Commit f208bd8d authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf trace: Handle legacy syscalls tracepoints 



Currently the code skips the first field with the expectation that it is 'nr'.
But older kernels do not have the 'nr' field:

    field:int nr;   offset:8;   size:4; signed:1;

Change perf-trace to drop the field if it exists after parsing the format file.

This fixes the off-by-one problem with older kernels (e.g., RHEL6). e.g,
perf-trace shows this for write:

  1.515 ( 0.006 ms): dd/4245 write(buf: 2</dev/pts/0>, count: 140733837536224       ) = 26

where 2 is really the fd, the huge number is really the buf address, etc.  With
this patch you get the more appropriate:

  1.813 ( 0.003 ms): dd/6330 write(fd: 2</dev/pts/0>, buf: 0x7fff22fc81f0, count: 25) = 25

Based-on-a-patch-by: default avatarDavid Ahern <dsahern@gmail.com>
Acked-by: default avatarDavid Ahern <dsahern@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-gvpdave4u2yq2jnzbcdznpvf@git.kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent e6c76d62

tools/perf/builtin-trace.c

+14 −4
Original line number Diff line number Diff line
@@ -1135,6 +1135,8 @@ static struct syscall_fmt *syscall_fmt__find(const char *name) 


struct syscall {

	struct event_format *tp_format;

	int		    nr_args;

	struct format_field *args;

	const char	    *name;

	bool		    filtered;

	bool		    is_exit;
@@ -1442,14 +1444,14 @@ static int syscall__set_arg_fmts(struct syscall *sc) 
	struct format_field *field;

	int idx = 0;



	sc->arg_scnprintf = calloc(sc->tp_format->format.nr_fields - 1, sizeof(void *));

	sc->arg_scnprintf = calloc(sc->nr_args, sizeof(void *));

	if (sc->arg_scnprintf == NULL)

		return -1;



	if (sc->fmt)

		sc->arg_parm = sc->fmt->arg_parm;



	for (field = sc->tp_format->format.fields->next; field; field = field->next) {

	for (field = sc->args; field; field = field->next) {

		if (sc->fmt && sc->fmt->arg_scnprintf[idx])

			sc->arg_scnprintf[idx] = sc->fmt->arg_scnprintf[idx];

		else if (field->flags & FIELD_IS_POINTER)
@@ -1515,6 +1517,14 @@ static int trace__read_syscall_info(struct trace *trace, int id) 
	if (sc->tp_format == NULL)

		return -1;



	sc->args = sc->tp_format->format.fields;

	sc->nr_args = sc->tp_format->format.nr_fields;

	/* drop nr field - not relevant here; does not exist on older kernels */

	if (sc->args && strcmp(sc->args->name, "nr") == 0) {

		sc->args = sc->args->next;

		--sc->nr_args;

	}



	sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit");



	return syscall__set_arg_fmts(sc);
@@ -1537,7 +1547,7 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size, 
	unsigned char *p;

	unsigned long val;



	if (sc->tp_format != NULL) {

	if (sc->args != NULL) {

		struct format_field *field;

		u8 bit = 1;

		struct syscall_arg arg = {
@@ -1547,7 +1557,7 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size, 
			.thread = thread,

		};



		for (field = sc->tp_format->format.fields->next; field;

		for (field = sc->args; field;

		     field = field->next, ++arg.idx, bit <<= 1) {

			if (arg.mask & bit)

				continue;

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