linux-kernel - Re: [PATCH v2 03/18] x86/dumpstack: Add get_stack

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Message-ID: <20171122121044.efeorbz2zjpyedh6@pd.tnic>
Date:   Wed, 22 Nov 2017 13:10:44 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>,
        "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: Re: [PATCH v2 03/18] x86/dumpstack: Add get_stack_info() support for
 the SYSENTER stack

On Tue, Nov 21, 2017 at 08:43:58PM -0800, Andy Lutomirski wrote:
> get_stack_info() doesn't currently know about the SYSENTER stack, so
> unwinding will fail if we entered the kernel on the SYSENTER stack
> and haven't fully switched off.  Teach get_stack_info() about the
> SYSENTER stack.
> 
> With future patches applied that run part of the entry code on the
> SYSENTER stack and introduce an intentional BUG(), I would get:
> 
> [    3.962218] PANIC: double fault, error_code: 0x0
> ...
> [    3.963998] task: ffff88001aa18000 task.stack: ffff88001aa20000
> [    3.964526] RIP: 0010:do_error_trap+0x33/0x1c0
> [    3.964947] RSP: 0000:ffffffffff1b8f78 EFLAGS: 00010096
> [    3.965439] RAX: dffffc0000000000 RBX: ffffffffff1b8f90 RCX: 0000000000000006
> [    3.966067] RDX: ffffffff82048b20 RSI: 0000000000000000 RDI: ffffffffff1b9110
> [    3.966696] RBP: ffffffffff1b9088 R08: 0000000000000004 R09: 0000000000000000
> [    3.967316] R10: 0000000000000000 R11: fffffbffffe3723f R12: 0000000000000006
> [    3.967939] R13: 0000000000000000 R14: 0000000000000004 R15: 0000000000000000
> [    3.968565] FS:  0000000000000000(0000) GS:ffff88001ae00000(0000) knlGS:0000000000000000
> [    3.969272] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    3.969776] CR2: ffffffffff1b8f68 CR3: 0000000019308002 CR4: 00000000003606f0
> [    3.970406] Call Trace:
> [    3.970632] Code: ...
> 
> With this patch, I get:
> 
> [    4.211553] PANIC: double fault, error_code: 0x0
> ...
> [    4.213536] task: ffff88001aa18000 task.stack: ffff88001aa20000
> [    4.214059] RIP: 0010:do_error_trap+0x33/0x1c0
> [    4.214449] RSP: 0000:ffffffffff1b8f78 EFLAGS: 00010096
> [    4.214934] RAX: dffffc0000000000 RBX: ffffffffff1b8f90 RCX: 0000000000000006
> [    4.215554] RDX: ffffffff82048b20 RSI: 0000000000000000 RDI: ffffffffff1b9110
> [    4.216176] RBP: ffffffffff1b9088 R08: 0000000000000004 R09: 0000000000000000
> [    4.216793] R10: 0000000000000000 R11: fffffbffffe3723f R12: 0000000000000006
> [    4.217419] R13: 0000000000000000 R14: 0000000000000004 R15: 0000000000000000
> [    4.218046] FS:  0000000000000000(0000) GS:ffff88001ae00000(0000) knlGS:0000000000000000
> [    4.218775] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    4.219280] CR2: ffffffffff1b8f68 CR3: 00000000193da002 CR4: 00000000003606f0
> [    4.219931] Call Trace:
> [    4.220156]  <SYSENTER>
> [    4.220383]  ? async_page_fault+0x36/0x60
> [    4.220768]  ? invalid_op+0x22/0x40
> [    4.221087]  ? async_page_fault+0x36/0x60
> [    4.221442]  ? sync_regs+0x3c/0x40
> [    4.221745]  ? sync_regs+0x2e/0x40
> [    4.222051]  ? error_entry+0x6c/0xd0
> [    4.222395]  ? async_page_fault+0x36/0x60
> [    4.222748]  </SYSENTER>
> [    4.223014] Code: ...

Please clean up those oopses: remove the timestamps, registers and the
offsets from the symbol names - they only clutter the text and have no
meaning.

> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
>  arch/x86/include/asm/stacktrace.h |  3 +++
>  arch/x86/kernel/dumpstack.c       | 19 +++++++++++++++++++
>  arch/x86/kernel/dumpstack_32.c    |  6 ++++++
>  arch/x86/kernel/dumpstack_64.c    |  6 ++++++
>  4 files changed, 34 insertions(+)

With that:

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--