On Wed, 24 Mar 2021 11:01:43 -0500 Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > On Wed, Mar 24, 2021 at 10:40:58AM +0900, Masami Hiramatsu wrote: > > On Tue, 23 Mar 2021 23:30:07 +0100 > > Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > On Mon, Mar 22, 2021 at 03:41:40PM +0900, Masami Hiramatsu wrote: > > > > ".global kretprobe_trampoline\n" > > > > ".type kretprobe_trampoline, @function\n" > > > > "kretprobe_trampoline:\n" > > > > #ifdef CONFIG_X86_64 > > > > > > So what happens if we get an NMI here? That is, after the RET but before > > > the push? Then our IP points into the trampoline but we've not done that > > > push yet. > > > > Not only NMI, but also interrupts can happen. There is no cli/sti here. > > > > Anyway, thanks for pointing! > > I think in UNWIND_HINT_TYPE_REGS and UNWIND_HINT_TYPE_REGS_PARTIAL cases > > ORC unwinder also has to check the state->ip and if it is kretprobe_trampoline, > > it should be recovered. > > What about this? > > I think the REGS and REGS_PARTIAL cases can also be affected by function > graph tracing. So should they use the generic unwind_recover_ret_addr() > instead of unwind_recover_kretprobe()? Yes, but I'm not sure this parameter can be applied. For example, it passed "state->sp - sizeof(unsigned long)" as where the return address stored address. Is that same on ftrace graph too? Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
