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Re: [PATCH v3 2/7] x86/arch_prctl: Fix ARCH_GET_FS and ARCH_GET_GS

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* Andy Lutomirski <luto@kernel.org> wrote:

> ARCH_GET_FS and ARCH_GET_GS attempted to figure out the fsbase and
> gsbase respectively from saved thread state.  This was wrong: fsbase
> and gsbase live in registers while a thread is running, not in
> memory.

So I'm wondering, the current code looks totally broken,what user-space code can 
possibly use this? I checked glibc and Wine, and neither of them does. Wine uses 
ARCH_SET_GS and glibc uses ARCH_SET_FS, but that's all - neither actually tries to 
use the ARCH_GET_* reading APIs.

So for backporting purposes I'd be much happier about simply returning -EINVAL or 
-ENOSYS, and we could re-introduce this code in v4.7.

Thanks,

	Ingo

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[PATCH v3 0/7] x86: Pile o' FS/GS changes Andy Lutomirski <luto@kernel.org> - 2016-04-08 02:40 +0200
  [PATCH v3 1/7] selftests/x86: Test the FSBASE/GSBASE API and context switching Andy Lutomirski <luto@kernel.org> - 2016-04-08 02:40 +0200
    [tip:x86/asm] selftests/x86: Test the FSBASE/GSBASE API and context  switching tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:40 +0200
  [PATCH v3 5/7] x86/cpu: Move X86_BUG_ESPFIX initialization to generic_identify Andy Lutomirski <luto@kernel.org> - 2016-04-08 02:40 +0200
    [tip:x86/asm] x86/cpu: Move X86_BUG_ESPFIX initialization to  generic_identify() tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:40 +0200
  [PATCH v3 7/7] x86/entry: Make gs_change a local label Andy Lutomirski <luto@kernel.org> - 2016-04-08 02:40 +0200
    [tip:x86/asm] x86/entry/64: Make gs_change a local label tip-bot for Borislav Petkov <tipbot@zytor.com> - 2016-04-13 13:40 +0200
  Re: [PATCH v3 6/7] x86/cpu: Add Erratum 88 detection on AMD Andy Lutomirski <luto@amacapital.net> - 2016-04-08 03:50 +0200
    Re: [PATCH v3 6/7] x86/cpu: Add Erratum 88 detection on AMD Borislav Petkov <bp@alien8.de> - 2016-04-08 12:00 +0200
  Re: [PATCH v3 2/7] x86/arch_prctl: Fix ARCH_GET_FS and ARCH_GET_GS Ingo Molnar <mingo@kernel.org> - 2016-04-08 09:20 +0200
    Re: [PATCH v3 2/7] x86/arch_prctl: Fix ARCH_GET_FS and ARCH_GET_GS Dmitry Safonov <0x7f454c46@gmail.com> - 2016-04-08 11:40 +0200
    Re: [PATCH v3 2/7] x86/arch_prctl: Fix ARCH_GET_FS and ARCH_GET_GS Andy Lutomirski <luto@amacapital.net> - 2016-04-08 18:10 +0200
  Re: [PATCH v3 0/7] x86: Pile o' FS/GS changes Borislav Petkov <bp@alien8.de> - 2016-04-08 12:40 +0200
  Re: [PATCH v3 0/7] x86: Pile o' FS/GS changes Borislav Petkov <bp@alien8.de> - 2016-04-08 12:50 +0200

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