[PATCH v3 5/8] perf trace: Pretty print buffer data

Howard Chu
2024-08-24T16:33:30Z

Define TRACE_AUG_MAX_BUF in trace_augment.h data, which is the maximum
buffer size we can augment. BPF will include this header too.

Print buffer in a way that's different than just printing a string, we
print all the control characters in \digits (such as \0 for null, and
\10 for newline, LF).

For character that has a bigger value than 127, we print the digits
instead of the character itself as well.

Committer notes:

Simplified the buffer scnprintf to avoid using multiple buffers as
discussed in the patch review thread.

Signed-off-by: Howard Chu <howardchu95@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240815013626.935097-8-howardchu95@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-trace.c | 33 +++++++++++++++++++++++++++++++++
tools/perf/util/trace_augment.h | 6 ++++++
2 files changed, 39 insertions(+)
create mode 100644 tools/perf/util/trace_augment.h

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 048bcb92624c..470d74e3f875 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -65,6 +65,7 @@
#include "syscalltbl.h"
#include "rb_resort.h"
#include "../perf.h"
+#include "trace_augment.h"

#include <errno.h>
#include <inttypes.h>
@@ -852,6 +853,10 @@ static size_t syscall_arg__scnprintf_filename(char *bf, size_t size,

#define SCA_FILENAME syscall_arg__scnprintf_filename

+static size_t syscall_arg__scnprintf_buf(char *bf, size_t size, struct syscall_arg *arg);
+
+#define SCA_BUF syscall_arg__scnprintf_buf
+
static size_t syscall_arg__scnprintf_pipe_flags(char *bf, size_t size,
struct syscall_arg *arg)
{
@@ -1745,6 +1750,32 @@ static size_t syscall_arg__scnprintf_filename(char *bf, size_t size,
return 0;
}

+#define MAX_CONTROL_CHAR 31
+#define MAX_ASCII 127
+
+static size_t syscall_arg__scnprintf_buf(char *bf, size_t size, struct syscall_arg *arg)
+{
+ struct augmented_arg *augmented_arg = arg->augmented.args;
+ unsigned char *orig = (unsigned char *)augmented_arg->value;
+ size_t printed = 0;
+ int consumed;
+
+ if (augmented_arg == NULL)
+ return 0;
+
+ for (int j = 0; j < augmented_arg->size; ++j) {
+ bool control_char = orig[j] <= MAX_CONTROL_CHAR || orig[j] >= MAX_ASCII;
+ /* print control characters (0~31 and 127), and non-ascii characters in \(digits) */
+ printed += scnprintf(bf + printed, size - printed, control_char ? "\\%d" : "%c", (int)orig[j]);
+ }
+
+ consumed = sizeof(*augmented_arg) + augmented_arg->size;
+ arg->augmented.args = ((void *)arg->augmented.args) + consumed;
+ arg->augmented.size -= consumed;
+
+ return printed;
+}
+
static bool trace__filter_duration(struct trace *trace, double t)
{
return t < (trace->duration_filter * NSEC_PER_MSEC);
@@ -1956,6 +1987,8 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
((len >= 4 && strcmp(field->name + len - 4, "name") == 0) ||
strstr(field->name, "path") != NULL))
arg->scnprintf = SCA_FILENAME;
+ else if (strstr(field->type, "char *") && strstr(field->name, "buf"))
+ arg->scnprintf = SCA_BUF;
else if ((field->flags & TEP_FIELD_IS_POINTER) || strstr(field->name, "addr"))
arg->scnprintf = SCA_PTR;
else if (strcmp(field->type, "pid_t") == 0)
diff --git a/tools/perf/util/trace_augment.h b/tools/perf/util/trace_augment.h
new file mode 100644
index 000000000000..57a3e5045937
--- /dev/null
+++ b/tools/perf/util/trace_augment.h
@@ -0,0 +1,6 @@
+#ifndef TRACE_AUGMENT_H
+#define TRACE_AUGMENT_H
+
+#define TRACE_AUG_MAX_BUF 32 /* for buffer augmentation in perf trace */
+
+#endif
--
2.45.2