perf script perl: Perl scripts now get a backtrace, like the python ones

We have some infrastructure to use perl or python to analyze logs
generated by perf.  Prior to this patch, only the python tools had
access to backtrace information.  This patch makes this information
available to perl scripts as well.  Example:

  Let's look at malloc() calls made by the seq utility.  First we
  create a probe point:

      $ perf probe -x /lib/x86_64-linux-gnu/libc.so.6 malloc
      Added new events:
      ...

  Now we run seq, while monitoring malloc() calls with perf

      $ perf record --call-graph=dwarf -e probe_libc:malloc seq 5
      1
      2
      3
      4
      5
      [ perf record: Woken up 1 times to write data ]
      [ perf record: Captured and wrote 0.064 MB perf.data (6 samples) ]

  We can use perf to look at its log to see the malloc calls and the backtrace

      $ perf script
      seq 14195 [000] 1927993.748254: probe_libc:malloc: (7f9ff8edd320) bytes=0x22
                  7f9ff8edd320 malloc (/lib/x86_64-linux-gnu/libc-2.22.so)
                  7f9ff8e8eab0 set_binding_values.part.0 (/lib/x86_64-linux-gnu/libc-2.22.so)
                  7f9ff8e8eda1 __bindtextdomain (/lib/x86_64-linux-gnu/libc-2.22.so)
                        401b22 main (/usr/bin/seq)
                  7f9ff8e82610 __libc_start_main (/lib/x86_64-linux-gnu/libc-2.22.so)
                        402799 _start (/usr/bin/seq)
      ...

  We can also use the scripting facilities.  We create a skeleton perl
  script that simply prints out the events

      $ perf script -g perl
      generated Perl script: perf-script.pl

  We can then use this script to see the malloc() calls with a
  backtrace.  Prior to this patch, the backtrace was not available to
  the perl scripts.

      $ perf script -s perf-script.pl
      probe_libc::malloc  0 1927993.748254260  14195 seq   __probe_ip=140325052863264, bytes=34
              [7f9ff8edd320] malloc
              [7f9ff8e8eab0] set_binding_values.part.0
              [7f9ff8e8eda1] __bindtextdomain
              [401b22] main
              [7f9ff8e82610] __libc_start_main
              [402799] _start
      ...

Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/r/87mvphzld0.fsf@secretsauce.net
Signed-off-by: Dima Kogan <dima@secretsauce.net>

tools/perf/util/scripting-engines/trace-event-perl.c

@@ -31,6 +31,8 @@
 #include <perl.h>
 
 #include "../../perf.h"
+#include "../callchain.h"
+#include "../machine.h"
 #include "../thread.h"
 #include "../event.h"
 #include "../trace-event.h"
@@ -248,10 +250,78 @@ static void define_event_symbols(struct event_format *event,
 		define_event_symbols(event, ev_name, args->next);
 }
 
+static SV *perl_process_callchain(struct perf_sample *sample,
+				  struct perf_evsel *evsel,
+				  struct addr_location *al)
+{
+	AV *list;
+
+	list = newAV();
+	if (!list)
+		goto exit;
+
+	if (!symbol_conf.use_callchain || !sample->callchain)
+		goto exit;
+
+	if (thread__resolve_callchain(al->thread, evsel,
+				      sample, NULL, NULL,
+				      PERF_MAX_STACK_DEPTH) != 0) {
+		pr_err("Failed to resolve callchain. Skipping\n");
+		goto exit;
+	}
+	callchain_cursor_commit(&callchain_cursor);
+
+
+	while (1) {
+		HV *elem;
+		struct callchain_cursor_node *node;
+		node = callchain_cursor_current(&callchain_cursor);
+		if (!node)
+			break;
+
+		elem = newHV();
+		if (!elem)
+			goto exit;
+
+		hv_stores(elem, "ip", newSVuv(node->ip));
+
+		if (node->sym) {
+			HV *sym = newHV();
+			if (!sym)
+				goto exit;
+			hv_stores(sym, "start",   newSVuv(node->sym->start));
+			hv_stores(sym, "end",     newSVuv(node->sym->end));
+			hv_stores(sym, "binding", newSVuv(node->sym->binding));
+			hv_stores(sym, "name",    newSVpvn(node->sym->name,
+							   node->sym->namelen));
+			hv_stores(elem, "sym",    newRV_noinc((SV*)sym));
+		}
+
+		if (node->map) {
+			struct map *map = node->map;
+			const char *dsoname = "[unknown]";
+			if (map && map->dso && (map->dso->name || map->dso->long_name)) {
+				if (symbol_conf.show_kernel_path && map->dso->long_name)
+					dsoname = map->dso->long_name;
+				else if (map->dso->name)
+					dsoname = map->dso->name;
+			}
+			hv_stores(elem, "dso", newSVpv(dsoname,0));
+		}
+
+		callchain_cursor_advance(&callchain_cursor);
+		av_push(list, newRV_noinc((SV*)elem));
+	}
+
+exit:
+	return newRV_noinc((SV*)list);
+}
+
 static void perl_process_tracepoint(struct perf_sample *sample,
 				    struct perf_evsel *evsel,
-				    struct thread *thread)
+				    struct addr_location *al)
 {
+	struct thread *thread = al->thread;
 	struct event_format *event = evsel->tp_format;
 	struct format_field *field;
 	static char handler[256];
@@ -295,6 +365,7 @@ static void perl_process_tracepoint(struct perf_sample *sample,
 	XPUSHs(sv_2mortal(newSVuv(ns)));
 	XPUSHs(sv_2mortal(newSViv(pid)));
 	XPUSHs(sv_2mortal(newSVpv(comm, 0)));
+	XPUSHs(sv_2mortal(perl_process_callchain(sample, evsel, al)));
 
 	/* common fields other than pid can be accessed via xsub fns */
 
@@ -329,6 +400,7 @@ static void perl_process_tracepoint(struct perf_sample *sample,
 		XPUSHs(sv_2mortal(newSVuv(nsecs)));
 		XPUSHs(sv_2mortal(newSViv(pid)));
 		XPUSHs(sv_2mortal(newSVpv(comm, 0)));
+		XPUSHs(sv_2mortal(perl_process_callchain(sample, evsel, al)));
 		call_pv("main::trace_unhandled", G_SCALAR);
 	}
 	SPAGAIN;
@@ -366,7 +438,7 @@ static void perl_process_event(union perf_event *event,
 			       struct perf_evsel *evsel,
 			       struct addr_location *al)
 {
-	perl_process_tracepoint(sample, evsel, al->thread);
+	perl_process_tracepoint(sample, evsel, al);
 	perl_process_event_generic(event, sample, evsel);
 }
 
@@ -490,7 +562,27 @@ static int perl_generate_script(struct pevent *pevent, const char *outfile)
 	fprintf(ofp, "use Perf::Trace::Util;\n\n");
 
 	fprintf(ofp, "sub trace_begin\n{\n\t# optional\n}\n\n");
-	fprintf(ofp, "sub trace_end\n{\n\t# optional\n}\n\n");
+	fprintf(ofp, "sub trace_end\n{\n\t# optional\n}\n");
+
+
+	fprintf(ofp, "\n\
+sub print_backtrace\n\
+{\n\
+	my $callchain = shift;\n\
+	for my $node (@$callchain)\n\
+	{\n\
+		if(exists $node->{sym})\n\
+		{\n\
+			printf( \"\\t[\\%%x] \\%%s\\n\", $node->{ip}, $node->{sym}{name});\n\
+		}\n\
+		else\n\
+		{\n\
+			printf( \"\\t[\\%%x]\\n\", $node{ip});\n\
+		}\n\
+	}\n\
+}\n\n\
+");
+
 
 	while ((event = trace_find_next_event(pevent, event))) {
 		fprintf(ofp, "sub %s::%s\n{\n", event->system, event->name);
@@ -502,7 +594,8 @@ static int perl_generate_script(struct pevent *pevent, const char *outfile)
 		fprintf(ofp, "$common_secs, ");
 		fprintf(ofp, "$common_nsecs,\n");
 		fprintf(ofp, "\t    $common_pid, ");
-		fprintf(ofp, "$common_comm,\n\t    ");
+		fprintf(ofp, "$common_comm, ");
+		fprintf(ofp, "$common_callchain,\n\t    ");
 
 		not_first = 0;
 		count = 0;
@@ -519,7 +612,7 @@ static int perl_generate_script(struct pevent *pevent, const char *outfile)
 
 		fprintf(ofp, "\tprint_header($event_name, $common_cpu, "
 			"$common_secs, $common_nsecs,\n\t             "
-			"$common_pid, $common_comm);\n\n");
+			"$common_pid, $common_comm, $common_callchain);\n\n");
 
 		fprintf(ofp, "\tprintf(\"");
 
@@ -581,17 +674,22 @@ static int perl_generate_script(struct pevent *pevent, const char *outfile)
 				fprintf(ofp, "$%s", f->name);
 		}
 
-		fprintf(ofp, ");\n");
+		fprintf(ofp, ");\n\n");
+
+		fprintf(ofp, "\tprint_backtrace($common_callchain);\n");
+
 		fprintf(ofp, "}\n\n");
 	}
 
 	fprintf(ofp, "sub trace_unhandled\n{\n\tmy ($event_name, $context, "
 		"$common_cpu, $common_secs, $common_nsecs,\n\t    "
-		"$common_pid, $common_comm) = @_;\n\n");
+		"$common_pid, $common_comm, $common_callchain) = @_;\n\n");
 
 	fprintf(ofp, "\tprint_header($event_name, $common_cpu, "
 		"$common_secs, $common_nsecs,\n\t             $common_pid, "
-		"$common_comm);\n}\n\n");
+		"$common_comm, $common_callchain);\n");
+	fprintf(ofp, "\tprint_backtrace($common_callchain);\n");
+	fprintf(ofp, "}\n\n");
 
 	fprintf(ofp, "sub print_header\n{\n"
 		"\tmy ($event_name, $cpu, $secs, $nsecs, $pid, $comm) = @_;\n\n"