linux-kernel - [PATCH 0/6][RFC] tracing/kprobes: Get ready for -mfentry

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Message-Id: <20120426022922.683707508@goodmis.org>
Date:	Wed, 25 Apr 2012 22:29:22 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 0/6][RFC] tracing/kprobes: Get ready for -mfentry

As I want to add the -mfentry to allow for function tracing without
frame pointers (as some distros are now disabling function tracing :-(

I have to handle the case that a kprobe is placed on a ftrace nop.
As ftrace nops with -mfentry will be the first instruction of a
function, it being the location of a kprobe is a likely occurrence.

Ideally, kprobes would just use the function tracing infrastructure
to make an automatic optimized jump. But that is for another day as it
requires a bit of work in the function tracer to handle regs and such.

So the quick fix for now is to simply move the probe to the next
instruction after the ftrace nop. As the nop shouldn't be doing anything
anyway (and tracing should return to the function in the same state)
moving the location of the probe should not cause any harm.

The first 5 patches are non controversial, and could probably just be
pushed for 3.5 inclusion. The last patch makes the change to move the
probe to the next instruction after the ftrace nop.

Anyone see any problem with this?

-- Steve

Steven Rostedt (6):
      ftrace: Sort all function addresses, not just per page
      ftrace: Remove extra helper functions
      ftrace: Speed up search by skipping pages by address
      ftrace: Consolidate ftrace_location() and ftrace_text_reserved()
      ftrace: Return record ip addr for ftrace_location()
      kprobes: Allow probe on ftrace reserved text (but move it)

----
 include/asm-generic/vmlinux.lds.h |    2 +-
 include/linux/ftrace.h            |    2 +-
 kernel/kprobes.c                  |   11 ++-
 kernel/trace/ftrace.c             |  173 ++++++++++++++++++++-----------------
 4 files changed, 104 insertions(+), 84 deletions(-)

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