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Date: Wed, 26 Aug 2015 17:43:53 +0800
From: "Wangnan (F)" <wangnan0@...wei.com>
To: 平松雅巳 / HIRAMATU，MASAMI
<masami.hiramatsu.pt@...achi.com>,
"acme@...nel.org" <acme@...nel.org>,
"rostedt@...dmis.org" <rostedt@...dmis.org>
CC: "mingo@...hat.com" <mingo@...hat.com>,
"namhyung@...nel.org" <namhyung@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"pi3orama@....com" <pi3orama@....com>,
sysp-manager <cti.systems-productivity-manager.ts@...achi.com>
Subject: Re: [PATCH v2 2/4] perf probe: Fix list result when address is zero
On 2015/8/26 17:29, 平松雅巳 / HIRAMATU，MASAMI wrote:
>> From: Wang Nan [mailto:wangnan0@...wei.com]
>>
>> 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 /tmp/oxygen_root/lib64/libc-2.18.so:0x (null) arg1=%ax
>>
>> This patch supports the above kernel output.
> Former part is OK to me.
>
>> In addition, this patch also fixes convert_to_perf_probe_point() that,
>> if failed to find probe point from both of dwarf and map, in all cases
>> pp->function should be filled with a strdup() result, or the following
>> ENOMEM error code is incorrect. Remove !tp->module && !is_kprobe
>> condition so always use address to build function name if symbol is not
>> found.
> No, I think this should be included in 3/4, since until that perf probe
> doesn't support absolute address on kernel.
This is for manually introduced probing points.
convert_to_perf_probe_point is called by:
perf probe -l -> show_perf_probe_events -> __show_perf_probe_events --> convert_to_perf_probe_event
If there is a manually inserted probing point there, 'perf probe -l' reports an error.
Here is the result if I remove the second part:
$ git log --oneline # I'm in 2/4
aae2c2c perf probe: Fix list result when address is zero
931dff5 perf probe: Prevent segfault when reading probe point with
absolute address
...
$ git diff # remove the second part
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 926bcec..de2c27e 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1888,7 +1888,7 @@ static int convert_to_perf_probe_point(struct
probe_trace_point *tp,
if (tp->symbol) {
pp->function = strdup(tp->symbol);
pp->offset = tp->offset;
- } else {
+ } else if (!tp->module && !is_kprobe) {
ret = e_snprintf(buf, 128, "0x%" PRIx64, (u64)tp->address);
if (ret < 0)
return ret;
...
# echo 'p:probe_libc/abs_5 /lib64/libc.so.6:0x5' >
/sys/kernel/debug/tracing/uprobe_events
# cat /sys/kernel/debug/tracing/uprobe_events
p:probe_libc/abs_5 /lib64/libc.so.6:0x0000000000000005
# perf probe -l
Error: Failed to show event list
Then add it back:
$ git reset --hard HEAD
...
# perf probe -l
probe_libc:abs_5 (on 0x5 in /lib64/libc.so.6)
Thank you.
> Thank you,
>
>> 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 | 30 ++++++++++++++++++++++++++----
>> 1 file changed, 26 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>> index ef325a2..3ce223d 100644
>> --- a/tools/perf/util/probe-event.c
>> +++ b/tools/perf/util/probe-event.c
>> @@ -1521,9 +1521,31 @@ 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) {
>> @@ -1868,7 +1890,7 @@ static int convert_to_perf_probe_point(struct probe_trace_point *tp,
>> if (tp->symbol) {
>> pp->function = strdup(tp->symbol);
>> pp->offset = tp->offset;
>> - } else if (!tp->module && !is_kprobe) {
>> + } else {
>> ret = e_snprintf(buf, 128, "0x%" PRIx64, (u64)tp->address);
>> if (ret < 0)
>> return ret;
>> --
>> 1.8.3.4
--
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