From: John Reiser <jreiser@bitwagon.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>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andi Kleen <andi@firstfloor.org>
Subject: Re: [RFC PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__
Date: Tue, 07 Aug 2012 16:57:58 -0700 [thread overview]
Message-ID: <5021AB86.30900@bitwagon.com> (raw)
In-Reply-To: <20120807194058.990674363@goodmis.org>
On 08/07/2012 12:38 PM, Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@redhat.com>
>
> With gcc 4.6.0 the -mfentry feature places the function profiling call at the start of the function. When this is used, the call is to __fentry__ and not mcount.
>
> Change recordmcount.c to record both callers to __fentry__ and mcount.
[snip]
> - (altmcount && strcmp(altmcount, symname) == 0))
> + (altmcount && strcmp(altmcount, symname) == 0) ||
> + (strcmp(fentry, symname) == 0))
The proposed change will work as long as all the *.o use the same name.
Only one of {"__fentry__", "mcount", "_mcount", altmcount} is allowed
for all the *.o as input for a particular run. [Modulo the hack
of ignoring a leading '.' for 64-bit PowerPC, of course.]
If the user changes compilers (or changes CFLAGS by insert/remove "-mfentry")
without doing a "make clean", then recordmcount will omit some calls.
Those restrictions are easy to guess, and recovery is easy. Therefore,
Ack'ed by: John Reiser <jreiser@bitwagon.com>
--
next prev parent reply other threads:[~2012-08-08 0:06 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-07 19:38 [RFC PATCH 0/4] ftrace: Add use of -mfentry for x86_64 Steven Rostedt
2012-08-07 19:38 ` [RFC PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__ Steven Rostedt
2012-08-07 23:57 ` John Reiser [this message]
2012-08-08 0:05 ` Steven Rostedt
2012-08-27 17:03 ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-08-07 19:38 ` [RFC PATCH 2/4] ftrace: Add -mfentry to Makefile on function tracer Steven Rostedt
2012-08-27 17:04 ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-08-07 19:38 ` [RFC PATCH 3/4] ftrace: Do not test frame pointers if -mfentry is used Steven Rostedt
2012-08-08 4:34 ` Masami Hiramatsu
2012-08-08 12:49 ` Steven Rostedt
2012-08-09 2:58 ` Masami Hiramatsu
2012-08-09 3:45 ` Linus Torvalds
2012-08-09 3:57 ` Steven Rostedt
2012-08-09 4:15 ` H. Peter Anvin
2012-08-09 12:37 ` Andi Kleen
2012-08-27 17:05 ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-08-07 19:38 ` [RFC PATCH 4/4] ftrace/x86: Add support for -mfentry to x86_64 Steven Rostedt
2012-08-09 8:34 ` Masami Hiramatsu
2012-08-09 13:46 ` Steven Rostedt
2012-08-09 13:48 ` Steven Rostedt
2012-08-10 7:45 ` Masami Hiramatsu
2012-08-27 17:06 ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-08-07 20:23 ` [RFC PATCH 0/4] ftrace: Add use of -mfentry for x86_64 H. Peter Anvin
2012-08-13 8:42 ` Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2011-02-09 20:02 [RFC][PATCH 0/4] ftrace: Use -mfentry when supported (this is for x86_64 right now) Steven Rostedt
2011-02-09 20:02 ` [RFC][PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__ Steven Rostedt
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