linux-kernel - Re: [PATCH untested] x86_32: fix extable entry for iret

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Date:   Wed, 6 Nov 2019 20:54:11 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Lai Jiangshan <laijs@...ux.alibaba.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH untested] x86_32: fix extable entry for iret

On Wed, Nov 6, 2019 at 8:41 PM Lai Jiangshan <laijs@...ux.alibaba.com> wrote:
>
> 3c88c692c287(x86/stackframe/32: Provide consistent pt_regs)
> added code after label .Lirq_return and before 'iret', an instruction
> which should be expected to be found in the extable when there is
> an exception on it. But the extable entry stores the address of
> .Lirq_return not the new address of 'iret', which disables
> the corresponding fixup. This patch fixes the extable entry
> by using a new label.

Egads!

What happens if you run tools/testing/selftests/x86/sigreturn_32 with
and without this patch?

--Andy