Messages in this thread | | | Date | Tue, 7 May 2019 14:41:31 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions |
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On Tue, May 07, 2019 at 08:27:16AM -0400, Steven Rostedt wrote: > On Tue, 7 May 2019 11:27:31 +0200 > Peter Zijlstra <peterz@infradead.org> wrote: > > > FWIW, both these trampolines assume a kprobe will not > > int3_emulate_{push/call}(), for both bitnesses. > > > > But then; I'm thinking kprobes should be inspection only and not modify > > things. So that might just be good enough. > > I believe there are kprobe calls that do modify things. Note, they can > modify regs->ip.
The kprobe pre_handler as used by kretprobes does, and that is indeed handled by the trampolines.
> Kprobes sets the FTRACE_OPS_FL_IPMODIFY flag, thus > they can never be put at the same location that is being live patched.
OK, so do we want to allow kprobes that also modify regs->sp ? Because then we need to change these trampolines a bit.
I'd prefer not to allow kprobes this.
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