linux-kernel - Re: X86 fpu registers in a signal handler's ucontext

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <m2a9ohusmp.fsf@firstfloor.org>
Date:	Mon, 29 Apr 2013 10:57:34 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	"Warlich\, Christof" <christof.warlich@...mens.com>
Cc:	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: X86 fpu registers in a signal handler's ucontext

"Warlich, Christof" <christof.warlich@...mens.com> writes:
>
> First, this link:
> http://valgrind.10908.n7.nabble.com/need-FPU-and-SSE-state-in-sigcontext-ucontext-td19844.html
> suggests that unlike the GPRs, the FP registers are _not_ restored after
> returnung from the signal handler. 

The FP registers are restored lazily, but the state for this is kept in
the kernel.

One easy way may be to catch the FPU exception too and clear from there?

There can be some complications with different save formats too (XSAVE
vs FXSAVE). So your solution may not be necessarily 100% portable
to all systems.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/