linux-kernel - [PATCH v2 2/3] perf probe: Fixup Arm64 SDT arguments

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Date:   Fri, 25 Dec 2020 13:27:50 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexandre Truong <alexandre.truong@....com>,
        Ian Rogers <irogers@...gle.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        He Zhe <zhe.he@...driver.com>,
        Sumanth Korikkar <sumanthk@...ux.ibm.com>,
        Alexis Berlemont <alexis.berlemont@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v2 2/3] 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@...aro.org>
---
 tools/perf/util/probe-file.c | 38 ++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index bbecb449ea94..52273542e6ef 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;
 	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);
-- 
2.17.1