[PATCH bpf-next] selftests/bpf: Use memfd_create instead of mkstemp in d_path

[PATCH bpf-next] selftests/bpf: Use memfd_create instead of mkstemp in d_path

[Jonathan Bastari Thamrin via B4 Relay]

From: Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>

check_mem_access currently creates a temp file in /dev/shm, which
isn't mounted under vmtest.sh in local runs. This causes mkstemp
to fail with ENOENT. The fix is similar to
commit 47687a29b2c3 ("selftests/bpf: Use memfd_create instead of
shm_open in cgroup_iter_memcg") where memfd_create gives a
shmem-backed file with no mount needed while still reaching
vfs_fallocate.

Signed-off-by: Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>
---
 tools/testing/selftests/bpf/prog_tests/d_path.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c b/tools/testing/selftests/bpf/prog_tests/d_path.c
index 1a2a2f1abf03..0f0150d73262 100644
--- a/tools/testing/selftests/bpf/prog_tests/d_path.c
+++ b/tools/testing/selftests/bpf/prog_tests/d_path.c
@@ -4,6 +4,7 @@
 #include <sys/stat.h>
 #include <linux/sched.h>
 #include <sys/syscall.h>
+#include <sys/mman.h>
 
 #define MAX_PATH_LEN		128
 #define MAX_FILES		7
@@ -220,7 +221,6 @@ static void test_d_path_check_types(void)
 static void test_d_path_mem_access(void)
 {
 	int localfd = -1;
-	char path_template[] = "/dev/shm/d_path_loadgen.XXXXXX";
 	struct test_d_path__bss *bss;
 	struct test_d_path *skel;
 
@@ -230,13 +230,12 @@ static void test_d_path_mem_access(void)
 
 	bss = skel->bss;
 
-	localfd = mkstemp(path_template);
-	if (CHECK(localfd < 0, "trigger", "mkstemp failed\n"))
+	localfd = memfd_create("d_path_loadgen", 0);
+	if (CHECK(localfd < 0, "trigger", "memfd_create failed\n"))
 		goto cleanup;
 
 	if (CHECK(fallocate(localfd, 0, 0, 1024) < 0, "trigger", "fallocate failed\n"))
 		goto cleanup;
-	remove(path_template);
 
 	if (CHECK(!bss->path_match_fallocate, "check",
 		  "failed to read fallocate path"))

---
base-commit: a30c772627b2ef4bc715332b1b04938a914556cd
change-id: 20261102-d-path-memfd-981879bcd3d7

Best regards,
-- 
Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>

[PATCH bpf-next] selftests/bpf: Use memfd_create instead of mkstemp in d_path

[Jonathan Bastari Thamrin]

check_mem_access currently creates a temp file in /dev/shm, which
isn't mounted under vmtest.sh in local runs. This causes mkstemp
to fail with ENOENT. The fix is similar to
commit 47687a29b2c3 ("selftests/bpf: Use memfd_create instead of
shm_open in cgroup_iter_memcg") where memfd_create gives a
shmem-backed file with no mount needed while still reaching
vfs_fallocate.

Signed-off-by: Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>
---
 tools/testing/selftests/bpf/prog_tests/d_path.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c b/tools/testing/selftests/bpf/prog_tests/d_path.c
index 1a2a2f1abf03..0f0150d73262 100644
--- a/tools/testing/selftests/bpf/prog_tests/d_path.c
+++ b/tools/testing/selftests/bpf/prog_tests/d_path.c
@@ -4,6 +4,7 @@
 #include <sys/stat.h>
 #include <linux/sched.h>
 #include <sys/syscall.h>
+#include <sys/mman.h>
 
 #define MAX_PATH_LEN		128
 #define MAX_FILES		7
@@ -220,7 +221,6 @@ static void test_d_path_check_types(void)
 static void test_d_path_mem_access(void)
 {
 	int localfd = -1;
-	char path_template[] = "/dev/shm/d_path_loadgen.XXXXXX";
 	struct test_d_path__bss *bss;
 	struct test_d_path *skel;
 
@@ -230,13 +230,12 @@ static void test_d_path_mem_access(void)
 
 	bss = skel->bss;
 
-	localfd = mkstemp(path_template);
-	if (CHECK(localfd < 0, "trigger", "mkstemp failed\n"))
+	localfd = memfd_create("d_path_loadgen", 0);
+	if (CHECK(localfd < 0, "trigger", "memfd_create failed\n"))
 		goto cleanup;
 
 	if (CHECK(fallocate(localfd, 0, 0, 1024) < 0, "trigger", "fallocate failed\n"))
 		goto cleanup;
-	remove(path_template);
 
 	if (CHECK(!bss->path_match_fallocate, "check",
 		  "failed to read fallocate path"))

---
base-commit: a30c772627b2ef4bc715332b1b04938a914556cd
change-id: 20261102-d-path-memfd-981879bcd3d7

Best regards,
-- 
Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>

Re: [PATCH bpf-next] selftests/bpf: Use memfd_create instead of mkstemp in d_path

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] selftests/bpf: deprecated CHECK() used in test_d_path_mem_access()
--

commit 70ec4540d31dab1fed0411808b9f6ef87d380925
Author: Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>

selftests/bpf: Use memfd_create instead of mkstemp in d_path

This commit replaces mkstemp() in /dev/shm with memfd_create() in
test_d_path_mem_access() so the check_mem_access subtest can run under
vmtest.sh when /dev/shm is not mounted.

> diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c b/tools/testing/selftests/bpf/prog_tests/d_path.c
> index 1a2a2f1abf033..0f0150d73262b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/d_path.c
> +++ b/tools/testing/selftests/bpf/prog_tests/d_path.c

[ ... ]

> @@ -230,13 +230,12 @@ static void test_d_path_mem_access(void)
>  
>  	bss = skel->bss;
>  
> -	localfd = mkstemp(path_template);
> -	if (CHECK(localfd < 0, "trigger", "mkstemp failed\n"))
> +	localfd = memfd_create("d_path_loadgen", 0);
> +	if (CHECK(localfd < 0, "trigger", "memfd_create failed\n"))
>  		goto cleanup;

[Severity: Low]
This isn't a bug, but since CHECK() is deprecated in BPF selftests, should
this updated check in test_d_path_mem_access() use ASSERT_OK_FD() from
tools/testing/selftests/bpf/test_progs.h instead (similar to commit
47687a29b2c3 ("selftests/bpf: Use memfd_create instead of shm_open in
cgroup_iter_memcg"))?

	if (!ASSERT_OK_FD(localfd, "memfd_create"))
		goto cleanup;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261102-d-path-memfd-v1-1-692a5664b36d@gmail.com?part=1