idle: Add the stack canary init to cpu_startup_entry()

Moving x86 to the generic idle implementation (commit 7d1a9417 "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>

1 files changed, 0 insertions, 12 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 4e7a37ff03ab..81a5f5e8f142 100644
--- 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();