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From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: [RFC PATCH 0/4] Nop out the preceding mflr with -mprofile-kernel
Date: Sat, 18 May 2019 00:32:44 +0530
Message-ID: <cover.1558115654.git.naveen.n.rao@linux.vnet.ibm.com> (raw)

On powerpc64, -mprofile-kernel results in two instructions being 
emitted: 'mflr r0' and 'bl _mcount'. So far, we were only nop'ing out 
the branch to _mcount(). This series implements an approach to also nop 
out the preceding mflr.

Patches 1-3 are generic changes. Patch 2 is a fix for x86, but has not 
been tested. Patch 4 implements the changes for powerpc64.


- Naveen

Naveen N. Rao (4):
  ftrace: Expose flags used for ftrace_replace_code()
  x86/ftrace: Fix use of flags in ftrace_replace_code()
  ftrace: Expose __ftrace_replace_code()
  powerpc/ftrace: Additionally nop out the preceding mflr with
    -mprofile-kernel

 arch/powerpc/kernel/trace/ftrace.c | 188 +++++++++++++++++++++++++----
 arch/x86/kernel/ftrace.c           |   3 +-
 include/linux/ftrace.h             |   6 +
 kernel/trace/ftrace.c              |  13 +-
 4 files changed, 178 insertions(+), 32 deletions(-)

-- 
2.21.0


             reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-17 19:02 Naveen N. Rao [this message]
2019-05-17 19:02 ` [RFC PATCH 1/4] ftrace: Expose flags used for ftrace_replace_code() Naveen N. Rao
2019-05-20 13:08   ` Steven Rostedt
2019-05-17 19:02 ` [RFC PATCH 2/4] x86/ftrace: Fix use of flags in ftrace_replace_code() Naveen N. Rao
2019-05-20 13:13   ` Steven Rostedt
2019-05-20 13:44     ` Steven Rostedt
2019-05-20 14:42       ` Naveen N. Rao
2019-05-20 14:55         ` Steven Rostedt
2019-05-17 19:02 ` [RFC PATCH 3/4] ftrace: Expose __ftrace_replace_code() Naveen N. Rao
2019-05-17 19:02 ` [RFC PATCH 4/4] powerpc/ftrace: Additionally nop out the preceding mflr with -mprofile-kernel Naveen N. Rao
2019-05-18  2:08   ` Nicholas Piggin
2019-05-20  8:57     ` Naveen N. Rao

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