5.15-stable review patch. If anyone has any objections, please let me know.
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From: Jiri Olsa jolsa@kernel.org
commit 6d08340d1e354787d6c65a8c3cdd4d41ffb8a5ed upstream.
This reverts commit 83f44ae0f8afcc9da659799db8693f74847e66b3.
Currently we store initial stacktrace entry twice for non-HW ot_regs, which means callers that fail perf_hw_regs(regs) condition in perf_callchain_kernel.
It's easy to reproduce this bpftrace:
# bpftrace -e 'tracepoint:sched:sched_process_exec { print(kstack()); }' Attaching 1 probe...
bprm_execve+1767 bprm_execve+1767 do_execveat_common.isra.0+425 __x64_sys_execve+56 do_syscall_64+133 entry_SYSCALL_64_after_hwframe+118
When perf_callchain_kernel calls unwind_start with first_frame, AFAICS we do not skip regs->ip, but it's added as part of the unwind process. Hence reverting the extra perf_callchain_store for non-hw regs leg.
I was not able to bisect this, so I'm not really sure why this was needed in v5.2 and why it's not working anymore, but I could see double entries as far as v5.10.
I did the test for both ORC and framepointer unwind with and without the this fix and except for the initial entry the stacktraces are the same.
Acked-by: Song Liu song@kernel.org Signed-off-by: Jiri Olsa jolsa@kernel.org Link: https://lore.kernel.org/r/20251104215405.168643-2-jolsa@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/events/core.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
--- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2772,13 +2772,13 @@ perf_callchain_kernel(struct perf_callch return; }
- if (perf_callchain_store(entry, regs->ip)) - return; - - if (perf_hw_regs(regs)) + if (perf_hw_regs(regs)) { + if (perf_callchain_store(entry, regs->ip)) + return; unwind_start(&state, current, regs, NULL); - else + } else { unwind_start(&state, current, NULL, (void *)regs->sp); + }
for (; !unwind_done(&state); unwind_next_frame(&state)) { addr = unwind_get_return_address(&state);