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: [PATCH v9 3.2 1/9] uprobes: Install and remove breakpoints.
Date: Thu, 26 Jan 2012 23:14:38 +0900 [thread overview]
Message-ID: <4F215FCE.8010209@hitachi.com> (raw)
In-Reply-To: <CAK1hOcMeYDrLpgbyQXFAkrqk3Le-rLkoVwCN3wjkT61YJg0G6Q@mail.gmail.com>
(2012/01/26 0:32), Denys Vlasenko wrote:
> On Wed, Jan 25, 2012 at 4:13 PM, Denys Vlasenko
> <vda.linux@googlemail.com> wrote:
>>> + /*
>>> + * Convert from rip-relative addressing to indirect addressing
>>> + * via a scratch register. Change the r/m field from 0x5 (%rip)
>>> + * to 0x0 (%rax) or 0x1 (%rcx), and squeeze out the offset field.
>>> + */
>>> + reg = MODRM_REG(insn);
>>> + if (reg == 0) {
>>> + /*
>>> + * The register operand (if any) is either the A register
>>> + * (%rax, %eax, etc.) or (if the 0x4 bit is set in the
>>> + * REX prefix) %r8. In any case, we know the C register
>>> + * is NOT the register operand, so we use %rcx (register
>>> + * #1) for the scratch register.
>>> + */
>>> + uprobe->arch_info.fixups = UPROBES_FIX_RIP_CX;
>>> + /* Change modrm from 00 000 101 to 00 000 001. */
>>> + *cursor = 0x1;
>
> Hmm. I think we have a bug here.
>
> What if this instruction has REX.B = 1? Granted, REX.B = 1 has no effect on
> rip-relative addressing and therefore normally won't be generated by gcc/as,
> but still. If you replace md and r/m fields as above, you are trying to convert
> 0x12345678(%rip) reference to (%rcx), but if REX.B = 1, then you in fact
> converted it to (%r9)!
Right, thanks for finding :)
And %rax register reference encoding has same problem, doesn't it?
Thank you,
--
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:[~2012-01-26 14:14 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-10 11:48 [PATCH v9 3.2 0/9] Uprobes patchset with perf probe support Srikar Dronamraju
2012-01-10 11:48 ` [PATCH v9 3.2 1/9] uprobes: Install and remove breakpoints Srikar Dronamraju
2012-01-25 14:39 ` Denys Vlasenko
2012-01-25 16:31 ` Oleg Nesterov
2012-01-25 15:13 ` Denys Vlasenko
2012-01-25 15:32 ` Denys Vlasenko
2012-01-26 14:14 ` Masami Hiramatsu [this message]
2012-01-26 18:28 ` Denys Vlasenko
2012-01-30 9:51 ` Masami Hiramatsu
2012-01-26 13:38 ` Masami Hiramatsu
2012-01-26 13:45 ` Masami Hiramatsu
2012-01-10 11:48 ` [PATCH v9 3.2 2/9] uprobes: handle breakpoint and signal step exception Srikar Dronamraju
2012-01-18 8:39 ` Anton Arapov
2012-01-18 9:02 ` Srikar Dronamraju
2012-01-18 10:18 ` Mike Frysinger
2012-01-18 10:47 ` Srikar Dronamraju
2012-01-18 11:01 ` Mike Frysinger
2012-01-20 22:57 ` Mike Frysinger
2012-01-25 8:12 ` Srikar Dronamraju
2012-01-10 11:48 ` [PATCH v9 3.2 3/9] uprobes: slot allocation Srikar Dronamraju
2012-01-10 11:49 ` [PATCH v9 3.2 4/9] uprobes: counter to optimize probe hits Srikar Dronamraju
2012-01-10 11:49 ` [PATCH v9 3.2 5/9] tracing: modify is_delete, is_return from ints to bool Srikar Dronamraju
2012-01-10 11:49 ` [PATCH v9 3.2 6/9] tracing: Extract out common code for kprobes/uprobes traceevents Srikar Dronamraju
2012-01-10 11:49 ` [PATCH v9 3.2 7/9] tracing: uprobes trace_event interface Srikar Dronamraju
2012-01-16 13:11 ` Jiri Olsa
2012-01-16 14:45 ` Srikar Dronamraju
2012-01-16 15:33 ` Jiri Olsa
2012-01-16 16:41 ` Srikar Dronamraju
2012-01-17 9:28 ` Ingo Molnar
2012-01-17 10:22 ` Srikar Dronamraju
2012-01-17 10:59 ` Ingo Molnar
2012-01-17 11:03 ` Srikar Dronamraju
2012-01-17 11:22 ` Ingo Molnar
2012-01-17 11:57 ` Srikar Dronamraju
2012-01-17 12:23 ` Ingo Molnar
2012-01-17 12:27 ` Ingo Molnar
2012-01-17 12:11 ` Ingo Molnar
2012-01-17 12:21 ` Ingo Molnar
2012-01-18 10:07 ` Srikar Dronamraju
2012-01-10 11:49 ` [PATCH v9 3.2 8/9] perf: rename target_module to target Srikar Dronamraju
2012-01-16 8:34 ` [PATCH v9 3.2 0/9] Uprobes patchset with perf probe support Ingo Molnar
2012-01-16 15:17 ` Srikar Dronamraju
2012-01-17 9:39 ` Ingo Molnar
2012-01-25 14:11 ` Peter Zijlstra
2012-01-26 11:10 ` Ingo Molnar
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