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Subject[PATCH v2] tools/lib/traceevent, perf tools: Handle %pU format correctly
Date
[BUG]
For btrfs related events, there is a field for fsid, but perf never
parse it correctly.

# perf trace -e btrfs:qgroup_meta_convert xfs_io -f -c "pwrite 0 4k" \
/mnt/btrfs/file1
0.000 xfs_io/77915 btrfs:qgroup_meta_reserve:(nil)U: refroot=5(FS_TREE) type=0x0 diff=2
^^^^^^ Not a correct UUID
...

[CAUSE]
The pretty_print() function doesn't handle the %pU format correctly.
In fact it doesn't handle %pU as uuid at all.

[FIX]
Add a new function, print_uuid_arg(), to handle %pU correctly.

Now perf trace can at least print fsid correctly:
0.000 xfs_io/79619 btrfs:qgroup_meta_reserve:23ad1511-dd83-47d4-a79c-e96625a15a6e refroot=5(FS_TREE) type=0x0 diff=2

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
Changelog:
v2:
- Use more comment explaining the finetunings we skipped for %pU*
- Use more elegant way to output uuid string
---
tools/lib/traceevent/event-parse.c | 56 ++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index d948475585ce..3c9473f46efe 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -18,6 +18,7 @@
#include <errno.h>
#include <stdint.h>
#include <limits.h>
+#include <linux/uuid.h>
#include <linux/time64.h>

#include <netinet/in.h>
@@ -4508,6 +4509,45 @@ get_bprint_format(void *data, int size __maybe_unused,
return format;
}

+static void print_uuid_arg(struct trace_seq *s, void *data, int size,
+ struct tep_event *event, struct tep_print_arg *arg)
+{
+ unsigned char *buf;
+ int i;
+
+ if (arg->type != TEP_PRINT_FIELD) {
+ trace_seq_printf(s, "ARG TYPE NOT FIELID but %d", arg->type);
+ return;
+ }
+
+ if (!arg->field.field) {
+ arg->field.field = tep_find_any_field(event, arg->field.name);
+ if (!arg->field.field) {
+ do_warning("%s: field %s not found",
+ __func__, arg->field.name);
+ return;
+ }
+ }
+ if (arg->field.field->size < 16) {
+ trace_seq_printf(s, "INVALID UUID: size have %u expect 16",
+ arg->field.field->size);
+ return;
+ }
+ buf = data + arg->field.field->offset;
+ /* first segment, %02x *4 */
+ for (i = 0; i < 4; i++, buf++)
+ trace_seq_printf(s, "%02x", *buf);
+
+ /* 2nd, 3rd, 4th segment, each segment is "-%02x%02x" */
+ for (i = 0; i < 3; i++, buf += 2)
+ trace_seq_printf(s, "-%02x%02x", buf[i * 2], buf[i * 2 + 1]);
+
+ /* Final segment, '-' and '%02x' *6 */
+ trace_seq_putc(s, '-');
+ for (i = 0; i < 6; i++, buf++)
+ trace_seq_printf(s, "%02x", *buf);
+}
+
static void print_mac_arg(struct trace_seq *s, int mac, void *data, int size,
struct tep_event *event, struct tep_print_arg *arg)
{
@@ -5074,6 +5114,22 @@ static void pretty_print(struct trace_seq *s, void *data, int size, struct tep_e
arg = arg->next;
break;
}
+ } else if (*ptr == 'U') {
+ /*
+ * %pU has several finetunings variants
+ * like %pUb and %pUL.
+ * Here we ignore them, default to
+ * byte-order no endian, lower case
+ * letters.
+ */
+ if (isalpha(ptr[1]))
+ ptr += 2;
+ else
+ ptr++;
+
+ print_uuid_arg(s, data, size, event, arg);
+ arg = arg->next;
+ break;
}

/* fall through */
--
2.23.0
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