linux-kernel - Re: [PATCH v10 3.3-rc2 1/9] uprobes: Install and remove breakpoints.

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: <CAK1hOcOd3hd31vZYw1yAVGK=gMV=vQotL1mRZkVgM=7M8mbMyw@mail.gmail.com>
Date:	Wed, 8 Feb 2012 10:40:30 +0100
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Roland McGrath <roland@...k.frob.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Anton Arapov <anton@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH v10 3.3-rc2 1/9] uprobes: Install and remove breakpoints.

On Tue, Feb 7, 2012 at 6:17 PM, Srikar Dronamraju
<srikar@...ux.vnet.ibm.com> wrote:
> Changelog: (Since v10): Add code to clear REX.B prefix pointed out by Denys Vlasenko
> and fix suggested by Masami Hiramatsu.
...
> +       /*
> +        * Point cursor at the modrm byte.  The next 4 bytes are the
> +        * displacement.  Beyond the displacement, for some instructions,
> +        * is the immediate operand.
> +        */
> +       cursor = uprobe->insn + insn_offset_modrm(insn);
> +       insn_get_length(insn);
> +       if (insn->rex_prefix.nbytes)
> +               *cursor &= 0xfe;        /* Clearing REX.B bit */

It looks like cursor points to mod/reg/rm byte, not rex byte.
Comment above says it too. You seem to be clearing a bit
in a wrong byte. I think it should be

        /* Clear REX.b bit (extension of MODRM.rm field):
         * we want to encode rax/rcx, not r8/r9.
         */
        if (insn->rex_prefix.nbytes)
                insn->rex_prefix.bytes[0] &= 0xfe;

-- 
vda
--
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/