linux-kernel - [PATCH 36/40] trace syscalls: Early terminate search for sys_ni

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Date:	Wed, 23 Jun 2010 20:03:17 +1000
From:	"Ian Munsie" <imunsie@....ibm.com>
To:	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Cc:	Jason Baron <jbaron@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <michael@...erman.id.au>,
	Ian Munsie <imunsie@....ibm.com>,
	Masami Hiramatsu <mhiramat@...hat.com>
Subject: [PATCH 36/40] trace syscalls: Early terminate search for sys_ni_syscall

From: Ian Munsie <imunsie@....ibm.com>

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@....ibm.com>
---
 kernel/trace/trace_syscalls.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 264441e..58ef002 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -95,6 +95,9 @@ static struct syscall_metadata *find_syscall_meta(unsigned long syscall)
 	stop = (struct syscall_metadata *)__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;
-- 
1.7.1

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