[RFC PATCH 0/4] Nop out the preceding mflr with -mprofile-kernel

From: Naveen N. Rao
Date: Fri May 17 2019 - 15:05:09 EST

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

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(-)