linux-kernel - [RFC PATCH 0/2] x86/kprobes: add exception opcode detector and boost more opcodes

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Date: Fri, 26 Jan 2024 22:41:22 -0600
From: Jinghao Jia <jinghao7@...inois.edu>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jinghao Jia <jinghao7@...inois.edu>
Subject: [RFC PATCH 0/2] x86/kprobes: add exception opcode detector and boost more opcodes

Hi everyone,

This patch set makes the following 2 changes:

- It adds an exception opcode detector to prevent kprobing on INTs and UDs.
  These opcodes serves special purposes in the kernel and kprobing them
  will also cause the stack trace to be polluted by the copy buffer
  address. This is suggested by Masami.

- At the same time, this patch set also boosts more opcodes from the group
  2/3/4/5. The newly boosted opcodes are all arithmetic instructions with
  semantics that are easy to reason about, and therefore, they are able to
  be boosted and executed out-of-line. These instructions were not boosted
  previously because they use opcode extensions that are not handled by the
  kernel. But now with the instruction decoder they can be easily handled.
  Boosting (and further jump optimizing) these instructions leads to a 10x
  performance gain for a single probe on QEMU.

Jinghao Jia (2):
  x86/kprobes: Prohibit kprobing on INT and UD
  x86/kprobes: boost more instructions from grp2/3/4/5

 arch/x86/kernel/kprobes/core.c | 54 ++++++++++++++++++++++++++--------
 1 file changed, 41 insertions(+), 13 deletions(-)

--
2.43.0