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| author | Masami Hiramatsu <mhiramat@kernel.org> | 2018-06-20 01:16:46 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-06-21 12:33:20 +0200 |
| commit | dcce32d952eddcd427f648ebd04339cfbf305e23 (patch) | |
| tree | 921eccc1bc4a0e1b08aac07418d48fdeec0e0d4e /Documentation/kprobes.txt | |
| parent | 2bbda764d720aacabaad38374d26fcccb7843f17 (diff) | |
Documentation/kprobes: Add how to change the execution path
Add a section that explaining how to change the execution
path with kprobes and warnings for some arch.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-arch@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Link: https://lore.kernel.org/lkml/152942500680.15209.12374262914863044775.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/kprobes.txt')
| -rw-r--r-- | Documentation/kprobes.txt | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt index cbb545910634..13d8efdb9718 100644 --- a/Documentation/kprobes.txt +++ b/Documentation/kprobes.txt @@ -80,6 +80,26 @@ After the instruction is single-stepped, Kprobes executes the "post_handler," if any, that is associated with the kprobe. Execution then continues with the instruction following the probepoint. +Changing Execution Path +----------------------- + +Since the kprobes can probe into a running kernel code, it can change +the register set, including instruction pointer. This operation +requires maximum attention, such as keeping the stack frame, recovering +execution path etc. Since it is operated on running kernel and need deep +knowladge of the archtecture and concurrent computing, you can easily +shot your foot. + +If you change the instruction pointer (and set up other related +registers) in pre_handler, you must return !0 so that the kprobes +stops single stepping and just returns to given address. +This also means post_handler should not be called anymore. + +Note that this operation may be harder on some architectures which +use TOC (Table of Contents) for function call, since you have to +setup new TOC for your function in your module, and recover old +one after back from it. + Return Probes ------------- |