From: Michael Davidson <md@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Potapenko <glider@google.com>,
Michal Marek <mmarek@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Shaohua Li <shli@kernel.org>, Dmitry Vyukov <dvyukov@google.com>,
Matthias Kaehlcke <mka@chromium.org>,
x86@kernel.org, linux-kbuild@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
linux-crypto@vger.kernel.org, linux-raid@vger.kernel.org
Subject: Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array
Date: Fri, 17 Mar 2017 11:52:01 -0700 [thread overview]
Message-ID: <CA+=D-XXy9yEQc-jLxSqRUwq=4ADnFqaxnsjSzV4=8jOisym=bQ@mail.gmail.com> (raw)
In-Reply-To: <20170317124404.mt3jd5q5vyk63q2w@hirez.programming.kicks-ass.net>
On Fri, Mar 17, 2017 at 5:44 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> Be that as it may; what you construct above is disgusting. Surely the
> code can be refactored to not look like dog vomit?
>
> Also; its not immediately obvious conf->copies is 'small' and this
> doesn't blow up the stack; I feel that deserves a comment somewhere.
>
I agree that the code is horrible.
It is, in fact, exactly the same solution that was used to remove
variable length arrays in structs from several of the crypto drivers a
few years ago - see the definition of SHASH_DESC_ON_STACK() in
"crypto/hash.h" - I did not, however, hide the horrors in a macro
preferring to leave the implementation visible as a warning to whoever
might touch the code next.
I believe that the actual stack usage is exactly the same as it was previously.
I can certainly wrap this up in a macro and add comments with
appropriately dire warnings in it if you feel that is both necessary
and sufficient.
next prev parent reply other threads:[~2017-03-17 19:22 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-17 0:15 [PATCH 0/7] LLVM: make x86_64 kernel build with clang Michael Davidson
2017-03-17 0:15 ` [PATCH 1/7] Makefile, LLVM: add -no-integrated-as to KBUILD_[AC]FLAGS Michael Davidson
2017-04-03 22:49 ` Matthias Kaehlcke
2017-04-21 7:49 ` Masahiro Yamada
2017-03-17 0:15 ` [PATCH 2/7] Makefile, x86, LLVM: disable unsupported optimization flags Michael Davidson
2017-03-17 21:32 ` H. Peter Anvin
2017-03-17 21:34 ` H. Peter Anvin
2017-04-05 18:08 ` Masahiro Yamada
2017-04-05 19:01 ` Matthias Kaehlcke
2017-04-05 19:11 ` Michael Davidson
2017-04-10 14:54 ` Masahiro Yamada
2017-03-17 0:15 ` [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses Michael Davidson
2017-03-17 23:50 ` hpa
2017-04-03 23:01 ` Matthias Kaehlcke
2017-04-13 23:14 ` Matthias Kaehlcke
2017-04-13 23:55 ` H. Peter Anvin
2017-04-14 0:23 ` Matthias Kaehlcke
2017-04-14 5:30 ` hpa
2017-03-17 0:15 ` [PATCH 4/7] x86, boot, LLVM: #undef memcpy etc in string.c Michael Davidson
2017-06-22 22:31 ` Matthias Kaehlcke
2017-06-22 22:37 ` H. Peter Anvin
2017-06-30 18:32 ` Matthias Kaehlcke
2017-03-17 0:15 ` [PATCH 5/7] x86, boot, LLVM: Use regparm=0 for memcpy and memset Michael Davidson
2017-03-17 12:08 ` Peter Zijlstra
2017-06-22 22:38 ` H. Peter Anvin
2017-03-17 0:15 ` [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Michael Davidson
2017-03-17 12:08 ` Peter Zijlstra
2017-03-17 12:31 ` Alexander Potapenko
2017-03-17 12:32 ` Alexander Potapenko
2017-03-17 18:03 ` Borislav Petkov
2017-03-17 18:47 ` Dmitry Vyukov
2017-03-17 18:57 ` Borislav Petkov
2017-03-17 19:05 ` Dmitry Vyukov
2017-03-17 19:26 ` Peter Zijlstra
2017-03-17 19:29 ` Peter Zijlstra
2017-03-24 13:50 ` Dmitry Vyukov
2017-03-24 14:10 ` Peter Zijlstra
2017-03-24 14:22 ` Dmitry Vyukov
2017-03-18 0:41 ` Fengguang Wu
2017-03-17 12:44 ` Peter Zijlstra
2017-03-17 18:52 ` Michael Davidson [this message]
2017-03-17 19:27 ` Peter Zijlstra
2017-03-17 20:04 ` hpa
2017-03-24 13:47 ` Dmitry Vyukov
2017-03-24 14:09 ` Peter Zijlstra
2017-03-17 0:15 ` [PATCH 7/7] crypto, x86, LLVM: aesni - fix token pasting Michael Davidson
2017-04-03 23:14 ` Matthias Kaehlcke
2017-03-17 8:17 ` [PATCH 0/7] LLVM: make x86_64 kernel build with clang Dmitry Vyukov
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