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 <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1468406646-21642-6-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 60 insertions, 5 deletions

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index f22701497112..1f12e4e40006 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -37,6 +37,9 @@ DEFINE_PRINT_FN(info, 1)
 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;
@@ -118,6 +121,8 @@ clear_prog_priv(struct bpf_program *prog __maybe_unused,
         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);
 }
 
@@ -269,7 +274,8 @@ nextline:
 }
 
 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);
@@ -277,6 +283,22 @@ parse_prog_config(const char *config_str, struct perf_probe_event *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",
@@ -292,7 +314,8 @@ config_bpf_program(struct bpf_program *prog)
 {
         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 */
@@ -313,10 +336,19 @@ config_bpf_program(struct bpf_program *prog)
         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",
                          config_str, PERF_BPF_PROBE_GROUP);
@@ -339,6 +371,7 @@ config_bpf_program(struct bpf_program *prog)
         }
         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);
@@ -387,7 +420,7 @@ preproc_gen_prologue(struct bpf_program *prog, int n,
         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;
@@ -544,6 +577,11 @@ static int hook_load_preprocessor(struct bpf_program *prog)
                 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];
@@ -610,6 +648,13 @@ int bpf__probe(struct bpf_object *obj)
                         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);
@@ -650,7 +695,7 @@ int bpf__unprobe(struct bpf_object *obj)
                 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++) {
@@ -711,6 +756,16 @@ int bpf__foreach_event(struct bpf_object *obj,
                         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;
                 for (i = 0; i < pev->ntevs; i++) {
                         tev = &pev->tevs[i];