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Re: kprobes vs __ex_table[]

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Hi Peter,

On Fri, 24 Feb 2017 10:26:46 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> One more complication with __ex_table and optimized kprobes is that we
> need to be careful not to clobber __ex_table[].fixup. It would be very
> bad if the optimized probe were to clobber the address we let the fixup
> return to -- or that needs fixups too, _after_ running
> __ex_table[].handler().

This gave me a chance to read closer current code, and I found that
I made a mistake 5 years ago on kprobe-booster. The commit 464846888d9a
("x86/kprobes: Fix a bug which can modify kernel code permanently")
introduced another bug -- which passed the address of copied instruction
instead of probing address to search_exception_tables() when preparing
kprobe-booster (skips singlestep.)

I'll send a fix patch.

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

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Thread

kprobes vs __ex_table[] Peter Zijlstra <peterz@infradead.org> - 2017-02-23 19:40 +0100
  Re: kprobes vs __ex_table[] Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-24 02:10 +0100
    Re: kprobes vs __ex_table[] Peter Zijlstra <peterz@infradead.org> - 2017-02-24 10:30 +0100
      Re: kprobes vs __ex_table[] Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-24 17:40 +0100
        Re: kprobes vs __ex_table[] Peter Zijlstra <peterz@infradead.org> - 2017-02-24 18:50 +0100
          [RFC PATCH 1/2] kprobes/x86: Use probe_kernel_read instead of memcpy Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-27 17:20 +0100
          [RFC PATCH 2/2] kprobes/x86: Exit single-stepping before trying fixup_exception Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-27 17:20 +0100
            Re: [RFC PATCH 2/2] kprobes/x86: Exit single-stepping before trying  fixup_exception Masami Hiramatsu <mhiramat@kernel.org> - 2017-03-02 00:40 +0100
          [RFC PATCH 0/2] kprobes/x86: Handle probing on ex_table cases Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-27 17:20 +0100
      Re: kprobes vs __ex_table[] Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-28 17:30 +0100
        [PATCH] [BUGFIX] kprobes/x86: Fix to check __ex_table entry by probed address Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-28 18:50 +0100
          [tip:perf/urgent] kprobes/x86: Fix kernel panic when certain  exception-handling addresses are probed tip-bot for Masami Hiramatsu <tipbot@zytor.com> - 2017-03-01 10:20 +0100

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