[PATCH v6 11/11] kunit: uapi: Validate usability of /proc

[Thomas Weißschuh]

Show that the selftests are executed from a fairly "normal"
userspace context.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
---
 MAINTAINERS                 |  1 +
 lib/kunit/Makefile          |  9 ++++++++
 lib/kunit/kunit-test-uapi.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
 lib/kunit/kunit-test.c      | 24 ++++++++++++++++++++-
 4 files changed, 84 insertions(+), 1 deletion(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 4e8cf9fa7aa9..693aafe4d3f9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14400,6 +14400,7 @@ M:	Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
 S:	Maintained
 F:	include/kunit/uapi.h
 F:	lib/kunit/kunit-example-uapi.c
+F:	lib/kunit/kunit-test-uapi.c
 F:	lib/kunit/kunit-uapi.c
 F:	lib/kunit/uapi-preinit.c
 
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 05991d69aa70..1a4af6b66524 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -29,6 +29,15 @@ endif
 obj-$(if $(CONFIG_KUNIT),y) +=		hooks.o
 
 obj-$(CONFIG_KUNIT_TEST) +=		kunit-test.o
+
+userprogs +=				kunit-test-uapi
+kunit-test-uapi-userccflags :=		-static $(NOLIBC_USERCFLAGS)
+
+ifdef CONFIG_KUNIT_UAPI
+CFLAGS_kunit-test.o :=			-Wa,-I$(obj)
+$(obj)/kunit-test.o: $(obj)/kunit-test-uapi
+endif
+
 obj-$(CONFIG_KUNIT_TEST) +=		platform-test.o
 
 # string-stream-test compiles built-in only.
diff --git a/lib/kunit/kunit-test-uapi.c b/lib/kunit/kunit-test-uapi.c
new file mode 100644
index 000000000000..2e75e57865e3
--- /dev/null
+++ b/lib/kunit/kunit-test-uapi.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit Userspace selftest.
+ *
+ * Copyright (C) 2026, Linutronix GmbH.
+ * Author: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
+ *
+ * This is *userspace* code.
+ */
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "../../tools/testing/selftests/kselftest.h"
+
+static void test_procfs(void)
+{
+	char buf[256];
+	ssize_t r;
+	int fd;
+
+	fd = open("/proc/self/comm", O_RDONLY);
+	if (fd == -1) {
+		ksft_test_result_fail("procfs: open() failed: %s\n", strerror(errno));
+		return;
+	}
+
+	r = read(fd, buf, sizeof(buf));
+	close(fd);
+
+	if (r == -1) {
+		ksft_test_result_fail("procfs: read() failed: %s\n", strerror(errno));
+		return;
+	}
+
+	if (r != 16 || strncmp("kunit-test-uapi\n", buf, 16) != 0) {
+		ksft_test_result_fail("procfs: incorrect comm\n");
+		return;
+	}
+
+	ksft_test_result_pass("procfs\n");
+}
+
+int main(void)
+{
+	ksft_print_header();
+	ksft_set_plan(1);
+	test_procfs();
+	ksft_finished();
+}
diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c
index 126e30879dad..b62e24fb9c55 100644
--- a/lib/kunit/kunit-test.c
+++ b/lib/kunit/kunit-test.c
@@ -9,6 +9,7 @@
 #include <kunit/test.h>
 #include <kunit/test-bug.h>
 #include <kunit/static_stub.h>
+#include <kunit/uapi.h>
 
 #include <linux/device.h>
 #include <kunit/device.h>
@@ -914,10 +915,31 @@ static struct kunit_suite kunit_stub_test_suite = {
 	.test_cases = kunit_stub_test_cases,
 };
 
+static void kunit_uapi_test(struct kunit *test)
+{
+	KUNIT_UAPI_EMBED_BLOB(kunit_test_uapi, "kunit-test-uapi");
+
+	if (IS_ENABLED(CONFIG_KUNIT_UAPI))
+		kunit_uapi_run_kselftest(test, &kunit_test_uapi);
+	else
+		kunit_skip(test, "CONFIG_KUNIT_UAPI is not enabled");
+}
+
+static struct kunit_case kunit_uapi_test_cases[] = {
+	KUNIT_CASE(kunit_uapi_test),
+	{}
+};
+
+static struct kunit_suite kunit_uapi_test_suite = {
+	.name = "kunit_uapi",
+	.test_cases = kunit_uapi_test_cases,
+};
+
 kunit_test_suites(&kunit_try_catch_test_suite, &kunit_resource_test_suite,
 		  &kunit_log_test_suite, &kunit_status_test_suite,
 		  &kunit_current_test_suite, &kunit_device_test_suite,
-		  &kunit_fault_test_suite, &kunit_stub_test_suite);
+		  &kunit_fault_test_suite, &kunit_stub_test_suite,
+		  &kunit_uapi_test_suite);
 
 MODULE_DESCRIPTION("KUnit test for core test infrastructure");
 MODULE_LICENSE("GPL v2");

-- 
2.53.0