RE: [RFC/PATCH] perf tools: Introduce perf_thread for backtrace

[åæéå / HIRAMATUïMASAMI]

>From: Namhyung Kim [mailto:namhyung@xxxxxxxxxx]
>
>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.

Hmm, I doubt that this can work for debugging situation, because
sometimes backtrace facilities has to debug itself by itself.

For the some (static) functions, I'd rather like to use glibc's 
backtrace_symbols and addr2line or even with raw address for
reliability...

Thank you,

>
>The backtrace output from TUI is changed like below.  (I made a key
>action to generate a segfault for testing):
>
>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]
>  [0x0]
>
>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]
>  [0x0]
>
>Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
>Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
>Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
>---
> tools/perf/perf.c         |  7 +++++-
> tools/perf/ui/tui/setup.c | 21 ++++++++++++++--
> tools/perf/util/util.c    | 62 +++++++++++++++++++++++++++++++++++++++++++++++
> tools/perf/util/util.h    |  5 ++++
> 4 files changed, 92 insertions(+), 3 deletions(-)
>
>diff --git a/tools/perf/perf.c b/tools/perf/perf.c
>index 4bee53c3f796..f77eb440b05c 100644
>--- a/tools/perf/perf.c
>+++ b/tools/perf/perf.c
>@@ -604,6 +604,8 @@ int main(int argc, const char **argv)
> 	 */
> 	pthread__block_sigwinch();
>
>+	create_perf_thread();
>+
> 	while (1) {
> 		static int done_help;
> 		int was_alias = run_argv(&argc, &argv);
>@@ -615,7 +617,7 @@ 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 +628,9 @@ 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..bc2da884e65a 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 +98,29 @@ 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,
>+		};
>+
>+		thread__find_addr_location(perf_thread, PERF_RECORD_MISC_USER,
>+					   MAP__FUNCTION, (long)stackdump[i], &al);
>+
>+		if (al.sym)
>+			printf("%s(+0x%"PRIx64") in ", al.sym->name,
>+			       map__map_ip(al.map, (u64)stackdump[i]) - al.sym->start);
>+		if (al.map)
>+			printf("%s ", al.map->dso->short_name);
>+		printf("[0x%lx]\n", (unsigned long)stackdump[i]);
>+	}
>
> 	exit(0);
> }
>diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
>index 75759aebc7b8..f1a26ea14053 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 +699,62 @@ 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;
>+
>+void 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;
>+
>+	tm = thread_map__new_dummy();
>+	if (tm == NULL) {
>+		machine__delete(machine);
>+		return;
>+	}
>+
>+	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);
>+}
>+
>+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..630e145049aa 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;
>+
>+void create_perf_thread(void);
>+void destroy_perf_thread(void);
>+
> #endif /* GIT_COMPAT_UTIL_H */
>--
>2.6.2