From 18aa8bb12dcb10adc3d7c9d69714d53667c0ab7f Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 14 Feb 2008 09:42:02 +0100
Subject: [PATCH] stackprotector: add boot_init_stack_canary()

add the boot_init_stack_canary() and make the secondary idle threads
use it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/process_64.c     |  6 ++----
 include/asm-x86/stackprotector.h | 20 ++++++++++++++++++++
 include/linux/stackprotector.h   |  4 ++++
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index d4c7ac7aa430..5107cb214c7b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -147,7 +147,6 @@ void cpu_idle(void)
 {
 	current_thread_info()->status |= TS_POLLING;
 
-#ifdef CONFIG_CC_STACKPROTECTOR
 	/*
 	 * If we're the non-boot CPU, nothing set the PDA stack
 	 * canary up for us - and if we are the boot CPU we have
@@ -156,9 +155,8 @@ void cpu_idle(void)
 	 * invalid canaries already on the stack wont ever
 	 * trigger):
 	 */
-	current->stack_canary = get_random_int();
-	write_pda(stack_canary, current->stack_canary);
-#endif
+	boot_init_stack_canary();
+
 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_stop_sched_tick();
diff --git a/include/asm-x86/stackprotector.h b/include/asm-x86/stackprotector.h
index dcac7a6bdba2..0f91f7a2688c 100644
--- a/include/asm-x86/stackprotector.h
+++ b/include/asm-x86/stackprotector.h
@@ -1,4 +1,24 @@
 #ifndef _ASM_STACKPROTECTOR_H
 #define _ASM_STACKPROTECTOR_H 1
 
+/*
+ * Initialize the stackprotector canary value.
+ *
+ * NOTE: this must only be called from functions that never return,
+ * and it must always be inlined.
+ */
+static __always_inline void boot_init_stack_canary(void)
+{
+	/*
+	 * If we're the non-boot CPU, nothing set the PDA stack
+	 * canary up for us - and if we are the boot CPU we have
+	 * a 0 stack canary. 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):
+	 */
+	current->stack_canary = get_random_int();
+	write_pda(stack_canary, current->stack_canary);
+}
+
 #endif
diff --git a/include/linux/stackprotector.h b/include/linux/stackprotector.h
index d3e8bbe602f8..422e71aafd0b 100644
--- a/include/linux/stackprotector.h
+++ b/include/linux/stackprotector.h
@@ -3,6 +3,10 @@
 
 #ifdef CONFIG_CC_STACKPROTECTOR
 # include <asm/stackprotector.h>
+#else
+static inline void boot_init_stack_canary(void)
+{
+}
 #endif
 
 #endif