Re: [PATCH v10 3.3-rc2 1/9] uprobes: Install and removebreakpoints.
From: Srikar Dronamraju
Date: Wed Feb 08 2012 - 04:53:17 EST
* Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx> [2012-02-08 10:40:30]:
> On Tue, Feb 7, 2012 at 6:17 PM, Srikar Dronamraju
> <srikar@xxxxxxxxxxxxxxxxxx> 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
Oh okay, Will correct this and send out a new patch.
>
> /* 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;
--
Thanks and Regards
Srikar
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/