From: Kees Cook <keescook@chromium.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Aaron Durbin <adurbin@google.com>,
Eric Northup <digitaleric@google.com>,
Julien Tinnes <jln@google.com>, Will Drewry <wad@google.com>,
Mathias Krause <minipli@googlemail.com>,
Zhang Yanfei <zhangyanfei@cn.fujitsu.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH] x86, boot: fix word-size assumptions in has_eflag() inline asm
Date: Wed, 29 Jan 2014 08:57:40 -0800 [thread overview]
Message-ID: <CAGXu5jKnabMPHF2iNph5QFue0ZADSXoCzoCJXPgh_QC7SUN8mw@mail.gmail.com> (raw)
In-Reply-To: <1390996897.20153.123.camel@i7.infradead.org>
On Wed, Jan 29, 2014 at 4:01 AM, David Woodhouse <dwmw2@infradead.org> wrote:
> Commit dd78b97367bd575918204cc89107c1479d3fc1a7 ("x86, boot: Move CPU
> flags out of cpucheck") introduced ambiguous inline asm in the
> has_eflag() function. We want the instruction to be 'pushfl', but we
> just say 'pushf' and hope the compiler does what we wanted.
>
> When building with 'clang -m16', it won't, because clang doesn't use
> the horrid '.code16gcc' hack that even 'gcc -m16' uses internally.
>
> Say what we mean and don't make the compiler make assumptions.
>
> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Yes, excellent point. Thanks!
Acked-by: Kees Cook <keescook@chromium.org>
-Kees
--
Kees Cook
Chrome OS Security
next prev parent reply other threads:[~2014-01-29 16:57 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-03 20:53 [PATCH v7 0/7] Kernel base address randomization on x86 Kees Cook
2013-10-03 20:53 ` [PATCH 1/7] x86, boot: move CPU flags out of cpucheck Kees Cook
2014-01-29 12:01 ` [PATCH] x86, boot: fix word-size assumptions in has_eflag() inline asm David Woodhouse
2014-01-29 16:57 ` Kees Cook [this message]
2014-01-29 17:13 ` [tip:x86/build] x86, boot: Fix word-size assumptions in has_eflag () " tip-bot for David Woodhouse
2014-01-30 9:09 ` Ingo Molnar
2014-01-30 10:28 ` Woodhouse, David
2014-01-30 11:00 ` [PATCH v2] " David Woodhouse
2014-01-30 13:45 ` H. Peter Anvin
2014-01-30 14:08 ` David Woodhouse
2014-01-30 16:10 ` [tip:x86/build] " tip-bot for David Woodhouse
2014-01-30 23:01 ` [PATCH v2] " David Rientjes
2013-10-03 20:53 ` [PATCH 2/7] x86, kaslr: return location from decompress_kernel Kees Cook
2013-10-03 20:53 ` [PATCH 3/7] x86, kaslr: find minimum safe relocation position Kees Cook
2013-10-03 22:23 ` H. Peter Anvin
2013-10-03 22:43 ` Kees Cook
2013-10-03 22:46 ` H. Peter Anvin
2013-10-03 20:53 ` [PATCH 4/7] x86, kaslr: select random base offset Kees Cook
2013-10-03 20:53 ` [PATCH 5/7] x86, kaslr: select memory region from e820 maps Kees Cook
2013-10-03 20:53 ` [PATCH 6/7] x86, kaslr: report kernel offset on panic Kees Cook
2013-10-03 20:53 ` [PATCH 7/7] x86, kaslr: raise max positions to 1GiB on x86_64 Kees Cook
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