From: David Laight <David.Laight@ACULAB.COM>
To: 'Arnd Bergmann' <arnd@arndb.de>, Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Ilie Halip <ilie.halip@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: RE: objtool warning "uses BP as a scratch register" with clang-9
Date: Fri, 30 Aug 2019 16:12:04 +0000 [thread overview]
Message-ID: <7fb03b2951e04c5f9b2529a6b8d5c746@AcuMS.aculab.com> (raw)
In-Reply-To: <CAK8P3a33LQAzsReSUyB_aZxkws28RP=oJocQXonYbxxBky7aaQ@mail.gmail.com>
From: Arnd Bergmann
> Sent: 30 August 2019 16:59
...
> > Or even better, it would be great if we could get Clang to change their
> > memset() insertion heuristics, so that KASAN acts more like non-KASAN
> > code in that regard.
>
> I suspect that's going to be harder. The clang-9 release is going to be
> soon, and that change probably wouldn't be considered a regression fix.
>
> Maybe Nick can find what happens, but I don't actually see any reference
> to KASAN in the llvm source code related to the memset generation.
>
> https://github.com/llvm-mirror/clang/blob/master/lib/CodeGen/CGExprAgg.cpp#L1803
> has a check for >16 bytes, but that again does not match my observation.
That looks like the code for initialising a local structure variable,
not for merging 'random' writes into a memset().
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2019-08-30 16:12 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 12:30 Arnd Bergmann
2019-08-27 14:51 ` Josh Poimboeuf
2019-08-27 14:59 ` Ilie Halip
2019-08-27 19:00 ` Arnd Bergmann
2019-08-27 19:22 ` Josh Poimboeuf
2019-08-27 19:47 ` Arnd Bergmann
2019-08-27 21:21 ` Nick Desaulniers
2019-08-28 9:00 ` Arnd Bergmann
2019-08-28 14:06 ` Arnd Bergmann
2019-08-28 14:51 ` Josh Poimboeuf
2019-08-28 15:29 ` Arnd Bergmann
2019-08-28 17:57 ` Josh Poimboeuf
2019-08-28 19:41 ` Arnd Bergmann
2019-08-28 15:13 ` Arnd Bergmann
2019-08-28 15:22 ` Josh Poimboeuf
2019-08-28 15:28 ` Arnd Bergmann
2019-08-28 15:40 ` Arnd Bergmann
2019-08-29 23:24 ` Josh Poimboeuf
2019-08-30 10:44 ` Arnd Bergmann
2019-08-30 15:14 ` Josh Poimboeuf
2019-08-30 15:58 ` Arnd Bergmann
2019-08-30 16:12 ` David Laight [this message]
2019-08-30 16:03 ` Linus Torvalds
2019-08-29 17:34 ` Josh Poimboeuf
2019-08-29 18:30 ` Linus Torvalds
2019-08-29 20:21 ` Arnd Bergmann
2019-08-29 22:26 ` Linus Torvalds
2019-08-30 15:02 ` Josh Poimboeuf
2019-08-30 15:39 ` David Laight
2019-08-30 15:48 ` Linus Torvalds
2019-08-30 15:55 ` David Laight
2019-08-30 16:01 ` Linus Torvalds
2019-08-30 16:42 ` David Laight
2019-08-30 16:49 ` Josh Poimboeuf
2019-09-02 9:02 ` David Laight
2019-09-04 11:53 ` Geert Uytterhoeven
2019-08-28 22:13 ` Nick Desaulniers
2019-08-29 0:28 ` Josh Poimboeuf
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