From: "Mika Penttilä" <mika.penttila@nextfour.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack
Date: Wed, 2 Mar 2016 18:38:15 +0200 [thread overview]
Message-ID: <56D716F7.3080407@nextfour.com> (raw)
In-Reply-To: <20160302161532.GK16954@pd.tnic>
On 02.03.2016 18:15, Borislav Petkov wrote:
> On Wed, Mar 02, 2016 at 05:55:14PM +0200, Mika Penttilä wrote:
>>> + /* Setup a stack for verify_cpu */
>>> + movq stack_start - __START_KERNEL_map, %rsp
>>> + subq $__START_KERNEL_map, %rsp
>>> +
>> You subtract __START_KERNEL_map twice ?
> Yes. That's not very obvious and it took me a while. I probably should
> add a comment.
>
> Want to stare at it a little bit more and try to figure it out or should
> I explain?
>
> :-)
>
I actually looked at it a while too...
The
movq stack_start - __START_KERNEL_map, %rsp
turns into (objdump disassembly)
mov 0x0,%rsp
with relocation
0000000000000004 R_X86_64_32S stack_start+0x0000000080000000
Now stack_start is at ffffffff81ef3380, so the relocation gives 1ef3380 which would be correct, so why the
second subq ?
You may explain :)
--Mika
next prev parent reply other threads:[~2016-03-02 16:38 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-02 11:20 [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov
2016-03-02 15:55 ` Mika Penttilä
2016-03-02 16:15 ` Borislav Petkov
2016-03-02 16:38 ` Mika Penttilä [this message]
2016-03-02 16:55 ` Borislav Petkov
2016-03-02 17:44 ` Mika Penttilä
2016-03-02 16:22 ` Brian Gerst
2016-03-02 16:25 ` Borislav Petkov
2016-03-02 17:53 ` H. Peter Anvin
2016-03-02 18:15 ` Borislav Petkov
2016-03-02 18:25 ` H. Peter Anvin
2016-03-02 18:39 ` H. Peter Anvin
2016-03-02 19:50 ` Borislav Petkov
2016-03-02 20:46 ` Borislav Petkov
2016-03-02 21:35 ` H. Peter Anvin
2016-03-02 21:46 ` Borislav Petkov
2016-03-02 21:54 ` H. Peter Anvin
2016-03-02 22:09 ` Borislav Petkov
2016-03-02 22:11 ` H. Peter Anvin
2016-03-02 22:28 ` Borislav Petkov
2016-03-02 22:32 ` H. Peter Anvin
2016-03-02 22:40 ` Borislav Petkov
2016-03-03 0:13 ` Yinghai Lu
2016-03-03 1:00 ` Yinghai Lu
2016-03-03 2:50 ` Yinghai Lu
2016-03-03 12:28 ` Borislav Petkov
2016-03-03 15:26 ` H. Peter Anvin
2016-03-03 16:29 ` Borislav Petkov
2016-03-03 20:22 ` H. Peter Anvin
2016-03-03 20:54 ` Borislav Petkov
2016-03-03 21:22 ` H. Peter Anvin
2016-03-03 21:38 ` Borislav Petkov
2016-03-04 1:18 ` Yinghai Lu
2016-03-04 2:25 ` Yinghai Lu
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