tracing/syscalls: Early terminate search for sys_ni_syscall

Many system calls are unimplemented and mapped to sys_ni_syscall, but at
boot ftrace would still search through every syscall metadata entry for
a match which wouldn't be there.

This patch adds causes the search to terminate early if the system call
is not mapped.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
LKML-Reference: <1296703645-18718-7-git-send-email-imunsie@au1.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 86a23e7de031..ee7b5a0bb9f8 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -85,6 +85,9 @@ find_syscall_meta(unsigned long syscall)
         stop = __stop_syscalls_metadata;
         kallsyms_lookup(syscall, NULL, NULL, NULL, str);
 
+        if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
+                return NULL;
+
         for ( ; start < stop; start++) {
                 if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
                         return *start;