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authorTejun Heo <tj@kernel.org>2009-02-09 22:17:40 +0900
committerIngo Molnar <mingo@elte.hu>2009-02-10 00:42:01 +0100
commit60a5317ff0f42dd313094b88f809f63041568b08 (patch)
tree307dfd9715fbc9ff83c3c3ae3b0e8f03888083f2 /arch/x86/kernel/entry_32.S
parentccbeed3a05908d201b47b6c3dd1a373138bba566 (diff)
x86: implement x86_32 stack protector
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>
Diffstat (limited to 'arch/x86/kernel/entry_32.S')
-rw-r--r--arch/x86/kernel/entry_32.S2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 82e6868bee4..5f5bd22adcd 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -186,7 +186,7 @@
/*CFI_REL_OFFSET gs, PT_GS*/
.endm
.macro SET_KERNEL_GS reg
- xorl \reg, \reg
+ movl $(__KERNEL_STACK_CANARY), \reg
movl \reg, %gs
.endm