[lkml]   [2009]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 11/11] x86: implement x86_32 stack protector
Brian Gerst wrote:
> On Mon, Feb 9, 2009 at 8:39 AM, Tejun Heo <> wrote:
>> 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 <>
> Am I missing something, or does this patch not actually implement the
> offset of the start of the segment by 20 from the stack_canary
> variable?

Yeah, it seems I forgot to subtract 20 from the address. Will prep a
patch. Thanks for spotting it.


 \ /
  Last update: 2009-02-10 16:43    [W:0.078 / U:11.400 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site