From: Will Deacon <will@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Marco Elver <elver@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen
Date: Thu, 14 May 2020 13:01:04 +0100 [thread overview]
Message-ID: <20200514120104.GD4280@willie-the-truck> (raw)
In-Reply-To: <20200514112142.GV2978@hirez.programming.kicks-ass.net>
On Thu, May 14, 2020 at 01:21:42PM +0200, Peter Zijlstra wrote:
> On Wed, May 13, 2020 at 03:58:30PM +0200, Marco Elver wrote:
> > On Wed, 13 May 2020 at 15:24, Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > On Wed, May 13, 2020 at 03:15:55PM +0200, Marco Elver wrote:
> > > > So far so good, except: both __no_sanitize_or_inline and
> > > > __no_kcsan_or_inline *do* avoid KCSAN instrumenting plain accesses, it
> > > > just doesn't avoid explicit kcsan_check calls, like those in
> > > > READ/WRITE_ONCE if KCSAN is enabled for the compilation unit. That's
> > > > just because macros won't be redefined just for __no_sanitize
> > > > functions. Similarly, READ_ONCE_NOCHECK does work as expected, and its
> > > > access is unchecked.
> > > >
> > > > This will have the expected result:
> > > > __no_sanitize_or_inline void foo(void) { x++; } // no data races reported
> > > >
> > > > This will not work as expected:
> > > > __no_sanitize_or_inline void foo(void) { READ_ONCE(x); } // data
> > > > races are reported
> > > >
> > > > All this could be fixed if GCC devs would finally take my patch to
> > > > make -fsanitize=thread distinguish volatile [1], but then we have to
> > > > wait ~years for the new compilers to reach us. So please don't hold
> > > > your breath for this one any time soon.
> > > > [1] https://gcc.gnu.org/pipermail/gcc-patches/2020-April/544452.html
> > >
> > > Right, but that does not address the much larger issue of the attribute
> > > vs inline tranwreck :/
> >
> > Could you check if Clang is equally broken for you? I think GCC and
> > Clang have differing behaviour on this. No idea what it takes to fix
> > GCC though.
>
> So I have some good and some maybe not so good news.
>
> Given the patch below (on top of tglx's entry-v5-the-rest tag); I did
> find that I could actually build alternative.o for gcc-{8,9,10} and
> indeed clang-10. Any earlier gcc (I tried, 5,6,7) does not build:
>
> ../arch/x86/include/asm/ptrace.h:126:28: error: inlining failed in call to always_inline ‘user_mode’: function attribute mismatch
>
> I dumped the poke_int3_handler output using objdump, find the attached
> files.
>
> It looks like clang-10 doesn't want to turn UBSAN off :/ The GCC files
> look OK, no funny calls in those.
>
> (the config has KASAN/UBSAN on, it looks like KCSAN and KASAN are
> mutually exclusive)
>
> ---
>
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 77c83833d91e..06d8db612efc 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -990,7 +990,7 @@ static __always_inline int patch_cmp(const void *key, const void *elt)
> return 0;
> }
>
> -int noinstr poke_int3_handler(struct pt_regs *regs)
> +int noinstr __no_kcsan __no_sanitize_address __no_sanitize_undefined poke_int3_handler(struct pt_regs *regs)
> {
> struct bp_patching_desc *desc;
> struct text_poke_loc *tp;
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index 2cb42d8bdedc..5e83aada6553 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -15,6 +15,13 @@
> /* all clang versions usable with the kernel support KASAN ABI version 5 */
> #define KASAN_ABI_VERSION 5
>
> +#if __has_feature(undefined_sanitizer)
Hmm, this might want to be __has_feature(undefined_behavior_sanitizer)
(and damn is that hard for a Brit to type out!)
Will
next prev parent reply other threads:[~2020-05-14 12:01 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-11 20:41 [PATCH v5 00/18] Rework READ_ONCE() to improve codegen Will Deacon
2020-05-11 20:41 ` [PATCH v5 01/18] sparc32: mm: Fix argument checking in __srmmu_get_nocache() Will Deacon
2020-05-12 14:37 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 02/18] sparc32: mm: Restructure sparc32 MMU page-table layout Will Deacon
2020-05-12 14:37 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 03/18] sparc32: mm: Change pgtable_t type to pte_t * instead of struct page * Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-17 0:00 ` [PATCH v5 04/18] " Guenter Roeck
2020-05-17 0:07 ` Guenter Roeck
2020-05-18 8:37 ` Will Deacon
2020-05-18 9:18 ` Mike Rapoport
2020-05-18 9:48 ` Guenter Roeck
2020-05-18 14:23 ` Mike Rapoport
2020-05-18 16:08 ` Guenter Roeck
2020-05-18 18:11 ` Ira Weiny
2020-05-18 18:14 ` Ira Weiny
2020-05-18 18:09 ` Guenter Roeck
2020-05-18 18:21 ` Ira Weiny
2020-05-18 19:15 ` Mike Rapoport
2020-05-19 16:40 ` Guenter Roeck
2020-05-20 17:03 ` Mike Rapoport
2020-05-20 19:03 ` Guenter Roeck
2020-05-20 19:51 ` Mike Rapoport
2020-05-21 23:02 ` Guenter Roeck
2020-05-24 12:32 ` Mike Rapoport
2020-05-24 14:01 ` Guenter Roeck
2020-05-26 13:26 ` Will Deacon
2020-05-26 14:01 ` Will Deacon
2020-05-26 15:21 ` Mike Rapoport
2020-05-26 16:18 ` Guenter Roeck
2020-05-26 16:29 ` Mike Rapoport
2020-05-26 17:15 ` Guenter Roeck
2020-05-11 20:41 ` [PATCH v5 05/18] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8 Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 06/18] netfilter: Avoid assigning 'const' pointer to non-const pointer Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 07/18] net: tls: " Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 08/18] fault_inject: Don't rely on "return value" from WRITE_ONCE() Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 09/18] arm64: csum: Disable KASAN for do_csum() Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 10/18] READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE() Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 11/18] READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 12/18] READ_ONCE: Drop pointer qualifiers when reading from scalar types Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 13/18] locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 14/18] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 15/18] gcov: Remove old GCC 3.4 support Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 16/18] kcsan: Rework data_race() so that it can be used by READ_ONCE() Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-11 20:41 ` [PATCH v5 17/18] READ_ONCE: Use data_race() to avoid KCSAN instrumentation Will Deacon
2020-05-12 8:23 ` Peter Zijlstra
2020-05-12 9:49 ` Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-20 22:17 ` Borislav Petkov
2020-05-20 22:30 ` Marco Elver
2020-05-21 7:25 ` Borislav Petkov
2020-05-21 9:37 ` Marco Elver
2020-05-21 3:30 ` Nathan Chancellor
2020-05-22 16:08 ` [tip: locking/kcsan] compiler.h: Avoid nested statement expression in data_race() tip-bot2 for Marco Elver
2020-05-11 20:41 ` [PATCH v5 18/18] linux/compiler.h: Remove redundant '#else' Will Deacon
2020-05-12 14:36 ` [tip: locking/kcsan] " tip-bot2 for Will Deacon
2020-05-12 8:18 ` [PATCH v5 00/18] Rework READ_ONCE() to improve codegen Peter Zijlstra
2020-05-12 17:53 ` Marco Elver
2020-05-12 18:55 ` Marco Elver
2020-05-12 19:07 ` Peter Zijlstra
2020-05-12 20:31 ` Marco Elver
2020-05-13 11:10 ` Peter Zijlstra
2020-05-13 11:14 ` Peter Zijlstra
2020-05-13 11:48 ` Marco Elver
2020-05-13 12:32 ` Peter Zijlstra
2020-05-13 12:40 ` Will Deacon
2020-05-13 13:15 ` Marco Elver
2020-05-13 13:24 ` Peter Zijlstra
2020-05-13 13:58 ` Marco Elver
2020-05-14 11:21 ` Peter Zijlstra
2020-05-14 11:24 ` Peter Zijlstra
2020-05-14 11:35 ` Peter Zijlstra
2020-05-14 12:01 ` Will Deacon [this message]
2020-05-14 12:27 ` Peter Zijlstra
2020-05-14 13:07 ` Marco Elver
2020-05-14 13:14 ` Peter Zijlstra
2020-05-14 12:20 ` Peter Zijlstra
2020-05-14 14:13 ` Peter Zijlstra
2020-05-14 14:20 ` Marco Elver
2020-05-15 9:20 ` Peter Zijlstra
2020-05-13 16:50 ` Will Deacon
2020-05-13 17:32 ` Marco Elver
2020-05-13 17:47 ` Will Deacon
2020-05-13 18:54 ` Marco Elver
2020-05-13 21:25 ` Will Deacon
2020-05-14 7:31 ` Marco Elver
2020-05-14 11:05 ` Will Deacon
2020-05-14 13:35 ` Marco Elver
2020-05-14 13:47 ` Peter Zijlstra
2020-05-14 13:50 ` Peter Zijlstra
2020-05-14 13:56 ` Peter Zijlstra
2020-05-14 14:24 ` Peter Zijlstra
2020-05-14 15:09 ` Thomas Gleixner
2020-05-14 15:29 ` Marco Elver
2020-05-14 19:37 ` Thomas Gleixner
2020-05-15 13:55 ` David Laight
2020-05-15 14:04 ` Marco Elver
2020-05-15 14:07 ` Peter Zijlstra
2020-05-14 15:38 ` Paul E. McKenney
2020-05-22 16:08 ` [tip: locking/kcsan] kcsan: Restrict supported compilers tip-bot2 for Marco Elver
2020-06-03 18:52 ` [PATCH v5 00/18] Rework READ_ONCE() to improve codegen Borislav Petkov
2020-06-03 19:23 ` Marco Elver
2020-06-03 22:05 ` Borislav Petkov
2020-06-08 17:32 ` Martin Liška
2020-06-08 19:56 ` Marco Elver
2020-06-09 11:55 ` Martin Liška
2020-06-09 12:36 ` Martin Liška
2020-06-09 13:45 ` Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] kcsan: Remove 'noinline' from __no_kcsan_or_inline tip-bot2 for Marco Elver
2020-05-13 13:21 ` [PATCH v5 00/18] Rework READ_ONCE() to improve codegen David Laight
2020-05-13 16:32 ` Thomas Gleixner
2020-05-12 21:14 ` Will Deacon
2020-05-12 22:00 ` Marco Elver
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=20200514120104.GD4280@willie-the-truck \
--to=will@kernel.org \
--cc=dvyukov@google.com \
--cc=elver@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).