perf annotate browser: Add 'P' hotkey to dump annotation to file

Just like we have in the histograms browser used as the main screen for
'perf top --tui' and 'perf report --tui', to print the current
annotation to a file with a named composed by the symbol name and the
".annotation" suffix.

Here is one example of pressing 'A' on 'perf top' to live annotate a
kernel function and then press 'P' to dump that annotation, the
resulting file:

  # cat _raw_spin_lock_irqsave.annotation
  _raw_spin_lock_irqsave() /proc/kcore
  Event: cycles:ppp

    7.14        nop
   21.43        push   %rbx
    7.14        pushfq
                pop    %rax
                nop
                mov    %rax,%rbx
                cli
                nop
                xor    %eax,%eax
                mov    $0x1,%edx
   64.29        lock   cmpxchg %edx,(%rdi)
                test   %eax,%eax
              ↓ jne    2b
                mov    %rbx,%rax
                pop    %rbx
              ← retq
          2b:   mov    %eax,%esi
              → callq  queued_spin_lock_slowpath
                mov    %rbx,%rax
                pop    %rbx
              ← retq
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-zzmnrwugb5vtk7bvg0rbx150@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/ui/browsers/annotate.c

@@ -661,6 +661,7 @@ static int annotate_browser__run(struct annotate_browser *browser,
 		"t             Circulate percent, total period, samples view\n"
 		"/             Search string\n"
 		"k             Toggle line numbers\n"
+		"P             Print to [symbol_name].annotation file.\n"
 		"r             Run available scripts\n"
 		"?             Search string backwards\n");
 			continue;
@@ -737,6 +738,9 @@ static int annotate_browser__run(struct annotate_browser *browser,
 			}
 			continue;
 		}
+		case 'P':
+			map_symbol__annotation_dump(ms, evsel);
+			continue;
 		case 't':
 			if (notes->options->show_total_period) {
 				notes->options->show_total_period = false;

tools/perf/util/annotate.c

@@ -2037,6 +2037,37 @@ int symbol__annotate_fprintf2(struct symbol *sym, FILE *fp)
 	return 0;
 }
 
+int map_symbol__annotation_dump(struct map_symbol *ms, struct perf_evsel *evsel)
+{
+	const char *ev_name = perf_evsel__name(evsel);
+	char buf[1024];
+	char *filename;
+	int err = -1;
+	FILE *fp;
+
+	if (asprintf(&filename, "%s.annotation", ms->sym->name) < 0)
+		return -1;
+
+	fp = fopen(filename, "w");
+	if (fp == NULL)
+		goto out_free_filename;
+
+	if (perf_evsel__is_group_event(evsel)) {
+		perf_evsel__group_desc(evsel, buf, sizeof(buf));
+		ev_name = buf;
+	}
+
+	fprintf(fp, "%s() %s\nEvent: %s\n\n",
+		ms->sym->name, ms->map->dso->long_name, ev_name);
+	symbol__annotate_fprintf2(ms->sym, fp);
+
+	fclose(fp);
+	err = 0;
+out_free_filename:
+	free(filename);
+	return err;
+}
+
 void symbol__annotate_zero_histogram(struct symbol *sym, int evidx)
 {
 	struct annotation *notes = symbol__annotation(sym);

tools/perf/util/annotate.h

@@ -288,6 +288,8 @@ void symbol__annotate_zero_histogram(struct symbol *sym, int evidx);
 void symbol__annotate_decay_histogram(struct symbol *sym, int evidx);
 void annotated_source__purge(struct annotated_source *as);
 
+int map_symbol__annotation_dump(struct map_symbol *ms, struct perf_evsel *evsel);
+
 bool ui__has_annotation(void);
 
 int symbol__tty_annotate(struct symbol *sym, struct map *map,