From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jamie Lokier <jamie@shareable.org>,
ville.syrjala@linux.intel.com, Borislav Petkov <bp@alien8.de>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
linux-tip-commits@vger.kernel.org,
"H.J. Lu" <hjl.tools@gmail.com>
Subject: Re: [tip:x86/mm] x86, mm: Use a bitfield to mask nuisance get_user() warnings
Date: Mon, 11 Feb 2013 23:12:49 -0800 [thread overview]
Message-ID: <5119EB71.6080508@zytor.com> (raw)
In-Reply-To: <CA+55aFzmWfOQzVMPJUah3oEsn-aaeN5qtO=7P3MQUfLZmEFJZA@mail.gmail.com>
Just to be sure, I re-ran the comparison using gcc 4.6.3 instead of gcc
4.7.2. With gcc 4.6.3 I consistently get a few hundred bytes longer
with the bitfield variant than with the pre-get_user() baseline.
I looked at some of the diffed disassembly, and the differences seem to
be in the code generated downstream of __get_user_1 and __get_user_2,
which I guess is to be expected, mostly in the form of padding.
Annoyingly enough in *both* cases I found unnecessary instructions like:
+c12f6fbb: 0f b7 d2 movzwl %dx,%edx
-hpa
next prev parent reply other threads:[~2013-02-12 7:13 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-12 11:34 [PATCH] x86: Add support for 64bit get_user() on x86-32 ville.syrjala
2012-12-12 16:15 ` H. Peter Anvin
2012-12-12 16:32 ` Ville Syrjälä
2012-12-12 16:45 ` H. Peter Anvin
2013-02-07 16:53 ` Ville Syrjälä
2013-02-07 17:59 ` H. Peter Anvin
2013-02-08 16:24 ` Ville Syrjälä
2013-02-08 17:30 ` H. Peter Anvin
2013-02-08 18:23 ` Ville Syrjälä
2013-02-08 19:08 ` H. Peter Anvin
2013-02-09 10:41 ` Borislav Petkov
2013-02-09 11:00 ` Russell King - ARM Linux
2013-02-12 1:37 ` [tip:x86/mm] x86, mm: Use a bitfield to mask nuisance get_user() warnings tip-bot for H. Peter Anvin
2013-02-12 3:33 ` Linus Torvalds
2013-02-12 4:21 ` H. Peter Anvin
2013-02-12 4:42 ` Linus Torvalds
2013-02-12 4:47 ` Linus Torvalds
2013-02-12 4:51 ` H. Peter Anvin
2013-02-12 7:12 ` H. Peter Anvin [this message]
2013-02-12 8:10 ` Ingo Molnar
2013-02-12 16:38 ` H.J. Lu
2013-02-12 17:00 ` Linus Torvalds
2013-02-12 17:14 ` H. Peter Anvin
2013-02-12 17:30 ` H.J. Lu
2013-02-12 18:25 ` H. Peter Anvin
2013-02-12 18:29 ` H.J. Lu
2013-02-12 18:46 ` Linus Torvalds
2013-02-12 18:58 ` H. Peter Anvin
2013-02-12 20:55 ` [tip:x86/mm] x86, mm: Redesign get_user with a __builtin_choose_expr hack tip-bot for H. Peter Anvin
2013-02-12 23:06 ` Linus Torvalds
2013-02-12 23:19 ` H. Peter Anvin
2013-02-12 23:49 ` Linus Torvalds
2013-02-12 23:52 ` H. Peter Anvin
2013-02-13 0:01 ` [tip:x86/mm] x86, doc: Clarify the use of asm("%edx") in uaccess.h tip-bot for H. Peter Anvin
2013-02-12 23:21 ` [tip:x86/mm] x86, mm: Redesign get_user with a __builtin_choose_expr hack Russell King - ARM Linux
2013-02-12 17:32 ` [tip:x86/mm] x86, mm: Use a bitfield to mask nuisance get_user() warnings Linus Torvalds
2013-02-12 17:35 ` H. Peter Anvin
2013-02-12 17:49 ` Linus Torvalds
2013-02-12 17:57 ` Russell King - ARM Linux
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