linux-kernel - [PATCH 6/6] ftrace syscalls: Early terminate search for sys_ni

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Date:	Thu,  3 Feb 2011 14:27:25 +1100
From:	"Ian Munsie" <imunsie@....ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	Andreas Dilger <adilger@...ger.ca>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Jason Baron <jbaron@...hat.com>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Alexander Graf <agraf@...e.de>, Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Scott Wood <scottwood@...escale.com>,
	Nathan Lynch <ntl@...ox.com>,
	Avantika Mathur <mathur@...ux.vnet.ibm.com>,
	David Gibson <dwg@....ibm.com>,
	Andreas Schwab <schwab@...ux-m68k.org>,
	Namhyung Kim <namhyung@...il.com>,
	Ian Munsie <imunsie@....ibm.com>
Subject: [PATCH 6/6] ftrace 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 7b76a65..f498154 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -84,6 +84,9 @@ 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;
-- 
1.7.2.3

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