linux-kernel - Re: WARNING: can't dereference registers at ffffc90004dfff60 for ip error_entry+0x7d/0xd0 (Re: [PATCH v2 00/18] Entry stack switching)

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Date:   Wed, 22 Nov 2017 08:35:19 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: WARNING: can't dereference registers at ffffc90004dfff60 for ip
 error_entry+0x7d/0xd0 (Re: [PATCH v2 00/18] Entry stack switching)

On Wed, Nov 22, 2017 at 7:56 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Andy Lutomirski <luto@...nel.org> wrote:
>
>> >  .Lerror_entry_from_usermode_after_swapgs:
>> >         /* Put us onto the real thread stack. */
>> > -       leaq    8(%rsp), %rdi                   /* pt_regs pointer */
>> > -       movq    (%rsp), %r12
>> > +       popq    %r12                            /* function return address */
>> > +       leaq    (%rsp), %rdi                    /* pt_regs pointer */
>> >         call    sync_regs
>> >         movq    %rax, %rsp                      /* switch stack */
>> >         ENCODE_FRAME_POINTER
>>
>> Ah, I see -- SAVE_C_REGS contains an UNWIND_HINT_REGS hint.  I had
>> thought I needed to fix it differently.
>>
>> Ingo, if you want to apply this, I attached it.  I'll fold it in next
>> time I resend the whole  series.
>
> Ok.
>
> Also please fold back the minor fixes below - spelling fix plus ugly line breaks
> elimination.

Done.