linux-kernel - Re: x86: get rid of the insane TIF_ABI

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <4B79A996.2090606@zytor.com>
Date:	Mon, 15 Feb 2010 12:07:50 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Roland McGrath <roland@...hat.com>
CC:	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: x86: get rid of the insane TIF_ABI_PENDING bit

On 02/15/2010 11:41 AM, Roland McGrath wrote:
>> I suspect the purpose of TS_COMPAT is actually so you can ptrace() the
>> newly exec'd process (and see it as a 32-bit process!) before it returns
>> to userspace.  The comment, obviously, is wrong -- that again refers to
>> TIF_IA32.
> 
> I don't follow you.  TS_COMPAT does not affect ptrace.
> It affects syscall-audit, but only at syscall entry time.
> It affects asm/syscall.h accessors, but ptrace does not use those.
> It affects whatever uses is_compat_task(), but I can't see anything
> where that matters except inside some particular syscall or for
> syscall restart after signals.
> 
> TS_COMPAT does not affect the syscall return machinery itself.
> The return path just follows from the particular entry path.

It's entirely possible it is completely superfluous.  The patch in
question only moves the setting.  I don't know what gdb or strace use to
distinguish a 32-bit and a 64-bit process, which is why I thought it
might have something to do with ptrace.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

--
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/