[PATCH 33/57] perf trace: Initialize evsel_trace->fmt for syscalls:sys_enter_* tracepoints

Arnaldo Carvalho de Melo
2019-10-21T13:40:33Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

From the syscall_fmts->arg entries for formatting strace-like syscalls.

This is when resolving the string "whence" on a filter expression for
the syscalls:sys_enter_lseek:

Breakpoint 3, perf_evsel__syscall_arg_fmt (evsel=0xc91ed0, arg=0x7fffffff7cd0 "whence") at builtin-trace.c:3626
3626 {
(gdb) n
3628 struct syscall_arg_fmt *fmt = __evsel__syscall_arg_fmt(evsel);
(gdb) n
3630 if (evsel->tp_format == NULL || fmt == NULL)
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) p field->name
$3 = 0xc945e0 "__syscall_nr"
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) p *fmt
$4 = {scnprintf = 0x0, strtoul = 0x0, mask_val = 0x0, parm = 0x0, name = 0x0, nr_entries = 0, show_zero = false}
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) p field->name
$5 = 0xc94690 "fd"
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) p *fmt
$9 = {scnprintf = 0x489be2 <syscall_arg__scnprintf_strarray>, strtoul = 0x0, mask_val = 0x0, parm = 0xa2da80 <strarray.whences>, name = 0x0,
nr_entries = 0, show_zero = false}
(gdb) p field->name
$10 = 0xc947b0 "whence"
(gdb) p fmt->parm
$11 = (void *) 0xa2da80 <strarray.whences>
(gdb) p *(struct strarray *)fmt->parm
$12 = {offset = 0, nr_entries = 5, prefix = 0x724d37 "SEEK_", entries = 0xa2da40 <whences>}
(gdb) p (struct strarray *)fmt->parm)->entries
Junk after end of expression.
(gdb) p ((struct strarray *)fmt->parm)->entries
$13 = (const char **) 0xa2da40 <whences>
(gdb) p ((struct strarray *)fmt->parm)->entries[0]
$14 = 0x724d21 "SET"
(gdb) p ((struct strarray *)fmt->parm)->entries[1]
$15 = 0x724d25 "CUR"
(gdb) p ((struct strarray *)fmt->parm)->entries[2]
$16 = 0x724d29 "END"
(gdb) p ((struct strarray *)fmt->parm)->entries[2]
$17 = 0x724d29 "END"
(gdb) p ((struct strarray *)fmt->parm)->entries[3]
$18 = 0x724d2d "DATA"
(gdb) p ((struct strarray *)fmt->parm)->entries[4]
$19 = 0x724d32 "HOLE"
(gdb)

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-lc8h9jgvbnboe0g7ic8tra1y@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-trace.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 5792278065f6..3502417dc7f2 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -4366,6 +4366,25 @@ static void evlist__set_default_evsel_handler(struct evlist *evlist, void *handl
}
}

+static void evsel__set_syscall_arg_fmt(struct evsel *evsel, const char *name)
+{
+ struct syscall_arg_fmt *fmt = evsel__syscall_arg_fmt(evsel);
+
+ if (fmt) {
+ struct syscall_fmt *scfmt = syscall_fmt__find(name);
+
+ if (scfmt) {
+ int skip = 0;
+
+ if (strcmp(evsel->tp_format->format.fields->name, "__syscall_nr") == 0 ||
+ strcmp(evsel->tp_format->format.fields->name, "nr") == 0)
+ ++skip;
+
+ memcpy(fmt + skip, scfmt->arg, (evsel->tp_format->format.nr_fields - skip) * sizeof(*fmt));
+ }
+ }
+}
+
static int evlist__set_syscall_tp_fields(struct evlist *evlist)
{
struct evsel *evsel;
@@ -4387,11 +4406,15 @@ static int evlist__set_syscall_tp_fields(struct evlist *evlist)

if (__tp_field__init_ptr(&sc->args, sc->id.offset + sizeof(u64)))
return -1;
+
+ evsel__set_syscall_arg_fmt(evsel, evsel->tp_format->name + sizeof("sys_enter_") - 1);
} else if (!strncmp(evsel->tp_format->name, "sys_exit_", 9)) {
struct syscall_tp *sc = __evsel__syscall_tp(evsel);

if (__tp_field__init_uint(&sc->ret, sizeof(u64), sc->id.offset + sizeof(u64), evsel->needs_swap))
return -1;
+
+ evsel__set_syscall_arg_fmt(evsel, evsel->tp_format->name + sizeof("sys_exit_") - 1);
}
}

--
2.21.0