Messages in this thread | | | Date | Wed, 19 Aug 2009 01:43:42 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH -tip v14 03/12] kprobes: checks probe address is instruction boudary on x86 |
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On Tue, Aug 18, 2009 at 07:17:39PM -0400, Masami Hiramatsu wrote: > Frederic Weisbecker wrote: > >> + while (addr < paddr) { > >> + kernel_insn_init(&insn, (void *)addr); > >> + insn_get_opcode(&insn); > >> + > >> + /* Check if the instruction has been modified. */ > >> + if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) { > >> + ret = recover_probed_instruction(buf, addr); > > > > > > > > I'm confused about the reason of this recovering. Is it to remove > > kprobes behind the current setting one in the current function? > > No, it recovers just an instruction which is probed by a kprobe, > because we need to know the first byte of this instruction for > decoding it. > > Perhaps we'd better to have more generic interface (text_peek?) > for it because another subsystem (e.g. kgdb) may want to insert int3... > > Thank you,
Aah, I see now, it's to keep a sane check of the instructions boundaries without int 3 artifacts in the middle.
But in that case, you should re-arm the breakpoint after your check, right?
Or may be you could do the check without repatching? May be by doing a copy of insn.opcode.bytes and replacing bytes[0] with what a random kprobe has stolen?
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