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6d08340d1e
This reverts commit 83f44ae0f8.
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>