[PATCH v3] perf tools: Introduce perf_thread for backtrace

[Namhyung Kim]

Backtrace is a crucial info for debugging.  And upcoming refcnt
tracking facility also wants to use it.

So instead of relying on glibc's backtrace_symbols[_fd] which misses
some (static) functions , use our own symbol searching mechanism.  To
do that, add perf_thread global variable to keep its maps and symbols.

The backtrace output from TUI is changed like below.  (I made a key
action to generate a segfault):

Before:
  perf: Segmentation fault
  -------- backtrace --------
  perf[0x544a8b]
  /usr/lib/libc.so.6(+0x33680)[0x7fc46420b680]
  perf[0x54041b]
  perf(perf_evlist__tui_browse_hists+0x91)[0x5432e1]
  perf(cmd_report+0x1d20)[0x43cb10]
  perf[0x487073]
  perf(main+0x62f)[0x42cb1f]
  /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7fc4641f8610]
  perf(_start+0x29)[0x42cc39]

After:
  perf: Segmentation fault
  -------- backtrace --------
  perf_evsel__hists_browse(+0x43b) in perf [0x54066b]
  perf_evlist__tui_browse_hists(+0x91) in perf [0x543531]
  cmd_report(+0x1d20) in perf [0x43cb50]
  run_builtin(+0x53) in perf [0x4870b3]
  main(+0x634) in perf [0x42cb54]
  __libc_start_main(+0xf0) in libc-2.22.so [0x7fea3577c610]
  _start(+0x29) in perf [0x42cc79]

Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
v3) check return value of create_perf_thread()

v2) fallback to glibc's backtrace_symbols_fd() if failed

 tools/perf/perf.c         | 10 +++++++-
 tools/perf/ui/tui/setup.c | 31 +++++++++++++++++++++--
 tools/perf/util/util.c    | 63 +++++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/util.h    |  5 ++++
 4 files changed, 106 insertions(+), 3 deletions(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 4bee53c3f796..f27dc5fa9534 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -604,6 +604,11 @@ int main(int argc, const char **argv)
 	 */
 	pthread__block_sigwinch();
 
+	if (create_perf_thread() < 0) {
+		fprintf(stderr, "Failed to reserve information for backtrace\n");
+		goto out;
+	}
+
 	while (1) {
 		static int done_help;
 		int was_alias = run_argv(&argc, &argv);
@@ -615,7 +620,7 @@ int main(int argc, const char **argv)
 			fprintf(stderr, "Expansion of alias '%s' failed; "
 				"'%s' is not a perf-command\n",
 				cmd, argv[0]);
-			goto out;
+			goto out_destroy;
 		}
 		if (!done_help) {
 			cmd = argv[0] = help_unknown_cmd(cmd);
@@ -626,6 +631,9 @@ int main(int argc, const char **argv)
 
 	fprintf(stderr, "Failed to run command '%s': %s\n",
 		cmd, strerror_r(errno, sbuf, sizeof(sbuf)));
+
+out_destroy:
+	destroy_perf_thread();
 out:
 	return 1;
 }
diff --git a/tools/perf/ui/tui/setup.c b/tools/perf/ui/tui/setup.c
index 7dfeba0a91f3..ba0ff1c4e6b7 100644
--- a/tools/perf/ui/tui/setup.c
+++ b/tools/perf/ui/tui/setup.c
@@ -13,6 +13,8 @@
 #include "../libslang.h"
 #include "../keysyms.h"
 #include "tui.h"
+#include "../../util/symbol.h"
+#include "../../util/thread.h"
 
 static volatile int ui__need_resize;
 
@@ -96,14 +98,39 @@ int ui__getch(int delay_secs)
 static void ui__signal_backtrace(int sig)
 {
 	void *stackdump[32];
-	size_t size;
+	size_t size, i;
 
 	ui__exit(false);
 	psignal(sig, "perf");
 
 	printf("-------- backtrace --------\n");
 	size = backtrace(stackdump, ARRAY_SIZE(stackdump));
-	backtrace_symbols_fd(stackdump, size, STDOUT_FILENO);
+	/* skip first two stack frame (for this function and signal stack) */
+	for (i = 2; i < size; i++) {
+		struct addr_location al = {
+			.sym = NULL,
+		};
+
+		/* valid callchain ends with 0 address */
+		if (stackdump[i] == NULL && i == (size - 1))
+			continue;
+
+		thread__find_addr_location(perf_thread, PERF_RECORD_MISC_USER,
+					   MAP__FUNCTION, (long)stackdump[i], &al);
+
+		if (!al.sym)
+			break;
+
+		printf("%s(+0x%"PRIx64") in %s [0x%lx]\n", al.sym->name,
+		       map__map_ip(al.map, (u64)stackdump[i]) - al.sym->start,
+		       al.map->dso->short_name, (unsigned long)stackdump[i]);
+	}
+
+	if (i != size) {
+		printf("\nperf backtrace seems broken, try again with glibc\n");
+		printf("-------- backtrace --------\n");
+		backtrace_symbols_fd(stackdump, size, STDOUT_FILENO);
+	}
 
 	exit(0);
 }
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 75759aebc7b8..b1e591b13131 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -16,6 +16,9 @@
 #include <linux/kernel.h>
 #include <unistd.h>
 #include "callchain.h"
+#include "machine.h"
+#include "thread.h"
+#include "thread_map.h"
 
 struct callchain_param	callchain_param = {
 	.mode	= CHAIN_GRAPH_ABS,
@@ -696,3 +699,63 @@ fetch_kernel_version(unsigned int *puint, char *str,
 		*puint = (version << 16) + (patchlevel << 8) + sublevel;
 	return 0;
 }
+
+
+static int process_event(struct perf_tool *tool, union perf_event *event,
+			 struct perf_sample *sample, struct machine *machine)
+{
+	switch (event->header.type) {
+	case PERF_RECORD_COMM:
+		return tool->comm(tool, event, sample, machine);
+	case PERF_RECORD_MMAP:
+		return tool->mmap(tool, event, sample, machine);
+	case PERF_RECORD_MMAP2:
+		return tool->mmap2(tool, event, sample, machine);
+	default:
+		break;
+	}
+	return 0;
+}
+
+struct thread *perf_thread;
+
+int create_perf_thread(void)
+{
+	struct perf_tool tool = {
+		.comm	= perf_event__process_comm,
+		.mmap	= perf_event__process_mmap,
+		.mmap2	= perf_event__process_mmap2,
+	};
+	struct thread_map *tm;
+	struct machine *machine;
+	int pid = getpid();
+
+	machine = machine__new_host();
+	if (machine == NULL)
+		return -1;
+
+	tm = thread_map__new_dummy();
+	if (tm == NULL) {
+		machine__delete(machine);
+		return -1;
+	}
+
+	thread_map__set_pid(tm, 0, pid);
+
+	perf_event__synthesize_thread_map(&tool, tm, process_event, machine,
+					  false, 500);
+
+	perf_thread = machine__find_thread(machine, pid, pid);
+	BUG_ON(perf_thread == NULL);
+
+	thread_map__put(tm);
+	return 0;
+}
+
+void destroy_perf_thread(void)
+{
+	struct machine *machine = perf_thread->mg->machine;
+
+	machine__delete_threads(machine);
+	machine__delete(machine);
+}
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index dcc659017976..769986044a7a 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -358,4 +358,9 @@ int fetch_kernel_version(unsigned int *puint,
 #define KVER_FMT	"%d.%d.%d"
 #define KVER_PARAM(x)	KVER_VERSION(x), KVER_PATCHLEVEL(x), KVER_SUBLEVEL(x)
 
+extern struct thread *perf_thread;
+
+int create_perf_thread(void);
+void destroy_perf_thread(void);
+
 #endif /* GIT_COMPAT_UTIL_H */
-- 
2.6.2

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