Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1233261
| From | Ard Biesheuvel <ard.biesheuvel@linaro.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime |
| Date | 2015-09-26 20:20 +0200 |
| Message-ID | <qd2eK-7JC-25@gated-at.bofh.it> (permalink) |
| References | <qcJlL-5Zx-9@gated-at.bofh.it> <qcJlL-5Zx-7@gated-at.bofh.it> <qcQGB-7R0-1@gated-at.bofh.it> <qd18Z-6cT-9@gated-at.bofh.it> <qd1sl-6zC-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 26 September 2015 at 10:20, H. Peter Anvin <hpa@zytor.com> wrote:
> I think it "works" because the affected BIOSes don't put spaces between the chunks. I have discussed this with Matt.
>
Forgive the ASCII art but perhaps an illustration might help:
before the 2.5 feature, PE/COFF runtime images were remapped as
illustrated here:
PA VA
+---------------+ +---------------+
| | | |
| PE/COFF .text | | EFI |
| | | Runtime |
+- - - - - - - -+ => | Services |----+
| | | Code | | : :
| PE/COFF .data | | | | : :
| | | | | +---------------+
+---------------+ +---------------+ | | |
| | | | | | EFI |
: : : : | | Runtime |
: : : : +--->| Services |
| | | | | Code |
+---------------+ +---------------+ | |
| | | | | |
| PE/COFF .text | | EFI | +---------------+
| | | Runtime | : gap :
+- - - - - - - -+ => | Services |---+ +---------------+
| | | Code | | | |
| PE/COFF .data | | | | | EFI |
| | | | | | Runtime |
+---------------+ +---------------+ +---->| Services |
| | | | | Code |
: : : : | |
: : : : | |
: : : : +---------------+
: : : : : :
Since the affected symbol references only exist between PE/COFF .text
and PE/COFF .data, there is never a problem since each is PE/COFF
image is mapped as a single region.
However, with the new feature enabled, this no longer holds:
PA VA
+---------------+ +---------------+
| | | |
| PE/COFF .text | | RtServices |----+
| | | Code | |
+- - - - - - - -+ => +---------------+ | +---------------+
| | | RtServices | +--->| RtServices |
| PE/COFF .data | | Data | | Code |
| | | |----+ +---------------+
+---------------+ +---------------+ | : gap :
| | | | | +---------------+
: : : : +--->| RtServices |
: : : : | Data |
| | | | +---------------+
+---------------+ +---------------+ : gap :
| | | | +---------------+
| PE/COFF .text | | RtServices |-------->| RtServices |
| | | Code | | Code |
+- - - - - - - -+ => +---------------+ +---------------+
| | | RtServices | : gap :
| PE/COFF .data | | Data |---+ +---------------+
| | | | | | RtServices |
+---------------+ +---------------+ +---->| Data |
| | | | | |
: : : : +---------------+
: : : : : :
: : : : : :
The illustration uses gaps, but obviously, this applies equally to
inverting the mapping order, since the PE/COFF .text and .data
sections will end up out of order.
--
Ard.
> On September 26, 2015 10:01:14 AM PDT, Andy Lutomirski <luto@amacapital.net> wrote:
>>On Fri, Sep 25, 2015 at 10:56 PM, Ingo Molnar <mingo@kernel.org> wrote:
>>>
>>> So this commit worries me.
>>>
>>> This bug is a good find, and the fix is obviously needed and urgent,
>>but I'm not
>>> sure about the implementation at all. (I've Cc:-ed a few more x86 low
>>level
>>> gents.)
>>>
>>> * Matt Fleming <matt@codeblueprint.co.uk> wrote:
>>>> + /*
>>>> + * Starting in UEFI v2.5 the EFI_PROPERTIES_TABLE
>>>> + * config table feature requires us to map all entries
>>>> + * in the same order as they appear in the EFI memory
>>>> + * map. That is to say, entry N must have a lower
>>>> + * virtual address than entry N+1. This is because the
>>>> + * firmware toolchain leaves relative references in
>>>> + * the code/data sections, which are split and become
>>>> + * separate EFI memory regions. Mapping things
>>>> + * out-of-order leads to the firmware accessing
>>>> + * unmapped addresses.
>>>> + *
>>
>>I'm clearly missing something. What is EFI doing that it doesn't care
>>how big the gap between sections is but it still requires them to be
>>in order? It's not as though x86_64 has an addressing mode that
>>allows only non-negative offsets.
>>
>>--Andy
>
> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matt Fleming <matt@codeblueprint.co.uk> - 2015-09-26 00:10 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ingo Molnar <mingo@kernel.org> - 2015-09-26 08:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-26 08:50 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matt Fleming <matt@codeblueprint.co.uk> - 2015-09-26 15:50 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ingo Molnar <mingo@kernel.org> - 2015-09-27 09:10 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-28 08:50 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ingo Molnar <mingo@kernel.org> - 2015-09-28 10:30 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-28 12:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ingo Molnar <mingo@kernel.org> - 2015-09-29 11:20 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-29 12:50 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matt Fleming <matt@codeblueprint.co.uk> - 2015-09-29 16:20 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matt Fleming <matt@codeblueprint.co.uk> - 2015-09-29 16:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Andy Lutomirski <luto@amacapital.net> - 2015-09-26 19:10 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime "H. Peter Anvin" <hpa@zytor.com> - 2015-09-26 19:30 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-26 20:20 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matt Fleming <matt@codeblueprint.co.uk> - 2015-09-26 22:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-26 22:10 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime "H. Peter Anvin" <hpa@zytor.com> - 2015-09-26 22:30 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Andy Lutomirski <luto@amacapital.net> - 2015-09-27 18:40 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matthew Garrett <mjg59@srcf.ucam.org> - 2015-09-27 20:40 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ingo Molnar <mingo@kernel.org> - 2015-09-28 08:20 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matthew Garrett <mjg59@srcf.ucam.org> - 2015-09-28 09:10 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Laszlo Ersek <lersek@redhat.com> - 2015-09-30 00:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-30 11:40 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Andy Lutomirski <luto@amacapital.net> - 2015-09-30 18:50 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime James Bottomley <jbottomley@odin.com> - 2015-09-30 19:30 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime "H. Peter Anvin" <hpa@zytor.com> - 2015-09-30 03:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime "H. Peter Anvin" <hpa@zytor.com> - 2015-09-26 22:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matt Fleming <matt@codeblueprint.co.uk> - 2015-09-26 22:00 +0200
Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Ingo Molnar <mingo@kernel.org> - 2015-09-27 09:00 +0200
[tip:core/urgent] x86/efi: Fix boot crash by mapping EFI memmap entries bottom-up at runtime, instead of top-down tip-bot for Matt Fleming <tipbot@zytor.com> - 2015-10-01 15:00 +0200
Re: [tip:core/urgent] x86/efi: Fix boot crash by mapping EFI memmap entries bottom-up at runtime, instead of top-down Matt Fleming <matt@codeblueprint.co.uk> - 2015-10-02 11:50 +0200
csiph-web