long __stop_syscalls_metadata[];
+extern unsigned int sys_call_table[];
+
+static struct syscall_metadata **syscalls_metadata;
+
+struct syscall_metadata *syscall_nr_to_meta(int nr)
+{
+	if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
+		return NULL;
+
+	return syscalls_metadata[nr];
+}
+
+static struct syscall_metadata *find_syscall_meta(unsigned long syscall)
+{
+	struct syscall_metadata *start;
+	struct syscall_metadata *stop;
+	char str[KSYM_SYMBOL_LEN];
+
+	start = (struct syscall_metadata *)__start_syscalls_metadata;
+	stop = (struct syscall_metadata *)__stop_syscalls_metadata;
+	kallsyms_lookup(syscall, NULL, NULL, NULL, str);
+
+	for ( ; start < stop; start++) {
+		if (start->name && !strcmp(start->name + 3, str + 3))
+			return start;
+	}
+	return NULL;
+}
+
+void arch_init_ftrace_syscalls(void)
+{
+	struct syscall_metadata *meta;
+	int i;
+	static atomic_t refs;
+
+	if (atomic_inc_return(&refs) != 1)
+		goto out;
+	syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) * NR_syscalls,
+				    GFP_KERNEL);
+	if (!syscalls_metadata)
+		goto out;
+	for (i = 0; i < NR_syscalls; i++) {
+		meta = find_syscall_meta((unsigned long)sys_call_table[i]);
+		syscalls_metadata[i] = meta;
+	}
+	return;
+out:
+	atomic_dec(&refs);
+}
+#endif

arch/s390/kernel/ptrace.c

···
 #include <linux/regset.h>
 #include <linux/tracehook.h>
 #include <linux/seccomp.h>
+#include <trace/syscall.h>
 #include <asm/compat.h>
 #include <asm/segment.h>
 #include <asm/page.h>
···
 		ret = -1;
 	}
 
+	if (unlikely(test_thread_flag(TIF_SYSCALL_FTRACE)))
+		ftrace_syscall_enter(regs);
+
 	if (unlikely(current->audit_context))
 		audit_syscall_entry(is_compat_task() ?
 					AUDIT_ARCH_S390 : AUDIT_ARCH_S390X,
···
 	if (unlikely(current->audit_context))
 		audit_syscall_exit(AUDITSC_RESULT(regs->gprs[2]),
 				   regs->gprs[2]);
+
+	if (unlikely(test_thread_flag(TIF_SYSCALL_FTRACE)))
+		ftrace_syscall_exit(regs);
 
 	if (test_thread_flag(TIF_SYSCALL_TRACE))
 		tracehook_report_syscall_exit(regs, 0);