For RISC-V, when tracing with tracepoint events, the IP and status are
set to 0, preventing the perf code parsing the callchain and resolving
the symbols correctly.
./ply 'tracepoint:kmem/kmem_cache_alloc { @[stack]=count(); }'
@:
{ <STACKID4294967282> }: 1
The fix is to implement perf_arch_fetch_caller_regs for riscv, which
fills several necessary registers used for callchain unwinding,
including epc, sp, s0 and status. It's similar to commit b3eac0265b
("arm: perf: Fix callchain parse error with kernel tracepoint events")
and commit 5b09a094f2 ("arm64: perf: Fix callchain parse error with
kernel tracepoint events").
With this patch, callchain can be parsed correctly as:
./ply 'tracepoint:kmem/kmem_cache_alloc { @[stack]=count(); }'
@:
{
__traceiter_kmem_cache_alloc+68
__traceiter_kmem_cache_alloc+68
kmem_cache_alloc+354
__sigqueue_alloc+94
__send_signal_locked+646
send_signal_locked+154
do_send_sig_info+84
__kill_pgrp_info+130
kill_pgrp+60
isig+150
n_tty_receive_signal_char+36
n_tty_receive_buf_standard+2214
n_tty_receive_buf_common+280
n_tty_receive_buf2+26
tty_ldisc_receive_buf+34
tty_port_default_receive_buf+62
flush_to_ldisc+158
process_one_work+458
worker_thread+138
kthread+178
riscv_cpufeature_patch_func+832
}: 1
Signed-off-by: Ism Hong <ism.hong@gmail.com>
Link: https://lore.kernel.org/r/20230601095355.1168910-1-ism.hong@gmail.com
Fixes: 178e9fc47a ("perf: riscv: preliminary RISC-V support")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
9a7e8ec0d4