Re: Regression [Was: Boot hang with stack protector on x86_64]

Ingo Molnar
2008-02-23T06:19:52Z

James,

could you try the fix below ontop of x86.git#testing, does it solve your
boot hang?

Ingo

--------------->
Subject: x86: stackprotector fix: do not zap %gs
From: Ingo Molnar <mingo@elte.hu>
Date: Sat Feb 23 07:06:55 CET 2008

pda_init() puts 0 into %gs - that's wrong because any %gs access will
fault from now on and we already have a dummy PDA set up that can be
accessed just fine.

This normally does not matter because almost nothing accesses %gs this
early ... but the stackprotector now does to read the canary ...

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/setup64.c | 2 --
1 file changed, 2 deletions(-)

Index: linux-x86.q/arch/x86/kernel/setup64.c
===================================================================
--- linux-x86.q.orig/arch/x86/kernel/setup64.c
+++ linux-x86.q/arch/x86/kernel/setup64.c
@@ -165,8 +165,6 @@ void pda_init(int cpu)
{
struct x8664_pda *pda = cpu_pda(cpu);

- /* Setup up data that may be needed in __get_free_pages early */
- asm volatile("movl %0,%%fs ; movl %0,%%gs" :: "r" (0));
/* Memory clobbers used to order PDA accessed */
mb();
wrmsrl(MSR_GS_BASE, pda);