[PATCH 1/3] perf tools: Set proper module name when build-id event found

[PATCH 1/3] perf tools: Set proper module name when build-id event found

[Namhyung Kim]

When perf processes build-id event, it creates DSOs with the build-id.
But it didn't set the module short name (like '[module-name]') so when
processing a kernel mmap event of the module, it cannot found the DSO as
it only checks the short names.

That leads for perf to create a same DSO without the build-id info and
it'll lookup the system path even if the DSO is already in the build-id
cache.  After kernel was updated, perf cannot find the DSO  and cannot show
symbols in it anymore.

You can see this if you have an old data file (w/ old kernel version):

  $ perf report -i perf.data.old -v |& grep scsi_mod
  build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz : cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
  Failed to open /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz, continuing without symbols
  ...

The second message didn't show the build-id.  With this patch:

  $ perf report -i perf.data.old -v |& grep scsi_mod
  build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz: cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
  /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz with build id cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1 not found, continuing without symbols
  ...

Now it shows the build-id but still cannot load the symbol table.  This
is a different problem which will be fixed in the next patch.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/header.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 314a07151fb7..56b8a479223b 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1469,8 +1469,16 @@ static int __event_process_build_id(struct build_id_event *bev,
 
 		dso__set_build_id(dso, &bev->build_id);
 
-		if (!is_kernel_module(filename, cpumode))
-			dso->kernel = dso_type;
+		if (dso_type != DSO_TYPE_USER) {
+			struct kmod_path m = {};
+
+			if (!kmod_path__parse_name(&m, filename) && m.kmod)
+				dso__set_short_name(dso, strdup(m.name), true);
+			else
+				dso->kernel = dso_type;
+
+			free(m.name);
+		}
 
 		build_id__sprintf(dso->build_id, sizeof(dso->build_id),
 				  sbuild_id);
-- 
2.13.0

[PATCH 2/3] perf tools: Set module info when build-id event found

[Namhyung Kim]

Like machine__findnew_module_dso(), it should set necessary info for
kernel modules to find symbol info from the file.  Factor out
dso__set_module_info() to do it.

This is needed for dso__needs_decompress() to detect such DSOs.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/dso.c     | 15 +++++++++++++++
 tools/perf/util/dso.h     |  3 +++
 tools/perf/util/header.c  |  2 +-
 tools/perf/util/machine.c | 11 +----------
 4 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index a96a99d2369f..b27d127cdf68 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -335,6 +335,21 @@ int __kmod_path__parse(struct kmod_path *m, const char *path,
 	return 0;
 }
 
+void dso__set_module_info(struct dso *dso, struct kmod_path *m,
+			  struct machine *machine)
+{
+	if (machine__is_host(machine))
+		dso->symtab_type = DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE;
+	else
+		dso->symtab_type = DSO_BINARY_TYPE__GUEST_KMODULE;
+
+	/* _KMODULE_COMP should be next to _KMODULE */
+	if (m->kmod && m->comp)
+		dso->symtab_type++;
+
+	dso__set_short_name(dso, strdup(m->name), true);
+}
+
 /*
  * Global list of open DSOs and the counter.
  */
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 12350b171727..5fe2ab5877bd 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -259,6 +259,9 @@ int __kmod_path__parse(struct kmod_path *m, const char *path,
 #define kmod_path__parse_name(__m, __p) __kmod_path__parse(__m, __p, true , false)
 #define kmod_path__parse_ext(__m, __p)  __kmod_path__parse(__m, __p, false, true)
 
+void dso__set_module_info(struct dso *dso, struct kmod_path *m,
+			  struct machine *machine);
+
 /*
  * The dso__data_* external interface provides following functions:
  *   dso__data_get_fd
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 56b8a479223b..8b3dd430c63c 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1473,7 +1473,7 @@ static int __event_process_build_id(struct build_id_event *bev,
 			struct kmod_path m = {};
 
 			if (!kmod_path__parse_name(&m, filename) && m.kmod)
-				dso__set_short_name(dso, strdup(m.name), true);
+				dso__set_module_info(dso, &m, machine);
 			else
 				dso->kernel = dso_type;
 
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index d97e014c3df3..d7f31cb0a4cb 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -572,16 +572,7 @@ static struct dso *machine__findnew_module_dso(struct machine *machine,
 		if (dso == NULL)
 			goto out_unlock;
 
-		if (machine__is_host(machine))
-			dso->symtab_type = DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE;
-		else
-			dso->symtab_type = DSO_BINARY_TYPE__GUEST_KMODULE;
-
-		/* _KMODULE_COMP should be next to _KMODULE */
-		if (m->kmod && m->comp)
-			dso->symtab_type++;
-
-		dso__set_short_name(dso, strdup(m->name), true);
+		dso__set_module_info(dso, m, machine);
 		dso__set_long_name(dso, strdup(filename), true);
 	}
 
-- 
2.13.0

[PATCH 3/3] perf tools: Use correct filename for compressed modules in build-id cache

[Namhyung Kim]

The decompress_kmodule() is to decompress kernel module in order to load
symbols from it.  In DSO_BINARY_TYPE__BUILD_ID_CACHE case, it needs full
file path to extract the file extension to determine decompress method.
But overwriting 'name' will fail to decompress since it might point to a
non-existing old file.

Instead, use dso->long_name for extension and use real filename to
decompress.  In DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP case, both
name should be same.  This can show symbols in the old modules.

Before:

  $ perf report -i perf.data.old | grep scsi_mod
     0.00%  cc1      [scsi_mod]    [k] 0x0000000000004aa6
     0.00%  as       [scsi_mod]    [k] 0x00000000000099e1
     0.00%  cc1      [scsi_mod]    [k] 0x0000000000009830
     0.00%  cc1      [scsi_mod]    [k] 0x0000000000001b8f

After:

     0.00%  cc1      [scsi_mod]    [k] scsi_handle_queue_ramp_up
     0.00%  as       [scsi_mod]    [k] scsi_sg_alloc
     0.00%  cc1      [scsi_mod]    [k] scsi_setup_cmnd
     0.00%  cc1      [scsi_mod]    [k] scsi_get_command

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/symbol-elf.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index e7ee47f7377a..1fb2efae4f02 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -649,10 +649,7 @@ static int decompress_kmodule(struct dso *dso, const char *name,
 	    type != DSO_BINARY_TYPE__BUILD_ID_CACHE)
 		return -1;
 
-	if (type == DSO_BINARY_TYPE__BUILD_ID_CACHE)
-		name = dso->long_name;
-
-	if (kmod_path__parse_ext(&m, name) || !m.comp)
+	if (kmod_path__parse_ext(&m, dso->long_name) || !m.comp)
 		return -1;
 
 	fd = mkstemp(tmpbuf);
-- 
2.13.0

Re: [PATCH 1/3] perf tools: Set proper module name when build-id event found

[Jiri Olsa]

On Wed, May 31, 2017 at 09:01:03PM +0900, Namhyung Kim wrote:
> When perf processes build-id event, it creates DSOs with the build-id.
> But it didn't set the module short name (like '[module-name]') so when
> processing a kernel mmap event of the module, it cannot found the DSO as
> it only checks the short names.
> 
> That leads for perf to create a same DSO without the build-id info and
> it'll lookup the system path even if the DSO is already in the build-id
> cache.  After kernel was updated, perf cannot find the DSO  and cannot show
> symbols in it anymore.
> 
> You can see this if you have an old data file (w/ old kernel version):
> 
>   $ perf report -i perf.data.old -v |& grep scsi_mod
>   build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz : cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
>   Failed to open /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz, continuing without symbols
>   ...
> 
> The second message didn't show the build-id.  With this patch:
> 
>   $ perf report -i perf.data.old -v |& grep scsi_mod
>   build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz: cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
>   /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz with build id cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1 not found, continuing without symbols
>   ...
> 
> Now it shows the build-id but still cannot load the symbol table.  This
> is a different problem which will be fixed in the next patch.
> 
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

for all 3:

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka

Re: [PATCH 1/3] perf tools: Set proper module name when build-id event found

[Arnaldo Carvalho de Melo]

Em Thu, Jun 01, 2017 at 12:24:52AM +0200, Jiri Olsa escreveu:
> On Wed, May 31, 2017 at 09:01:03PM +0900, Namhyung Kim wrote:
> > Now it shows the build-id but still cannot load the symbol table.  This
> > is a different problem which will be fixed in the next patch.

> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>

> for all 3:

> Acked-by: Jiri Olsa <jolsa@kernel.org>

Thanks, applied.

- Arnaldo

Re: [PATCH 1/3] perf tools: Set proper module name when build-id event found

[Arnaldo Carvalho de Melo]

Em Wed, May 31, 2017 at 09:01:03PM +0900, Namhyung Kim escreveu:
> +++ b/tools/perf/util/header.c
> @@ -1469,8 +1469,16 @@ static int __event_process_build_id(struct build_id_event *bev,
>  
>  		dso__set_build_id(dso, &bev->build_id);
>  
> -		if (!is_kernel_module(filename, cpumode))
> -			dso->kernel = dso_type;
> +		if (dso_type != DSO_TYPE_USER) {
> +			struct kmod_path m = {};
> +

This fails in several distros, among them centos:7, debian:8

  CC       /tmp/build/perf/util/header.o
util/header.c: In function '__event_process_build_id':
util/header.c:1473:11: error: missing initializer for field 'name' of 'struct kmod_path' [-Werror=missing-field-initializers]
    struct kmod_path m = {};
           ^
In file included from util/symbol.h:24:0,
                 from util/evsel.h:10,
                 from util/evlist.h:11,
                 from util/header.c:19:
util/dso.h:249:8: note: 'name' declared here
  char *name;
        ^
cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/util/.header.o.tmp': No such file or directory
make[4]: *** [/tmp/build/perf/util/header.o] Error 1
make[3]: *** [util] Error 2
make[3]: *** Waiting for unfinished jobs....

centos:5, centos:6, debian:7 have a slightly different message:

  CC       /tmp/build/perf/util/callchain.o
cc1: warnings being treated as errors
util/header.c: In function '__event_process_build_id':
util/header.c:1473: warning: missing initializer
util/header.c:1473: warning: (near initialization for 'm.name')
  MKDIR    /tmp/build/perf/util/
  CC       /tmp/build/perf/util/values.o
mv: cannot stat `/tmp/build/perf/util/.header.o.tmp': No such file or directory


I'll fix this.

- Arnaldo

[tip:perf/urgent] perf header: Set proper module name when build-id event found

[tip-bot for Namhyung Kim]

Commit-ID:  1deec1bd96ccd8beb04d2112a6d12fe20505c3a6
Gitweb:     http://git.kernel.org/tip/1deec1bd96ccd8beb04d2112a6d12fe20505c3a6
Author:     Namhyung Kim <namhyung@kernel.org>
AuthorDate: Wed, 31 May 2017 21:01:03 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 5 Jun 2017 14:16:49 -0300

perf header: Set proper module name when build-id event found

When perf processes build-id event, it creates DSOs with the build-id.
But it didn't set the module short name (like '[module-name]') so when
processing a kernel mmap event of the module, it cannot found the DSO as
it only checks the short names.

That leads for perf to create a same DSO without the build-id info and
it'll lookup the system path even if the DSO is already in the build-id
cache.  After kernel was updated, perf cannot find the DSO  and cannot
show symbols in it anymore.

You can see this if you have an old data file (w/ old kernel version):

  $ perf report -i perf.data.old -v |& grep scsi_mod
  build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz : cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
  Failed to open /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz, continuing without symbols
  ...

The second message didn't show the build-id.  With this patch:

  $ perf report -i perf.data.old -v |& grep scsi_mod
  build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz: cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
  /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz with build id cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1 not found, continuing without symbols
  ...

Now it shows the build-id but still cannot load the symbol table.  This
is a different problem which will be fixed in the next patch.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170531120105.21731-1-namhyung@kernel.org
[ Fix the build on older compilers (debian <= 8, fedora <= 21, etc) wrt kmod_path var init ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/header.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 314a071..c40a4d8 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1469,8 +1469,16 @@ static int __event_process_build_id(struct build_id_event *bev,
 
 		dso__set_build_id(dso, &bev->build_id);
 
-		if (!is_kernel_module(filename, cpumode))
-			dso->kernel = dso_type;
+		if (dso_type != DSO_TYPE_USER) {
+			struct kmod_path m = { .name = NULL, };
+
+			if (!kmod_path__parse_name(&m, filename) && m.kmod)
+				dso__set_short_name(dso, strdup(m.name), true);
+			else
+				dso->kernel = dso_type;
+
+			free(m.name);
+		}
 
 		build_id__sprintf(dso->build_id, sizeof(dso->build_id),
 				  sbuild_id);

[tip:perf/urgent] perf symbols: Set module info when build-id event found

[tip-bot for Namhyung Kim]

Commit-ID:  6b335e8f545591c07df0f34231bd7ff7506c98c1
Gitweb:     http://git.kernel.org/tip/6b335e8f545591c07df0f34231bd7ff7506c98c1
Author:     Namhyung Kim <namhyung@kernel.org>
AuthorDate: Wed, 31 May 2017 21:01:04 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 5 Jun 2017 14:17:58 -0300

perf symbols: Set module info when build-id event found

Like machine__findnew_module_dso(), it should set necessary info for
kernel modules to find symbol info from the file.  Factor out
dso__set_module_info() to do it.

This is needed for dso__needs_decompress() to detect such DSOs.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170531120105.21731-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/dso.c     | 15 +++++++++++++++
 tools/perf/util/dso.h     |  3 +++
 tools/perf/util/header.c  |  2 +-
 tools/perf/util/machine.c | 11 +----------
 4 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index a96a99d..b27d127 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -335,6 +335,21 @@ int __kmod_path__parse(struct kmod_path *m, const char *path,
 	return 0;
 }
 
+void dso__set_module_info(struct dso *dso, struct kmod_path *m,
+			  struct machine *machine)
+{
+	if (machine__is_host(machine))
+		dso->symtab_type = DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE;
+	else
+		dso->symtab_type = DSO_BINARY_TYPE__GUEST_KMODULE;
+
+	/* _KMODULE_COMP should be next to _KMODULE */
+	if (m->kmod && m->comp)
+		dso->symtab_type++;
+
+	dso__set_short_name(dso, strdup(m->name), true);
+}
+
 /*
  * Global list of open DSOs and the counter.
  */
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 12350b1..5fe2ab5 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -259,6 +259,9 @@ int __kmod_path__parse(struct kmod_path *m, const char *path,
 #define kmod_path__parse_name(__m, __p) __kmod_path__parse(__m, __p, true , false)
 #define kmod_path__parse_ext(__m, __p)  __kmod_path__parse(__m, __p, false, true)
 
+void dso__set_module_info(struct dso *dso, struct kmod_path *m,
+			  struct machine *machine);
+
 /*
  * The dso__data_* external interface provides following functions:
  *   dso__data_get_fd
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c40a4d8..5cac8d5 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1473,7 +1473,7 @@ static int __event_process_build_id(struct build_id_event *bev,
 			struct kmod_path m = { .name = NULL, };
 
 			if (!kmod_path__parse_name(&m, filename) && m.kmod)
-				dso__set_short_name(dso, strdup(m.name), true);
+				dso__set_module_info(dso, &m, machine);
 			else
 				dso->kernel = dso_type;
 
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index d97e014..d7f31cb 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -572,16 +572,7 @@ static struct dso *machine__findnew_module_dso(struct machine *machine,
 		if (dso == NULL)
 			goto out_unlock;
 
-		if (machine__is_host(machine))
-			dso->symtab_type = DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE;
-		else
-			dso->symtab_type = DSO_BINARY_TYPE__GUEST_KMODULE;
-
-		/* _KMODULE_COMP should be next to _KMODULE */
-		if (m->kmod && m->comp)
-			dso->symtab_type++;
-
-		dso__set_short_name(dso, strdup(m->name), true);
+		dso__set_module_info(dso, m, machine);
 		dso__set_long_name(dso, strdup(filename), true);
 	}
 

[tip:perf/urgent] perf symbols: Use correct filename for compressed modules in build-id cache

[tip-bot for Namhyung Kim]

Commit-ID:  a09935b878dc8efd4b030ed1ffa0553fc9011fb8
Gitweb:     http://git.kernel.org/tip/a09935b878dc8efd4b030ed1ffa0553fc9011fb8
Author:     Namhyung Kim <namhyung@kernel.org>
AuthorDate: Wed, 31 May 2017 21:01:05 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 5 Jun 2017 14:17:59 -0300

perf symbols: Use correct filename for compressed modules in build-id cache

The decompress_kmodule() decompresses kernel modules in order to load
symbols from it.  In the DSO_BINARY_TYPE__BUILD_ID_CACHE case, it needs
the full file path to extract the file extension to determine the
decompression method.  But overwriting 'name' will fail the
decompression since it might point to a non-existing old file.

Instead, use dso->long_name for having the correct extension and use the
real filename to decompress.

In the DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP case, both names should
be the same.  This allows resolving symbols in the old modules.

Before:

  $ perf report -i perf.data.old | grep scsi_mod
     0.00%  cc1      [scsi_mod]    [k] 0x0000000000004aa6
     0.00%  as       [scsi_mod]    [k] 0x00000000000099e1
     0.00%  cc1      [scsi_mod]    [k] 0x0000000000009830
     0.00%  cc1      [scsi_mod]    [k] 0x0000000000001b8f

After:

     0.00%  cc1      [scsi_mod]    [k] scsi_handle_queue_ramp_up
     0.00%  as       [scsi_mod]    [k] scsi_sg_alloc
     0.00%  cc1      [scsi_mod]    [k] scsi_setup_cmnd
     0.00%  cc1      [scsi_mod]    [k] scsi_get_command

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170531120105.21731-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/symbol-elf.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index e7ee47f..1fb2efa 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -649,10 +649,7 @@ static int decompress_kmodule(struct dso *dso, const char *name,
 	    type != DSO_BINARY_TYPE__BUILD_ID_CACHE)
 		return -1;
 
-	if (type == DSO_BINARY_TYPE__BUILD_ID_CACHE)
-		name = dso->long_name;
-
-	if (kmod_path__parse_ext(&m, name) || !m.comp)
+	if (kmod_path__parse_ext(&m, dso->long_name) || !m.comp)
 		return -1;
 
 	fd = mkstemp(tmpbuf);