On Mon, Mar 01, 2021 at 11:08:15PM +0900, Masami Hiramatsu wrote: > Use int3 instead of debug trap exception for single-stepping the > probed instructions. Some instructions which change the ip > registers or modify IF flags are emulated because those are not > able to be single-stepped by int3 or may allow the interrupt > while single-stepping. > > This actually changes the kprobes behavior. > > - kprobes can not probe following instructions; int3, iret, > far jmp/call which get absolute address as immediate, > indirect far jmp/call, indirect near jmp/call with addressing > by memory (register-based indirect jmp/call are OK), and > vmcall/vmlaunch/vmresume/vmxoff. > > - If the kprobe post_handler doesn't set before registering, > it may not be called in some case even if you set it afterwards. > (IOW, kprobe booster is enabled at registration, user can not > change it) > > But both are rare issue, unsupported instructions will not be > used in the kernel (or rarely used), and post_handlers are > rarely used (I don't see it except for the test code). > > Suggested-by: Andy Lutomirski <[email protected]> > Signed-off-by: Masami Hiramatsu <[email protected]>
Very nice! Aside of a few nits: Acked-by: Peter Zijlstra (Intel) <[email protected]>
