+ espfix-code-cleanup.patch added to -mm tree

[Chuck Ebbert]

In-Reply-To: <200607300016.k6U0GYu4023664@xxxxxxxxxxxxxxxxxxx>

On Sat, 29 Jul 2006 17:16:34 -0700, Andrew Morton wrote:

>     espfix-code-cleanup.patch

After the fixup code does this:

       movl %esp, %eax         # pt_regs pointer
       movl %esp, %edx
       call patch_espfix_gdt
       pushl $__ESPFIX_SS
       CFI_ADJUST_CFA_OFFSET 4
       pushl %eax
       CFI_ADJUST_CFA_OFFSET 4
==>    lss (%esp), %esp
       CFI_ADJUST_CFA_OFFSET -8
       jmp restore_nocheck

we are on a ring0 32-bit stack that's not zero-based.  If an exception
occurs in that state, UNWIND_ESPFIX_STACK restores the proper kernel
SS and ESP but on return from the exception nothing restores the espfix
stack.  I guess this isn't a problem now because exceptions in kernel
mode are fatal but a kernel debugger might have problems here?

-- 
Chuck
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