[RFC PATCH tip/master V3 0/8] kprobes/x86: Make kprobes instruction buffers read-only

[Masami Hiramatsu <mhiramat@kernel.org>]

Hi,

This is the 3rd version of the series. I just updated 4/8 according
to Ingo's comment.

This series tries to make kprobes instruction buffers read-only
pages. Since those buffers are used for trampoline code, those
are a part of "text area" and it should be marked as ro for
avoiding unexpected modification. And this actually fix a warning
rodata sanity check reported by lkp-robot.

https://lkml.org/lkml/2017/2/27/161

This change requires changing the kprobe-booster at first
because it can modify the instruction buffer to add a jump while
resuming from single-stepping. Of course after we make the buffer
readonly, we may not be able to modify it while probing.

So, at first this series checks the current bootable instructions
and fixes a missed instruction (call far), modifies can_boost to
use x86 instruction decoder, and inserts "booster" jump while
preparing instruction buffer instead of resuming from single-stepping.
At last, it makes the buffers for kprobes and optprobe readonly.

This series also has some cleanup patches related to above 
changes.

Changes from V2:
 - [4/8]: Fix imbalanced curly braces and remove unneeded
   (void *) cast.

---

Masami Hiramatsu (8):
      kprobes/x86: Fix not to boost call far instruction
      kprobes/x86: Fix the description of __copy_instruction()
      kprobes/x86: Use instruction decoder for booster
      kprobes/x86: Do not modify singlestep buffer while resuming
      kprobes/x86: Make boostable flag boolean
      kprobes/x86: Set kprobes pages readonly
      kprobes/x86: Use probe_kernel_read instead of memcpy
      kprobes/x86: Consolidate insn decoder users for copying code


 arch/x86/include/asm/kprobes.h   |    7 +-
 arch/x86/kernel/kprobes/common.h |    4 +
 arch/x86/kernel/kprobes/core.c   |  149 +++++++++++++++++++-------------------
 arch/x86/kernel/kprobes/ftrace.c |    2 -
 arch/x86/kernel/kprobes/opt.c    |   13 +++
 5 files changed, 90 insertions(+), 85 deletions(-)

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>