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x86: implement x86_32 stack protector

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Impact: stack protector for x86_32

Implement stack protector for x86_32.  GDT entry 28 is used for it.
It's set to point to stack_canary-20 and have the length of 24 bytes.
CONFIG_CC_STACKPROTECTOR turns off CONFIG_X86_32_LAZY_GS and sets %gs
to the stack canary segment on entry.  As %gs is otherwise unused by
the kernel, the canary can be anywhere.  It's defined as a percpu
variable.

x86_32 exception handlers take register frame on stack directly as
struct pt_regs.  With -fstack-protector turned on, gcc copies the
whole structure after the stack canary and (of course) doesn't copy
back on return thus losing all changed.  For now, -fno-stack-protector
is added to all files which contain those functions.  We definitely
need something better.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Tejun Heo
2009-02-09 22:17:40 +09:00
committed by Ingo Molnar
parent ccbeed3a05
commit 60a5317ff0
12 changed files with 180 additions and 16 deletions
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2
arch/x86/kernel/setup_percpu.c
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@ -16,6 +16,7 @@
#include <asm/proto.h>
#include <asm/cpumask.h>
#include <asm/cpu.h>
#include <asm/stackprotector.h>
#ifdef CONFIG_DEBUG_PER_CPU_MAPS
# define DBG(x...) printk(KERN_DEBUG x)
@ -95,6 +96,7 @@ void __init setup_per_cpu_areas(void)
per_cpu(this_cpu_off, cpu) = per_cpu_offset(cpu);
per_cpu(cpu_number, cpu) = cpu;
setup_percpu_segment(cpu);
setup_stack_canary_segment(cpu);
/*
* Copy data used in early init routines from the
* initial arrays to the per cpu data areas. These