[PATCH 3.4 119/177] tracing/syscalls: Fix perf syscall tracing when syscall_nr == -1

From: Will Deacon <redacted>

3.4.106-rc1 review patch.  If anyone has any objections, please let me know.

------------------


commit 60916a9382e88fbf5e54fd36a3e658efd7ab7bed upstream.

syscall_get_nr can return -1 in the case that the task is not executing
a system call.

This patch fixes perf_syscall_{enter,exit} to check that the syscall
number is valid before using it as an index into a bitmap.

Link: http://lkml.kernel.org/r/1345137254-7377-1-git-send-email-will.deacon@arm.com

Cc: Jason Baron <redacted>
Cc: Wade Farnsworth <redacted>
Cc: Frederic Weisbecker <redacted>
Signed-off-by: Will Deacon <redacted>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Zefan Li <redacted>
---
 kernel/trace/trace_syscalls.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index c9ce09a..aed38fd 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c

@@ -519,6 +519,8 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 	int size;
 
 	syscall_nr = syscall_get_nr(current, regs);
+	if (syscall_nr < 0)
+		return;
 	if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 		return;
 

@@ -593,6 +595,8 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 	int size;
 
 	syscall_nr = syscall_get_nr(current, regs);
+	if (syscall_nr < 0)
+		return;
 	if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 		return;
 

-- 
1.9.1