Date: Thu, 13 Jun 2024 12:27:47 +0800
From: Howard Chu <howardchu95@...il.com>
To: peterz@...radead.org
Cc: mingo@...hat.com,
	acme@...nel.org,
	namhyung@...nel.org,
	mark.rutland@....com,
	alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org,
	irogers@...gle.com,
	adrian.hunter@...el.com,
	kan.liang@...ux.intel.com,
	mic@...ikod.net,
	gnoack@...gle.com,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	bpf@...r.kernel.org
Subject: [PATCH v4] perf trace: BTF-based enum pretty printing

changes in v4:

- Add enum support to tracepoint arguments

- For tracing syscalls, move trace__load_vmlinux_btf() to
syscall__set_arg_fmts() to make it more elegant

changes in v3:

- Fixed another awkward formatting issue in trace__load_vmlinux_btf()

changes in v2:

- Fix formatting issues

- Pass a &use_btf to syscall_arg_fmt__init_array(), instead of
traversing all the arguments again.

- Add a trace__load_vmlinux_btf() function to load vmlinux BTF

- Add member 'btf_entry' in 'struct syscall_arg_fmt' to save the entry to
the corresponding 'struct btf_member' object, without having to do
btf__find_by_name(), btf__type_by_id(), btf_enum(), and btf_vlen()
everytime a syscall enters.

===

v4 notes

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: 0xffff974466c25f18, function: 0xffffffff89da5be0, expires: 377732805560049, softexpires: 377732805560049, mode: HRTIMER_MODE_ABS_PINNED_HARD)

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,
};

this: HRTIMER_MODE_ABS_PINNED_HARD = 10,

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 tracepoints because they happen quite frequently.)

By using the command above, I got:

perf $ ./perf trace -e pagemap:mm_lru_insertion,timer:hrtimer_start,timer:hrtimer_init,skb:kfree_skb --max-events=10
     0.000 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466c25f18, function: 0xffffffff89da5be0, expires: 376189979047665, softexpires: 376189979047665, mode: HRTIMER_MODE_ABS_PINNED_HARD)
     0.053 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466ca5f18, function: 0xffffffff89da5be0, expires: 376230939043569, softexpires: 376230939043569, mode: HRTIMER_MODE_ABS_PINNED_HARD)
     0.099 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466ca5f18, function: 0xffffffff89da5be0, expires: 376111885722141, softexpires: 376111885722141, mode: HRTIMER_MODE_ABS_PINNED_HARD)
     0.242 tmux: server/296019 timer:hrtimer_init(hrtimer: 0xffffb872caa1f628, clockid: 1, mode: HRTIMER_MODE_ABS)
     0.244 tmux: server/296019 timer:hrtimer_start(hrtimer: 0xffffb872caa1f628, function: 0xffffffff89d90420, expires: 376111894496606, softexpires: 376111894446606, mode: HRTIMER_MODE_ABS)
     0.349 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466ca5f18, function: 0xffffffff89da5be0, expires: 376230939043569, softexpires: 376230939043569, mode: HRTIMER_MODE_ABS_PINNED_HARD)
     0.486 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466ca5f18, function: 0xffffffff89da5be0, expires: 376111885722141, softexpires: 376111885722141, mode: HRTIMER_MODE_ABS_PINNED_HARD)
     0.499 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466ca5f18, function: 0xffffffff89da5be0, expires: 376230939043569, softexpires: 376230939043569, mode: HRTIMER_MODE_ABS_PINNED_HARD)
     0.501 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466ca5f18, function: 0xffffffff89da5be0, expires: 376111885722141, softexpires: 376111885722141, mode: HRTIMER_MODE_ABS_PINNED_HARD)
     0.506 :0/0 timer:hrtimer_start(hrtimer: 0xffff974466ca5f18, function: 0xffffffff89da5be0, expires: 376230939043569, softexpires: 376230939043569, mode: HRTIMER_MODE_ABS_PINNED_HARD)

If you want to test all tracepoints that has enum arguments, and
that enum argument is retrievable in vmlinux:

./perf trace -e power:dev_pm_qos_add_request,power:dev_pm_qos_remove_request,power:dev_pm_qos_update_request,error_report:error_report_end,error_report:error_report_end,timer:hrtimer_init,timer:hrtimer_start,i2c_slave:i2c_slave,cfg80211:cfg80211_get_bss,pagemap:mm_lru_insertion,migrate:mm_migrate_pages,migrate:mm_migrate_pages_start,cfg80211:rdev_auth,cfg80211:rdev_connect,cfg80211:rdev_start_ap,cfg80211:cfg80211_chandef_dfs_required,cfg80211:cfg80211_ch_switch_notify,cfg80211:cfg80211_ch_switch_started_notify,cfg80211:cfg80211_get_bss,cfg80211:cfg80211_ibss_joined,cfg80211:cfg80211_inform_bss_frame,cfg80211:cfg80211_radar_event,cfg80211:cfg80211_ready_on_channel_expired,cfg80211:cfg80211_ready_on_channel,cfg80211:cfg80211_reg_can_beacon,cfg80211:cfg80211_return_bss,cfg80211:cfg80211_tx_mgmt_expired,cfg80211:rdev_channel_switch,cfg80211:rdev_inform_bss,cfg80211:rdev_libertas_set_mesh_channel,cfg80211:rdev_mgmt_tx,cfg80211:rdev_remain_on_channel,cfg80211:rdev_return_chandef,cfg80211:rdev_return_int_survey_info,cfg80211:rdev_set_ap_chanwidth,cfg80211:rdev_set_monitor_channel,cfg80211:rdev_set_radar_background,cfg80211:rdev_start_ap,cfg80211:rdev_start_radar_detection,cfg80211:rdev_tdls_channel_switch,cfg80211:cfg80211_reg_can_beacon,cfg80211:rdev_add_virtual_intf,cfg80211:rdev_change_virtual_intf,sched:sched_skip_vma_numa,power:pm_qos_update_flags,power:pm_qos_update_target,pwm:pwm_apply,pwm:pwm_get,skb:kfree_skb,thermal:thermal_zone_trip,xen:xen_mc_batch,xen:xen_mc_issue,xen:xen_mc_extend_args,xen:xen_mc_extend_args,xen:xen_mc_flush_reason,xen:xen_mc_flush_reason,compaction:mm_compaction_defer_compaction,compaction:mm_compaction_deferred,compaction:mm_compaction_defer_reset,compaction:mm_compaction_finished,compaction:mm_compaction_kcompactd_wake,compaction:mm_compaction_suitable,compaction:mm_compaction_wakeup_kcompactd --max-events=20

But whether this enum is in vmlinux may vary on different versions.
If you want to find out which enum type is in vmlinux, please 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

This is how I got the crazy long list of tracepoints above.

>From there, please use the command below to get the events, and use it as ./perf trace -e's
argument

vmlinux_dir $ grep -f good_enums -l /sys/kernel/tracing/events/*/*/format | sed "s/.*events\/\(.*\)\/\(.*\)\/.*/\1:\2/g"
cfg80211:cfg80211_chandef_dfs_required
cfg80211:cfg80211_ch_switch_notify
cfg80211:cfg80211_ch_switch_started_notify
cfg80211:cfg80211_get_bss
cfg80211:cfg80211_ibss_joined
cfg80211:cfg80211_inform_bss_frame
cfg80211:cfg80211_radar_event
cfg80211:cfg80211_ready_on_channel_expired
cfg80211:cfg80211_ready_on_channel
cfg80211:cfg80211_reg_can_beacon
cfg80211:cfg80211_return_bss
cfg80211:cfg80211_tx_mgmt_expired
cfg80211:rdev_add_virtual_intf
cfg80211:rdev_auth
cfg80211:rdev_change_virtual_intf
cfg80211:rdev_channel_switch
cfg80211:rdev_connect
cfg80211:rdev_inform_bss
cfg80211:rdev_libertas_set_mesh_channel
cfg80211:rdev_mgmt_tx
cfg80211:rdev_remain_on_channel
cfg80211:rdev_return_chandef
cfg80211:rdev_return_int_survey_info
cfg80211:rdev_set_ap_chanwidth
cfg80211:rdev_set_monitor_channel
cfg80211:rdev_set_radar_background
cfg80211:rdev_start_ap
cfg80211:rdev_start_radar_detection
cfg80211:rdev_tdls_channel_switch
compaction:mm_compaction_defer_compaction
compaction:mm_compaction_deferred
compaction:mm_compaction_defer_reset
compaction:mm_compaction_finished
compaction:mm_compaction_kcompactd_wake
compaction:mm_compaction_suitable
compaction:mm_compaction_wakeup_kcompactd
error_report:error_report_end
i2c_slave:i2c_slave
migrate:mm_migrate_pages
migrate:mm_migrate_pages_start
pagemap:mm_lru_insertion
power:dev_pm_qos_add_request
power:dev_pm_qos_remove_request
power:dev_pm_qos_update_request
power:pm_qos_update_flags
power:pm_qos_update_target
pwm:pwm_apply
pwm:pwm_get
sched:sched_skip_vma_numa
skb:kfree_skb
thermal:thermal_zone_trip
timer:hrtimer_init
timer:hrtimer_start
xen:xen_mc_batch
xen:xen_mc_extend_args
xen:xen_mc_flush_reason
xen:xen_mc_issue

===

v2 notes

In 'struct syscall_arg_fmt':
```
	struct {
		void	*entry;
		u16	nr_entries;
	}	   btf_entry;
```

This is the new member btf_entry. 'struct btf_member' object, so that
we don't have to do btf__find_by_name(), btf__type_by_id(), btf_enum(),
and btf_vlen() everytime a landlock_add_rule() syscall entered.

Note that entry is of type 'void *', because this btf_entry can also be
applied to 'struct btf_member *' for 'BTF_KIND_STRUCT', hopefully in the
future.

===

v1 notes

This is a feature implemented on the basis of the previous bug fix
https://lore.kernel.org/linux-perf-users/d18a9606-ac9f-4ca7-afaf-fcf4c951cb90@web.de/T/#t

In this patch, BTF is used to turn enum value to the corresponding
name. There is only one system call that uses enum value as its
argument, that is `landlock_add_rule()`.

The vmlinux btf is loaded lazily, when user decided to trace the
`landlock_add_rule` syscall. But if one decide to run `perf trace`
without any arguments, the behaviour is to trace `landlock_add_rule`,
so vmlinux btf will be loaded by default.

The laziest behaviour is to load vmlinux btf when a
`landlock_add_rule` syscall hits. But I think you could lose some
samples when loading vmlinux btf at run time, for it can delay the
handling of other samples. I might need your precious opinions on
this...

before:

```
perf $ ./perf trace -e landlock_add_rule
     0.000 ( 0.008 ms): ldlck-test/438194 landlock_add_rule(rule_type: 2)                                       = -1 EBADFD (File descriptor in bad state)
     0.010 ( 0.001 ms): ldlck-test/438194 landlock_add_rule(rule_type: 1)                                       = -1 EBADFD (File descriptor in bad state)
```

after:

```
perf $ ./perf trace -e landlock_add_rule
     0.000 ( 0.029 ms): ldlck-test/438194 landlock_add_rule(rule_type: LANDLOCK_RULE_NET_PORT)                  = -1 EBADFD (File descriptor in bad state)
     0.036 ( 0.004 ms): ldlck-test/438194 landlock_add_rule(rule_type: LANDLOCK_RULE_PATH_BENEATH)              = -1 EBADFD (File descriptor in bad state)
```

Signed-off-by: Howard Chu <howardchu95@...il.com>
---
 tools/perf/builtin-trace.c | 121 ++++++++++++++++++++++++++++++++++---
 1 file changed, 111 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 5cbe1748911d..0a168cb9b0c2 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -19,6 +19,7 @@
 #ifdef HAVE_LIBBPF_SUPPORT
 #include <bpf/bpf.h>
 #include <bpf/libbpf.h>
+#include <bpf/btf.h>
 #ifdef HAVE_BPF_SKEL
 #include "bpf_skel/augmented_raw_syscalls.skel.h"
 #endif
@@ -110,6 +111,11 @@ struct syscall_arg_fmt {
 	const char *name;
 	u16	   nr_entries; // for arrays
 	bool	   show_zero;
+	bool	   is_enum;
+	struct {
+		void	*entry;
+		u16	nr_entries;
+	}	   btf_entry;
 };
 
 struct syscall_fmt {
@@ -140,6 +146,7 @@ struct trace {
 #ifdef HAVE_BPF_SKEL
 	struct augmented_raw_syscalls_bpf *skel;
 #endif
+	struct btf		*btf;
 	struct record_opts	opts;
 	struct evlist	*evlist;
 	struct machine		*host;
@@ -887,6 +894,56 @@ static size_t syscall_arg__scnprintf_getrandom_flags(char *bf, size_t size,
 
 #define SCA_GETRANDOM_FLAGS syscall_arg__scnprintf_getrandom_flags
 
+static int btf_enum_find_entry(struct btf *btf, char *type, struct syscall_arg_fmt *arg_fmt)
+{
+	const struct btf_type *bt;
+	char enum_prefix[][16] = { "enum", "const enum" }, *ep;
+	int id;
+	size_t i;
+
+	for (i = 0; i < ARRAY_SIZE(enum_prefix); i++) {
+		ep = enum_prefix[i];
+		if (strlen(type) > strlen(ep) + 1 && strstarts(type, ep))
+			type += strlen(ep) + 1;
+	}
+
+	id = btf__find_by_name(btf, type);
+	if (id < 0)
+		return -1;
+
+	bt = btf__type_by_id(btf, id);
+	if (bt == NULL)
+		return -1;
+
+	arg_fmt->btf_entry.entry      = btf_enum(bt);
+	arg_fmt->btf_entry.nr_entries = btf_vlen(bt);
+
+	return 0;
+}
+
+static size_t btf_enum_scnprintf(char *bf, size_t size, int val, struct btf *btf, char *type,
+				 struct syscall_arg_fmt *arg_fmt)
+{
+	struct btf_enum *be;
+	int i;
+
+	/* if btf_entry is NULL, find and save it to arg_fmt */
+	if (arg_fmt->btf_entry.entry == NULL)
+		if (btf_enum_find_entry(btf, type, arg_fmt))
+			return 0;
+
+	be = (struct btf_enum *)arg_fmt->btf_entry.entry;
+
+	for (i = 0; i < arg_fmt->btf_entry.nr_entries; ++i, ++be) {
+		if (be->val == val) {
+			return scnprintf(bf, size, "%s",
+					 btf__name_by_offset(btf, be->name_off));
+		}
+	}
+
+	return 0;
+}
+
 #define STRARRAY(name, array) \
 	  { .scnprintf	= SCA_STRARRAY, \
 	    .strtoul	= STUL_STRARRAY, \
@@ -1238,6 +1295,7 @@ struct syscall {
 	bool		    is_exit;
 	bool		    is_open;
 	bool		    nonexistent;
+	bool		    use_btf;
 	struct tep_format_field *args;
 	const char	    *name;
 	const struct syscall_fmt  *fmt;
@@ -1699,6 +1757,15 @@ static void trace__symbols__exit(struct trace *trace)
 	symbol__exit();
 }
 
+static void trace__load_vmlinux_btf(struct trace *trace)
+{
+	trace->btf = btf__load_vmlinux_btf();
+	if (verbose > 0) {
+		fprintf(trace->output, trace->btf ? "vmlinux BTF loaded\n" :
+						    "Failed to load vmlinux BTF\n");
+	}
+}
+
 static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
 {
 	int idx;
@@ -1744,7 +1811,8 @@ static const struct syscall_arg_fmt *syscall_arg_fmt__find_by_name(const char *n
 }
 
 static struct tep_format_field *
-syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field *field)
+syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field *field,
+			    bool *use_btf)
 {
 	struct tep_format_field *last_field = NULL;
 	int len;
@@ -1756,6 +1824,7 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
 			continue;
 
 		len = strlen(field->name);
+		arg->is_enum = false;
 
 		if (strcmp(field->type, "const char *") == 0 &&
 		    ((len >= 4 && strcmp(field->name + len - 4, "name") == 0) ||
@@ -1782,6 +1851,8 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
 			 * 7 unsigned long
 			 */
 			arg->scnprintf = SCA_FD;
+		} else if (strstr(field->type, "enum") && use_btf != NULL) {
+			*use_btf = arg->is_enum = true;
 		} else {
 			const struct syscall_arg_fmt *fmt =
 				syscall_arg_fmt__find_by_name(field->name);
@@ -1796,9 +1867,14 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
 	return last_field;
 }
 
-static int syscall__set_arg_fmts(struct syscall *sc)
+static int syscall__set_arg_fmts(struct trace *trace, struct syscall *sc)
 {
-	struct tep_format_field *last_field = syscall_arg_fmt__init_array(sc->arg_fmt, sc->args);
+	bool use_btf;
+	struct tep_format_field *last_field = syscall_arg_fmt__init_array(sc->arg_fmt, sc->args,
+									  &use_btf);
+
+	if (use_btf && trace->btf == NULL)
+		trace__load_vmlinux_btf(trace);
 
 	if (last_field)
 		sc->args_size = last_field->offset + last_field->size;
@@ -1883,15 +1959,20 @@ static int trace__read_syscall_info(struct trace *trace, int id)
 	sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit");
 	sc->is_open = !strcmp(name, "open") || !strcmp(name, "openat");
 
-	return syscall__set_arg_fmts(sc);
+	return syscall__set_arg_fmts(trace, sc);
 }
 
-static int evsel__init_tp_arg_scnprintf(struct evsel *evsel)
+static int evsel__init_tp_arg_scnprintf(struct trace *trace, struct evsel *evsel)
 {
 	struct syscall_arg_fmt *fmt = evsel__syscall_arg_fmt(evsel);
+	bool use_btf;
 
 	if (fmt != NULL) {
-		syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields);
+		syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields, &use_btf);
+
+		if (use_btf && trace->btf == NULL)
+			trace__load_vmlinux_btf(trace);
+
 		return 0;
 	}
 
@@ -2103,6 +2184,16 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size,
 			if (trace->show_arg_names)
 				printed += scnprintf(bf + printed, size - printed, "%s: ", field->name);
 
+			if (sc->arg_fmt[arg.idx].is_enum && trace->btf) {
+				size_t p = btf_enum_scnprintf(bf + printed, size - printed, val,
+							      trace->btf, field->type,
+							      &sc->arg_fmt[arg.idx]);
+				if (p) {
+					printed += p;
+					continue;
+				}
+			}
+
 			printed += syscall_arg_fmt__scnprintf_val(&sc->arg_fmt[arg.idx],
 								  bf + printed, size - printed, &arg, val);
 		}
@@ -2791,7 +2882,7 @@ 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 ? ", " : "");
@@ -2799,6 +2890,15 @@ 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);
 	}
 
@@ -4461,8 +4561,9 @@ 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 trace *trace)
 {
+	struct evlist *evlist = trace->evlist;
 	struct evsel *evsel;
 
 	evlist__for_each_entry(evlist, evsel) {
@@ -4470,7 +4571,7 @@ 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(trace, evsel);
 			continue;
 		}
 
@@ -4949,7 +5050,7 @@ int cmd_trace(int argc, const char **argv)
 
 	if (trace.evlist->core.nr_entries > 0) {
 		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)) {
 			perror("failed to set syscalls:* tracepoint fields");
 			goto out;
 		}
-- 
2.45.2

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