Frederic Weisbecker wrote: > 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. Ah, sorry, it was not accurate. the function recovers an instruction on the buffer(buf), not on the real kernel text. :) >> >> 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? Yes, it doesn't modify kernel text, just recover an original instruction from kernel text and backup byte on a buffer. > May be by doing a copy of insn.opcode.bytes and replacing bytes[0] > with what a random kprobe has stolen? Hm, no, this function is protected from other kprobes by kprobe_mutex. Thank you, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html