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

[Arnaldo Carvalho de Melo]

Em Fri, Nov 20, 2015 at 03:03:03PM +0900, Namhyung Kim escreveu:
> 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 for testing):

This is a really nice use of what we have, I guess we could simplify
things further, not having to create a struct machine, as we have just
one thread, and we're not interested in kernel addresses, so no need for
kmaps, etc.

But as-is it already looks better than what we were using :-)

I'll try testing it further and will probably switch to using it if
nobody voices any problem we haven't realised with such approach.

- Arnaldo
 
> 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
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