linux-kernel - [PATCH 5/6] selftests: vDSO: vdso_test_correctness: Use facilities from parse

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Message-Id: <20260115-vdso-selftest-cleanups-v1-5-103e1ccbfdc3@linutronix.de>
Date: Thu, 15 Jan 2026 09:29:57 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...nel.org>, 
 Vincenzo Frascino <vincenzo.frascino@....com>, 
 Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH 5/6] selftests: vDSO: vdso_test_correctness: Use facilities
 from parse_vdso.c

The soname from the vDSO is not a public API. Furthermore it requires
libc to implement dlsym() and friends.

Use the facilities from parse_vdso.c instead which uses the official
vDSO ABI to find it, aligned with the other vDSO selftests.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 tools/testing/selftests/vDSO/Makefile              |  4 +--
 .../testing/selftests/vDSO/vdso_test_correctness.c | 30 ++++++++++------------
 2 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/tools/testing/selftests/vDSO/Makefile b/tools/testing/selftests/vDSO/Makefile
index 2de5cef311c8..a61047bdcd57 100644
--- a/tools/testing/selftests/vDSO/Makefile
+++ b/tools/testing/selftests/vDSO/Makefile
@@ -26,13 +26,11 @@ CFLAGS_NOLIBC := -nostdlib -nostdinc -ffreestanding -fno-asynchronous-unwind-tab
 $(OUTPUT)/vdso_test_gettimeofday: parse_vdso.c vdso_test_gettimeofday.c
 $(OUTPUT)/vdso_test_getcpu: parse_vdso.c vdso_test_getcpu.c
 $(OUTPUT)/vdso_test_abi: parse_vdso.c vdso_test_abi.c
+$(OUTPUT)/vdso_test_correctness: parse_vdso.c vdso_test_correctness.c
 
 $(OUTPUT)/vdso_standalone_test_x86: vdso_standalone_test_x86.c parse_vdso.c | headers
 $(OUTPUT)/vdso_standalone_test_x86: CFLAGS:=$(CFLAGS_NOLIBC) $(CFLAGS)
 
-$(OUTPUT)/vdso_test_correctness: vdso_test_correctness.c
-$(OUTPUT)/vdso_test_correctness: LDFLAGS += -ldl
-
 $(OUTPUT)/vdso_test_getrandom: parse_vdso.c
 $(OUTPUT)/vdso_test_getrandom: CFLAGS += -isystem $(top_srcdir)/tools/include \
                                          $(KHDR_INCLUDES) \
diff --git a/tools/testing/selftests/vDSO/vdso_test_correctness.c b/tools/testing/selftests/vDSO/vdso_test_correctness.c
index 9b564888e74d..a94ab4d597b1 100644
--- a/tools/testing/selftests/vDSO/vdso_test_correctness.c
+++ b/tools/testing/selftests/vDSO/vdso_test_correctness.c
@@ -11,18 +11,20 @@
 #include <time.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <sys/auxv.h>
 #include <sys/syscall.h>
-#include <dlfcn.h>
 #include <string.h>
 #include <errno.h>
 #include <sched.h>
 #include <stdbool.h>
 #include <limits.h>
 
+#include "parse_vdso.h"
 #include "vdso_config.h"
 #include "vdso_call.h"
 #include "kselftest.h"
 
+static const char *version;
 static const char **name;
 
 #ifndef __NR_clock_gettime64
@@ -102,39 +104,32 @@ static void *vsyscall_getcpu(void)
 
 static void fill_function_pointers(void)
 {
-	void *vdso = dlopen("linux-vdso.so.1",
-			    RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
-	if (!vdso)
-		vdso = dlopen("linux-gate.so.1",
-			      RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
-	if (!vdso)
-		vdso = dlopen("linux-vdso32.so.1",
-			      RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
-	if (!vdso)
-		vdso = dlopen("linux-vdso64.so.1",
-			      RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
-	if (!vdso) {
+	unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR);
+
+	if (!sysinfo_ehdr) {
 		printf("[WARN]\tfailed to find vDSO\n");
 		return;
 	}
 
-	vdso_getcpu = (getcpu_t)dlsym(vdso, name[4]);
+	vdso_init_from_sysinfo_ehdr(sysinfo_ehdr);
+
+	vdso_getcpu = (getcpu_t)vdso_sym(version, name[4]);
 	if (!vdso_getcpu)
 		printf("Warning: failed to find getcpu in vDSO\n");
 
 	vgetcpu = (getcpu_t) vsyscall_getcpu();
 
-	vdso_clock_gettime = (vgettime_t)dlsym(vdso, name[1]);
+	vdso_clock_gettime = (vgettime_t)vdso_sym(version, name[1]);
 	if (!vdso_clock_gettime)
 		printf("Warning: failed to find clock_gettime in vDSO\n");
 
 #if defined(VDSO_32BIT)
-	vdso_clock_gettime64 = (vgettime64_t)dlsym(vdso, name[5]);
+	vdso_clock_gettime64 = (vgettime64_t)vdso_sym(version, name[5]);
 	if (!vdso_clock_gettime64)
 		printf("Warning: failed to find clock_gettime64 in vDSO\n");
 #endif
 
-	vdso_gettimeofday = (vgtod_t)dlsym(vdso, name[0]);
+	vdso_gettimeofday = (vgtod_t)vdso_sym(version, name[0]);
 	if (!vdso_gettimeofday)
 		printf("Warning: failed to find gettimeofday in vDSO\n");
 
@@ -429,6 +424,7 @@ static void test_gettimeofday(void)
 
 int main(int argc, char **argv)
 {
+	version = versions[VDSO_VERSION];
 	name = (const char **)&names[VDSO_NAMES];
 
 	fill_function_pointers();

-- 
2.52.0