linux-kernel - Re: [PATCH V4 1/3] tools/perf: Fix the string match for "/tmp/perf-$PID.map" files in dso_

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Date: Tue, 25 Jun 2024 15:02:11 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, acme@...nel.org,
 jolsa@...nel.org, irogers@...gle.com, namhyung@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, akanksha@...ux.ibm.com, maddy@...ux.ibm.com,
 kjain@...ux.ibm.com, disgoel@...ux.vnet.ibm.com
Subject: Re: [PATCH V4 1/3] tools/perf: Fix the string match for
 "/tmp/perf-$PID.map" files in dso__load

On 25/06/24 14:57, Adrian Hunter wrote:
> On 23/06/24 09:48, 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. In "struct dso",
>> dso->long_name holds the long name of the dso file. Since the
>> /tmp/perf-$PID.map check uses the complete name, use dso___long_name for
>> the string name.
>>
>> 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@...ux.vnet.ibm.com>
> 
> Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>
> 

Although it could use a Fixes tag