From: "H. Peter Anvin" <hpa@zytor.com>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org,
kernel-hardening@lists.openwall.com,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, Jarkko Sakkinen <jarkko.sakkinen@intel.com>,
Matthew Garrett <mjg@redhat.com>,
Matt Fleming <matt.fleming@intel.com>,
Eric Northup <digitaleric@google.com>,
Dan Rosenberg <drosenberg@vsecurity.com>,
Julien Tinnes <jln@google.com>, Will Drewry <wad@chromium.org>
Subject: Re: [PATCH 2/6] x86: kaslr: move CPU flags out of cpucheck
Date: Fri, 26 Apr 2013 14:47:02 -0700 [thread overview]
Message-ID: <517AF5D6.1040800@zytor.com> (raw)
In-Reply-To: <1367003005-5560-3-git-send-email-keescook@chromium.org>
On 04/26/2013 12:03 PM, Kees Cook wrote:
> +
> +static inline void cpuid(u32 id, u32 *a, u32 *b, u32 *c, u32 *d)
> +{
> + /* Handle x86_32 PIC using ebx. */
> + asm volatile("movl %%ebx, %%edi \n\t"
> + "cpuid \n\t"
> + "xchgl %%edi, %%ebx\n\t"
> + : "=a" (*a),
> + "=D" (*b),
> + "=c" (*c),
> + "=d" (*d)
> + : "a" (id)
> + );
> +}
Please don't constrain registers unnecessarily.
You can use "=r" there and let gcc assign whatever free register it pleases.
You can also limit that to only:
#if defined(__i386__) && defined(__PIC__)
-hpa
next prev parent reply other threads:[~2013-04-26 21:47 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-26 19:03 [PATCH v4 0/6] kernel ASLR Kees Cook
2013-04-26 19:03 ` [PATCH 1/6] x86: kaslr: move ELF relocation handling to C Kees Cook
2013-04-26 19:03 ` [PATCH 2/6] x86: kaslr: move CPU flags out of cpucheck Kees Cook
2013-04-26 21:47 ` H. Peter Anvin [this message]
2013-04-26 22:14 ` H. Peter Anvin
2013-04-29 17:49 ` Kees Cook
2013-04-29 17:52 ` Kees Cook
2013-04-26 19:03 ` [PATCH 3/6] x86: kaslr: return location from decompress_kernel Kees Cook
2013-04-26 21:47 ` H. Peter Anvin
2013-04-29 1:25 ` [kernel-hardening] " James Morris
2013-04-29 17:43 ` Kees Cook
2013-04-26 19:03 ` [PATCH 4/6] x86: kaslr: select random base offset Kees Cook
2013-04-26 21:50 ` H. Peter Anvin
2013-04-29 19:15 ` Kees Cook
2013-04-26 19:03 ` [PATCH 5/6] x86: kaslr: select memory region from e820 maps Kees Cook
2013-04-26 21:51 ` Yinghai Lu
2013-04-26 22:01 ` H. Peter Anvin
2013-04-26 22:01 ` Kees Cook
2013-04-26 19:03 ` [PATCH 6/6] x86: kaslr: report kernel offset on panic Kees Cook
2013-04-26 22:13 ` Borislav Petkov
2013-04-26 22:15 ` H. Peter Anvin
2013-04-26 22:19 ` Borislav Petkov
-- strict thread matches above, loose matches on Subject: below --
2013-04-25 21:54 [PATCH v3 0/6] kernel ASLR Kees Cook
2013-04-25 21:54 ` [PATCH 2/6] x86: kaslr: move CPU flags out of cpucheck Kees Cook
2013-04-25 22:00 ` H. Peter Anvin
2013-04-26 15:28 ` Kees Cook
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