linux-kernel - [PATCH 0/7] powerpc/ftrace: Patch out -mprofile-kernel instructions

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Date:   Tue, 18 Jun 2019 20:16:59 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     <linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 0/7] powerpc/ftrace: Patch out -mprofile-kernel instructions

Changes since RFC:
- Patches 1 and 2: No changes
- Patch 3: rename function to ftrace_replace_code_rec() to signify that 
  it acts on a ftrace record.
- Patch 4: numerous small changes, including those suggested by Nick 
  Piggin.
- Patch 4: additionally handle scenario where __ftrace_make_call() can 
  be invoked without having called __ftrace_make_call_prep(), when a 
  kernel module is loaded while function tracing is active.
- Patch 5 to 7: new, to have ftrace claim ownership of two instructions, 
  and to have kprobes work properly with this.


--
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.


- Naveen


Naveen N. Rao (7):
  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
  powerpc/ftrace: Update ftrace_location() for powerpc -mprofile-kernel
  kprobes/ftrace: Use ftrace_location() when [dis]arming probes
  powerpc/kprobes: Allow probing on any ftrace address

 arch/powerpc/kernel/kprobes-ftrace.c |  30 +++
 arch/powerpc/kernel/trace/ftrace.c   | 272 ++++++++++++++++++++++++---
 arch/x86/kernel/ftrace.c             |   3 +-
 include/linux/ftrace.h               |   7 +
 kernel/kprobes.c                     |  10 +-
 kernel/trace/ftrace.c                |  17 +-
 6 files changed, 300 insertions(+), 39 deletions(-)

-- 
2.22.0