From: ebiederm@xmission•com (Eric W. Biederman)
To: linux-arm-kernel@lists•infradead.org
Subject: sparc/ppc/arm compat siginfo ABI regressions: sending SIGFPE via kill() returns wrong values in si_pid and si_uid
Date: Sun, 15 Apr 2018 10:22:31 -0500 [thread overview]
Message-ID: <87lgdocx54.fsf@xmission.com> (raw)
In-Reply-To: <20180415131206.GR16141@n2100.armlinux.org.uk> (Russell King's message of "Sun, 15 Apr 2018 14:12:06 +0100")
Russell King - ARM Linux <linux@armlinux•org.uk> writes:
> On Fri, Apr 13, 2018 at 12:53:49PM -0700, Linus Torvalds wrote:
>> On Fri, Apr 13, 2018 at 11:45 AM, Dave Martin <Dave.Martin@arm•com> wrote:
>> >
>> > Most uses I've seen do nothing more than use the FPE_xyz value to
>> > format diagnostic messages while dying. I struggled to find code that
>> > made a meaningful functional decision based on the value, though that's
>> > not proof...
>>
>> Yeah. I've seen code that cares about SIGFPE deeply, but it's almost
>> invariably about some emulated environment (eg Java VM, or CPU
>> emulation).
>>
>> And the siginfo data is basically never good enough for those
>> environments anyway on its own, so they will go and look at the actual
>> instruction that caused the fault and the register state instead,
>> because they need *all* the information.
>>
>> The cases that use si_code are the ones that just trapped signals in
>> order to give a more helpful abort message.
>>
>> So I could certainly imagine that si_code is actually used by somebody
>> who then decides to actuall act differently on it, but aside from
>> perhaps printing out a different message, it sounds far-fetched.
>
> Okay, in that case let's just use FPE_FLTINV. That makes the patch
> easily back-portable for stable kernels.
If we want to I don't think backporting 266da65e9156 ("signal: Add
FPE_FLTUNK si_code for undiagnosable fp exceptions") would be at
all difficult.
What it is changing has been stable for quite a while. The surroundings
might change and so it might require some trivial manual fixup but I
don't expect any problems.
Not that I want to derail the consensus but if we want to backport
similar fixes for arm64 or the other architectures that wind up using
FPE_FLTUNK for their fix we would need to backport 266da65e9156 anyway.
Eric
next prev parent reply other threads:[~2018-04-15 15:22 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180409152253.GD10489@altlinux.org>
2018-04-12 1:34 ` sparc/ppc/arm compat siginfo ABI regressions: sending SIGFPE via kill() returns wrong values in si_pid and si_uid Dmitry V. Levin
2018-04-12 1:45 ` Linus Torvalds
2018-04-12 9:58 ` Russell King - ARM Linux
2018-04-12 11:03 ` Dmitry V. Levin
2018-04-12 12:19 ` Russell King - ARM Linux
2018-04-12 12:49 ` Dmitry V. Levin
2018-04-12 13:14 ` Russell King - ARM Linux
2018-04-12 16:50 ` Linus Torvalds
2018-04-12 17:20 ` Russell King - ARM Linux
2018-04-12 17:22 ` Linus Torvalds
2018-04-13 9:42 ` Russell King - ARM Linux
2018-04-13 16:33 ` Linus Torvalds
2018-04-13 17:08 ` Dave Martin
2018-04-13 17:54 ` Russell King - ARM Linux
2018-04-13 18:23 ` Linus Torvalds
2018-04-13 18:45 ` Dave Martin
2018-04-13 19:53 ` Linus Torvalds
2018-04-15 13:12 ` Russell King - ARM Linux
2018-04-15 15:22 ` Eric W. Biederman [this message]
2018-04-15 15:56 ` [RFC PATCH 0/3] Dealing with the aliases of SI_USER Eric W. Biederman
2018-04-15 15:57 ` [RFC PATCH 1/3] signal: Ensure every siginfo we send has all bits initialized Eric W. Biederman
2018-04-17 13:23 ` Dave Martin
2018-04-17 19:37 ` Eric W. Biederman
2018-04-18 12:47 ` Dave Martin
2018-04-18 14:22 ` Eric W. Biederman
2018-04-19 8:26 ` Dave Martin
2018-04-15 15:58 ` [RFC PATCH 2/3] signal: Reduce copy_siginfo_to_user to just copy_to_user Eric W. Biederman
2018-04-15 15:59 ` [RFC PATCH 3/3] signal: Stop special casing TRAP_FIXME and FPE_FIXME in siginfo_layout Eric W. Biederman
2018-04-15 18:16 ` [RFC PATCH 0/3] Dealing with the aliases of SI_USER Linus Torvalds
2018-04-16 2:03 ` Eric W. Biederman
2018-04-18 17:58 ` Eric W. Biederman
2018-04-19 9:28 ` Dave Martin
2018-04-19 14:40 ` Eric W. Biederman
2018-04-13 18:35 ` sparc/ppc/arm compat siginfo ABI regressions: sending SIGFPE via kill() returns wrong values in si_pid and si_uid Dave Martin
2018-04-13 18:50 ` Russell King - ARM Linux
2018-04-13 18:56 ` Dave Martin
2018-04-12 17:35 ` Dmitry V. Levin
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