perf bpf: Support BPF program attach to tracepoints

To support 98b5c2c65c29 ("perf, bpf: allow bpf programs attach to
tracepoints"), this patch allows BPF scripts to select tracepoints in
their section name.

Example:

# cat test_tracepoint.c
/*********************************************/
#include <uapi/linux/bpf.h>
#define SEC(NAME) __attribute__((section(NAME), used))
SEC("raw_syscalls:sys_enter")
int func(void *ctx)
{
/*
* /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/format:
* ...
* field:long id; offset:8; size:8; signed:1;
* ...
* ctx + 8 select 'id'
*/
u64 id = *((u64 *)(ctx + 8));
if (id == 1)
return 1;
return 0;
}
SEC("_write=sys_write")
int _write(void *ctx)
{
return 1;
}
char _license[] SEC("license") = "GPL";
int _version SEC("version") = LINUX_VERSION_CODE;
/*********************************************/
# perf record -e ./test_tracepoint.c dd if=/dev/zero of=/dev/null count=5
5+0 records in
5+0 records out
2560 bytes (2.6 kB) copied, 6.2281e-05 s, 41.1 MB/s
[ perf record: Woken up 1 times to write data ]
# perf script
dd 13436 [005] 1596.490869: raw_syscalls:sys_enter: NR 1 (1, 178d000, 200, 7ffe82470d60, ffffffffffffe020, fffff
dd 13436 [005] 1596.490871: perf_bpf_probe:_write: (ffffffff812351e0)
dd 13436 [005] 1596.490873: raw_syscalls:sys_enter: NR 1 (1, 178d000, 200, ffffffffffffe000, ffffffffffffe020, f
dd 13436 [005] 1596.490874: perf_bpf_probe:_write: (ffffffff812351e0)
dd 13436 [005] 1596.490876: raw_syscalls:sys_enter: NR 1 (1, 178d000, 200, ffffffffffffe000, ffffffffffffe020, f
dd 13436 [005] 1596.490876: perf_bpf_probe:_write: (ffffffff812351e0)
dd 13436 [005] 1596.490878: raw_syscalls:sys_enter: NR 1 (1, 178d000, 200, ffffffffffffe000, ffffffffffffe020, f
dd 13436 [005] 1596.490879: perf_bpf_probe:_write: (ffffffff812351e0)
dd 13436 [005] 1596.490881: raw_syscalls:sys_enter: NR 1 (1, 178d000, 200, ffffffffffffe000, ffffffffffffe020, f
dd 13436 [005] 1596.490882: perf_bpf_probe:_write: (ffffffff812351e0)
dd 13436 [005] 1596.490900: raw_syscalls:sys_enter: NR 1 (2, 7ffe8246e640, 1f, 40acb8, 7f44bac74700, 7f44baa4fba
dd 13436 [005] 1596.490901: perf_bpf_probe:_write: (ffffffff812351e0)
dd 13436 [005] 1596.490917: raw_syscalls:sys_enter: NR 1 (2, 7ffe8246e640, 1a, fffffffa, 7f44bac74700, 7f44baa4f
dd 13436 [005] 1596.490918: perf_bpf_probe:_write: (ffffffff812351e0)
dd 13436 [005] 1596.490932: raw_syscalls:sys_enter: NR 1 (2, 7ffe8246e640, 1a, fffffff9, 7f44bac74700, 7f44baa4f
dd 13436 [005] 1596.490933: perf_bpf_probe:_write: (ffffffff812351e0)

Committer note:

Further testing:

# trace --no-sys --event /home/acme/bpf/tracepoint.c cat /etc/passwd > /dev/null
0.000 raw_syscalls:sys_enter:NR 1 (1, 7f0490504000, c48, 7f0490503010, ffffffffffffffff, 0))
0.006 perf_bpf_probe:_write:(ffffffff81241bc0))
#

Signed-off-by: Wang Nan <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Zefan Li <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/bpf-loader.c

···
 DEFINE_PRINT_FN(debug, 1)
 
 struct bpf_prog_priv {
+	bool is_tp;
+	char *sys_name;
+	char *evt_name;
 	struct perf_probe_event pev;
 	bool need_prologue;
 	struct bpf_insn *insns_buf;
···
 	cleanup_perf_probe_events(&priv->pev, 1);
 	zfree(&priv->insns_buf);
 	zfree(&priv->type_mapping);
+	zfree(&priv->sys_name);
+	zfree(&priv->evt_name);
 	free(priv);
 }
 
···
 }
 
 static int
-parse_prog_config(const char *config_str, struct perf_probe_event *pev)
+parse_prog_config(const char *config_str, const char **p_main_str,
+		  bool *is_tp, struct perf_probe_event *pev)
 {
 	int err;
 	const char *main_str = parse_prog_config_kvpair(config_str, pev);
···
 	if (IS_ERR(main_str))
 		return PTR_ERR(main_str);
 
+	*p_main_str = main_str;
+	if (!strchr(main_str, '=')) {
+		/* Is a tracepoint event? */
+		const char *s = strchr(main_str, ':');
+
+		if (!s) {
+			pr_debug("bpf: '%s' is not a valid tracepoint\n",
+				 config_str);
+			return -BPF_LOADER_ERRNO__CONFIG;
+		}
+
+		*is_tp = true;
+		return 0;
+	}
+
+	*is_tp = false;
 	err = parse_perf_probe_command(main_str, pev);
 	if (err < 0) {
 		pr_debug("bpf: '%s' is not a valid config string\n",
···
 {
 	struct perf_probe_event *pev = NULL;
 	struct bpf_prog_priv *priv = NULL;
-	const char *config_str;
+	const char *config_str, *main_str;
+	bool is_tp = false;
 	int err;
 
 	/* Initialize per-program probing setting */
···
 	pev = &priv->pev;
 
 	pr_debug("bpf: config program '%s'\n", config_str);
-	err = parse_prog_config(config_str, pev);
+	err = parse_prog_config(config_str, &main_str, &is_tp, pev);
 	if (err)
 		goto errout;
+
+	if (is_tp) {
+		char *s = strchr(main_str, ':');
+
+		priv->is_tp = true;
+		priv->sys_name = strndup(main_str, s - main_str);
+		priv->evt_name = strdup(s + 1);
+		goto set_priv;
+	}
 
 	if (pev->group && strcmp(pev->group, PERF_BPF_PROBE_GROUP)) {
 		pr_debug("bpf: '%s': group for event is set and not '%s'.\n",
···
 	}
 	pr_debug("bpf: config '%s' is ok\n", config_str);
 
+set_priv:
 	err = bpf_program__set_priv(prog, priv, clear_prog_priv);
 	if (err) {
 		pr_debug("Failed to set priv for program '%s'\n", config_str);
···
 	size_t prologue_cnt = 0;
 	int i, err;
 
-	if (IS_ERR(priv) || !priv)
+	if (IS_ERR(priv) || !priv || priv->is_tp)
 		goto errout;
 
 	pev = &priv->pev;
···
 		return -BPF_LOADER_ERRNO__INTERNAL;
 	}
 
+	if (priv->is_tp) {
+		priv->need_prologue = false;
+		return 0;
+	}
+
 	pev = &priv->pev;
 	for (i = 0; i < pev->ntevs; i++) {
 		struct probe_trace_event *tev = &pev->tevs[i];
···
 			err = PTR_ERR(priv);
 			goto out;
 		}
+
+		if (priv->is_tp) {
+			bpf_program__set_tracepoint(prog);
+			continue;
+		}
+
+		bpf_program__set_kprobe(prog);
 		pev = &priv->pev;
 
 		err = convert_perf_probe_events(pev, 1);
···
 		struct bpf_prog_priv *priv = bpf_program__priv(prog);
 		int i;
 
-		if (IS_ERR(priv) || !priv)
+		if (IS_ERR(priv) || !priv || priv->is_tp)
 			continue;
 
 		for (i = 0; i < priv->pev.ntevs; i++) {
···
 		if (IS_ERR(priv) || !priv) {
 			pr_debug("bpf: failed to get private field\n");
 			return -BPF_LOADER_ERRNO__INTERNAL;
+		}
+
+		if (priv->is_tp) {
+			fd = bpf_program__fd(prog);
+			err = (*func)(priv->sys_name, priv->evt_name, fd, arg);
+			if (err) {
+				pr_debug("bpf: tracepoint call back failed, stop iterate\n");
+				return err;
+			}
+			continue;
 		}
 
 		pev = &priv->pev;