From: Ism Hong ism.hong@gmail.com
commit 9a7e8ec0d4cc64870ea449b4fce5779b77496cbb upstream.
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 b3eac0265bf6 ("arm: perf: Fix callchain parse error with kernel tracepoint events") and commit 5b09a094f2fb ("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: 178e9fc47aae ("perf: riscv: preliminary RISC-V support") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/riscv/include/asm/perf_event.h | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/arch/riscv/include/asm/perf_event.h +++ b/arch/riscv/include/asm/perf_event.h @@ -10,4 +10,11 @@
#include <linux/perf_event.h> #define perf_arch_bpf_user_pt_regs(regs) (struct user_regs_struct *)regs + +#define perf_arch_fetch_caller_regs(regs, __ip) { \ + (regs)->epc = (__ip); \ + (regs)->s0 = (unsigned long) __builtin_frame_address(0); \ + (regs)->sp = current_stack_pointer; \ + (regs)->status = SR_PP; \ +} #endif /* _ASM_RISCV_PERF_EVENT_H */