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: David Ahern <dsahern@gmail.com>
Acked-by: David 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: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 6af6bce..001c6ae 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1135,6 +1135,8 @@
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 @@
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 @@
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 @@
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 @@
.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;