Messages in this thread | | | Date | Fri, 20 Feb 2015 13:52:23 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/2] kprobes/x86: Use 5-byte NOP when the code might be modified by ftrace |
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* Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
> (2015/02/20 19:26), Ingo Molnar wrote: > > > > * Petr Mladek <pmladek@suse.cz> wrote: > > > >> can_probe() checks if the given address points to the > >> beginning of an instruction. It analyzes all the > >> instructions from the beginning of the function until the > >> given address. The code might be modified by another > >> Kprobe. In this case, the current code is read into a > >> buffer, int3 breakpoint is replaced by the saved opcode > >> in the buffer, and can_probe() analyzes the buffer > >> instead. > >> > >> [...] > > > > Had to drop this patch due to build failures on 32-bit x86: > > > > arch/x86/kernel/kprobes/core.c:258:40: error: ‘MCOUNT_INSN_SIZE’ undeclared (first use in this function) > > Oops, MCOUNT_INSN_SIZE actually depends on > CONFIG_FUNCTION_TRACER... I think we can use 5 instead of > that since we are copying NOP_ATOMIC5.
Or just make the define more widely available? It's not like the size changes from disabling the function tracer.
Thanks,
Ingo
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