linux-kernel - [RFC PATCH tip/master V2 0/8] kprobes/x86: Make kprobes instruction buffers read-only

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Date:   Mon, 27 Mar 2017 16:48:46 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ye Xiaolong <xiaolong.ye@...el.com>, mhiramat@...nel.org
Subject: [RFC PATCH tip/master V2 0/8] kprobes/x86: Make kprobes instruction buffers read-only

Hi,

This is the 2nd version of the series, which has been updated
only 8/8, built and tested correctly. (Sorry, in previous version
I missed to build and tested different kernel.)

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 V1:
 - [8/8]: Fix build errors.

---

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   |  148 +++++++++++++++++++-------------------
 arch/x86/kernel/kprobes/ftrace.c |    2 -
 arch/x86/kernel/kprobes/opt.c    |   13 +++
 5 files changed, 89 insertions(+), 85 deletions(-)

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