linux-kernel - [PATCH v3 3/6] perf probe: Fix list result when address is zero

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Date:	Wed, 26 Aug 2015 10:57:43 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...nel.org>, <masami.hiramatsu.pt@...achi.com>,
	<rostedt@...dmis.org>
CC:	<mingo@...hat.com>, <namhyung@...nel.org>, <pi3orama@....com>,
	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	Wang Nan <wangnan0@...wei.com>
Subject: [PATCH v3 3/6] perf probe: Fix list result when address is zero

When manually added uprobe point with zero address, 'perf probe -l'
reports error. For example:

 # echo p:probe_libc/abs_0 /path/to/lib.bin:0x0 arg1=%ax > \
           /sys/kernel/debug/tracing/uprobe_events

 # perf probe -l
 Error: Failed to show event list.

Probing at 0x0 is possible and useful when lib.bin is not a normal
shared object but is manually mapped. However, in this case kernel
report:

 # cat /sys/kernel/debug/tracing/uprobe_events
 p:probe_libc/abs_0 /path/to/lib.bin:0x          (null) arg1=%ax

This patch supports the above kernel output.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
---
 tools/perf/util/probe-event.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index f7bacbb..926bcec 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1519,9 +1519,31 @@ int parse_probe_trace_command(const char *cmd, struct probe_trace_event *tev)
 	} else
 		p = argv[1];
 	fmt1_str = strtok_r(p, "+", &fmt);
-	if (fmt1_str[0] == '0')	/* only the address started with 0x */
-		tp->address = strtoul(fmt1_str, NULL, 0);
-	else {
+	/* only the address started with 0x */
+	if (fmt1_str[0] == '0')	{
+		/*
+		 * Fix a special case:
+		 * if address == 0, kernel reports something like:
+		 * p:probe_libc/abs_0 /lib/libc-2.18.so:0x          (null) arg1=%ax
+		 * Newer kernel may fix that, but we want to
+		 * support old kernel also.
+		 */
+		if (strcmp(fmt1_str, "0x") == 0) {
+			if (!argv[2] || strcmp(argv[2], "(null)")) {
+				ret = -EINVAL;
+				goto out;
+			}
+			tp->address = 0;
+
+			free(argv[2]);
+			for (i = 2; argv[i + 1] != NULL; i++)
+				argv[i] = argv[i + 1];
+
+			argv[i] = NULL;
+			argc -= 1;
+		} else
+			tp->address = strtoul(fmt1_str, NULL, 0);
+	} else {
 		/* Only the symbol-based probe has offset */
 		tp->symbol = strdup(fmt1_str);
 		if (tp->symbol == NULL) {
-- 
1.8.3.4

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