From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: "H.J. Lu" <hjl.tools@gmail.com>, gcc-patches@gcc.gnu.org
Cc: nd@arm.com, Uros Bizjak <ubizjak@gmail.com>
Subject: Re: RFC: [PATCH] x86: Add -mzero-caller-saved-regs=[skip|used|all]
Date: Thu, 27 Sep 2018 13:10:00 -0000 [thread overview]
Message-ID: <b6629ac7-15be-d871-aa31-9a547f61edd9@arm.com> (raw)
In-Reply-To: <20180926181029.GA20898@intel.com>
On 26/09/18 19:10, H.J. Lu wrote:
> Add -mzero-caller-saved-regs=[skip|used|all] command-line option and
> zero_caller_saved_regs("skip|used|all") function attribue:
>
> 1. -mzero-caller-saved-regs=skip and zero_caller_saved_regs("skip")
>
> Don't zero caller-saved integer registers upon function return.
>
> 2. -mzero-caller-saved-regs=used and zero_caller_saved_regs("used")
>
> Zero used caller-saved integer registers upon function return.
>
> 3. -mzero-caller-saved-regs=all and zero_caller_saved_regs("all")
>
> Zero all caller-saved integer registers upon function return.
>
> Tested on i686 and x86-64 with bootstrapping GCC trunk and
> -mzero-caller-saved-regs=used as well as -mzero-caller-saved-regs=all
> enabled by default.
>
from this description and the documentation it's
not clear to me what this tries to achieve.
is it trying to prevent information leak?
or some pcs hack the caller may rely on?
if it's for information leak then i'd expect such
attribute to be used on crypto code.. however i'd
expect crypto code to use simd registers as well,
so integer only cleaning needs explanation.
next prev parent reply other threads:[~2018-09-27 13:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-26 18:11 H.J. Lu
2018-09-27 11:01 ` Richard Biener
2018-09-27 13:08 ` H.J. Lu
2018-09-27 13:10 ` Szabolcs Nagy [this message]
2018-09-27 13:41 ` H.J. Lu
2018-09-27 15:13 ` Richard Biener
2018-09-27 19:41 ` H.J. Lu
2018-10-31 21:53 ` PATCH] x86: Add -mzero-caller-saved-regs=[skip|used-gpr|all-gpr|used|all] H.J. Lu
2018-11-29 23:16 ` PING [PATCH] " H.J. Lu
2018-12-21 13:23 ` PING^2 " H.J. Lu
2018-09-27 14:04 ` RFC: [PATCH] x86: Add -mzero-caller-saved-regs=[skip|used|all] Rich Felker
2018-09-27 20:07 ` H.J. Lu
2018-09-27 19:29 ` Florian Weimer
2018-09-27 19:51 ` H.J. Lu
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