[PATCH 1/1] perf trace: Collect sys_nanosleep first argument
From: Arnaldo Carvalho de Melo
Date: Wed Jan 31 2024 - 16:32:00 EST
That is a 'struct timespec' passed from userspace to the kernel as we
can see with a system wide syscall tracing:
root@number:~# perf trace -e nanosleep
0.000 (10.102 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
38.924 (10.077 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
100.177 (10.107 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
139.171 (10.063 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
200.603 (10.105 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
239.399 (10.064 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
300.994 (10.096 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
339.584 (10.067 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
401.335 (10.057 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
439.758 (10.166 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
501.814 (10.110 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
539.983 (10.227 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
602.284 (10.199 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
640.208 (10.105 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
702.662 (10.163 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
740.440 (10.107 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
802.993 (10.159 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
^Croot@number:~# strace -p 9150 -e nanosleep
If we then use the ptrace method to look at that podman process:
root@number:~# strace -p 9150 -e nanosleep
strace: Process 9150 attached
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
^Cstrace: Process 9150 detached
root@number:~#
With some changes we can get something closer to the strace output,
still in system wide mode:
root@number:~# perf config trace.show_arg_names=false
root@number:~# perf config trace.show_duration=false
root@number:~# perf config trace.show_timestamp=false
root@number:~# perf config trace.show_zeros=true
root@number:~# perf config trace.args_alignment=0
root@number:~# perf trace -e nanosleep --max-events=10
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
root@number:~#
root@number:~# perf config
trace.show_arg_names=false
trace.show_duration=false
trace.show_timestamp=false
trace.show_zeros=true
trace.args_alignment=0
root@number:~# cat ~/.perfconfig
# this file is auto-generated.
[trace]
show_arg_names = false
show_duration = false
show_timestamp = false
show_zeros = true
args_alignment = 0
root@number:~#
This will not get reused by any other syscall as nanosleep is the only
one to have as its first argument a 'struct timespec" pointer argument
passed from userspace to the kernel:
root@number:~# grep timespec /sys/kernel/tracing/events/syscalls/sys_enter_*/format | grep offset:16
/sys/kernel/tracing/events/syscalls/sys_enter_nanosleep/format: field:struct __kernel_timespec * rqtp; offset:16; size:8; signed:0;
root@number:~#
BTF based pretty printing will simplify all this, but then lets just get
the low hanging fruits first.
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Link: https://lore.kernel.org/lkml/
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/builtin-trace.c | 2 ++
.../bpf_skel/augmented_raw_syscalls.bpf.c | 21 +++++++++++++++++++
2 files changed, 23 insertions(+)
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 109b8e64fe69ae32..6abe280dc38f1921 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1048,6 +1048,8 @@ static const struct syscall_fmt syscall_fmts[] = {
.arg = { [3] = { .scnprintf = SCA_MREMAP_FLAGS, /* flags */ }, }, },
{ .name = "name_to_handle_at",
.arg = { [0] = { .scnprintf = SCA_FDAT, /* dfd */ }, }, },
+ { .name = "nanosleep",
+ .arg = { [0] = { .scnprintf = SCA_TIMESPEC, /* req */ }, }, },
{ .name = "newfstatat",
.arg = { [0] = { .scnprintf = SCA_FDAT, /* dfd */ }, }, },
{ .name = "open",
diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
index 52c270330ae0d2f3..baecffbece14fb68 100644
--- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
+++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
@@ -354,6 +354,27 @@ int sys_enter_clock_nanosleep(struct syscall_enter_args *args)
return 1; /* Failure: don't filter */
}
+SEC("tp/syscalls/sys_enter_nanosleep")
+int sys_enter_nanosleep(struct syscall_enter_args *args)
+{
+ struct augmented_args_payload *augmented_args = augmented_args_payload();
+ const void *req_arg = (const void *)args->args[0];
+ unsigned int len = sizeof(augmented_args->args);
+ __u32 size = sizeof(struct timespec64);
+
+ if (augmented_args == NULL)
+ goto failure;
+
+ if (size > sizeof(augmented_args->__data))
+ goto failure;
+
+ bpf_probe_read_user(&augmented_args->__data, size, req_arg);
+
+ return augmented__output(args, augmented_args, len + size);
+failure:
+ return 1; /* Failure: don't filter */
+}
+
static pid_t getpid(void)
{
return bpf_get_current_pid_tgid();
--
2.43.0