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@arm.com

Cc: Jason Baron <jbaron@redhat.com>
Cc: Wade Farnsworth <wade_farnsworth@mentor.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 60e4d7875672..6b245f64c8dd 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;