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From: Borislav Petkov <bp@alien8.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [patch 01/10] x86/fpu/signal: Clarify exception handling in restore_fpregs_from_user()
Date: Mon, 30 Aug 2021 21:33:42 +0200	[thread overview]
Message-ID: <YS0ylo9nTHD9NiAp@zn.tnic> (raw)
In-Reply-To: <20210830162545.374070793@linutronix.de>

On Mon, Aug 30, 2021 at 06:27:22PM +0200, Thomas Gleixner wrote:
> FPU restore from a signal frame can trigger various exceptions. The
> exceptions are caught with an exception table entry. The handler of this
> entry sets the error return value to the negated exception number.
> 
> Any other exception than #PF is fatal and recovery is not possible. This
> relies on the fact that the #PF exception number is the same as EFAULT, but
> that's not really obvious.
> 
> Check the error code for -X86_TRAP_PF instead of checking it for -EFAULT to
> make it clear how that works.

I guess you wanna fixup the comment over XSTATE_OP() too and perhaps
mention ex_handler_fault() explicitly so that one can make her/his way
around the code and pinpoint quickly where it sticks that exception
number into rAX.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  reply	other threads:[~2021-08-30 19:33 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-30 16:27 [patch 00/10] x86/fpu: Clean up error handling in sigframe related code Thomas Gleixner
2021-08-30 16:27 ` [patch 01/10] x86/fpu/signal: Clarify exception handling in restore_fpregs_from_user() Thomas Gleixner
2021-08-30 19:33   ` Borislav Petkov [this message]
2021-08-30 20:07     ` Borislav Petkov
2021-08-30 20:09     ` Thomas Gleixner
2021-08-30 21:02       ` Al Viro
2021-08-30 21:26         ` Linus Torvalds
2021-08-30 21:30           ` Al Viro
2021-08-30 22:00             ` Linus Torvalds
2021-08-30 22:12               ` Thomas Gleixner
2021-08-30 22:26                 ` Linus Torvalds
2021-08-31  0:06               ` Al Viro
2021-08-31  0:34               ` Thomas Gleixner
2021-08-31  7:39                 ` Borislav Petkov
2021-08-31 18:39                   ` Luck, Tony
2021-09-01  7:27                     ` Borislav Petkov
2021-08-30 22:01           ` Thomas Gleixner
2021-08-30 22:11             ` Linus Torvalds
2021-09-01 12:00           ` Thomas Gleixner
2021-09-01 15:52             ` Thomas Gleixner
2021-09-01 16:47               ` Sean Christopherson
2021-09-01 19:22                 ` Thomas Gleixner
2021-09-01 19:22                 ` Dave Hansen
2021-09-02 13:08                 ` Jarkko Sakkinen
2021-09-02 14:08                   ` Thomas Gleixner
2021-09-03  6:00                     ` Jarkko Sakkinen
2021-09-03  6:05                       ` Jarkko Sakkinen
2021-08-30 16:27 ` [patch 02/10] x86/fpu/signal: Move header zeroing out of xsave_to_user_sigframe() Thomas Gleixner
2021-08-30 16:27 ` [patch 03/10] x86/fpu/signal: Move xstate clearing out of copy_fpregs_to_sigframe() Thomas Gleixner
2021-08-30 16:27 ` [patch 04/10] x86/fpu/signal: Change return type of copy_fpstate_to_sigframe() to boolean Thomas Gleixner
2021-08-30 16:27 ` [patch 05/10] x86/fpu/signal: Change return type of copy_fpregs_to_sigframe() helpers " Thomas Gleixner
2021-08-30 16:27 ` [patch 06/10] x86/signal: Change return type of restore_sigcontext() " Thomas Gleixner
2021-08-30 16:27 ` [patch 07/10] x86/fpu/signal: Change return type of fpu__restore_sig() " Thomas Gleixner
2021-08-30 16:27 ` [patch 08/10] x86/fpu/signal: Change return type of __fpu_restore_sig() " Thomas Gleixner
2021-08-30 16:27 ` [patch 09/10] x86/fpu/signal: Change return code of check_xstate_in_sigframe() " Thomas Gleixner
2021-08-30 16:27 ` [patch 10/10] x86/fpu/signal: Change return code of restore_fpregs_from_user() " Thomas Gleixner
2021-08-30 17:39 ` [patch 00/10] x86/fpu: Clean up error handling in sigframe related code Linus Torvalds
2021-08-30 18:51   ` Thomas Gleixner

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