linux-kernel - [PATCH] x86: remove redundant stack canary initialization

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Date:	Fri, 26 Feb 2010 04:19:28 -0800
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH] x86: remove redundant stack canary initialization

After we moved boot_init_stack_canary to the secondary CPU start code, there is
no need to do this again in cpu_idle(). Stack canary are initialized earlier than
cpu_idle() for both boot and secondary CPUs.

This is suggested by Thomas Gleixner in http://lkml.org/lkml/2010/2/20/14

Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
---
 arch/x86/kernel/process_32.c |   10 ----------
 arch/x86/kernel/process_64.c |   10 ----------
 2 files changed, 0 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 37ad1e0..6dae5bf 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -9,7 +9,6 @@
  * This file handles the architecture-dependent parts of process handling..
  */
 
-#include <linux/stackprotector.h>
 #include <linux/cpu.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
@@ -85,15 +84,6 @@ void cpu_idle(void)
 {
 	int cpu = smp_processor_id();
 
-	/*
-	 * If we're the non-boot CPU, nothing set the stack canary up
-	 * for us.  CPU0 already has it initialized but no harm in
-	 * doing it again.  This is a good place for updating it, as
-	 * we wont ever return from this function (so the invalid
-	 * canaries already on the stack wont ever trigger).
-	 */
-	boot_init_stack_canary();
-
 	current_thread_info()->status |= TS_POLLING;
 
 	/* endless idle loop with no priority at all */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 41a26a8..68ecec1 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -14,7 +14,6 @@
  * This file handles the architecture-dependent parts of process handling..
  */
 
-#include <linux/stackprotector.h>
 #include <linux/cpu.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
@@ -110,15 +109,6 @@ void cpu_idle(void)
 {
 	current_thread_info()->status |= TS_POLLING;
 
-	/*
-	 * If we're the non-boot CPU, nothing set the stack canary up
-	 * for us.  CPU0 already has it initialized but no harm in
-	 * doing it again.  This is a good place for updating it, as
-	 * we wont ever return from this function (so the invalid
-	 * canaries already on the stack wont ever trigger).
-	 */
-	boot_init_stack_canary();
-
 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_stop_sched_tick(1);
-- 
1.5.6.5

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