On Thu, 17 Jun 2021 13:21:59 -0500 Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > On Thu, Jun 17, 2021 at 10:45:41AM -0700, Andrii Nakryiko wrote: > > > > > > I know I suggested this patch, but I believe it would only be useful in > > > > > > combination with the use of UNWIND_HINT_REGS in SAVE_REGS_STRING. But I > > > > > > think that would be tricky to pull off correctly. Instead, we have > > > > > > UNWIND_HINT_FUNC, which is working fine. > > > > > > > > > > > > So I'd suggest dropping this patch, as the unwinder isn't actually > > > > > > reading regs->ip after all. > > > > > > > > > > ... and I guess this means patches 6-8 are no longer necessary. > > > > > > > > OK, I also confirmed that dropping those patche does not make any change > > > > on the stacktrace. > > > > Let me update the series without those. > > > > > > Oops, Andrii, can you also test the kernel without this patch? > > > (you don't need to drop patch 6-8) > > > > Hi Masami, > > > > Dropping this patch and leaving all the other in place breaks stack > > traces from kretprobes for BPF. I double checked with and without this > > patch. Without this patch we are back to having broken stack traces. I > > see either > > > > kretprobe_trampoline+0x0 > > > > or > > > > ftrace_trampoline+0xc8 > > kretprobe_trampoline+0x0 Thanks for confirmation. > > > > Is there any problem if you leave this patch as is? > > Hm, I must be missing something then. The patch is probably fine to > keep, we just may need to improve the commit log so that it makes sense > to me. Yeah, I need to update the commit message so that this will help the stacktrace from kretprobe's pt_regs, which will be used in bpf. Thank you! > > Which unwinder are you using (CONFIG_UNWINDER_*)? > > -- > Josh > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
