[PATCH v5 0/6] arm64: ftrace: fix incorrect output from stack tracer

AKASHI Takahiro takahiro.akashi at linaro.org
Thu Nov 5 22:44:39 PST 2015

This is the fifth patch series for fixing stack tracer on arm64.
The original issue was reported by Jungseok[1], and then I found more

We don't have to care about the original issue because the root cause
(patch "ARM64: unwind: Fix PC calculation") has been reverted in v4.3.

I address here all the issues and implement fixes described in [2] except
for interrupt-triggered problems(II-3) and leaf function(II-5).  Recent
discussions[3] about introducing a dedicated interrupt stack suggests that
we may avoid walking through from an interrupt stack to a process stack.
(So interrupt-stack patch is a prerequisite.)

patch1 is a proactive improvement of function_graph tracer. 
patch2 corresponds to II-4(functions under function_graph tracer).
patch3, 4 and 5 correspond to II-1(slurping stack) and II-2(differences
between x86 and arm64).
patch6 is a function prologue analyzer test. This won't attest
the correctness of the functionality, but it can suggest that all
the traced functions are treated properly by this function.
(Please note that patch3 has already been queued in Steven's for-next.)

I tested the code with v4.3 + Jungseok's patch v5[4].

Changes from v4:
- removed a patch("arm64: ftrace: adjust callsite addresses examined
		by stack tracer")
- added a function prologue analyzer test(patch 6)

Changes from v3:
- fixed build errors/warnings reported by kbuild test robot
- addressed Steven's comments around check_stack()
- removed a patch ("arm64: ftrace: allow for tracing leaf functions")
  I don't remember why I thought this was necessary, but anyhow "-pg" seems
  to disable omit-leaf-stack-frame.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/354126.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/355920.html 
[3] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-September/368003.html
[4] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/378699.html

AKASHI Takahiro (6):
  arm64: ftrace: modify a stack frame in a safe way
  arm64: ftrace: fix a stack tracer's output under function graph
  ftrace: allow arch-specific stack tracer
  arm64: insn: add instruction decoders for ldp/stp and add/sub
  arm64: ftrace: add arch-specific stack tracer
  arm64: ftrace: add a test of function prologue analyzer

 arch/arm64/include/asm/ftrace.h     |    2 +
 arch/arm64/include/asm/insn.h       |   18 +++
 arch/arm64/include/asm/stacktrace.h |    4 +
 arch/arm64/kernel/ftrace.c          |   75 +++++++++-
 arch/arm64/kernel/insn.c            |  102 ++++++++++++++
 arch/arm64/kernel/stacktrace.c      |  258 ++++++++++++++++++++++++++++++++++-
 include/linux/ftrace.h              |   10 ++
 kernel/trace/trace_stack.c          |   80 ++++++-----
 8 files changed, 502 insertions(+), 47 deletions(-)


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