[PATCH 19/22] perf probe: Fix list result when address is zero

From: Arnaldo Carvalho de Melo
Date: Wed Aug 26 2015 - 12:00:15 EST


From: Wang Nan <wangnan0@xxxxxxxxxx>

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@xxxxxxxxxx>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
Link: http://lkml.kernel.org/r/1440586666-235233-5-git-send-email-wangnan0@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
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 f7bacbb98865..926bcecc4a44 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) {
--
2.1.0

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