linux-kernel - 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 08:39:07 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     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>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: WARNING: can't dereference registers at ffffc90004dfff60 for ip
 error_entry+0x7d/0xd0 (Re: [PATCH v2 00/18] Entry stack switching)


* Andy Lutomirski <luto@...nel.org> wrote:

> This sets up stack switching, including for SYSCALL.  I think it's
> in decent shape.
> 
> Known issues:
>  - I think we're going to want a way to turn the stack switching on and
>    off either at boot time or at runtime.  It should be fairly straightforward
>    to make it work.
> 
>  - I think the ORC unwinder isn't so good at dealing with stack overflows.
>    It bails too early (I think), resulting in lots of ? entries.  This
>    isn't a regression with this series -- it's just something that could
>    be improved.

Note that with the attached config on an Intel testbox I get the following new ORC 
unwinder warning during bootup:

[   12.200554] calling  ghash_pclmulqdqni_mod_init+0x0/0x54 @ 1
[   12.209536] WARNING: can't dereference registers at ffffc90004dfff60 for ip error_entry+0x7d/0xd0
[   12.231388] initcall ghash_pclmulqdqni_mod_init+0x0/0x54 returned 0 after 23480 usecs

Thanks,

	Ingo

View attachment "config" of type "text/plain" (115159 bytes)