[tip:perf/urgent] tracing/syscalls: Fix perf syscall tracing when syscall_nr == -1

[tip-bot for Will Deacon]

Commit-ID:  60916a9382e88fbf5e54fd36a3e658efd7ab7bed
Gitweb:     http://git.kernel.org/tip/60916a9382e88fbf5e54fd36a3e658efd7ab7bed
Author:     Will Deacon <will.deacon@xxxxxxx>
AuthorDate: Thu, 16 Aug 2012 18:14:14 +0100
Committer:  Steven Rostedt <rostedt@xxxxxxxxxxx>
CommitDate: Fri, 17 Aug 2012 15:19:46 -0400

tracing/syscalls: Fix perf syscall tracing when syscall_nr == -1

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@xxxxxxx

Cc: Jason Baron <jbaron@xxxxxxxxxx>
Cc: Wade Farnsworth <wade_farnsworth@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_syscalls.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 60e4d78..6b245f64 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -506,6 +506,8 @@ 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;
 
@@ -580,6 +582,8 @@ 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;
 
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