From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux-mm <linux-mm@kvack.org>, Andi Kleen <andi@firstfloor.org>,
Christoph Hellwig <hch@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Roland McGrath <roland@hack.frob.com>,
Thomas Gleixner <tglx@linutronix.de>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Anton Arapov <anton@redhat.com>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Jim Keniston <jkenisto@linux.vnet.ibm.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
yrl.pp-manager.tt@hitachi.com
Subject: Re: Re: [PATCH v10 3.3-rc2 1/9] uprobes: Install and remove breakpoints.
Date: Thu, 09 Feb 2012 10:27:01 +0900 [thread overview]
Message-ID: <4F3320E5.1050707@hitachi.com> (raw)
In-Reply-To: <CAK1hOcOd3hd31vZYw1yAVGK=gMV=vQotL1mRZkVgM=7M8mbMyw@mail.gmail.com>
(2012/02/08 18:40), Denys Vlasenko wrote:
> On Tue, Feb 7, 2012 at 6:17 PM, Srikar Dronamraju
> <srikar@linux.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
Right, but...
>
> /* 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;
No, that is a meaningless operation.
As I originally said,
> insn_get_length(insn);
> if (insn->rex_prefix.nbytes) {
> cursor = uprobe->insn + insn_offset_rex_prefix(insn);
> *cursor &= 0xfe; /* Clearing REX.B bit */
> }
You have to move the cursor itself, since the .rex_prefix
is just a copied data...
Thanks,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2012-02-09 1:27 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-02 14:18 [PATCH v10 3.3-rc2 0/9] Uprobes patchset with perf probe support Srikar Dronamraju
2012-02-02 14:18 ` [PATCH v10 3.3-rc2 1/9] uprobes: Install and remove breakpoints Srikar Dronamraju
2012-02-03 12:01 ` Masami Hiramatsu
2012-02-07 17:17 ` Srikar Dronamraju
2012-02-08 9:40 ` Denys Vlasenko
2012-02-08 9:40 ` Srikar Dronamraju
2012-02-09 1:27 ` Masami Hiramatsu [this message]
2012-02-09 6:37 ` Srikar Dronamraju
2012-02-09 7:53 ` Ingo Molnar
2012-02-09 8:14 ` Srikar Dronamraju
2012-02-09 8:17 ` Masami Hiramatsu
2012-02-09 8:27 ` Srikar Dronamraju
2012-02-08 14:08 ` Srikar Dronamraju
2012-02-09 9:26 ` [PATCH v10 take 3 " Srikar Dronamraju
2012-02-17 9:58 ` [tip:perf/uprobes] uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints tip-bot for Srikar Dronamraju
2012-05-21 21:37 ` Andrew Morton
2012-05-21 22:00 ` Linus Torvalds
2012-05-21 22:13 ` Andrew Morton
2012-05-22 1:16 ` Stephen Rothwell
2012-05-22 2:27 ` Andrew Morton
2012-05-22 6:50 ` Stephen Rothwell
2012-05-23 0:37 ` Stephen Rothwell
2012-05-22 1:10 ` Stephen Rothwell
2012-05-22 6:01 ` Srikar Dronamraju
2012-05-22 8:05 ` Srikar Dronamraju
2012-02-02 14:19 ` [PATCH v10 3.3-rc2 2/9] uprobes: handle breakpoint and signal step exception Srikar Dronamraju
2012-02-02 14:19 ` [PATCH v10 3.3-rc2 3/9] uprobes: slot allocation Srikar Dronamraju
2012-02-02 14:19 ` [PATCH v10 3.3-rc2 4/9] uprobes: counter to optimize probe hits Srikar Dronamraju
2012-02-02 14:19 ` [PATCH v10 3.3-rc2 5/9] tracing: modify is_delete, is_return from ints to bool Srikar Dronamraju
2012-02-02 14:20 ` [PATCH v10 3.3-rc2 6/9] tracing: Extract out common code for kprobes/uprobes traceevents Srikar Dronamraju
2012-02-02 14:20 ` [PATCH v10 3.3-rc2 7/9] tracing: uprobes trace_event interface Srikar Dronamraju
2012-02-02 14:20 ` [PATCH v10 3.3-rc2 8/9] perf: rename target_module to target Srikar Dronamraju
2012-02-07 19:33 ` [tip:perf/core] perf probe: Rename " tip-bot for Srikar Dronamraju
2012-02-02 14:20 ` [PATCH v10 3.3-rc2 9/9] perf: perf interface for uprobes Srikar Dronamraju
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