Messages in this thread | | | Date | Mon, 5 Sep 2022 17:20:30 +0200 | From | Peter Zijlstra <> | Subject | Re: CONFIG_RETHUNK int3 filling prevents kprobes in function body |
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On Mon, Sep 05, 2022 at 05:10:27PM +0200, Peter Zijlstra wrote: > On Mon, Sep 05, 2022 at 10:57:58AM -0400, Steven Rostedt wrote: > > On Sun, 4 Sep 2022 23:07:13 +0900 > > Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: > > > > > Can we use another instruction for padding instead of INT3? (e.g. NOP or UD2) > > > > > > Or, can I expect the instruction length in __return_sites[] are always 5? > > > If so, I can just skip 5 bytes if the address is in __return_sites[]. > > > > Perhaps another option is to have a table of where the padding is placed > > (tagged), and that kprobes could check to see if the int3 is due to this > > padding or not? > > I don't see need for that. If you want to be strict you can simply > follow the branches found earlier, if you want to be lazy, you can > decode until you run out of the symbol size.
Another lazy option is to teach the thing that 'ret' is followed by 0,1 or 4 'int3' instructions depending on CONFIG_SLS, CONFIG_RETHUNK, but that'll get you into trouble with future SLS compiler options, like the aforementioned JMP-SLS option.
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