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 10:59:44 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, acme@...nel.org, jolsa@...nel.org, 
	irogers@...gle.com, 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

Hello,

On Tue, Jun 25, 2024 at 5:02 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> 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
>

Thanks, I will add

Fixes: 56cbeacf1435 ("perf probe: Add test for regression introduced
by switch to die_get_decl_file()")

Namhyung