Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1348393

Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack

From "H. Peter Anvin" <hpa@zytor.com>
Newsgroups linux.kernel
Subject Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack
Date 2016-03-02 19:40 +0100
Message-ID <r8jQL-3th-49@gated-at.bofh.it> (permalink)
References <r8d8C-6UP-9@gated-at.bofh.it> <r8hOW-1I2-5@gated-at.bofh.it> <r8hOW-1I2-3@gated-at.bofh.it> <r8je2-2XE-7@gated-at.bofh.it> <r8jxo-3k9-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On 03/02/16 10:15, Borislav Petkov wrote:
> On Wed, Mar 02, 2016 at 09:53:28AM -0800, H. Peter Anvin wrote:
>> Please explain why we can't use rip-relative addressing in some form...
> 
> We *can* do almost what Brian suggested:
> 
>         movq    stack_start(%rip), %rsp
>         subq    $__START_KERNEL_map, %rsp
> 
> But we still have to subtract __START_KERNEL_map.
> 

Well, we definitely should use %rip-relative addressing if we can.

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.

	-hpa

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 12:30 +0100
  Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 17:20 +0100
    Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Mika Penttilä <mika.penttila@nextfour.com> - 2016-03-02 17:40 +0100
      Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 18:00 +0100
        Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Mika Penttilä <mika.penttila@nextfour.com> - 2016-03-02 18:50 +0100
  Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Mika Penttilä <mika.penttila@nextfour.com> - 2016-03-02 17:20 +0100
  Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 17:30 +0100
    Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-02 19:00 +0100
      Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 19:20 +0100
        Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-02 19:30 +0100
        Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-02 19:40 +0100
          Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 21:00 +0100
            Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 21:50 +0100
            Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-02 22:40 +0100
              Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 22:50 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-02 23:00 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-02 23:20 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 23:30 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-02 23:40 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 23:50 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Yinghai Lu <yinghai@kernel.org> - 2016-03-03 01:20 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Yinghai Lu <yinghai@kernel.org> - 2016-03-03 02:10 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Yinghai Lu <yinghai@kernel.org> - 2016-03-03 04:00 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-03 13:30 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-03 16:30 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-03 17:40 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-03 21:30 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-03 22:00 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack "H. Peter Anvin" <hpa@zytor.com> - 2016-03-03 22:30 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-03 22:40 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Yinghai Lu <yinghai@kernel.org> - 2016-03-04 02:20 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Yinghai Lu <yinghai@kernel.org> - 2016-03-04 03:30 +0100
                Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Borislav Petkov <bp@alien8.de> - 2016-03-02 23:20 +0100
  Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Brian Gerst <brgerst@gmail.com> - 2016-03-02 17:30 +0100

csiph-web