From: "H. Peter Anvin" <hpa@zytor.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.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 13:35:09 -0800 [thread overview]
Message-ID: <56D75C8D.90800@zytor.com> (raw)
In-Reply-To: <20160302195053.GG8362@pd.tnic>
On 03/02/16 11:50, Borislav Petkov wrote:
> On Wed, Mar 02, 2016 at 10:39:05AM -0800, H. Peter Anvin wrote:
>> Well, we definitely should use %rip-relative addressing if we can.
>
> Right you are.
>
>> However, even so I believe this breaks if the kernel is loaded anywhere
>> but its default load address. I think we need to do something like:
>>
>> movq stack_start(%rip), %rax
>> leaq __START_KERNEL_map(%rip), %rdx
>> subq %rdx, %rax
>> movq %rax, %rsp
>>
>> The use of temporary registers avoids clobbering a valid stack pointer
>> for even a single instruction if we are given one.
>
> Yeah, we should be prudent and make this as sturdy as possible. I did this:
>
> CONFIG_PHYSICAL_START=0x100beef
>
> and it aligned startup_64 up to ffffffff82000000. It seems to boot fine
> in kvm. But better safe than sorry.
>
You're not actually testing anything as the real issue is what happens
with a relocating bootloader. That's okay; I think we can be pretty
sure the above works by inspection.
-hpa
next prev parent reply other threads:[~2016-03-02 21:35 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
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 [this message]
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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