[PATCH 09/86] perf trace beauty: Allow accessing syscall args values in a syscall arg formatter

Arnaldo Carvalho de Melo
2017-07-19T14:31:03Z

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

For instance, fcntl's upcoming 'arg' formatter needs to look at the
'cmd' value to decide how to format its value, sometimes it is a file
flags, sometimes an fd, a pointer to a structure, etc.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-2tw2jfaqm48dtw8a4addghze@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-trace.c | 23 ++++++++++++++++-------
tools/perf/trace/beauty/beauty.h | 13 +++++++++++++
2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index b7f79dea3c44..40bc0a326096 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1369,19 +1369,32 @@ static int trace__validate_ev_qualifier(struct trace *trace)
* variable to read it. Most notably this avoids extended load instructions
* on unaligned addresses
*/
+static unsigned long __syscall_arg__val(unsigned char *args, u8 idx)
+{
+ unsigned long val;
+ unsigned char *p = args + sizeof(unsigned long) * idx;
+
+ memcpy(&val, p, sizeof(val));
+ return val;
+}
+
+unsigned long syscall_arg__val(struct syscall_arg *arg, u8 idx)
+{
+ return __syscall_arg__val(arg->args, idx);
+}

static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size,
unsigned char *args, struct trace *trace,
struct thread *thread)
{
size_t printed = 0;
- unsigned char *p;
unsigned long val;

if (sc->args != NULL) {
struct format_field *field;
u8 bit = 1;
struct syscall_arg arg = {
+ .args = args,
.idx = 0,
.mask = 0,
.trace = trace,
@@ -1393,9 +1406,7 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size,
if (arg.mask & bit)
continue;

- /* special care for unaligned accesses */
- p = args + sizeof(unsigned long) * arg.idx;
- memcpy(&val, p, sizeof(val));
+ val = syscall_arg__val(&arg, arg.idx);

/*
* Suppress this argument if its value is zero and
@@ -1431,9 +1442,7 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size,
int i = 0;

while (i < 6) {
- /* special care for unaligned accesses */
- p = args + sizeof(unsigned long) * i;
- memcpy(&val, p, sizeof(val));
+ val = __syscall_arg__val(args, i);
printed += scnprintf(bf + printed, size - printed,
"%sarg%d: %ld",
printed ? ", " : "", i, val);
diff --git a/tools/perf/trace/beauty/beauty.h b/tools/perf/trace/beauty/beauty.h
index ce01079d8422..6fbac0c8120d 100644
--- a/tools/perf/trace/beauty/beauty.h
+++ b/tools/perf/trace/beauty/beauty.h
@@ -6,8 +6,19 @@
struct trace;
struct thread;

+/**
+ * @val: value of syscall argument being formatted
+ * @args: All the args, use syscall_args__val(arg, nth) to access one
+ * @thread: tid state (maps, pid, tid, etc)
+ * @trace: 'perf trace' internals: all threads, etc
+ * @parm: private area, may be an strarray, for instance
+ * @idx: syscall arg idx (is this the first?)
+ * @mask: a syscall arg may mask another arg, see syscall_arg__scnprintf_futex_op
+ */
+
struct syscall_arg {
unsigned long val;
+ unsigned char *args;
struct thread *thread;
struct trace *trace;
void *parm;
@@ -15,6 +26,8 @@ struct syscall_arg {
u8 mask;
};

+unsigned long syscall_arg__val(struct syscall_arg *arg, u8 idx);
+
size_t syscall_arg__scnprintf_strarrays(char *bf, size_t size, struct syscall_arg *arg);
#define SCA_STRARRAYS syscall_arg__scnprintf_strarrays

--
2.9.4