LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Jan Beulich" <jbeulich@novell.com>
To: "Jeff Dike" <jdike@addtoit.com>, "Andi Kleen" <ak@suse.de>
Cc: <linux-kernel@vger.kernel.org>, <patches@x86-64.org>
Subject: Re: [patches] [PATCH 2.6.21 review I] [4/25] x86: kernel-mode faults pollute current->thead
Date: Mon, 12 Feb 2007 09:32:10 +0000	[thread overview]
Message-ID: <45D0422A.76E4.0078.0@novell.com> (raw)
In-Reply-To: <20070210115016.652C913DCE@wotan.suse.de>

>>> Andi Kleen <ak@suse.de> 10.02.07 12:50 >>>
>
>From: Jeff Dike <jdike@addtoit.com>
>
>Kernel-mode traps on x86_64 can pollute the trap information for a previous
>userspace trap for which the signal has not yet been delivered to the
>process.
>
>do_trap and do_general_protection set task->thread.error_code and .trapno
>for kernel traps.  If a kernel-mode trap arrives between the arrival of a
>userspace trap and the delivery of the associated SISGEGV to the process,
>the process will get the kernel trap information in its sigcontext.
>
>This causes UML process segfaults, as the trapno that the UML kernel sees
>is 13, rather than the 14 for normal page faults.  So, the UML kernel
>passes the SIGSEGV along to its process.
>
>I don't claim to fully understand the problem.  On the one hand, a check in
>do_general_protection for a pending SIGSEGV turned up nothing.  On the
>other hand, this patch fixed the UML process segfault problem.
>
>The patch below moves the setting of error_code and trapno so that that
>only happens in the case of userspace faults.  As a side-effect, this
>should speed up kernel-mode fault handling a tiny bit.

This breaks consumers of notify_die() relying on the proper trap number being
passed, as the call to notify_die() from die() currently reads
current->thread.trap_no.

Also, you seem to leave other places where trap_no gets set untouched -
is this intentional (do_debug - probably correct here, kernel_math_error -
probably incorrect here)?

>I looked at i386, and there is a similar situation.  In this case, there is
>duplicate code setting task->thread.error_code and trapno.  I deleted one,
>leaving the copy that runs in the case of a userspace fault.

Likewise.

Jan

  reply	other threads:[~2007-02-12  9:32 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-10 11:50 [PATCH 2.6.21 review I] [1/25] x86_64: Add __copy_from_user_nocache Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [2/25] x86_64: Make the NUMA hash function nodemap allocation Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [3/25] i386: Convert i386 PDA code to use %fs Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [4/25] x86: kernel-mode faults pollute current->thead Andi Kleen
2007-02-12  9:32   ` Jan Beulich [this message]
2007-02-12 16:42     ` [patches] " Jeff Dike
2007-02-12 17:01       ` Jan Beulich
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [5/25] i386: revert i386-fix-the-verify_quirk_intel_irqbalance Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [6/25] x86_64: revert x86_64-mm-add-genapic_force Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [7/25] x86: revert x86_64-mm-fix-the-irqbalance-quirk-for-e7320-e7520-e7525 Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [8/25] x86_64: optimize & fix APIC mode setup Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [9/25] x86_64: always use physical delivery mode on > 8 CPUs Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [10/25] x86_64: remove clustered APIC mode Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [11/25] x86: default to physical mode on hotplug CPU kernels Andi Kleen
2007-02-11 11:13   ` Eric W. Biederman
2007-02-12 22:36     ` Andi Kleen
2007-02-12 23:10       ` Eric W. Biederman
2007-02-12 23:51         ` Siddha, Suresh B
2007-02-12 23:43       ` Siddha, Suresh B
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [12/25] x86_64: x86_64-make-the-numa-hash-function-nodemap-allocation fix fix Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [13/25] i386: Fix a typo in an IRQ handler name Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [14/25] x86: Share what's shareable Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [15/25] i386: Only call unreachable_devices() when type 1 is available Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [16/25] i386: Detect and support the E7520 and the 945G/GZ/P/PL Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [17/25] i386: Reserve resources but only when we're sure about them Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [18/25] x86_64: Fix x86_64 ioremap base_address Andi Kleen
2007-02-10 11:58   ` Arjan van de Ven
2007-02-10 12:07     ` Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [19/25] x86: Reject a broken MCFG tables on Asus etc Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [20/25] x86_64: get rid of ARCH_HAVE_XTIME_LOCK Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [21/25] x86_64: a memcpy that tries to reduce cache pressure Andi Kleen
2007-02-12  9:57   ` [patches] " Jan Beulich
2007-02-12 10:25     ` Andi Kleen
2007-02-13 11:27   ` Eric Dumazet
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [22/25] x86_64: use memcpy_uncached_read() in RDMA interrupt handler to reduce packet loss Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [23/25] x86_64: improved iommu documentation Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [24/25] x86_64: do not always end the stack trace with ULONG_MAX Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [25/25] i386: arch/i386/kernel/e820.c should #include <asm/setup.h Andi Kleen
2007-02-13  7:52 [patches] [PATCH 2.6.21 review I] [4/25] x86: kernel-mode faults pollute current->thead Jan Beulich
2007-02-13 10:00 ` Andi Kleen
2007-02-14 17:51 ` Jeff Dike
2007-02-15  8:01   ` Jan Beulich
2007-02-15 16:23     ` Jeff Dike

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=45D0422A.76E4.0078.0@novell.com \
    --to=jbeulich@novell.com \
    --cc=ak@suse.de \
    --cc=jdike@addtoit.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=patches@x86-64.org \
    --subject='Re: [patches] [PATCH 2.6.21 review I] [4/25] x86: kernel-mode faults pollute current->thead' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).