perf probe: Fixup Arm64 SDT arguments

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@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Truong <alexandre.truong@arm.com>
Cc: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: He Zhe <zhe.he@windriver.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lore.kernel.org/lkml/20201225052751.24513-3-leo.yan@linaro.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-file.c

@@ -794,6 +794,8 @@ static char *synthesize_sdt_probe_command(struct sdt_note *note,
 	char *ret = NULL;
 	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;
@@ -818,11 +820,43 @@ static char *synthesize_sdt_probe_command(struct sdt_note *note,
 		if (args == NULL)
 			goto error;
 
-		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) {
+				err = asprintf(&arg, "%s %s", args[i], args[i+1]);
+				i += 2;
+			} else {
+				err = asprintf(&arg, "%s", args[i]);
+				i += 1;
+			}
+
+			/* Failed to allocate memory */
+			if (err < 0) {
 				argv_free(args);
 				goto error;
 			}
+
+			if (synthesize_sdt_probe_arg(&buf, arg_idx, arg) < 0) {
+				free(arg);
+				argv_free(args);
+				goto error;
+			}
+
+			free(arg);
+			arg_idx++;
 		}
 
 		argv_free(args);