On Mon, 13 Sep 2021 10:14:55 -0700 Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > On Mon, Aug 23, 2021 at 10:32 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > On Mon, 23 Aug 2021 22:12:06 -0700 > > Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > > > > On Thu, Jul 29, 2021 at 4:35 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > > > > > On Thu, 29 Jul 2021 23:05:56 +0900 > > > > Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > > > > > > Hello, > > > > > > > > > > This is the 10th version of the series to fix the stacktrace with kretprobe on x86. > > > > > > > > > > The previous version is here; > > > > > > > > > > https://lore.kernel.org/bpf/162601048053.1318837.1550594515476777588.stgit@devnote2/ > > > > > > > > > > This version is rebased on top of new kprobes cleanup series(*1) and merging > > > > > Josh's objtool update series (*2)(*3) as [6/16] and [7/16]. > > > > > > > > > > (*1) https://lore.kernel.org/bpf/162748615977.59465.13262421617578791515.stgit@devnote2/ > > > > > (*2) https://lore.kernel.org/bpf/20210710192433.x5cgjsq2ksvaqnss@treble/ > > > > > (*3) https://lore.kernel.org/bpf/20210710192514.ghvksi3ozhez4lvb@treble/ > > > > > > > > > > Changes from v9: > > > > > - Add Josh's objtool update patches with a build error fix as [6/16] and [7/16]. > > > > > - Add a API document for kretprobe_find_ret_addr() and check cur != NULL in [5/16]. > > > > > > > > > > With this series, unwinder can unwind stack correctly from ftrace as below; > > > > > > > > > > # cd /sys/kernel/debug/tracing > > > > > # echo > trace > > > > > # echo 1 > options/sym-offset > > > > > # echo r vfs_read >> kprobe_events > > > > > # echo r full_proxy_read >> kprobe_events > > > > > # echo traceoff:1 > events/kprobes/r_vfs_read_0/trigger > > > > > # echo stacktrace:1 > events/kprobes/r_full_proxy_read_0/trigger > > > > > # echo 1 > events/kprobes/enable > > > > > # cat /sys/kernel/debug/kprobes/list > > > > > ffffffff8133b740 r full_proxy_read+0x0 [FTRACE] > > > > > ffffffff812560b0 r vfs_read+0x0 [FTRACE] > > > > > # echo 0 > events/kprobes/enable > > > > > # cat trace > > > > > # tracer: nop > > > > > # > > > > > # entries-in-buffer/entries-written: 3/3 #P:8 > > > > > # > > > > > # _-----=> irqs-off > > > > > # / _----=> need-resched > > > > > # | / _---=> hardirq/softirq > > > > > # || / _--=> preempt-depth > > > > > # ||| / delay > > > > > # TASK-PID CPU# |||| TIMESTAMP FUNCTION > > > > > # | | | |||| | | > > > > > <...>-134 [007] ...1 16.185877: r_full_proxy_read_0: (vfs_read+0x98/0x180 <- full_proxy_read) > > > > > <...>-134 [007] ...1 16.185901: <stack trace> > > > > > => kretprobe_trace_func+0x209/0x300 > > > > > => kretprobe_dispatcher+0x4a/0x70 > > > > > => __kretprobe_trampoline_handler+0xd4/0x170 > > > > > => trampoline_handler+0x43/0x60 > > > > > => kretprobe_trampoline+0x2a/0x50 > > > > > => vfs_read+0x98/0x180 > > > > > => ksys_read+0x5f/0xe0 > > > > > => do_syscall_64+0x37/0x90 > > > > > => entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > > <...>-134 [007] ...1 16.185902: r_vfs_read_0: (ksys_read+0x5f/0xe0 <- vfs_read) > > > > > > > > > > This shows the double return probes (vfs_read() and full_proxy_read()) on the stack > > > > > correctly unwinded. (vfs_read() returns to 'ksys_read+0x5f' and full_proxy_read() > > > > > returns to 'vfs_read+0x98') > > > > > > > > > > This also changes the kretprobe behavisor a bit, now the instraction pointer in > > > > > the 'pt_regs' passed to kretprobe user handler is correctly set the real return > > > > > address. So user handlers can get it via instruction_pointer() API, and can use > > > > > stack_trace_save_regs(). > > > > > > > > > > You can also get this series from > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/kretprobe-stackfix-v9 > > > > > > > > Oops, this is of course 'kprobes/kretprobe-stackfix-v10'. And this branch includes above (*1) series. > > > > > > Hi Masami, > > > > > > Was this ever merged/applied? This is a very important functionality > > > for BPF kretprobes, so I hope this won't slip through the cracks. > > > > No, not yet as far as I know. > > I'm waiting for any comment on this series. Since this is basically > > x86 ORC unwinder improvement, this series should be merged to -tip tree. > > > > Hey Masami, > > It's been a while since you posted v10. It seems like this series > doesn't apply cleanly anymore. Do you mind rebasing and resubmitting > it again to refresh the series and make it easier for folks to review > and test it? Yes, I'm planning to do that this week soon. Thank you for ping me :) > > Also, do I understand correctly that [0] is a dependency of this > series? If yes, please rebase and resubmit that one as well. Not sure > on the status of Josh's patches you have dependency on as well. Can > you please coordinate with him and maybe incorporate them into your > series? Sorry I can not see [0], could you tell me another URL or title? Or is that Kees's patch [1]? [1] https://lore.kernel.org/all/20210903021326.206548-1-keescook@xxxxxxxxxxxx/T/#u > > Please also cc Paul McKenney <paulmck@xxxxxxxxxx> for the future > revisions so he can follow along as well? Thanks! OK! > > > [0] https://patchwork.kernel.org/project/netdevbpf/list/?series=522757&state=* > > > > > Ingo and Josh, > > > > Could you give me any comment, please? > > > > Thank you, > > > > > > > Thanks! > > > > > > > > > > > Thank you, > > > > > > > > -- > > > > Masami Hiramatsu <mhiramat@xxxxxxxxxx> > > > > > > -- > > Masami Hiramatsu <mhiramat@xxxxxxxxxx> -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
