[v7,0/3] arm64: implement KPROBES_ON_FTRACE

Message

Jisheng Zhang Dec. 25, 2019, 9:40 a.m. UTC

KPROBES_ON_FTRACE avoids much of the overhead with regular kprobes as
it eliminates the need for a trap, as well as the need to emulate or
single-step instructions.

arm64 makes use of GCC -fpatchable-function-entry=2 option to insert
two nops. When the function is traced, the first nop will be modified
to the LR saver, then the second nop to "bl <ftrace-entry>". We need
to allow kprobe on any of these two instructions.

patch1 uses ftrace_location() when [dis]arming probes.
patch2 introduces FTRACE_IP_EXTENSION to let ftrace_location()
recognise these two instructions  as being part of ftrace
patch3 implement the KPROBES_ON_FTRACE for arm64

Changes since v6:
  - add patch1 and patch2
  - fix the automatic offset as pointed out by Masami

Changes since v5:
  - rebase v5.5-rc1
  - collect Acked-by and Reviewed-by tags

Changes since v4:
  - correct reg->pc: probed on foo, then pre_handler see foo+0x4, while
    post_handler see foo+0x8

Changes since v3:
  - move kprobe_lookup_name() and arch_kprobe_on_func_entry to ftrace.c since
    we only want to choose the ftrace entry for KPROBES_ON_FTRACE.
  - only choose ftrace entry if (addr && !offset)

Changes since v2:
  - remove patch1, make it a single cleanup patch
  - remove "This patch" in the change log
  - implement arm64's kprobe_lookup_name() and arch_kprobe_on_func_entry instead
    of patching the common kprobes code

Changes since v1:
  - make the kprobes/x86: use instruction_pointer and instruction_pointer_set
    as patch1
  - add Masami's ACK to patch1
  - add some description about KPROBES_ON_FTRACE and why we need it on
    arm64
  - correct the log before the patch
  - remove the consolidation patch, make it as TODO
  - only adjust kprobe's addr when KPROBE_FLAG_FTRACE is set
  - if KPROBES_ON_FTRACE, ftrace_call_adjust() the kprobe's addr before
    calling ftrace_location()
  - update the kprobes-on-ftrace/arch-support.txt in doc

Jisheng Zhang (2):
  ftrace: introduce FTRACE_IP_EXTENSION
  arm64: implement KPROBES_ON_FTRACE

Naveen N. Rao (1):
  kprobes/ftrace: Use ftrace_location() when [dis]arming probes

 .../debug/kprobes-on-ftrace/arch-support.txt  |  2 +-
 arch/arm64/Kconfig                            |  1 +
 arch/arm64/include/asm/ftrace.h               |  1 +
 arch/arm64/kernel/probes/Makefile             |  1 +
 arch/arm64/kernel/probes/ftrace.c             | 78 +++++++++++++++++++
 include/linux/ftrace.h                        |  4 +
 kernel/kprobes.c                              |  8 +-
 kernel/trace/ftrace.c                         |  2 +-
 8 files changed, 92 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/kernel/probes/ftrace.c