Re: [PATCH 00/10] x86: Various SYSENTER/SYSEXIT/#DB fixes and cleanups

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH 00/10] x86: Various SYSENTER/SYSEXIT/#DB fixes and cleanups
Date	2016-02-29 20:00 +0100
Message-ID	<r7Bd0-6NF-15@gated-at.bofh.it> (permalink)
References	<r7oz8-6aX-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Sun, Feb 28, 2016 at 9:28 PM, Andy Lutomirski <luto@kernel.org> wrote:
>
> While I was doing all this, I also noticed that DR6 and BTF handling
> in do_debug was a bit off.  Two of the patches in here try to fix it
> up.

It's worth noting that do_debug is really quite screwed up with or
without this patchset applied.  For example:

    /*
     * Let others (NMI) know that the debug stack is in use
     * as we may switch to the interrupt stack.
     */
    debug_stack_usage_inc();

    /* It's safe to allow irq's after DR6 has been saved */
    preempt_disable();
    cond_local_irq_enable(regs);

This has never really been valid.  It should be guarded by an
if(user_mode(regs)).  And we need to kill the die_notifier garbage in
here -- it makes it basically impossible to understand what's going
on.

--Andy

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[PATCH 00/10] x86: Various SYSENTER/SYSEXIT/#DB fixes and cleanups Andy Lutomirski <luto@kernel.org> - 2016-02-29 06:40 +0100
  [PATCH 06/10] x86/traps: Clear DR6 early in do_debug and improve the comment Andy Lutomirski <luto@kernel.org> - 2016-02-29 06:40 +0100
  [PATCH 08/10] x86/entry: Only allocate space for SYSENTER_stack if needed Andy Lutomirski <luto@kernel.org> - 2016-02-29 06:40 +0100
  [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing below the existing FLAGS test Andy Lutomirski <luto@kernel.org> - 2016-02-29 06:40 +0100
    Re: [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing  below the existing FLAGS test Borislav Petkov <bp@alien8.de> - 2016-02-29 21:40 +0100
      Re: [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing  below the existing FLAGS test Andy Lutomirski <luto@amacapital.net> - 2016-02-29 21:50 +0100
        Re: [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing  below the existing FLAGS test Borislav Petkov <bp@alien8.de> - 2016-02-29 23:10 +0100
          Re: [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing  below the existing FLAGS test Borislav Petkov <bp@alien8.de> - 2016-02-29 23:40 +0100
          Re: [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing  below the existing FLAGS test Brian Gerst <brgerst@gmail.com> - 2016-02-29 23:40 +0100
  Re: [PATCH 00/10] x86: Various SYSENTER/SYSEXIT/#DB fixes and cleanups Andy Lutomirski <luto@amacapital.net> - 2016-02-29 20:00 +0100

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