[PATCH v1] perf trace: Augment non-syscall tracepoints with enum arguments with BTF

From: Howard Chu
Date: Fri Jun 14 2024 - 23:28:06 EST

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Before:

perf $ ./perf trace -e timer:hrtimer_start --max-events=1
0.000 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466c25f18, function: 0xffffffff89da5be0, expires: 377432432256753, softexpires: 377432432256753, mode: 10)

After:

perf $ ./perf trace -e timer:hrtimer_start --max-events=1
0.000 :0/0 timer:hrtimer_start(hrtimer: 0xffff9498a6ca5f18, function: 0xffffffffa77a5be0, expires: 4382442895089, softexpires: 4382442895089, mode: HRTIMER_MODE_ABS_PINNED_HARD)

in which HRTIMER_MODE_ABS_PINNED_HARD is:

perf $ pahole hrtimer_mode
enum hrtimer_mode {
HRTIMER_MODE_ABS = 0,
HRTIMER_MODE_REL = 1,
HRTIMER_MODE_PINNED = 2,
HRTIMER_MODE_SOFT = 4,
HRTIMER_MODE_HARD = 8,
HRTIMER_MODE_ABS_PINNED = 2,
HRTIMER_MODE_REL_PINNED = 3,
HRTIMER_MODE_ABS_SOFT = 4,
HRTIMER_MODE_REL_SOFT = 5,
HRTIMER_MODE_ABS_PINNED_SOFT = 6,
HRTIMER_MODE_REL_PINNED_SOFT = 7,
HRTIMER_MODE_ABS_HARD = 8,
HRTIMER_MODE_REL_HARD = 9,
HRTIMER_MODE_ABS_PINNED_HARD = 10,
HRTIMER_MODE_REL_PINNED_HARD = 11,
};

Can also be tested by

./perf trace -e pagemap:mm_lru_insertion,timer:hrtimer_start,timer:hrtimer_init,skb:kfree_skb --max-events=10

(Chose these 4 events because they happen quite frequently.)

However some enum arguments may not be contained in vmlinux BTF. To see
what enum arguments are supported, use:

vmlinux_dir $ bpftool btf dump file /sys/kernel/btf/vmlinux > vmlinux

vmlinux_dir $ while read l; do grep "ENUM '$l'" vmlinux; done < <(grep field:enum /sys/kernel/tracing/events/*/*/format | awk '{print $3}' | sort | uniq) | awk '{print $3}' | sed "s/'$.*$'/\1/g"
dev_pm_qos_req_type
error_detector
hrtimer_mode
i2c_slave_event
ieee80211_bss_type
lru_list
migrate_mode
nl80211_auth_type
nl80211_band
nl80211_iftype
numa_vmaskip_reason
pm_qos_req_action
pwm_polarity
skb_drop_reason
thermal_trip_type
xen_lazy_mode
xen_mc_extend_args
xen_mc_flush_reason
zone_type

And what tracepoints have these enum types as their arguments:

vmlinux_dir $ while read l; do grep "ENUM '$l'" vmlinux; done < <(grep field:enum /sys/kernel/tracing/events/*/*/format | awk '{print $3}' | sort | uniq) | awk '{print $3}' | sed "s/'$.*$'/\1/g" > good_enums

vmlinux_dir $ cat good_enums
dev_pm_qos_req_type
error_detector
hrtimer_mode
i2c_slave_event
ieee80211_bss_type
lru_list
migrate_mode
nl80211_auth_type
nl80211_band
nl80211_iftype
numa_vmaskip_reason
pm_qos_req_action
pwm_polarity
skb_drop_reason
thermal_trip_type
xen_lazy_mode
xen_mc_extend_args
xen_mc_flush_reason
zone_type

vmlinux_dir $ grep -f good_enums -l /sys/kernel/tracing/events/*/*/format
/sys/kernel/tracing/events/cfg80211/cfg80211_chandef_dfs_required/format
/sys/kernel/tracing/events/cfg80211/cfg80211_ch_switch_notify/format
/sys/kernel/tracing/events/cfg80211/cfg80211_ch_switch_started_notify/format
/sys/kernel/tracing/events/cfg80211/cfg80211_get_bss/format
/sys/kernel/tracing/events/cfg80211/cfg80211_ibss_joined/format
/sys/kernel/tracing/events/cfg80211/cfg80211_inform_bss_frame/format
/sys/kernel/tracing/events/cfg80211/cfg80211_radar_event/format
/sys/kernel/tracing/events/cfg80211/cfg80211_ready_on_channel_expired/format
/sys/kernel/tracing/events/cfg80211/cfg80211_ready_on_channel/format
/sys/kernel/tracing/events/cfg80211/cfg80211_reg_can_beacon/format
/sys/kernel/tracing/events/cfg80211/cfg80211_return_bss/format
/sys/kernel/tracing/events/cfg80211/cfg80211_tx_mgmt_expired/format
/sys/kernel/tracing/events/cfg80211/rdev_add_virtual_intf/format
/sys/kernel/tracing/events/cfg80211/rdev_auth/format
/sys/kernel/tracing/events/cfg80211/rdev_change_virtual_intf/format
/sys/kernel/tracing/events/cfg80211/rdev_channel_switch/format
/sys/kernel/tracing/events/cfg80211/rdev_connect/format
/sys/kernel/tracing/events/cfg80211/rdev_inform_bss/format
/sys/kernel/tracing/events/cfg80211/rdev_libertas_set_mesh_channel/format
/sys/kernel/tracing/events/cfg80211/rdev_mgmt_tx/format
/sys/kernel/tracing/events/cfg80211/rdev_remain_on_channel/format
/sys/kernel/tracing/events/cfg80211/rdev_return_chandef/format
/sys/kernel/tracing/events/cfg80211/rdev_return_int_survey_info/format
/sys/kernel/tracing/events/cfg80211/rdev_set_ap_chanwidth/format
/sys/kernel/tracing/events/cfg80211/rdev_set_monitor_channel/format
/sys/kernel/tracing/events/cfg80211/rdev_set_radar_background/format
/sys/kernel/tracing/events/cfg80211/rdev_start_ap/format
/sys/kernel/tracing/events/cfg80211/rdev_start_radar_detection/format
/sys/kernel/tracing/events/cfg80211/rdev_tdls_channel_switch/format
/sys/kernel/tracing/events/compaction/mm_compaction_defer_compaction/format
/sys/kernel/tracing/events/compaction/mm_compaction_deferred/format
/sys/kernel/tracing/events/compaction/mm_compaction_defer_reset/format
/sys/kernel/tracing/events/compaction/mm_compaction_finished/format
/sys/kernel/tracing/events/compaction/mm_compaction_kcompactd_wake/format
/sys/kernel/tracing/events/compaction/mm_compaction_suitable/format
/sys/kernel/tracing/events/compaction/mm_compaction_wakeup_kcompactd/format
/sys/kernel/tracing/events/error_report/error_report_end/format
/sys/kernel/tracing/events/i2c_slave/i2c_slave/format
/sys/kernel/tracing/events/migrate/mm_migrate_pages/format
/sys/kernel/tracing/events/migrate/mm_migrate_pages_start/format
/sys/kernel/tracing/events/pagemap/mm_lru_insertion/format
/sys/kernel/tracing/events/power/dev_pm_qos_add_request/format
/sys/kernel/tracing/events/power/dev_pm_qos_remove_request/format
/sys/kernel/tracing/events/power/dev_pm_qos_update_request/format
/sys/kernel/tracing/events/power/pm_qos_update_flags/format
/sys/kernel/tracing/events/power/pm_qos_update_target/format
/sys/kernel/tracing/events/pwm/pwm_apply/format
/sys/kernel/tracing/events/pwm/pwm_get/format
/sys/kernel/tracing/events/sched/sched_skip_vma_numa/format
/sys/kernel/tracing/events/skb/kfree_skb/format
/sys/kernel/tracing/events/thermal/thermal_zone_trip/format
/sys/kernel/tracing/events/timer/hrtimer_init/format
/sys/kernel/tracing/events/timer/hrtimer_start/format
/sys/kernel/tracing/events/xen/xen_mc_batch/format
/sys/kernel/tracing/events/xen/xen_mc_extend_args/format
/sys/kernel/tracing/events/xen/xen_mc_flush_reason/format
/sys/kernel/tracing/events/xen/xen_mc_issue/format

Signed-off-by: Howard Chu <howardchu95@xxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Suggested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Reviewed-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

---
tools/perf/builtin-trace.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index d93f34e9af74..bd16679fb4c0 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1962,12 +1962,12 @@ static int trace__read_syscall_info(struct trace *trace, int id)
return err;
}

-static int evsel__init_tp_arg_scnprintf(struct evsel *evsel)
+static int evsel__init_tp_arg_scnprintf(struct evsel *evsel, bool *use_btf)
{
struct syscall_arg_fmt *fmt = evsel__syscall_arg_fmt(evsel);

if (fmt != NULL) {
- syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields, NULL);
+ syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields, use_btf);
return 0;
}

@@ -2171,7 +2171,8 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size,
* property isn't set.
*/
if (val == 0 && !trace->show_zeros &&
- !(sc->arg_fmt && sc->arg_fmt[arg.idx].show_zero))
+ !(sc->arg_fmt && sc->arg_fmt[arg.idx].show_zero) &&
+ !(sc->arg_fmt && sc->arg_fmt[arg.idx].is_enum))
continue;

printed += scnprintf(bf + printed, size - printed, "%s", printed ? ", " : "");
@@ -2877,7 +2878,7 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct evsel *evsel,
val = syscall_arg_fmt__mask_val(arg, &syscall_arg, val);

/* Suppress this argument if its value is zero and show_zero property isn't set. */
- if (val == 0 && !trace->show_zeros && !arg->show_zero)
+ if (val == 0 && !trace->show_zeros && !arg->show_zero && !arg->is_enum)
continue;

printed += scnprintf(bf + printed, size - printed, "%s", printed ? ", " : "");
@@ -2885,6 +2886,15 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct evsel *evsel,
if (trace->show_arg_names)
printed += scnprintf(bf + printed, size - printed, "%s: ", field->name);

+ if (arg->is_enum && trace->btf) {
+ size_t p = btf_enum_scnprintf(bf + printed, size - printed, val, trace->btf,
+ field->type, arg);
+ if (p) {
+ printed += p;
+ continue;
+ }
+ }
+
printed += syscall_arg_fmt__scnprintf_val(arg, bf + printed, size - printed, &syscall_arg, val);
}

@@ -4537,7 +4547,7 @@ static void evsel__set_syscall_arg_fmt(struct evsel *evsel, const char *name)
}
}

-static int evlist__set_syscall_tp_fields(struct evlist *evlist)
+static int evlist__set_syscall_tp_fields(struct evlist *evlist, bool *use_btf)
{
struct evsel *evsel;

@@ -4546,7 +4556,7 @@ static int evlist__set_syscall_tp_fields(struct evlist *evlist)
continue;

if (strcmp(evsel->tp_format->system, "syscalls")) {
- evsel__init_tp_arg_scnprintf(evsel);
+ evsel__init_tp_arg_scnprintf(evsel, use_btf);
continue;
}

@@ -5024,11 +5034,16 @@ int cmd_trace(int argc, const char **argv)
}

if (trace.evlist->core.nr_entries > 0) {
+ bool use_btf = false;
+
evlist__set_default_evsel_handler(trace.evlist, trace__event_handler);
- if (evlist__set_syscall_tp_fields(trace.evlist)) {
+ if (evlist__set_syscall_tp_fields(trace.evlist, &use_btf)) {
perror("failed to set syscalls:* tracepoint fields");
goto out;
}
+
+ if (use_btf && trace.btf == NULL)
+ trace__load_vmlinux_btf(&trace);
}

if (trace.sort_events) {
--
2.45.2

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