From: Marco Elver <elver@google.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Florian Weimer <fweimer@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Arnd Bergmann <arnd@arndb.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Collingbourne <pcc@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Alexander Potapenko <glider@google.com>,
sparclinux@vger.kernel.org,
linux-arch <linux-arch@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-api@vger.kernel.org, kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: siginfo_t ABI break on sparc64 from si_addr_lsb move 3y ago
Date: Thu, 29 Apr 2021 20:46:48 +0200 [thread overview]
Message-ID: <CANpmjNNeH7+7H3y-5BCNGx+Yo11HG-F3M5TLqCAXd11Up5PTWA@mail.gmail.com> (raw)
In-Reply-To: <m11rat9f85.fsf@fess.ebiederm.org>
On Thu, 29 Apr 2021 at 19:24, Eric W. Biederman <ebiederm@xmission.com> wrote:
[...]
> > Granted, nobody seems to have noticed because I don't even know if these
> > fields have use on sparc64. But I don't yet see this as justification to
> > leave things as-is...
> >
> > The collateral damage of this, and the acute problem that I'm having is
> > defining si_perf in a sort-of readable and portable way in siginfo_t
> > definitions that live outside the kernel, where sparc64 does not yet
> > have broken si_addr_lsb. And the same difficulty applies to the kernel
> > if we want to unbreak sparc64, while not wanting to move si_perf for
> > other architectures.
> >
> > There are 2 options I see to solve this:
> >
> > 1. Make things simple again. We could just revert the change moving
> > si_addr_lsb into the union, and sadly accept we'll have to live with
> > that legacy "design" mistake. (si_perf stays in the union, but will
> > unfortunately change its offset for all architectures... this one-off
> > move might be ok because it's new.)
> >
> > 2. Add special cases to retain si_addr_lsb in the union on architectures
> > that do not have __ARCH_SI_TRAPNO (the majority). I have added a
> > draft patch that would do this below (with some refactoring so that
> > it remains sort-of readable), as an experiment to see how complicated
> > this gets.
> >
> > Which option do you prefer? Are there better options?
>
> Personally the most important thing to have is a single definition
> shared by all architectures so that we consolidate testing.
>
> A little piece of me cries a little whenever I see how badly we
> implemented the POSIX design. As specified by POSIX the fields can be
> place in siginfo such that 32bit and 64bit share a common definition.
> Unfortunately we did not addpadding after si_addr on 32bit to
> accommodate a 64bit si_addr.
I think it's even worse than that, see the fun I had with siginfo last
week: https://lkml.kernel.org/r/20210422191823.79012-1-elver@google.com
... because of the 3 initial ints and no padding after them, we can't
portably add __u64 fields to siginfo, and are forever forced to have
subtly different behaviour between 32-bit and 64-bit architectures.
:-/
> I find it unfortunate that we are adding yet another definition that
> requires translation between 32bit and 64bit, but I am glad
> that at least the translation is not architecture specific. That common
> definition is what has allowed this potential issue to be caught
> and that makes me very happy to see.
>
> Let's go with Option 3.
>
> Confirm BUS_MCEERR_AR, BUS_MCEERR_AO, SEGV_BNDERR, SEGV_PKUERR are not
> in use on any architecture that defines __ARCH_SI_TRAPNO, and then fixup
> the userspace definitions of these fields.
>
> To the kernel I would add some BUILD_BUG_ON's to whatever the best
> maintained architecture (sparc64?) that implements __ARCH_SI_TRAPNO just
> to confirm we don't create future regressions by accident.
>
> I did a quick search and the architectures that define __ARCH_SI_TRAPNO
> are sparc, mips, and alpha. All have 64bit implementations. A further
> quick search shows that none of those architectures have faults that
> use BUS_MCEERR_AR, BUS_MCEERR_AO, SEGV_BNDERR, SEGV_PKUERR, nor do
> they appear to use mm/memory-failure.c
>
> So it doesn't look like we have an ABI regression to fix.
That sounds fine to me -- my guess was that they're not used on these
architectures, but I just couldn't make that call.
I have patches adding compile-time asserts for sparc64, arm, arm64
ready to go. I'll send them after some more testing.
Thanks,
-- Marco
next prev parent reply other threads:[~2021-04-29 18:47 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 7:48 siginfo_t ABI break on sparc64 from si_addr_lsb move 3y ago Marco Elver
2021-04-29 17:23 ` Eric W. Biederman
2021-04-29 18:46 ` Marco Elver [this message]
2021-04-29 20:48 ` Arnd Bergmann
2021-04-30 17:08 ` Eric W. Biederman
2021-04-30 19:07 ` Marco Elver
2021-04-30 20:15 ` Eric W. Biederman
2021-04-30 23:50 ` Marco Elver
2021-04-30 22:49 ` [RFC][PATCH 0/3] signal: Move si_trapno into the _si_fault union Eric W. Biederman
2021-04-30 22:50 ` [PATCH 1/3] siginfo: Move si_trapno inside the union inside _si_fault Eric W. Biederman
2021-05-01 10:31 ` Marco Elver
2021-05-02 18:27 ` Eric W. Biederman
2021-04-30 22:54 ` [PATCH 2/3] signal: Implement SIL_FAULT_TRAPNO Eric W. Biederman
2021-04-30 23:19 ` Eric W. Biederman
2021-05-01 10:33 ` Marco Elver
2021-05-02 18:24 ` Eric W. Biederman
2021-04-30 22:55 ` [PATCH 3/3] signal: Use dedicated helpers to send signals with si_trapno set Eric W. Biederman
2021-05-01 10:33 ` Marco Elver
2021-04-30 22:56 ` [PATCH 4/3] signal: Remove __ARCH_SI_TRAPNO Eric W. Biederman
2021-04-30 23:23 ` Is perf_sigtrap synchronous? Eric W. Biederman
2021-05-01 0:28 ` Marco Elver
2021-04-30 23:42 ` [PATCH 5/3] signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency Eric W. Biederman
2021-05-01 10:35 ` Marco Elver
2021-04-30 23:43 ` [PATCH 6/3] signal: Factor force_sig_perf out of perf_sigtrap Eric W. Biederman
2021-05-01 10:45 ` Marco Elver
2021-04-30 23:43 ` [PATCH 7/3] signal: Deliver all of the perf_data in si_perf Eric W. Biederman
2021-05-01 10:47 ` Marco Elver
2021-05-02 18:39 ` Eric W. Biederman
2021-05-02 19:13 ` Marco Elver
2021-05-03 12:44 ` Peter Zijlstra
2021-05-03 19:38 ` Eric W. Biederman
2021-05-03 19:53 ` Marco Elver
2021-04-30 23:47 ` [RFC][PATCH 0/3] signal: Move si_trapno into the _si_fault union Eric W. Biederman
2021-05-01 0:37 ` Marco Elver
2021-05-01 15:16 ` Eric W. Biederman
2021-05-01 16:24 ` Marco Elver
2021-05-03 20:25 ` [PATCH 00/12] signal: sort out si_trapno and si_perf Eric W. Biederman
2021-05-03 20:38 ` [PATCH 01/12] sparc64: Add compile-time asserts for siginfo_t offsets Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 02/12] arm: " Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 03/12] arm64: " Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 04/12] siginfo: Move si_trapno inside the union inside _si_fault Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 05/12] signal: Implement SIL_FAULT_TRAPNO Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 06/12] signal: Use dedicated helpers to send signals with si_trapno set Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 07/12] signal: Remove __ARCH_SI_TRAPNO Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 08/12] signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 09/12] signal: Factor force_sig_perf out of perf_sigtrap Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 10/12] signal: Redefine signinfo so 64bit fields are possible Eric W. Beiderman
2021-05-03 21:04 ` Eric W. Biederman
2021-05-03 22:47 ` Marco Elver
2021-05-04 3:42 ` Eric W. Biederman
2021-05-04 4:03 ` Peter Collingbourne
2021-05-04 9:52 ` Marco Elver
2021-05-04 16:16 ` Eric W. Biederman
2021-05-03 20:38 ` [PATCH 11/12] signal: Deliver all of the siginfo perf data in _perf Eric W. Beiderman
2021-05-03 20:38 ` [PATCH 12/12] signalfd: Remove SIL_FAULT_PERF_EVENT fields from signalfd_siginfo Eric W. Beiderman
2021-05-04 21:13 ` [PATCH v3 00/12] signal: sort out si_trapno and si_perf Eric W. Biederman
2021-05-04 22:05 ` Marco Elver
2021-05-05 14:12 ` Eric W. Biederman
2021-05-05 14:10 ` [PATCH v3 01/12] sparc64: Add compile-time asserts for siginfo_t offsets Eric W. Beiderman
2021-05-05 14:10 ` [PATCH v3 02/12] arm: " Eric W. Beiderman
2021-05-05 14:10 ` [PATCH v3 03/12] arm64: " Eric W. Beiderman
2021-05-05 14:10 ` [PATCH v3 04/12] signal: Verify the alignment and size of siginfo_t Eric W. Beiderman
2021-05-05 17:24 ` Marco Elver
2021-05-05 14:10 ` [PATCH v3 05/12] siginfo: Move si_trapno inside the union inside _si_fault Eric W. Beiderman
2021-05-05 14:10 ` [PATCH v3 06/12] signal: Implement SIL_FAULT_TRAPNO Eric W. Beiderman
2021-05-05 17:25 ` Marco Elver
2021-05-05 14:10 ` [PATCH v3 07/12] signal: Use dedicated helpers to send signals with si_trapno set Eric W. Beiderman
2021-05-05 17:25 ` Marco Elver
2021-05-05 14:10 ` [PATCH v3 08/12] signal: Remove __ARCH_SI_TRAPNO Eric W. Beiderman
2021-05-05 17:25 ` Marco Elver
2021-05-05 14:10 ` [PATCH v3 09/12] signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency Eric W. Beiderman
2021-05-05 17:26 ` Marco Elver
2021-05-05 14:10 ` [PATCH v3 10/12] signal: Factor force_sig_perf out of perf_sigtrap Eric W. Beiderman
2021-05-05 17:26 ` Marco Elver
2021-05-06 10:54 ` Peter Zijlstra
2021-05-05 14:11 ` [PATCH v3 11/12] signal: Deliver all of the siginfo perf data in _perf Eric W. Beiderman
2021-05-05 17:27 ` Marco Elver
2021-05-05 14:11 ` [PATCH v3 12/12] signalfd: Remove SIL_FAULT_PERF_EVENT fields from signalfd_siginfo Eric W. Beiderman
2021-05-05 17:27 ` Marco Elver
2021-05-05 17:28 ` [PATCH v3 00/12] signal: sort out si_trapno and si_perf Marco Elver
2021-05-06 7:00 ` Geert Uytterhoeven
2021-05-06 10:43 ` Marco Elver
2021-05-06 15:28 ` Eric W. Biederman
2021-05-06 15:14 ` Eric W. Biederman
2021-05-14 4:54 ` [GIT PULL] siginfo: ABI fixes for v5.13-rc2 Eric W. Biederman
2021-05-14 19:14 ` Linus Torvalds
2021-05-14 21:15 ` Eric W. Biederman
2021-05-14 22:38 ` Eric W. Biederman
2021-05-16 7:40 ` Ingo Molnar
2021-05-17 15:29 ` Eric W. Biederman
2021-05-21 14:59 ` [GIT PULL] siginfo: ABI fixes for v5.13-rc3 Eric W. Biederman
2021-05-21 16:34 ` pr-tracker-bot
2021-05-17 19:56 ` [PATCH v4 0/5] siginfo: ABI fixes for TRAP_PERF Eric W. Biederman
2021-05-17 19:57 ` [PATCH v4 1/5] siginfo: Move si_trapno inside the union inside _si_fault Eric W. Beiderman
2021-05-17 19:57 ` [PATCH v4 2/5] signal: Implement SIL_FAULT_TRAPNO Eric W. Beiderman
2021-05-17 19:57 ` [PATCH v4 3/5] signal: Factor force_sig_perf out of perf_sigtrap Eric W. Beiderman
2021-05-17 19:57 ` [PATCH v4 4/5] signal: Deliver all of the siginfo perf data in _perf Eric W. Beiderman
2021-05-17 19:57 ` [PATCH v4 5/5] signalfd: Remove SIL_PERF_EVENT fields from signalfd_siginfo Eric W. Beiderman
2021-05-17 20:53 ` [PATCH v4 0/5] siginfo: ABI fixes for TRAP_PERF Marco Elver
2021-05-18 3:46 ` Eric W. Biederman
2021-05-18 6:44 ` Marco Elver
2021-05-01 16:26 ` [RFC][PATCH 0/3] signal: Move si_trapno into the _si_fault union Marco Elver
2021-07-15 18:09 ` [PATCH 0/6] Final si_trapno bits Eric W. Biederman
2021-07-15 18:11 ` [PATCH 1/6] sparc64: Add compile-time asserts for siginfo_t offsets Eric W. Biederman
2021-07-15 18:11 ` [PATCH 2/6] arm: " Eric W. Biederman
2021-07-15 18:11 ` [PATCH 3/6] arm64: " Eric W. Biederman
2021-07-15 18:12 ` [PATCH 4/6] signal/sparc: si_trapno is only used with SIGILL ILL_ILLTRP Eric W. Biederman
2021-07-16 11:49 ` Marco Elver
2021-07-15 18:12 ` [PATCH 5/6] signal/alpha: si_trapno is only used with SIGFPE and SIGTRAP TRAP_UNK Eric W. Biederman
2021-07-16 11:48 ` Marco Elver
2021-07-15 18:13 ` [PATCH 6/6] signal: Remove the generic __ARCH_SI_TRAPNO support Eric W. Biederman
2021-07-16 11:48 ` Marco Elver
2021-07-16 11:50 ` [PATCH 0/6] Final si_trapno bits Marco Elver
2021-07-16 16:08 ` Eric W. Biederman
2021-07-16 17:15 ` Marco Elver
2021-07-16 16:06 ` [PATCH 7/7] signal: Verify the alignment and size of siginfo_t Eric W. Biederman
2021-07-16 16:07 ` [PATCH 8/6] signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency Eric W. Biederman
2021-04-30 20:43 ` siginfo_t ABI break on sparc64 from si_addr_lsb move 3y ago Arnd Bergmann
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