Re: [PATCH V3 1/3] tools/perf: Fix the string match for "/tmp/perf-$PID.map" files in dso__load

Athira Rajeev
2024-06-25T16:42:11Z

> On 23 Jun 2024, at 8:56 PM, Chaitanya S Prakash <chaitanyas.prakash@arm.com> wrote:
>
>
> On 6/18/24 19:33, Athira Rajeev wrote:
>> Perf test for perf probe of function from different CU fails
>> as below:
>>
>> ./perf test -vv "test perf probe of function from different CU"
>> 116: test perf probe of function from different CU:
>> --- start ---
>> test child forked, pid 2679
>> Failed to find symbol foo in /tmp/perf-uprobe-different-cu-sh.Msa7iy89bx/testfile
>> Error: Failed to add events.
>> --- Cleaning up ---
>> "foo" does not hit any event.
>> Error: Failed to delete events.
>> ---- end(-1) ----
>> 116: test perf probe of function from different CU : FAILED!
>>
>> The test does below to probe function "foo" :
>>
>> # gcc -g -Og -flto -c /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-foo.c
>> -o /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-foo.o
>> # gcc -g -Og -c /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-main.c
>> -o /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-main.o
>> # gcc -g -Og -o /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile
>> /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-foo.o
>> /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-main.o
>>
>> # ./perf probe -x /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile foo
>> Failed to find symbol foo in /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile
>> Error: Failed to add events.
>>
>> Perf probe fails to find symbol foo in the executable placed in
>> /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7
>>
>> Simple reproduce:
>>
>> # mktemp -d /tmp/perf-checkXXXXXXXXXX
>> /tmp/perf-checkcWpuLRQI8j
>>
>> # gcc -g -o test test.c
>> # cp test /tmp/perf-checkcWpuLRQI8j/
>> # nm /tmp/perf-checkcWpuLRQI8j/test | grep foo
>> 00000000100006bc T foo
>>
>> # ./perf probe -x /tmp/perf-checkcWpuLRQI8j/test foo
>> Failed to find symbol foo in /tmp/perf-checkcWpuLRQI8j/test
>> Error: Failed to add events.
>>
>> But it works with any files like /tmp/perf/test. Only for
>> patterns with "/tmp/perf-", this fails.
>>
>> Further debugging, commit 80d496be89ed ("perf report: Add support
>> for profiling JIT generated code") added support for profiling JIT
>> generated code. This patch handles dso's of form
>> "/tmp/perf-$PID.map" .
>>
>> The check used "if (strncmp(self->name, "/tmp/perf-", 10) == 0)"
>> to match "/tmp/perf-$PID.map". With this commit, any dso in
>> /tmp/perf- folder will be considered separately for processing
>> (not only JIT created map files ). Fix this by changing the
>> string pattern to check for "/tmp/perf-%d.map". Add a helper
>> function is_perf_pid_map_name to do this check.
>>
>> With the fix,
>> # ./perf test "test perf probe of function from different CU"
>> 117: test perf probe of function from different CU : Ok
>>
>> Signed-off-by: Athira Rajeev<atrajeev@linux.vnet.ibm.com>
>> ---
>> Changelog:
>> v2 -> v3:
>> Addressed review comment from Adrian and James.
>> Added perf_pid_map_tid to save the tid and modified
>> is_perf_pid_map_name to use this internally.
>>
>> v1 -> v2:
>> Addressed review comments from Adrian.
>> Added helper function is_perf_pid_map_name to check
>> dso name of form "/tmp/perf-%d.map". Used sscanf
>> instead of regex comparison.
>>
>> tools/perf/util/dso.c | 12 ++++++++++++
>> tools/perf/util/dso.h | 4 ++++
>> tools/perf/util/symbol.c | 3 ++-
>> 3 files changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
>> index dde706b71da7..2340c4f6d0c2 100644
>> --- a/tools/perf/util/dso.c
>> +++ b/tools/perf/util/dso.c
>> @@ -1652,3 +1652,15 @@ int dso__strerror_load(struct dso *dso, char *buf, size_t buflen)
>> scnprintf(buf, buflen, "%s", dso_load__error_str[idx]);
>> return 0;
>> }
>> +
>> +bool perf_pid_map_tid(const char *dso_name, int *tid)
>> +{
>> + return sscanf(dso_name, "/tmp/perf-%d.map", tid) == 1;
>> +}
>> +
>> +bool is_perf_pid_map_name(const char *dso_name)
>> +{
>> + int tid;
>> +
>> + return perf_pid_map_tid(dso_name, &tid);
>> +}
>> diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
>> index df2c98402af3..d72f3b8c37f6 100644
>> --- a/tools/perf/util/dso.h
>> +++ b/tools/perf/util/dso.h
>> @@ -809,4 +809,8 @@ void reset_fd_limit(void);
>> u64 dso__find_global_type(struct dso *dso, u64 addr);
>> u64 dso__findnew_global_type(struct dso *dso, u64 addr, u64 offset);
>> +/* Check if dso name is of format "/tmp/perf-%d.map" */
>> +bool perf_pid_map_tid(const char *dso_name, int *tid);
>> +bool is_perf_pid_map_name(const char *dso_name);
>> +
>> #endif /* __PERF_DSO */
>> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
>> index 9e5940b5bc59..aee0a4cfb383 100644
>> --- a/tools/perf/util/symbol.c
>> +++ b/tools/perf/util/symbol.c
>> @@ -1799,7 +1799,8 @@ int dso__load(struct dso *dso, struct map *map)
>> const char *map_path = dso__long_name(dso);
>> mutex_lock(dso__lock(dso));
>> - perfmap = strncmp(dso__name(dso), "/tmp/perf-", 10) == 0;
>> + perfmap = is_perf_pid_map_name(map_path);
>> +
>> if (perfmap) {
>> if (dso__nsinfo(dso) &&
>> (dso__find_perf_map(newmapname, sizeof(newmapname),
>
> Reviewed-by: Chaitanya S Prakash<chaitanyas.prakash@arm.com>

Thanks Chaitanya for the reviewed-by

Athira
>
> I will drop my fix for the same.
> https://lore.kernel.org/all/20240601125946.1741414-10-ChaitanyaS.Prakash@arm.com/
>
> The rest of my series can be reviewed as a string function tidy up.
>