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SubjectRe: [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##]
On Tue, 15 May 2018, Josh Poimboeuf wrote:
> On Wed, May 16, 2018 at 12:43:37AM +0300, Alexey Dobriyan wrote:
> > On Tue, May 15, 2018 at 09:25:53PM +0000, Anvin, H Peter wrote:
> > > Why is that a problem?
> > > Code: 00 00 00 eb e6 cc cc cc cc cc cc cc cc cc cc cc cc cc fa 8d b6 00 00 00 00 e8 5d e8 8f ff 8b 44 24 34 83 e0 03 83 f8 03 72 28 cc <cc> cc cc cc cc cc cc fa 8d b6 00 00 00 00 e8 3d e8 8f ff 89 e0
> > >
> > > EIP: ret_from_intr+0xd/0x14 SS:ESP: 0068:8603bfb4
> > >
> > > INT3 slipped through M586 => X86_ALIGNMENT_16 :-\
> >
> > I could make the patch x86_64 only, but!
> >
> > It crashed into the middle of the padding.
> >
> > 796ef8fc <ret_from_intr>:
> > 796ef8fc: 8b 44 24 34 mov eax,DWORD PTR [esp+0x34]
> > 796ef900: 83 e0 03 and eax,0x3
> > 796ef903: 83 f8 03 cmp eax,0x3
> > 796ef906: 72 28 jb 796ef930 <resume_kernel>
> > 796ef908: cc int3
> > 796ef909: cc <========> int3
> > 796ef90a: cc int3
> > 796ef90b: cc int3
> > 796ef90c: cc int3
> > 796ef90d: cc int3
> > 796ef90e: cc int3
> > 796ef90f: cc int3
>
> The padding isn't needed there, and the resume_userspace symbol is never
> used, so wouldn't this fix it?

Gack. Right you are. I assumed that the ENTRY() is used without checking ....

>
> diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
> index bef8e2b202a8..9e56243c984c 100644
> --- a/arch/x86/entry/entry_32.S
> +++ b/arch/x86/entry/entry_32.S
> @@ -338,7 +338,6 @@ ret_from_intr:
> cmpl $USER_RPL, %eax
> jb resume_kernel # not returning to v8086 or userspace
>
> -ENTRY(resume_userspace)
> DISABLE_INTERRUPTS(CLBR_ANY)
> TRACE_IRQS_OFF
> movl %esp, %eax
>

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