• Tejun Heo's avatar
    x86: implement x86_32 stack protector · 60a5317f
    Tejun Heo authored
    
    
    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: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    60a5317f
system.h 14.1 KB