From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
yrl.pp-manager.tt@hitachi.com
Subject: Re: Re: Re: [RFC][PATCH 2/4 v4] ftrace/x86: Add save_regs for i386 function calls
Date: Tue, 17 Jul 2012 12:13:32 +0900 [thread overview]
Message-ID: <5004D85C.70704@hitachi.com> (raw)
In-Reply-To: <1342494302.24525.4.camel@gandalf.stny.rr.com>
(2012/07/17 12:05), Steven Rostedt wrote:
> On Tue, 2012-07-17 at 11:08 +0900, Masami Hiramatsu wrote:
>
>>> I found that regs_get_register() doesn't honor this either. Thus,
>>> kprobes in tracing gets this:
>>>
>>> # echo 'p:ftrace sys_read+4 s=%sp' > /debug/tracing/kprobe_events
>>> # echo 1 > /debug/tracing/events/kprobes/enable
>>> # cat trace
>>> sshd-1345 [000] d... 489.117168: ftrace: (sys_read+0x4/0x70) s=b7e96768
>>> sshd-1345 [000] d... 489.117191: ftrace: (sys_read+0x4/0x70) s=b7e96768
>>> cat-1447 [000] d... 489.117392: ftrace: (sys_read+0x4/0x70) s=5a7
>>> cat-1447 [001] d... 489.118023: ftrace: (sys_read+0x4/0x70) s=b77ad05f
>>> less-1448 [000] d... 489.118079: ftrace: (sys_read+0x4/0x70) s=b7762e06
>>> less-1448 [000] d... 489.118117: ftrace: (sys_read+0x4/0x70) s=b7764970
>>>
>>
>> Yes, that is by design, since I made it so. :)
>> Instead of %sp, kprobe tracer provides $stack special argument
>> for stack address, because "sp" is not always means the stack
>> address on every arch.
>
> But is that useful? Wouldn't the actual stack pointer be more
> informative?
It is just FYI :). I rather like your "%sp" enhancement
than current meaningless "%sp" on i386...
However, I think "$stack" is more general and informative
for users, thus, at least perf probe uses it for getting
variables from stack.
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:[~2012-07-17 3:13 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-11 19:50 [RFC][PATCH 0/4 v4] ftrace/kprobes: Setting up ftrace for kprobes Steven Rostedt
2012-07-11 19:50 ` [RFC][PATCH 1/4 v4] ftrace/x86: Add separate function to save regs Steven Rostedt
2012-07-12 12:12 ` Masami Hiramatsu
2012-07-11 19:50 ` [RFC][PATCH 2/4 v4] ftrace/x86: Add save_regs for i386 function calls Steven Rostedt
2012-07-12 12:39 ` Masami Hiramatsu
2012-07-12 15:53 ` Steven Rostedt
2012-07-13 18:47 ` Steven Rostedt
2012-07-17 2:08 ` Masami Hiramatsu
2012-07-17 3:05 ` Steven Rostedt
2012-07-17 3:13 ` Masami Hiramatsu [this message]
2012-07-18 15:59 ` Steven Rostedt
2012-07-19 2:20 ` Masami Hiramatsu
2012-07-19 12:52 ` Steven Rostedt
2012-07-19 12:58 ` Steven Rostedt
2012-07-19 22:53 ` H. Peter Anvin
2012-07-19 23:04 ` Steven Rostedt
2012-07-19 23:07 ` H. Peter Anvin
2012-07-20 1:27 ` Steven Rostedt
2012-07-19 18:24 ` Steven Rostedt
2012-08-21 15:03 ` [tip:perf/core] ftrace/x86_32: Simplify parameter setup for ftrace_regs_caller tip-bot for Uros Bizjak
2012-07-11 19:50 ` [RFC][PATCH 3/4 v4] ftrace/x86: Remove function_trace_stop check from graph caller Steven Rostedt
2012-08-21 15:04 ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-07-11 19:50 ` [RFC][PATCH 4/4 v4] ftrace/x86_64: Add recursion protection inside mcount caller Steven Rostedt
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