Messages in this thread | | | Date | Thu, 03 Jan 2008 16:31:51 -0500 | From | Masami Hiramatsu <> | Subject | Re: [PATCH] x86: kprobes change kprobe_handler flow |
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Hi Abhishek,
Masami Hiramatsu wrote: >> Hmm, I can not agree, because it is possible to insert a kprobe >> into kprobe's instruction buffer. If it should be a bug, we must >> check it when registering the kprobe. > > I discussed it with other maintainers and knew that current kprobes > does not allow user to insert a kprobe to another kprobe's instruction > buffer, because register_kprobe ensures the insertion address is text. > Now I changed my mind. I think that case (p && kprobe_running() && > kcb->kprobe_status==KPROBE_HIT_SS) is BUG(), even if (*p->ainsn.insn == > BREAKPOINT_INSTRUCTION).
I could understand what the original code did at last. If a kprobe is inserted on a breakpoint which other debugger inserts, it single step inline instead of out-of-line.(this is done in prepare_singlestep) In this case, (p && kprobe_running() && kcb->kprobe_status==KPROBE_HIT_SS) is true and we need pass the control to the debugger. And if (*p->ainsn.insn != BREAKPOINT_INSTRUCTION) (or (p != kprobe_running())) in that case, there may be some bugs.
Now I think your original suggestion is correct. Please fix it in another patch.
Thank you very much,
-- Masami Hiramatsu
Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division
e-mail: mhiramat@redhat.com, masami.hiramatsu.pt@hitachi.com
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