[PATCH v1 1/2] perf probe: Fixup Arm64 SDT arguments

[Leo Yan]

Arm64 ELF section '.note.stapsdt' uses string format "-4@[sp, NUM]" if
the probe is to access data in stack, e.g. below is an example for
dumping Arm64 ELF file and shows the argument format:

  Arguments: -4@[sp, 12] -4@[sp, 8] -4@[sp, 4]

Comparing against other archs' argument format, Arm64's argument
introduces an extra space character in the middle of square brackets,
due to argv_split() uses space as splitter, the argument is wrongly
divided into two items.

To support Arm64 SDT, this patch fixes up for this case, if any item
contains sub string "[sp", concatenates the two continuous items.  And
adds the detailed explaination in comment.

Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
---
 tools/perf/util/probe-file.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index 064b63a6a3f3..60878c859e60 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -794,6 +794,8 @@ static char *synthesize_sdt_probe_command(struct sdt_note *note,
 	char *ret = NULL, **args;
 	int i, args_count, err;
 	unsigned long long ref_ctr_offset;
+	char *arg;
+	int arg_idx = 0;
 
 	if (strbuf_init(&buf, 32) < 0)
 		return NULL;
@@ -815,8 +817,34 @@ static char *synthesize_sdt_probe_command(struct sdt_note *note,
 	if (note->args) {
 		args = argv_split(note->args, &args_count);
 
-		for (i = 0; i < args_count; ++i) {
-			if (synthesize_sdt_probe_arg(&buf, i, args[i]) < 0)
+		for (i = 0; i < args_count; ) {
+			/*
+			 * FIXUP: Arm64 ELF section '.note.stapsdt' uses string
+			 * format "-4@[sp, NUM]" if a probe is to access data in
+			 * the stack, e.g. below is an example for the SDT
+			 * Arguments:
+			 *
+			 *   Arguments: -4@[sp, 12] -4@[sp, 8] -4@[sp, 4]
+			 *
+			 * Since the string introduces an extra space character
+			 * in the middle of square brackets, the argument is
+			 * divided into two items.  Fixup for this case, if an
+			 * item contains sub string "[sp,", need to concatenate
+			 * the two items.
+			 */
+			if (strstr(args[i], "[sp,") && (i+1) < args_count) {
+				arg = strcat(args[i], args[i+1]);
+				i += 2;
+			} else {
+				arg = strdup(args[i]);
+				i += 1;
+			}
+
+			err = synthesize_sdt_probe_arg(&buf, arg_idx, arg);
+			free(arg);
+			arg_idx++;
+
+			if (err < 0)
 				goto error;
 		}
 	}
-- 
2.17.1