idle: Add the stack canary init to cpu_startup_entry()

KAGA-KOKO · KAGA-KOKO · commit d7880812b359 · 2013-06-11T22:04:47.000+02:00
Moving x86 to the generic idle implementation (commit 7d1a941 "x86: Use generic idle loop") wreckaged the stack protector. I stupidly missed that boot_init_stack_canary() must be inlined from a function which never returns, but I put that call into arch_cpu_idle_prepare() which of course returns. I pondered to play tricks with arch_cpu_idle_prepare() first, but then I noticed, that the other archs which have implemented the stackprotector (ARM and SH) do not initialize the canary for the non-boot cpus. So I decided to move the boot_init_stack_canary() call into cpu_startup_entry() ifdeffed with an CONFIG_X86 for now. This #ifdef is just a temporary measure as I don't want to inflict the boot_init_stack_canary() call on ARM and SH that late in the cycle. I'll queue a patch for 3.11 which removes the #ifdef if the ARM/SH maintainers have no objection. Reported-by: Wouter van Kesteren <woutershep@gmail.com> Cc: x86@kernel.org Cc: Russell King <linux@arm.linux.org.uk> Cc: Paul Mundt <lethal@linux-sh.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
@@ -277,18 +277,6 @@ void exit_idle(void)
 }
 #endif
 
-void arch_cpu_idle_prepare(void)
-{
-	/*
-	 * 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();
-}
-
 void arch_cpu_idle_enter(void)
 {
 	local_touch_nmi();
diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
@@ -5,6 +5,7 @@
 #include <linux/cpu.h>
 #include <linux/tick.h>
 #include <linux/mm.h>
+#include <linux/stackprotector.h>
 
 #include <asm/tlb.h>
 
@@ -112,6 +113,21 @@ static void cpu_idle_loop(void)
 
 void cpu_startup_entry(enum cpuhp_state state)
 {
+	/*
+	 * This #ifdef needs to die, but it's too late in the cycle to
+	 * make this generic (arm and sh have never invoked the canary
+	 * init for the non boot cpus!). Will be fixed in 3.11
+	 */
+#ifdef CONFIG_X86
+	/*
+	 * If we're the non-boot CPU, nothing set the stack canary up
+	 * for us. The boot CPU 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();
+#endif
 	current_set_polling();
 	arch_cpu_idle_prepare();
 	cpu_idle_loop();
