[PATCH v5 00/15] kunit: Introduce UAPI testing framework

[PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Thomas Weißschuh]

Currently testing of userspace and in-kernel API use two different
frameworks. kselftests for the userspace ones and Kunit for the
in-kernel ones. Besides their different scopes, both have different
strengths and limitations:

Kunit:
* Tests are normal kernel code.
* They use the regular kernel toolchain.
* They can be packaged and distributed as modules conveniently.

Kselftests:
* Tests are normal userspace code
* They need a userspace toolchain.
  A kernel cross toolchain is likely not enough.
* A fair amout of userland is required to run the tests,
  which means a full distro or handcrafted rootfs.
* There is no way to conveniently package and run kselftests with a
  given kernel image.
* The kselftests makefiles are not as powerful as regular kbuild.
  For example they are missing proper header dependency tracking or more
  complex compiler option modifications.

Therefore kunit is much easier to run against different kernel
configurations and architectures.
This series aims to combine kselftests and kunit, avoiding both their
limitations. It works by compiling the userspace kselftests as part of
the regular kernel build, embedding them into the kunit kernel or module
and executing them from there. If the kernel toolchain is not fit to
produce userspace because of a missing libc, the kernel's own nolibc can
be used instead.
The structured TAP output from the kselftest is integrated into the
kunit KTAP output transparently, the kunit parser can parse the combined
logs together.

Further room for improvements:
* Call each test in its completely dedicated namespace
* Handle additional test files besides the test executable through
  archives. CPIO, cramfs, etc.
* Compatibility with kselftest_harness.h (in progress)
* Expose the blobs in debugfs
* Provide some convience wrappers around compat userprogs
* Figure out a migration path/coexistence solution for
  kunit UAPI and tools/testing/selftests/

Output from the kunit example testcase, note the output of
"example_uapi_tests".

$ ./tools/testing/kunit/kunit.py run --kunitconfig lib/kunit example
...
Running tests with:
$ .kunit/linux kunit.filter_glob=example kunit.enable=1 mem=1G console=tty kunit_shutdown=halt
[11:53:53] ================== example (10 subtests) ===================
[11:53:53] [PASSED] example_simple_test
[11:53:53] [SKIPPED] example_skip_test
[11:53:53] [SKIPPED] example_mark_skipped_test
[11:53:53] [PASSED] example_all_expect_macros_test
[11:53:53] [PASSED] example_static_stub_test
[11:53:53] [PASSED] example_static_stub_using_fn_ptr_test
[11:53:53] [PASSED] example_priv_test
[11:53:53] =================== example_params_test  ===================
[11:53:53] [SKIPPED] example value 3
[11:53:53] [PASSED] example value 2
[11:53:53] [PASSED] example value 1
[11:53:53] [SKIPPED] example value 0
[11:53:53] =============== [PASSED] example_params_test ===============
[11:53:53] [PASSED] example_slow_test
[11:53:53] ======================= (4 subtests) =======================
[11:53:53] [PASSED] procfs
[11:53:53] [PASSED] userspace test 2
[11:53:53] [SKIPPED] userspace test 3: some reason
[11:53:53] [PASSED] userspace test 4
[11:53:53] ================ [PASSED] example_uapi_test ================
[11:53:53] ===================== [PASSED] example =====================
[11:53:53] ============================================================
[11:53:53] Testing complete. Ran 16 tests: passed: 11, skipped: 5
[11:53:53] Elapsed time: 67.543s total, 1.823s configuring, 65.655s building, 0.058s running

Based on v6.16-rc1.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
Changes in v5:
- Initialize output variable of kernel_wait()
- Fix .incbin with in-tree builds
- Keep requirement of KTAP tests to have a number which was removed accidentally
- Only synthesize KTAP subtest failure if the outer one is TestStatus.FAILURE
- Use -I instead of -isystem in NOLIBC_USERCFLAGS to populate dependency files
- +To filesystem developers to all patches
- +To Luis Chamberlain for discussions about usage of usermodehelper
  (see patches 6 and 12)
- Link to v4: https://lore.kernel.org/r/20250626-kunit-kselftests-v4-0-48760534fef5@linutronix.de

Changes in v4:
- Move Kconfig.nolibc from tools/ to init/
- Drop generic userprogs nolibc integration
- Drop generic blob framework
- Pick up review tags from David
- Extend new kunit TAP parser tests
- Add MAINTAINERS entry
- Allow CONFIG_KUNIT_UAPI=m
- Split /proc validation into dedicated UAPI test
- Trim recipient list a bit
- Use KUNIT_FAIL_AND_ABORT() over KUNIT_FAIL()
- Link to v3: https://lore.kernel.org/r/20250611-kunit-kselftests-v3-0-55e3d148cbc6@linutronix.de

Changes in v3:
- Reintroduce CONFIG_CC_CAN_LINK_STATIC
- Enable CONFIG_ARCH_HAS_NOLIBC for m68k and SPARC
- Properly handle 'clean' target for userprogs
- Use ramfs over tmpfs to reduce dependencies
- Inherit userprogs byte order and ABI from kernel
- Drop now unnecessary "#ifndef NOLIBC"
- Pick up review tags
- Drop usage of __private in blob.h,
  sparse complains and it is not really necessary
- Fix execution on loongarch when using clang
- Drop userprogs libgcc handling, it was ugly and is not yet necessary
- Link to v2: https://lore.kernel.org/r/20250407-kunit-kselftests-v2-0-454114e287fd@linutronix.de

Changes in v2:
- Rebase onto v6.15-rc1
- Add documentation and kernel docs
- Resolve invalid kconfig breakages
- Drop already applied patch "kbuild: implement CONFIG_HEADERS_INSTALL for Usermode Linux"
- Drop userprogs CONFIG_WERROR integration, it doesn't need to be part of this series
- Replace patch prefix "kconfig" with "kbuild"
- Rename kunit_uapi_run_executable() to kunit_uapi_run_kselftest()
- Generate private, conflict-free symbols in the blob framework
- Handle kselftest exit codes
- Handle SIGABRT
- Forward output also to kunit debugfs log
- Install a fd=0 stdin filedescriptor
- Link to v1: https://lore.kernel.org/r/20250217-kunit-kselftests-v1-0-42b4524c3b0a@linutronix.de

---
Thomas Weißschuh (15):
      kbuild: userprogs: avoid duplication of flags inherited from kernel
      kbuild: userprogs: also inherit byte order and ABI from kernel
      kbuild: doc: add label for userprogs section
      init: re-add CONFIG_CC_CAN_LINK_STATIC
      init: add nolibc build support
      fs,fork,exit: export symbols necessary for KUnit UAPI support
      kunit: tool: Add test for nested test result reporting
      kunit: tool: Don't overwrite test status based on subtest counts
      kunit: tool: Parse skipped tests from kselftest.h
      kunit: Always descend into kunit directory during build
      kunit: qemu_configs: loongarch: Enable LSX/LSAX
      kunit: Introduce UAPI testing framework
      kunit: uapi: Add example for UAPI tests
      kunit: uapi: Introduce preinit executable
      kunit: uapi: Validate usability of /proc

 Documentation/dev-tools/kunit/api/index.rst        |   5 +
 Documentation/dev-tools/kunit/api/uapi.rst         |  14 +
 Documentation/kbuild/makefiles.rst                 |   2 +
 MAINTAINERS                                        |  11 +
 Makefile                                           |   7 +-
 fs/exec.c                                          |   2 +
 fs/file.c                                          |   1 +
 fs/filesystems.c                                   |   2 +
 fs/fs_struct.c                                     |   1 +
 fs/pipe.c                                          |   2 +
 include/kunit/uapi.h                               |  77 ++++++
 init/Kconfig                                       |   7 +
 init/Kconfig.nolibc                                |  15 +
 init/Makefile.nolibc                               |  13 +
 kernel/exit.c                                      |   3 +
 kernel/fork.c                                      |   2 +
 lib/Makefile                                       |   4 -
 lib/kunit/Kconfig                                  |  14 +
 lib/kunit/Makefile                                 |  30 +-
 lib/kunit/kunit-example-test.c                     |  15 +
 lib/kunit/kunit-example-uapi.c                     |  22 ++
 lib/kunit/kunit-test-uapi.c                        |  51 ++++
 lib/kunit/kunit-test.c                             |  23 +-
 lib/kunit/kunit-uapi.c                             | 305 +++++++++++++++++++++
 lib/kunit/uapi-preinit.c                           |  63 +++++
 tools/testing/kunit/kunit_parser.py                |  11 +-
 tools/testing/kunit/kunit_tool_test.py             |  11 +
 tools/testing/kunit/qemu_configs/loongarch.py      |   2 +
 .../test_is_test_passed-failure-nested.log         |  10 +
 .../test_data/test_is_test_passed-kselftest.log    |   3 +-
 30 files changed, 715 insertions(+), 13 deletions(-)
---
base-commit: 9d5898b413d17510b2a41664a42390a2c79f8bf4
change-id: 20241015-kunit-kselftests-56273bc40442

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@linutronix.de>

[PATCH v5 01/15] kbuild: userprogs: avoid duplication of flags inherited from kernel

[Thomas Weißschuh]

The duplication makes maintenance harder. Changes need to be done in two
places and the lines will grow overly long.

Use an intermediary variable instead.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
---
 Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 35e6e5240c61a8a329011929fcd0352b881dccdc..c4293cf91e968ca8ee64452841fb266e24df63f6 100644
--- a/Makefile
+++ b/Makefile
@@ -1130,8 +1130,9 @@ LDFLAGS_vmlinux	+= --emit-relocs --discard-none
 endif
 
 # Align the bit size of userspace programs with the kernel
-KBUILD_USERCFLAGS  += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
-KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
+USERFLAGS_FROM_KERNEL := -m32 -m64 --target=%
+KBUILD_USERCFLAGS  += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
+KBUILD_USERLDFLAGS += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
 
 # userspace programs are linked via the compiler, use the correct linker
 ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_LD_IS_LLD),yy)

-- 
2.50.0

[PATCH v5 02/15] kbuild: userprogs: also inherit byte order and ABI from kernel

[Thomas Weißschuh]

Make sure the byte order and ABI of the userprogs matches the one of the
kernel, similar to how the bit size is handled.
Otherwise the userprogs may not be executable.
This happens for example on powerpc little endian, or riscv32.

Reviewed-by: Nicolas Schier <n.schier@avm.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index c4293cf91e968ca8ee64452841fb266e24df63f6..b9aa1058321dabd3b3dd5610e45a2807dfa257f4 100644
--- a/Makefile
+++ b/Makefile
@@ -1129,8 +1129,8 @@ ifneq ($(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS),)
 LDFLAGS_vmlinux	+= --emit-relocs --discard-none
 endif
 
-# Align the bit size of userspace programs with the kernel
-USERFLAGS_FROM_KERNEL := -m32 -m64 --target=%
+# Align the bit size, byte order and architecture of userspace programs with the kernel
+USERFLAGS_FROM_KERNEL := -m32 -m64 -mlittle-endian -mbig-endian --target=% -march=% -mabi=%
 KBUILD_USERCFLAGS  += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
 KBUILD_USERLDFLAGS += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
 

-- 
2.50.0

[PATCH v5 03/15] kbuild: doc: add label for userprogs section

[Thomas Weißschuh]

Some upcoming documentation will link directly to the userprogs section.

Add a label to the section so it can be referenced.

Reviewed-by: Nicolas Schier <n.schier@avm.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
---
 Documentation/kbuild/makefiles.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index 8aef3650c1f32b6b197e0dc777e26775d371a081..c14c1f632f6069c8751c8388a35bef539e19f9e8 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -891,6 +891,8 @@ This is possible in two ways:
     This will tell kbuild to build lxdialog even if not referenced in
     any rule.
 
+.. _kbuild_userprogs:
+
 Userspace Program support
 =========================
 

-- 
2.50.0

[PATCH v5 04/15] init: re-add CONFIG_CC_CAN_LINK_STATIC

[Thomas Weißschuh]

For the kunit UAPI functionality this feature is needed again.

Effectively revert commit d1b99cdf22e0 ("init: remove unused
CONFIG_CC_CAN_LINK_STATIC"), which removed the option.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
---
 init/Kconfig | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/init/Kconfig b/init/Kconfig
index af4c2f0854554bbcdf193852cf5c1d2c2accc64f..26cafbad4f1560fb56b4bef31ae29baf54175661 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -87,6 +87,11 @@ config CC_CAN_LINK
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
 
+config CC_CAN_LINK_STATIC
+	bool
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
+
 # Fixed in GCC 14, 13.3, 12.4 and 11.5
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
 config GCC_ASM_GOTO_OUTPUT_BROKEN

-- 
2.50.0

[PATCH v5 05/15] init: add nolibc build support

[Thomas Weißschuh]

Building userspace applications through the kbuild "userprogs" framework
requires a libc. Kernel toolchains often do not contain a libc.
In this case it is useful to use the nolibc library from the kernel tree.
Nolibc does not support all architectures and requires compiler flags.

Add a kconfig option, so users can know where it is available and provide a
variable for common options.

Reviewed-by: Nicolas Schier <n.schier@avm.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 MAINTAINERS          |  2 ++
 init/Kconfig         |  2 ++
 init/Kconfig.nolibc  | 15 +++++++++++++++
 init/Makefile.nolibc | 13 +++++++++++++
 4 files changed, 32 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index a92290fffa163f9fe8fe3f04bf66426f9a894409..e806158cc6798cf97a4aab58c038fb5351d469aa 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17702,6 +17702,8 @@ M:	Willy Tarreau <w@1wt.eu>
 M:	Thomas Weißschuh <linux@weissschuh.net>
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/nolibc/linux-nolibc.git
+F:	init/Kconfig.nolibc
+F:	init/Makefile.nolibc
 F:	tools/include/nolibc/
 F:	tools/testing/selftests/nolibc/
 
diff --git a/init/Kconfig b/init/Kconfig
index 26cafbad4f1560fb56b4bef31ae29baf54175661..0af62f135192e0470e16eb6bb2fbb45ac38f4b81 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -92,6 +92,8 @@ config CC_CAN_LINK_STATIC
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
 
+source "init/Kconfig.nolibc"
+
 # Fixed in GCC 14, 13.3, 12.4 and 11.5
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
 config GCC_ASM_GOTO_OUTPUT_BROKEN
diff --git a/init/Kconfig.nolibc b/init/Kconfig.nolibc
new file mode 100644
index 0000000000000000000000000000000000000000..29cbc5437e70cbc5e256f00b74d0ab4801b40de7
--- /dev/null
+++ b/init/Kconfig.nolibc
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config ARCH_HAS_NOLIBC
+	bool
+	default y if ARM
+	default y if ARM64
+	default y if LOONGARCH
+	default y if M68K
+	default y if MIPS
+	default y if PPC
+	default y if RISCV
+	default y if S390
+	default y if SPARC
+	default y if UML_X86
+	default y if X86
diff --git a/init/Makefile.nolibc b/init/Makefile.nolibc
new file mode 100644
index 0000000000000000000000000000000000000000..dacc78ab4c81c93f3a24ebeb70e34253842f9a53
--- /dev/null
+++ b/init/Makefile.nolibc
@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0
+# Compiler flags, which are necessary to build userspace applications with the
+# in-kernel libc "nolibc".
+
+ifeq ($(and $(CONFIG_ARCH_HAS_NOLIBC),$(CONFIG_HEADERS_INSTALL)),y)
+
+NOLIBC_USERCFLAGS := -nostdlib -nostdinc -static -ffreestanding \
+		     -fno-asynchronous-unwind-tables -fno-stack-protector \
+		     -I$(objtree)/usr/include -I$(srctree)/tools/include/nolibc/
+
+NOLIBC_USERLDFLAGS := -nostdlib -nostdinc -static
+
+endif # CONFIG_ARCH_HAS_NOLIBC && CONFIG_HEADERS_INSTALL

-- 
2.50.0

[PATCH v5 06/15] fs,fork,exit: export symbols necessary for KUnit UAPI support

[Thomas Weißschuh]

The KUnit UAPI infrastructure starts userspace processes.
As it should be able to be built as a module, export the necessary symbols.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

---
For details on how these are used, see patch 12:
"kunit: Introduce UAPI testing framework".
Any ideas on how to make this work without new exports are very welcome.
---
 fs/exec.c        | 2 ++
 fs/file.c        | 1 +
 fs/filesystems.c | 2 ++
 fs/fs_struct.c   | 1 +
 fs/pipe.c        | 2 ++
 kernel/exit.c    | 3 +++
 kernel/fork.c    | 2 ++
 7 files changed, 13 insertions(+)

diff --git a/fs/exec.c b/fs/exec.c
index 1f5fdd2e096e392b342f122d35aba4cf035441c7..13f7f27641942eddcb179bdd93d99b799d155813 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -68,6 +68,7 @@
 #include <linux/user_events.h>
 #include <linux/rseq.h>
 #include <linux/ksm.h>
+#include <linux/export.h>
 
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
@@ -1919,6 +1920,7 @@ int kernel_execve(const char *kernel_filename,
 	putname(filename);
 	return retval;
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(kernel_execve, "kunit-uapi");
 
 static int do_execve(struct filename *filename,
 	const char __user *const __user *__argv,
diff --git a/fs/file.c b/fs/file.c
index 3a3146664cf37115624e12f7f06826d48827e9d7..89d07feb9c328337451ce40cb0f368b6cb986c2c 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1317,6 +1317,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags)
 	spin_unlock(&files->file_lock);
 	return err;
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(replace_fd, "kunit-uapi");
 
 /**
  * receive_fd() - Install received file into file descriptor table
diff --git a/fs/filesystems.c b/fs/filesystems.c
index 95e5256821a53494d88f496193305a2e50e04444..a3a588f387bbd8268246d1026389deaadf265d0b 100644
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -17,6 +17,7 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/fs_parser.h>
+#include <linux/export.h>
 
 /*
  * Handling of filesystem drivers list.
@@ -45,6 +46,7 @@ void put_filesystem(struct file_system_type *fs)
 {
 	module_put(fs->owner);
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(put_filesystem, "kunit-uapi");
 
 static struct file_system_type **find_filesystem(const char *name, unsigned len)
 {
diff --git a/fs/fs_struct.c b/fs/fs_struct.c
index 64c2d0814ed6889cc12603410e6e9dc44089586f..26340d225deba3f2ec30252293fdf417235a6a4a 100644
--- a/fs/fs_struct.c
+++ b/fs/fs_struct.c
@@ -46,6 +46,7 @@ void set_fs_pwd(struct fs_struct *fs, const struct path *path)
 	if (old_pwd.dentry)
 		path_put(&old_pwd);
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(set_fs_pwd, "kunit-uapi");
 
 static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
 {
diff --git a/fs/pipe.c b/fs/pipe.c
index 45077c37bad154ef146b047834d35d489fcc4d8d..d6cb743d2cfc041f08b498a5a764e9a96dc34069 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -27,6 +27,7 @@
 #include <linux/watch_queue.h>
 #include <linux/sysctl.h>
 #include <linux/sort.h>
+#include <linux/export.h>
 
 #include <linux/uaccess.h>
 #include <asm/ioctls.h>
@@ -971,6 +972,7 @@ int create_pipe_files(struct file **res, int flags)
 	file_set_fsnotify_mode(res[1], FMODE_NONOTIFY_PERM);
 	return 0;
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(create_pipe_files, "kunit-uapi");
 
 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 {
diff --git a/kernel/exit.c b/kernel/exit.c
index bd743900354ca5fc6c550f80e30393a632eb9a4e..610dffb1276ac60b475708587ca053f315fea9c3 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -70,6 +70,7 @@
 #include <linux/user_events.h>
 #include <linux/uaccess.h>
 #include <linux/pidfs.h>
+#include <linux/export.h>
 
 #include <uapi/linux/wait.h>
 
@@ -1005,6 +1006,7 @@ void __noreturn do_exit(long code)
 	lockdep_free_task(tsk);
 	do_task_dead();
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(do_exit, "kunit-uapi");
 
 void __noreturn make_task_dead(int signr)
 {
@@ -1887,6 +1889,7 @@ int kernel_wait(pid_t pid, int *stat)
 	put_pid(wo.wo_pid);
 	return ret;
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(kernel_wait, "kunit-uapi");
 
 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
 		int, options, struct rusage __user *, ru)
diff --git a/kernel/fork.c b/kernel/fork.c
index 1ee8eb11f38bae1d2eb6de9494aea94b7a19e6c3..5de7a9bc005ade6dcfbdfe1a63cadbef8782658c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -105,6 +105,7 @@
 #include <uapi/linux/pidfd.h>
 #include <linux/pidfs.h>
 #include <linux/tick.h>
+#include <linux/export.h>
 
 #include <asm/pgalloc.h>
 #include <linux/uaccess.h>
@@ -2676,6 +2677,7 @@ pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
 
 	return kernel_clone(&args);
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(user_mode_thread, "kunit-uapi");
 
 #ifdef __ARCH_WANT_SYS_FORK
 SYSCALL_DEFINE0(fork)

-- 
2.50.0

[PATCH v5 07/15] kunit: tool: Add test for nested test result reporting

[Thomas Weißschuh]

Currently there is a lack of tests validating the result reporting from
nested tests. Add one, it will also be used to validate upcoming changes
to the nested test parsing.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Rae Moar <rmoar@google.com>
---
 tools/testing/kunit/kunit_tool_test.py                         | 10 ++++++++++
 .../kunit/test_data/test_is_test_passed-failure-nested.log     |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/tools/testing/kunit/kunit_tool_test.py b/tools/testing/kunit/kunit_tool_test.py
index bbba921e0eacb18663abfcabb2bccf330d8666f5..b74dc05fc2fe5b3ff629172fc7aafeb5c3d29fb3 100755
--- a/tools/testing/kunit/kunit_tool_test.py
+++ b/tools/testing/kunit/kunit_tool_test.py
@@ -165,6 +165,16 @@ class KUnitParserTest(unittest.TestCase):
 		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.status)
 		self.assertEqual(result.counts.errors, 0)
 
+	def test_parse_failed_nested_tests_log(self):
+		nested_log = test_data_path('test_is_test_passed-failure-nested.log')
+		with open(nested_log) as file:
+			result = kunit_parser.parse_run_tests(file.readlines(), stdout)
+		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.status)
+		self.assertEqual(result.counts.failed, 2)
+		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.subtests[0].status)
+		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.subtests[1].status)
+		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.subtests[1].subtests[0].status)
+
 	def test_no_header(self):
 		empty_log = test_data_path('test_is_test_passed-no_tests_run_no_header.log')
 		with open(empty_log) as file:
diff --git a/tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log b/tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log
new file mode 100644
index 0000000000000000000000000000000000000000..2e528da39ab5b2be0fca6cf9160c10929fba3c9e
--- /dev/null
+++ b/tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log
@@ -0,0 +1,7 @@
+KTAP version 1
+1..2
+not ok 1 subtest 1
+    KTAP version 1
+    1..1
+        not ok 1 subsubtest 1
+not ok 2 subtest 2

-- 
2.50.0

[PATCH v5 08/15] kunit: tool: Don't overwrite test status based on subtest counts

[Thomas Weißschuh]

If a subtest itself reports success, but the outer testcase fails,
the whole testcase should be reported as a failure.
However the status is recalculated based on the test counts,
overwriting the outer test result.
Synthesize a failed test in this case to make sure the failure is not
swallowed.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
---
 tools/testing/kunit/kunit_parser.py                                  | 3 +++
 tools/testing/kunit/kunit_tool_test.py                               | 1 +
 tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/tools/testing/kunit/kunit_parser.py b/tools/testing/kunit/kunit_parser.py
index c176487356e6c94882046b19ea696d750905b8d5..a7a61e627e348db14b953080ec8789994fba955a 100644
--- a/tools/testing/kunit/kunit_parser.py
+++ b/tools/testing/kunit/kunit_parser.py
@@ -687,6 +687,9 @@ def bubble_up_test_results(test: Test) -> None:
 	elif test.counts.get_status() == TestStatus.TEST_CRASHED:
 		test.status = TestStatus.TEST_CRASHED
 
+	if status == TestStatus.FAILURE and test.counts.get_status() == TestStatus.SUCCESS:
+		counts.add_status(status)
+
 def parse_test(lines: LineStream, expected_num: int, log: List[str], is_subtest: bool, printer: Printer) -> Test:
 	"""
 	Finds next test to parse in LineStream, creates new Test object,
diff --git a/tools/testing/kunit/kunit_tool_test.py b/tools/testing/kunit/kunit_tool_test.py
index b74dc05fc2fe5b3ff629172fc7aafeb5c3d29fb3..d5bbcb95ab6abb1a8ee91439d87daaf29d159294 100755
--- a/tools/testing/kunit/kunit_tool_test.py
+++ b/tools/testing/kunit/kunit_tool_test.py
@@ -172,6 +172,7 @@ class KUnitParserTest(unittest.TestCase):
 		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.status)
 		self.assertEqual(result.counts.failed, 2)
 		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.subtests[0].status)
+		self.assertEqual(kunit_parser.TestStatus.SUCCESS, result.subtests[0].subtests[0].status)
 		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.subtests[1].status)
 		self.assertEqual(kunit_parser.TestStatus.FAILURE, result.subtests[1].subtests[0].status)
 
diff --git a/tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log b/tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log
index 2e528da39ab5b2be0fca6cf9160c10929fba3c9e..5498dfd0b0db24663e1a1e9bf78c587de6746522 100644
--- a/tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log
+++ b/tools/testing/kunit/test_data/test_is_test_passed-failure-nested.log
@@ -1,5 +1,8 @@
 KTAP version 1
 1..2
+    KTAP version 1
+    1..1
+        ok 1 test 1
 not ok 1 subtest 1
     KTAP version 1
     1..1

-- 
2.50.0

[PATCH v5 09/15] kunit: tool: Parse skipped tests from kselftest.h

[Thomas Weißschuh]

Skipped tests reported by kselftest.h use a different format than KTAP,
there is no explicit test name. Normally the test name is part of the
free-form string after the SKIP keyword:

	ok 3 # SKIP test: some reason

Extend the parser to handle those correctly. Use the free-form string as
test name instead.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
---
 tools/testing/kunit/kunit_parser.py                             | 8 +++++---
 tools/testing/kunit/test_data/test_is_test_passed-kselftest.log | 3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/tools/testing/kunit/kunit_parser.py b/tools/testing/kunit/kunit_parser.py
index a7a61e627e348db14b953080ec8789994fba955a..5338489dcbe48c01912c5e8f02a481d6860a5d15 100644
--- a/tools/testing/kunit/kunit_parser.py
+++ b/tools/testing/kunit/kunit_parser.py
@@ -352,9 +352,9 @@ def parse_test_plan(lines: LineStream, test: Test) -> bool:
 	lines.pop()
 	return True
 
-TEST_RESULT = re.compile(r'^\s*(ok|not ok) ([0-9]+) (- )?([^#]*)( # .*)?$')
+TEST_RESULT = re.compile(r'^\s*(ok|not ok) ([0-9]+) ?(- )?([^#]*)( # .*)?$')
 
-TEST_RESULT_SKIP = re.compile(r'^\s*(ok|not ok) ([0-9]+) (- )?(.*) # SKIP(.*)$')
+TEST_RESULT_SKIP = re.compile(r'^\s*(ok|not ok) ([0-9]+) ?(- )?(.*) # SKIP ?(.*)$')
 
 def peek_test_name_match(lines: LineStream, test: Test) -> bool:
 	"""
@@ -379,6 +379,8 @@ def peek_test_name_match(lines: LineStream, test: Test) -> bool:
 	if not match:
 		return False
 	name = match.group(4)
+	if not name:
+		return False
 	return name == test.name
 
 def parse_test_result(lines: LineStream, test: Test,
@@ -416,7 +418,7 @@ def parse_test_result(lines: LineStream, test: Test,
 
 	# Set name of test object
 	if skip_match:
-		test.name = skip_match.group(4)
+		test.name = skip_match.group(4) or skip_match.group(5)
 	else:
 		test.name = match.group(4)
 
diff --git a/tools/testing/kunit/test_data/test_is_test_passed-kselftest.log b/tools/testing/kunit/test_data/test_is_test_passed-kselftest.log
index 65d3f27feaf22a3f47ed831c4c24f6f11c625a92..30d9ef18bcec177067288d5242771236f29b7d56 100644
--- a/tools/testing/kunit/test_data/test_is_test_passed-kselftest.log
+++ b/tools/testing/kunit/test_data/test_is_test_passed-kselftest.log
@@ -1,5 +1,5 @@
 TAP version 13
-1..2
+1..3
 # selftests: membarrier: membarrier_test_single_thread
 # TAP version 13
 # 1..2
@@ -12,3 +12,4 @@ ok 1 selftests: membarrier: membarrier_test_single_thread
 # ok 1 sys_membarrier available
 # ok 2 sys membarrier invalid command test: command = -1, flags = 0, errno = 22. Failed as expected
 ok 2 selftests: membarrier: membarrier_test_multi_thread
+ok 3 # SKIP selftests: membarrier: membarrier_test_multi_thread

-- 
2.50.0

[PATCH v5 10/15] kunit: Always descend into kunit directory during build

[Thomas Weißschuh]

An upcoming change will add 'userprogs' to the kunit subdirectory.
For kbuild to properly clean up these build artifacts the subdirectory
needs to be always processed.

Pushing the special logic for hook.o into the kunit Makefile also makes the
logic easier to understand.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
---
 lib/Makefile       | 4 ----
 lib/kunit/Makefile | 2 +-
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/lib/Makefile b/lib/Makefile
index c38582f187dd81916113319072e5cfef26f26c84..698566135091cc3bf0054f1954b434dc3325364a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -108,11 +108,7 @@ test_fpu-y := test_fpu_glue.o test_fpu_impl.o
 CFLAGS_test_fpu_impl.o += $(CC_FLAGS_FPU)
 CFLAGS_REMOVE_test_fpu_impl.o += $(CC_FLAGS_NO_FPU)
 
-# Some KUnit files (hooks.o) need to be built-in even when KUnit is a module,
-# so we can't just use obj-$(CONFIG_KUNIT).
-ifdef CONFIG_KUNIT
 obj-y += kunit/
-endif
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 5aa51978e456ab3bb60c12071a26cf2bdcb1b508..656f1fa35abcc635e67d5b4cb1bc586b48415ac5 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -17,7 +17,7 @@ kunit-objs +=				debugfs.o
 endif
 
 # KUnit 'hooks' are built-in even when KUnit is built as a module.
-obj-y +=				hooks.o
+obj-$(if $(CONFIG_KUNIT),y) +=		hooks.o
 
 obj-$(CONFIG_KUNIT_TEST) +=		kunit-test.o
 obj-$(CONFIG_KUNIT_TEST) +=		platform-test.o

-- 
2.50.0

[PATCH v5 11/15] kunit: qemu_configs: loongarch: Enable LSX/LSAX

[Thomas Weißschuh]

The upcoming kunit UAPI framework will run userspace executables as part of
kunit. These may use the LSX or LASX instructions.

Make sure the kunit kernel can handle these instructions.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
---
 tools/testing/kunit/qemu_configs/loongarch.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/kunit/qemu_configs/loongarch.py b/tools/testing/kunit/qemu_configs/loongarch.py
index a92422967d1da9f1658ef1e80d0d7365ddbae307..1dba755284f11ffc94d8946105b0cfa49cb6f604 100644
--- a/tools/testing/kunit/qemu_configs/loongarch.py
+++ b/tools/testing/kunit/qemu_configs/loongarch.py
@@ -11,6 +11,8 @@ CONFIG_PVPANIC_PCI=y
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_OF_PLATFORM=y
+CONFIG_CPU_HAS_LSX=y
+CONFIG_CPU_HAS_LASX=y
 ''',
 			   qemu_arch='loongarch64',
 			   kernel_path='arch/loongarch/boot/vmlinux.elf',

-- 
2.50.0

[PATCH v5 12/15] kunit: Introduce UAPI testing framework

[Thomas Weißschuh]

Enable running UAPI tests as part of kunit.
The selftests are embedded into the kernel image and their output is
forwarded to kunit for unified reporting.

The implementation reuses parts of usermode drivers and usermode
helpers. However these frameworks are not used directly as they make it
impossible to retrieve a thread's exit code.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

---
This is similar to the usermode helper framework, but not using it as there
would be some issues. It gets neutered by CONFIG_STATIC_USERMODEHELPER_PATH.
That could be worked around by overriding sub_info->path, but that would be
a hack. Also it does not allow the implementation of a custom wait routine
to forward the process output to KUnit as implemented in
kunit_uapi_forward_to_printk(). That may be solved by adding another thread,
or messing with the internals of the framework, but that would also be ugly.
---
 Documentation/dev-tools/kunit/api/index.rst |   5 +
 Documentation/dev-tools/kunit/api/uapi.rst  |  14 ++
 MAINTAINERS                                 |   6 +
 include/kunit/uapi.h                        |  77 +++++++
 lib/kunit/Kconfig                           |  14 ++
 lib/kunit/Makefile                          |   2 +
 lib/kunit/kunit-uapi.c                      | 300 ++++++++++++++++++++++++++++
 7 files changed, 418 insertions(+)

diff --git a/Documentation/dev-tools/kunit/api/index.rst b/Documentation/dev-tools/kunit/api/index.rst
index 5cdb552a0808f25baeff5e47a9227b7b62c69e40..34d8fee9a97059d6da919a6fb1a7e359b5e0beef 100644
--- a/Documentation/dev-tools/kunit/api/index.rst
+++ b/Documentation/dev-tools/kunit/api/index.rst
@@ -9,6 +9,7 @@ API Reference
 	test
 	resource
 	functionredirection
+	uapi
 	clk
 	of
 	platformdevice
@@ -32,6 +33,10 @@ Documentation/dev-tools/kunit/api/functionredirection.rst
 
  - Documents the KUnit Function Redirection API
 
+Documentation/dev-tools/kunit/api/uapi.rst
+
+ - Documents the KUnit Userspace testing API
+
 Driver KUnit API
 ================
 
diff --git a/Documentation/dev-tools/kunit/api/uapi.rst b/Documentation/dev-tools/kunit/api/uapi.rst
new file mode 100644
index 0000000000000000000000000000000000000000..1f01b5c6c9db42f603f6507f2f33ef388f5b91d7
--- /dev/null
+++ b/Documentation/dev-tools/kunit/api/uapi.rst
@@ -0,0 +1,14 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
+Userspace Test API
+==================
+
+This file documents all of the userspace testing API.
+Userspace tests are built as :ref:`kbuild userprogs <kbuild_userprogs>`,
+linked statically and without any external dependencies.
+
+For the widest platform compatibility they should use nolibc, as provided by `init/Makefile.nolibc`.
+
+.. kernel-doc:: include/kunit/uapi.h
+   :internal:
diff --git a/MAINTAINERS b/MAINTAINERS
index e806158cc6798cf97a4aab58c038fb5351d469aa..0f60501c6de570723123b24eb930d15f1bd956eb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13540,6 +13540,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/leds/backlight/kinetic,ktz8866.yaml
 F:	drivers/video/backlight/ktz8866.c
 
+KUNIT UAPI TESTING FRAMEWORK (in addition to KERNEL UNIT TESTING FRAMEWORK)
+M:	Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+S:	Maintained
+F:	include/kunit/uapi.h
+F:	lib/kunit/kunit-uapi.c
+
 KVM PARAVIRT (KVM/paravirt)
 M:	Paolo Bonzini <pbonzini@redhat.com>
 R:	Vitaly Kuznetsov <vkuznets@redhat.com>
diff --git a/include/kunit/uapi.h b/include/kunit/uapi.h
new file mode 100644
index 0000000000000000000000000000000000000000..a5c923f5d82a91e0acd9dc17369f84f00b7d342f
--- /dev/null
+++ b/include/kunit/uapi.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KUnit Userspace testing API.
+ *
+ * Copyright (C) 2025, Linutronix GmbH.
+ * Author: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+ */
+
+#ifndef _KUNIT_UAPI_H
+#define _KUNIT_UAPI_H
+
+#include <linux/types.h>
+
+struct kunit;
+
+/**
+ * struct kunit_uapi_blob - Blob embedded build artifact
+ * @path: Path of the embedded artifact.
+ * @data: Start of the embedded data in memory.
+ * @end: End of the embedded data in memory.
+ */
+struct kunit_uapi_blob {
+	const char *const path;
+	const u8 *data;
+	const u8 *end;
+};
+
+#if IS_ENABLED(CONFIG_KUNIT_UAPI)
+
+/**
+ * KUNIT_UAPI_EMBED_BLOB() - Embed another build artifact into the kernel
+ * @_name: The name of symbol under which the artifact is embedded.
+ * @_path: Path to the artifact on disk.
+ *
+ * Embeds a build artifact like a userspace executable into the kernel or current module.
+ * The build artifact is read from disk and needs to be already built.
+ */
+#define KUNIT_UAPI_EMBED_BLOB(_name, _path)					\
+	asm (									\
+	"	.pushsection .rodata, \"a\"				\n"	\
+	"	.global " __stringify(CONCATENATE(_name, _data)) "	\n"	\
+	__stringify(CONCATENATE(_name, _data)) ":			\n"	\
+	"	.incbin " __stringify(_path) "				\n"	\
+	"	.size " __stringify(CONCATENATE(_name, _data)) ", "		\
+			". - " __stringify(CONCATENATE(_name, _data)) "	\n"	\
+	"	.global " __stringify(CONCATENATE(_name, _end)) "	\n"	\
+	__stringify(CONCATENATE(_name, _end)) ":			\n"	\
+	"	.popsection						\n"	\
+	);									\
+										\
+	extern const char CONCATENATE(_name, _data)[];				\
+	extern const char CONCATENATE(_name, _end)[];				\
+										\
+	static const struct kunit_uapi_blob _name = {				\
+		.path	= _path,						\
+		.data	= CONCATENATE(_name, _data),				\
+		.end	= CONCATENATE(_name, _end),				\
+	}									\
+
+#else /* !CONFIG_KUNIT_UAPI */
+
+/* Unresolved external reference, to be optimized away */
+#define KUNIT_UAPI_EMBED_BLOB(_name, _path)					\
+	extern const struct kunit_uapi_blob _name
+
+#endif /* CONFIG_KUNIT_UAPI */
+
+/**
+ * kunit_uapi_run_kselftest() - Run a userspace kselftest as part of kunit
+ * @test: The test context object.
+ * @executable: kselftest executable to run
+ *
+ * Runs the kselftest and forwards its TAP output and exit status to kunit.
+ */
+void kunit_uapi_run_kselftest(struct kunit *test, const struct kunit_uapi_blob *executable);
+
+#endif /* _KUNIT_UAPI_H */
diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig
index a97897edd9642f3e5df7fdd9dee26ee5cf00d6a4..c88e6cf5610bc8246c94d16b9025461f0cd3b2d2 100644
--- a/lib/kunit/Kconfig
+++ b/lib/kunit/Kconfig
@@ -93,4 +93,18 @@ config KUNIT_AUTORUN_ENABLED
 	  In most cases this should be left as Y. Only if additional opt-in
 	  behavior is needed should this be set to N.
 
+config KUNIT_UAPI
+	tristate "KUnit UAPI testing framework"
+	depends on KUNIT
+	depends on CC_CAN_LINK_STATIC || ARCH_HAS_NOLIBC
+	depends on !LTO_CLANG # https://github.com/llvm/llvm-project/issues/112920
+	select HEADERS_INSTALL
+	default KUNIT
+	help
+	  Enables support for building and running userspace selftests as part of kunit.
+	  These tests should be statically linked and use kselftest.h or kselftest_harness.h
+	  for status reporting.
+
+	  In most cases this should be left as Y.
+
 endif # KUNIT
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 656f1fa35abcc635e67d5b4cb1bc586b48415ac5..6059621a2d32c8e7384acda59793f05826af8c81 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -12,6 +12,8 @@ kunit-objs +=				test.o \
 					device.o \
 					platform.o
 
+obj-$(CONFIG_KUNIT_UAPI) +=		kunit-uapi.o
+
 ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
 kunit-objs +=				debugfs.o
 endif
diff --git a/lib/kunit/kunit-uapi.c b/lib/kunit/kunit-uapi.c
new file mode 100644
index 0000000000000000000000000000000000000000..24356f68eca0df07032fb8a9e92daffde01b21d3
--- /dev/null
+++ b/lib/kunit/kunit-uapi.c
@@ -0,0 +1,300 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit Userspace testing API.
+ *
+ * Copyright (C) 2025, Linutronix GmbH.
+ * Author: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+ */
+
+#include <linux/binfmts.h>
+#include <linux/export.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/fs_struct.h>
+#include <linux/pid.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/sched/task.h>
+#include <linux/types.h>
+
+#include <kunit/test.h>
+#include <kunit/uapi.h>
+
+#define KSFT_PASS	0
+#define KSFT_FAIL	1
+#define KSFT_XFAIL	2
+#define KSFT_XPASS	3
+#define KSFT_SKIP	4
+
+static struct vfsmount *kunit_uapi_mount_ramfs(void)
+{
+	struct file_system_type *type;
+	struct vfsmount *mnt;
+
+	type = get_fs_type("ramfs");
+	if (!type)
+		return ERR_PTR(-ENODEV);
+
+	/* FIXME
+	 * The mount setup is supposed to look like this:
+	 * kunit_uapi_mount_ramfs() sets up a private mount,
+	 * with nothing visible except the new tmpfs.
+	 * Then each executable execution gets a new namespace on top of that
+	 * on which it can mount whatever it needs.
+	 * However I didn't manage to set this up, so keep everything simple
+	 * for now and let somebody familiar with the VFS figure this out.
+	 */
+
+	mnt = kern_mount(type);
+	put_filesystem(type);
+
+	return mnt;
+}
+
+static int kunit_uapi_write_file(struct vfsmount *mnt, const char *name, mode_t mode,
+				 const u8 *data, size_t size)
+{
+	struct file *file;
+	ssize_t written;
+
+	file = file_open_root_mnt(mnt, name, O_CREAT | O_WRONLY, mode);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	written = kernel_write(file, data, size, NULL);
+	filp_close(file, NULL);
+	if (written != size) {
+		if (written >= 0)
+			return -ENOMEM;
+		return written;
+	}
+
+	/* Flush delayed fput so exec can open the file read-only */
+	flush_delayed_fput();
+
+	return 0;
+}
+
+static int kunit_uapi_write_executable(struct vfsmount *mnt,
+				       const struct kunit_uapi_blob *executable)
+{
+	return kunit_uapi_write_file(mnt, kbasename(executable->path), 0755,
+				     executable->data, executable->end - executable->data);
+}
+
+struct kunit_uapi_user_mode_thread_ctx {
+	const char *executable;
+
+	/* Signals mnt, out, pwd and tgid */
+	struct completion setup_done;
+	struct vfsmount *mnt;
+	struct file *out;
+	struct path pwd;
+	pid_t tgid;
+
+	/* Valid after wait(tgid) */
+	int exec_err;
+};
+
+static int kunit_uapi_user_mode_thread_init(void *data)
+{
+	struct kunit_uapi_user_mode_thread_ctx *ctx = data;
+	const char *const argv[] = {
+		ctx->executable,
+		NULL
+	};
+	struct file *out[2];
+	int err;
+
+	err = create_pipe_files(out, 0);
+	if (err)
+		return err;
+
+	/* stdin, use the *write* end to the pipe to have an unreadable input */
+	err = replace_fd(0, out[1], 0);
+	if (err < 0) {
+		fput(out[0]);
+		fput(out[1]);
+		return err;
+	}
+
+	/* stdout */
+	err = replace_fd(1, out[1], 0);
+	if (err < 0) {
+		replace_fd(0, NULL, 0);
+		fput(out[0]);
+		fput(out[1]);
+		return err;
+	}
+
+	/* stderr */
+	err = replace_fd(2, out[1], 0);
+	if (err < 0) {
+		replace_fd(0, NULL, 0);
+		replace_fd(1, NULL, 0);
+		fput(out[0]);
+		fput(out[1]);
+		return err;
+	}
+
+	fput(out[1]);
+
+	ctx->out = out[0];
+	ctx->tgid = current->tgid;
+
+	set_fs_pwd(current->fs, &ctx->pwd);
+	kernel_sigaction(SIGKILL, SIG_DFL);
+	kernel_sigaction(SIGABRT, SIG_DFL);
+
+	complete(&ctx->setup_done);
+	ctx->exec_err = kernel_execve(ctx->executable, argv, NULL);
+	if (!ctx->exec_err)
+		return 0;
+	do_exit(0);
+}
+
+static size_t kunit_uapi_printk_subtest_lines(struct kunit *test, char *buf, size_t s)
+{
+	const char *ptr = buf, *newline;
+	size_t n;
+
+	while (s) {
+		newline = strnchr(ptr, s, '\n');
+		if (!newline)
+			break;
+
+		n = newline - ptr + 1;
+
+		kunit_log(KERN_INFO, test, KUNIT_SUBSUBTEST_INDENT "%.*s", (int)n, ptr);
+		ptr += n;
+		s -= n;
+	}
+
+	memmove(buf, ptr, s);
+
+	return s;
+}
+
+static int kunit_uapi_forward_to_printk(struct kunit *test, struct file *output)
+{
+	/*
+	 * printk() automatically adds a newline after each message.
+	 * Therefore only fully accumulated lines can be forwarded.
+	 * Each line needs to fit into the buffer below.
+	 */
+	char buf[512];
+	size_t s = 0;
+	ssize_t n;
+
+	while (1) {
+		n = kernel_read(output, buf + s, sizeof(buf) - s, NULL);
+		if (n <= 0)
+			return n;
+		s = kunit_uapi_printk_subtest_lines(test, buf, s + n);
+	}
+}
+
+static void kunit_uapi_kill_pid(pid_t pid)
+{
+	struct pid *p;
+
+	p = find_get_pid(pid);
+	kill_pid(p, SIGKILL, 1);
+	put_pid(p);
+}
+
+static int kunit_uapi_run_executable_in_mount(struct kunit *test, const char *executable,
+						   struct vfsmount *mnt)
+{
+	struct kunit_uapi_user_mode_thread_ctx ctx = {
+		.setup_done	= COMPLETION_INITIALIZER_ONSTACK(ctx.setup_done),
+		.executable	= executable,
+		.pwd		= {
+			.mnt	= mnt,
+			.dentry	= mnt->mnt_root,
+		},
+	};
+	int forward_err, wait_err, ret = 0;
+	pid_t pid;
+
+	/* If SIGCHLD is ignored do_wait won't populate the status. */
+	kernel_sigaction(SIGCHLD, SIG_DFL);
+	pid = user_mode_thread(kunit_uapi_user_mode_thread_init, &ctx, SIGCHLD);
+	if (pid < 0) {
+		kernel_sigaction(SIGCHLD, SIG_IGN);
+		return pid;
+	}
+
+	wait_for_completion(&ctx.setup_done);
+
+	forward_err = kunit_uapi_forward_to_printk(test, ctx.out);
+	if (forward_err)
+		kunit_uapi_kill_pid(ctx.tgid);
+
+	wait_err = kernel_wait(ctx.tgid, &ret);
+
+	/* Restore default kernel sig handler */
+	kernel_sigaction(SIGCHLD, SIG_IGN);
+
+	if (ctx.exec_err)
+		return ctx.exec_err;
+	if (forward_err)
+		return forward_err;
+	if (wait_err < 0)
+		return wait_err;
+	return ret;
+}
+
+static int kunit_uapi_run_executable(struct kunit *test,
+				     const struct kunit_uapi_blob *executable)
+{
+	const char *exe_name = kbasename(executable->path);
+	struct vfsmount *mnt;
+	int err;
+
+	mnt = kunit_uapi_mount_ramfs();
+	if (IS_ERR(mnt))
+		return PTR_ERR(mnt);
+
+	err = kunit_uapi_write_executable(mnt, executable);
+
+	if (!err)
+		err = kunit_uapi_run_executable_in_mount(test, exe_name, mnt);
+
+	kern_unmount(mnt);
+
+	return err;
+}
+
+void kunit_uapi_run_kselftest(struct kunit *test, const struct kunit_uapi_blob *executable)
+{
+	u8 exit_code, exit_signal;
+	int err;
+
+	err = kunit_uapi_run_executable(test, executable);
+	if (err < 0)
+		KUNIT_FAIL_AND_ABORT(test, "Could not run test executable: %pe\n", ERR_PTR(err));
+
+	exit_code = err >> 8;
+	exit_signal = err & 0xff;
+
+	if (exit_signal)
+		KUNIT_FAIL_AND_ABORT(test, "kselftest exited with signal: %d\n", exit_signal);
+	else if (exit_code == KSFT_PASS)
+		; /* Noop */
+	else if (exit_code == KSFT_FAIL)
+		KUNIT_FAIL_AND_ABORT(test, "kselftest exited with code KSFT_FAIL\n");
+	else if (exit_code == KSFT_XPASS)
+		KUNIT_FAIL_AND_ABORT(test, "kselftest exited with code KSFT_XPASS\n");
+	else if (exit_code == KSFT_XFAIL)
+		; /* Noop */
+	else if (exit_code == KSFT_SKIP)
+		kunit_mark_skipped(test, "kselftest exited with code KSFT_SKIP\n");
+	else
+		KUNIT_FAIL_AND_ABORT(test, "kselftest exited with unknown exit code: %d\n",
+				     exit_code);
+}
+EXPORT_SYMBOL_GPL(kunit_uapi_run_kselftest);
+
+MODULE_DESCRIPTION("KUnit UAPI testing framework");
+MODULE_AUTHOR("Thomas Weißschuh <thomas.weissschuh@linutronix.de");
+MODULE_LICENSE("GPL");

-- 
2.50.0

[PATCH v5 13/15] kunit: uapi: Add example for UAPI tests

[Thomas Weißschuh]

Extend the example to show how to run a userspace executable.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
---
 MAINTAINERS                    |  1 +
 lib/kunit/Makefile             | 10 ++++++++++
 lib/kunit/kunit-example-test.c | 15 +++++++++++++++
 lib/kunit/kunit-example-uapi.c | 22 ++++++++++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 0f60501c6de570723123b24eb930d15f1bd956eb..b1405f0a0e638d1654d9dc9e51d784ddc838cf5b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13544,6 +13544,7 @@ KUNIT UAPI TESTING FRAMEWORK (in addition to KERNEL UNIT TESTING FRAMEWORK)
 M:	Thomas Weißschuh <thomas.weissschuh@linutronix.de>
 S:	Maintained
 F:	include/kunit/uapi.h
+F:	lib/kunit/kunit-example-uapi.c
 F:	lib/kunit/kunit-uapi.c
 
 KVM PARAVIRT (KVM/paravirt)
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 6059621a2d32c8e7384acda59793f05826af8c81..2434470e998525e5667ebc207d11659835b5e888 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -1,3 +1,5 @@
+include $(srctree)/init/Makefile.nolibc
+
 obj-$(CONFIG_KUNIT) +=			kunit.o
 
 kunit-objs +=				test.o \
@@ -31,3 +33,11 @@ obj-$(CONFIG_KUNIT_TEST) +=		assert_test.o
 endif
 
 obj-$(CONFIG_KUNIT_EXAMPLE_TEST) +=	kunit-example-test.o
+
+userprogs +=				kunit-example-uapi
+kunit-example-uapi-userccflags :=	-static $(NOLIBC_USERCFLAGS)
+
+ifdef CONFIG_KUNIT_UAPI
+CFLAGS_kunit-example-test.o :=		-Wa,-I$(obj)
+$(obj)/kunit-example-test.o: $(obj)/kunit-example-uapi
+endif
diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
index 3056d6bc705d0a8f196f0f4412e679dbb0e03114..0c5e1e59f9358b84aee2621e342d824a2f99f9aa 100644
--- a/lib/kunit/kunit-example-test.c
+++ b/lib/kunit/kunit-example-test.c
@@ -8,6 +8,7 @@
 
 #include <kunit/test.h>
 #include <kunit/static_stub.h>
+#include <kunit/uapi.h>
 
 /*
  * This is the most fundamental element of KUnit, the test case. A test case
@@ -277,6 +278,19 @@ static void example_slow_test(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, 1 + 1, 2);
 }
 
+/*
+ * This test shows the usage of UAPI tests.
+ */
+static void example_uapi_test(struct kunit *test)
+{
+	KUNIT_UAPI_EMBED_BLOB(kunit_example_uapi, "kunit-example-uapi");
+
+	if (IS_ENABLED(CONFIG_KUNIT_UAPI))
+		kunit_uapi_run_kselftest(test, &kunit_example_uapi);
+	else
+		kunit_skip(test, "CONFIG_KUNIT_UAPI is not enabled");
+}
+
 /*
  * Here we make a list of all the test cases we want to add to the test suite
  * below.
@@ -297,6 +311,7 @@ static struct kunit_case example_test_cases[] = {
 	KUNIT_CASE(example_priv_test),
 	KUNIT_CASE_PARAM(example_params_test, example_gen_params),
 	KUNIT_CASE_SLOW(example_slow_test),
+	KUNIT_CASE(example_uapi_test),
 	{}
 };
 
diff --git a/lib/kunit/kunit-example-uapi.c b/lib/kunit/kunit-example-uapi.c
new file mode 100644
index 0000000000000000000000000000000000000000..4ce657050dd4a576632a41ca0309c4cb5134ce14
--- /dev/null
+++ b/lib/kunit/kunit-example-uapi.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit Userspace example test.
+ *
+ * Copyright (C) 2025, Linutronix GmbH.
+ * Author: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+ *
+ * This is *userspace* code.
+ */
+
+#include "../../tools/testing/selftests/kselftest.h"
+
+int main(void)
+{
+	ksft_print_header();
+	ksft_set_plan(4);
+	ksft_test_result_pass("userspace test 1\n");
+	ksft_test_result_pass("userspace test 2\n");
+	ksft_test_result_skip("userspace test 3: some reason\n");
+	ksft_test_result_pass("userspace test 4\n");
+	ksft_finished();
+}

-- 
2.50.0

[PATCH v5 14/15] kunit: uapi: Introduce preinit executable

[Thomas Weißschuh]

UAPI selftests may expect a "normal" userspace environment.
For example the normal kernel API pseudo-filesystems should be mounted.
This could be done from kernel code but it is non-idiomatic.

Add a preinit userspace executable which performs these setup steps
before running the final test executable.
This preinit executable is only ever run from the kernel.
Give it access to autoconf.h and kconfig.h to adapt itself to the
tested kernel.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
---
 MAINTAINERS              |  1 +
 lib/kunit/Makefile       |  7 ++++++
 lib/kunit/kunit-uapi.c   |  9 +++++--
 lib/kunit/uapi-preinit.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 78 insertions(+), 2 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index b1405f0a0e638d1654d9dc9e51d784ddc838cf5b..e81dfa180ab374ef91c7a45e546e6e9a8f454fa7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13546,6 +13546,7 @@ S:	Maintained
 F:	include/kunit/uapi.h
 F:	lib/kunit/kunit-example-uapi.c
 F:	lib/kunit/kunit-uapi.c
+F:	lib/kunit/uapi-preinit.c
 
 KVM PARAVIRT (KVM/paravirt)
 M:	Paolo Bonzini <pbonzini@redhat.com>
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 2434470e998525e5667ebc207d11659835b5e888..e52a31b0852caef5669f11f6059c29ce5911aa43 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -14,8 +14,15 @@ kunit-objs +=				test.o \
 					device.o \
 					platform.o
 
+userprogs +=				uapi-preinit
+uapi-preinit-userccflags +=		-static $(NOLIBC_USERCFLAGS) \
+					-include include/generated/autoconf.h \
+					-include $(srctree)/tools/include/linux/kconfig.h
 obj-$(CONFIG_KUNIT_UAPI) +=		kunit-uapi.o
 
+CFLAGS_kunit-uapi.o :=			-Wa,-I$(obj)
+$(obj)/kunit-uapi.o: $(obj)/uapi-preinit
+
 ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
 kunit-objs +=				debugfs.o
 endif
diff --git a/lib/kunit/kunit-uapi.c b/lib/kunit/kunit-uapi.c
index 24356f68eca0df07032fb8a9e92daffde01b21d3..382a2bfee3c78a6e042a56a9ccdefcd55b5265a1 100644
--- a/lib/kunit/kunit-uapi.c
+++ b/lib/kunit/kunit-uapi.c
@@ -25,6 +25,8 @@
 #define KSFT_XPASS	3
 #define KSFT_SKIP	4
 
+KUNIT_UAPI_EMBED_BLOB(kunit_uapi_preinit, "uapi-preinit");
+
 static struct vfsmount *kunit_uapi_mount_ramfs(void)
 {
 	struct file_system_type *type;
@@ -146,7 +148,7 @@ static int kunit_uapi_user_mode_thread_init(void *data)
 	kernel_sigaction(SIGABRT, SIG_DFL);
 
 	complete(&ctx->setup_done);
-	ctx->exec_err = kernel_execve(ctx->executable, argv, NULL);
+	ctx->exec_err = kernel_execve(kbasename(kunit_uapi_preinit.path), argv, NULL);
 	if (!ctx->exec_err)
 		return 0;
 	do_exit(0);
@@ -255,7 +257,10 @@ static int kunit_uapi_run_executable(struct kunit *test,
 	if (IS_ERR(mnt))
 		return PTR_ERR(mnt);
 
-	err = kunit_uapi_write_executable(mnt, executable);
+	err = kunit_uapi_write_executable(mnt, &kunit_uapi_preinit);
+
+	if (!err)
+		err = kunit_uapi_write_executable(mnt, executable);
 
 	if (!err)
 		err = kunit_uapi_run_executable_in_mount(test, exe_name, mnt);
diff --git a/lib/kunit/uapi-preinit.c b/lib/kunit/uapi-preinit.c
new file mode 100644
index 0000000000000000000000000000000000000000..81182039965a8c93aebb2d5d76f4113bfef277a6
--- /dev/null
+++ b/lib/kunit/uapi-preinit.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit Userspace environment setup.
+ *
+ * Copyright (C) 2025, Linutronix GmbH.
+ * Author: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+ *
+ * This is *userspace* code.
+ */
+
+#include <sys/mount.h>
+#include <sys/stat.h>
+
+#include "../../tools/testing/selftests/kselftest.h"
+
+static int setup_api_mount(const char *target, const char *fstype)
+{
+	int ret;
+
+	ret = mkdir(target, 0755);
+	if (ret && errno != EEXIST)
+		return -errno;
+
+	ret = mount("none", target, fstype, 0, NULL);
+	if (ret && errno != EBUSY)
+		return -errno;
+
+	return 0;
+}
+
+static void exit_failure(const char *stage, int err)
+{
+	/* If preinit fails synthesize a failed test report. */
+	ksft_print_header();
+	ksft_set_plan(1);
+	ksft_test_result_fail("Failed during test setup: %s: %s\n", stage, strerror(-err));
+	ksft_finished();
+}
+
+int main(int argc, char **argv, char **envp)
+{
+	int ret;
+
+	ret = setup_api_mount("/proc", "proc");
+	if (ret)
+		exit_failure("mount /proc", ret);
+
+	ret = setup_api_mount("/sys", "sysfs");
+	if (ret)
+		exit_failure("mount /sys", ret);
+
+	if (IS_ENABLED(CONFIG_DEVTMPFS)) {
+		ret = setup_api_mount("/dev", "devtmpfs");
+		if (ret)
+			exit_failure("mount /dev", ret);
+	}
+
+	ret = execve(argv[0], argv, envp);
+	if (ret)
+		exit_failure("execve", ret);
+
+	return 0;
+}

-- 
2.50.0

[PATCH v5 15/15] 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@linutronix.de>
---
 MAINTAINERS                 |  1 +
 lib/kunit/Makefile          |  9 ++++++++
 lib/kunit/kunit-test-uapi.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
 lib/kunit/kunit-test.c      | 23 +++++++++++++++++++-
 4 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index e81dfa180ab374ef91c7a45e546e6e9a8f454fa7..d86e8e0bfee75acecfeb9569d53ea8ea99727985 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13545,6 +13545,7 @@ M:	Thomas Weißschuh <thomas.weissschuh@linutronix.de>
 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 e52a31b0852caef5669f11f6059c29ce5911aa43..44a93c59a48fb7b4bb34b26333a28283c704cdef 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -31,6 +31,15 @@ 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 0000000000000000000000000000000000000000..ec5395d809ee2a4bd3c47a573a576e2f98ef5c1b
--- /dev/null
+++ b/lib/kunit/kunit-test-uapi.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit Userspace selftest.
+ *
+ * Copyright (C) 2025, Linutronix GmbH.
+ * Author: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+ *
+ * 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 d9c781c859fde1f3623eb71b6829e82aa4803762..03972a3cb172d4af61bec17be800ddfb4bbd7268 100644
--- a/lib/kunit/kunit-test.c
+++ b/lib/kunit/kunit-test.c
@@ -8,6 +8,7 @@
 #include "linux/gfp_types.h"
 #include <kunit/test.h>
 #include <kunit/test-bug.h>
+#include <kunit/uapi.h>
 
 #include <linux/device.h>
 #include <kunit/device.h>
@@ -868,10 +869,30 @@ static struct kunit_suite kunit_current_test_suite = {
 	.test_cases = kunit_current_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_fault_test_suite, &kunit_uapi_test_suite);
 
 MODULE_DESCRIPTION("KUnit test for core test infrastructure");
 MODULE_LICENSE("GPL v2");

-- 
2.50.0

Re: [PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Christoph Hellwig]

On Thu, Jul 17, 2025 at 10:48:02AM +0200, Thomas Weißschuh wrote:
> Currently testing of userspace and in-kernel API use two different
> frameworks.

Which is kinda expected as one has to run in the kernel to test
in-kernel kernel space APIs, and the other tests externally provided
kernel functionality.

> Therefore kunit is much easier to run against different kernel
> configurations and architectures.

Which is is normal.  unit tests are always easier to run than
integration tests.

> This series aims to combine kselftests and kunit, avoiding both their
> limitations. It works by compiling the userspace kselftests as part of
> the regular kernel build, embedding them into the kunit kernel or module
> and executing them from there.

This is really weird.  "Running userspace code is hard, so we package
it in the kernel".  I had my own fair share of problems with kselftests,
mostly because of the lack of structure and automated way to run them,
but adding them to the kernel (or a module) is overshooting the target
by far.

> If the kernel toolchain is not fit to
> produce userspace because of a missing libc, the kernel's own nolibc can
> be used instead.

Is nolibc enough to run all the selftests?  If so we should just do
it unconditionally, but linking to different libraries by availability
seems a bit problematic.

> The structured TAP output from the kselftest is integrated into the
> kunit KTAP output transparently, the kunit parser can parse the combined
> logs together.

Good idea!

Re: [PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 630 bytes --]

On Thu, Jul 17, 2025 at 03:23:00PM +0200, Christoph Hellwig wrote:
> On Thu, Jul 17, 2025 at 10:48:02AM +0200, Thomas Weißschuh wrote:

> > If the kernel toolchain is not fit to
> > produce userspace because of a missing libc, the kernel's own nolibc can
> > be used instead.

> Is nolibc enough to run all the selftests?  If so we should just do
> it unconditionally, but linking to different libraries by availability
> seems a bit problematic.

There's some that rely on standard userspace libraries for accessing the
functionality they're testing or for things like crypto which would
require a bunch more work.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: [PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Thomas Weißschuh]

On Thu, Jul 17, 2025 at 03:23:00PM +0200, Christoph Hellwig wrote:
> On Thu, Jul 17, 2025 at 10:48:02AM +0200, Thomas Weißschuh wrote:

(...)

> > This series aims to combine kselftests and kunit, avoiding both their
> > limitations. It works by compiling the userspace kselftests as part of
> > the regular kernel build, embedding them into the kunit kernel or module
> > and executing them from there.

(...)

> I had my own fair share of problems with kselftests,
> mostly because of the lack of structure and automated way to run them,

How did you overcome these issues? Why does everbody need to reinvent the
wheel here? KUnit already exists and provides a lot of structure and tooling.

> but adding them to the kernel (or a module) is overshooting the target
> by far.

That's a subjective statement without any reasoning I can engange with.
I would be happy to do so, but for now I can only say that I disagree.
The patches have been on the testing-related lists for
some time and so far nobody had an issue with this aspect.

> > If the kernel toolchain is not fit to
> > produce userspace because of a missing libc, the kernel's own nolibc can
> > be used instead.
> 
> Is nolibc enough to run all the selftests?

It is not and most probably won't ever be. The maintainers of each testcase
will decide which libc to use. Like it is in tools/testing/selftests/ today.
Some use glibc, some nolibc and some can do both.

> If so we should just do it unconditionally, but linking to different
> libraries by availability seems a bit problematic.

Agreed. But as mentioned above it will be the maintainers decision.

Only the preinit executable will need to support all configurations so needs
the availability check. For the framework selftest it also makes sense to
support as many configurations as possible. For the example test, any
configuration is fine. 

(...)

While having this discussion, can we also work on dealing with the symbol
exports, as discussed before?


Thomas

Re: [PATCH v5 06/15] fs,fork,exit: export symbols necessary for KUnit UAPI support

[Al Viro]

On Thu, Jul 17, 2025 at 10:48:08AM +0200, Thomas Weißschuh wrote:
> The KUnit UAPI infrastructure starts userspace processes.
> As it should be able to be built as a module, export the necessary symbols.
> 
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

No.  This is just plain wrong.  This is way too low-level; teach kernel/umh.c
to provide what you need, but do *not* add more kernel_execve() callers.
And the situation with ramfs needs cleaning up, but "export put_filesystem()"
is not a solution.

Re: [PATCH v5 06/15] fs,fork,exit: export symbols necessary for KUnit UAPI support

[Thomas Weißschuh]

On Fri, Jul 18, 2025 at 05:44:12PM +0100, Al Viro wrote:
> On Thu, Jul 17, 2025 at 10:48:08AM +0200, Thomas Weißschuh wrote:
> > The KUnit UAPI infrastructure starts userspace processes.
> > As it should be able to be built as a module, export the necessary symbols.
> > 
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> 
> No.  This is just plain wrong.  This is way too low-level; teach kernel/umh.c
> to provide what you need, but do *not* add more kernel_execve() callers.

Sounds good.

> And the situation with ramfs needs cleaning up, but "export put_filesystem()"
> is not a solution.

Cleaning up would mean to stop calling put_filesystem(), as it is a no-op
here anyways, right?


This would still leave the exports for replace_fd(), create_pipe_files()
and set_fs_pwd(). Instead of using kernel/umh.c, I can also extend
kernel/usermode_driver.c to provide these in a way that works for me.
But kernel/usermode_driver.c is dead code, unused since commit
98e20e5e13d2 ("bpfilter: remove bpfilter")
Would it be fine to export those symbols? And delete usermode_driver.c,
as carrying around an unused generic framework seems pointless.


Thomas

Re: [PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Christoph Hellwig]

On Fri, Jul 18, 2025 at 08:22:26AM +0200, Thomas Weißschuh wrote:
> > I had my own fair share of problems with kselftests,
> > mostly because of the lack of structure and automated way to run them,
> 
> How did you overcome these issues? Why does everbody need to reinvent the
> wheel here?

Told people to use everything remotely file system related to use
xfstests instead, and either ignore or suffer from the rest.

> KUnit already exists and provides a lot of structure and tooling.

That's great.  Let's reuse it without having to drive running userspace
programs from kernel code.

> > but adding them to the kernel (or a module) is overshooting the target
> > by far.
> 
> That's a subjective statement without any reasoning I can engange with.

Well, then we're done here if you can't engage.

> I would be happy to do so, but for now I can only say that I disagree.
> The patches have been on the testing-related lists for
> some time and so far nobody had an issue with this aspect.

Has anyone actually chimed in and said "it's great that we bloat the
kernel to run userspace tests", or have people just mostly ignored it
like most things?

> > > If the kernel toolchain is not fit to
> > > produce userspace because of a missing libc, the kernel's own nolibc can
> > > be used instead.
> > 
> > Is nolibc enough to run all the selftests?
> 
> It is not and most probably won't ever be. The maintainers of each testcase
> will decide which libc to use. Like it is in tools/testing/selftests/ today.
> Some use glibc, some nolibc and some can do both.

So why do you want to use it here?  And how is is related to the rest
of the series?

> While having this discussion, can we also work on dealing with the symbol
> exports, as discussed before?

Well, the scope of the entire series makes it pretty clear that this
series as is simply should not go in.

You present running pure userspace tests as the solution to a problem
you don't even explain, or rather just state very highlevel.  Yes,
kselftests suck as most people will agree.  But the answer is not
to add a lot of kernel bloat to treat userspace integration tests
like kernel units tests.  How about you just fix kselftests, preferably
by reusing well known and teststed userland code?

Re: [PATCH v5 06/15] fs,fork,exit: export symbols necessary for KUnit UAPI support

[Christoph Hellwig]

On Mon, Jul 21, 2025 at 08:42:40AM +0200, Thomas Weißschuh wrote:
> This would still leave the exports for replace_fd(), create_pipe_files()
> and set_fs_pwd(). Instead of using kernel/umh.c,

Please look into a way to just run your userspace tests from userspace.

It's not that hard, people have done this novel concept for at least
a few decades if you look into it.

> I can also extend
> kernel/usermode_driver.c to provide these in a way that works for me.
> But kernel/usermode_driver.c is dead code, unused since commit
> 98e20e5e13d2 ("bpfilter: remove bpfilter")
> Would it be fine to export those symbols? And delete usermode_driver.c,
> as carrying around an unused generic framework seems pointless.

Unused code should always go away.  Weirdly enough USERMODE_DRIVER is
selected by BPF_PRELOAD despite that not really using any code from
it, though.

Re: [PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Thomas Weißschuh]

Hi Christoph,

On Mon, Jul 21, 2025 at 09:09:58AM +0200, Christoph Hellwig wrote:
> On Fri, Jul 18, 2025 at 08:22:26AM +0200, Thomas Weißschuh wrote:
> > > I had my own fair share of problems with kselftests,
> > > mostly because of the lack of structure and automated way to run them,
> > 
> > How did you overcome these issues? Why does everbody need to reinvent the
> > wheel here?
> 
> Told people to use everything remotely file system related to use
> xfstests instead, and either ignore or suffer from the rest.

Suffering from the rest is what I am trying to avoid.
(More on that below)

> > KUnit already exists and provides a lot of structure and tooling.
> 
> That's great.  Let's reuse it without having to drive running userspace
> programs from kernel code.

Running in the kernel is the point behind KUnit. It could be done by putting
all the userspace test into a initramfs and run them on boot from there.
But that has other drawbacks:
* The tests can't be run on an existing system.
* All tests need to be loaded into memory together, and not on demand.
* The tests can not be rerun.

> > > but adding them to the kernel (or a module) is overshooting the target
> > > by far.
> > 
> > That's a subjective statement without any reasoning I can engange with.
> 
> Well, then we're done here if you can't engage.

This was a response to one specific statement. Could you be a bit more specific
in your critique? I am not sure what exactly you mean in some cases, making it
hard to respond properly. For example "bloat", it is bloaty
* source code,
* object code for users enabling the new kconfig options,
* object code for other users *not* enabling the new kconfig options?
 
> > I would be happy to do so, but for now I can only say that I disagree.
> > The patches have been on the testing-related lists for
> > some time and so far nobody had an issue with this aspect.
> 
> Has anyone actually chimed in and said "it's great that we bloat the
> kernel to run userspace tests", or have people just mostly ignored it
> like most things?

That specific wording wasn't used. Obviously...
So far nobody had any issues with the overall goal of the series.
There was criticism around implementation details and I have been and will be
working on resolving those.

Some feedback I got:

David [0]: "I've taken quite a liking to it: it'd definitely have made my
life easier more than once."
Benjamin is already playing with it, having built his own testcase [1].
I asked Shuah about it before starting development and she gave a go-ahead.
A collegue of mine is also using it to validate the PREEMPT_RT safety of
various UAPIs by combining KUnit UAPI with a runtime validator [2].

> > > > If the kernel toolchain is not fit to
> > > > produce userspace because of a missing libc, the kernel's own nolibc can
> > > > be used instead.
> > > 
> > > Is nolibc enough to run all the selftests?
> > 
> > It is not and most probably won't ever be. The maintainers of each testcase
> > will decide which libc to use. Like it is in tools/testing/selftests/ today.
> > Some use glibc, some nolibc and some can do both.
> 
> So why do you want to use it here?  And how is is related to the rest
> of the series?

To make it easier to test a wide range of architectures by not requiring a
libc from the toolchain. It also avoids relying on a bunch of out-of-tree
code (glibc) as part of the test. And there are existing kselftests which
use it over glibc for their own reasons.

But using nolibc in test code is not necessary and nobody is forced to do so.

(Maybe a disclaimer that I'm one of the nolibc maintainers is in order)

(...)

> You present running pure userspace tests as the solution to a problem
> you don't even explain, or rather just state very highlevel.

To run kselftests we need the following things:
a) A toolchain which can build userspace executables.
b) Quite a bit of supporting userland, at least glibc, coreutils and bash.
c) A rootfs assembled out of these.
d) An efficient way to incrementally rebuild the test executables and rootfs.
e) A way to put that rootfs into the system under test.
f) A way to configure a kernel which
   * is as small as possible and as fast as possible to build,
   * can run on QEMU or a real machine,
   * can run the functionality under test.
g) A way to select the tests to run in the system under test.
h) A way to communicate back the results.
i) Something to interpret the results.
j) Hook up everything into a CI system.

And for all of this there should be good in-tree tooling.

For a) and b) I am not aware of any toolchain provider or distribution which
provides this for all necessary architectures. And the existing userspace test
frameworks don't even try to address the points a) to e)/f) and let the user
figure it out. This is the case for xfstests and LTP. virtme(-ng) provide most
of it but don't support cross-architecture setups. On the other hand the tree
already contains solutions for most of those points. a) and d) are solved by
kbuild userprogs, e) to j) by KUnit and my new framework plugs b) and c).
Moving to a pure userspace solution would preclude the usage of KUnit as far as
I can see.

This all started when I worked on the generic vDSO data storage patches [3].
I needed to run the existing vDSO selftests against a bunch of architectures,
including some esoteric ones [4]. With my framework, running the vDSO selftests
for any architecture is now trivial and blazingly fast.

Does this make more sense?

> Yes, kselftests suck as most people will agree. But the answer is not
> to add a lot of kernel bloat to treat userspace integration tests
> like kernel units tests.

I fail to understand how this test code is worse than the existing KUnit test
code. This is not meant to test complex scenarios, but single system calls or
specific UAPIs, which may depend on architecture features. For example timers,
signals, vDSO, mm etc.

> How about you just fix kselftests, preferably
> by reusing well known and teststed userland code?

Is "well known and tested userland code" referring to glibc or testing
frameworks? As mentioned above, glibc can be used just fine and the frameworks
I know about are lacking.


Thomas


[0] https://lore.kernel.org/all/CABVgOSn+530YJ3OPNJQncLDQNbd9JEDtZ04Amyyxk57jOVYUyQ@mail.gmail.com/
[1] https://lore.kernel.org/all/20250626195714.2123694-3-benjamin@sipsolutions.net/
[2] https://lore.kernel.org/lkml/cover.1752088709.git.namcao@linutronix.de/
[3] https://lore.kernel.org/lkml/20250204-vdso-store-rng-v3-0-13a4669dfc8c@linutronix.de/
[4] https://lore.kernel.org/lkml/20250724-vdso-sparc64-generic-2-v1-0-e376a3bd24d1@linutronix.de/

Re: [PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Christoph Hellwig]

On Mon, Aug 04, 2025 at 05:01:35PM +0200, Thomas Weißschuh wrote:
> > That's great.  Let's reuse it without having to drive running userspace
> > programs from kernel code.
> 
> Running in the kernel is the point behind KUnit.

When using kunit as is to unit test kernel functionality - obviously.

When running it to integration test the syscall boundary - not at all.

> It could be done by putting
> all the userspace test into a initramfs and run them on boot from there.
> But that has other drawbacks:
> * The tests can't be run on an existing system.
> * All tests need to be loaded into memory together, and not on demand.
> * The tests can not be rerun.

None of that is true.  While running syscall level tests from an
initramfs could be a nice feature for an automatd kernel CI system,
nothin in this tests should require running from an initramfs.

> This was a response to one specific statement. Could you be a bit more specific
> in your critique? I am not sure what exactly you mean in some cases, making it
> hard to respond properly. For example "bloat", it is bloaty
> * source code,
> * object code for users enabling the new kconfig options,
> * object code for other users *not* enabling the new kconfig options?

You are adding kernel code both at the source and object level to run
userspace tests.  That is very clearly bloat.  Even more so as it adds
functionality and exports that don't fit in with what the kernel already
does for actual kernel functionality.

> > > It is not and most probably won't ever be. The maintainers of each testcase
> > > will decide which libc to use. Like it is in tools/testing/selftests/ today.
> > > Some use glibc, some nolibc and some can do both.
> > 
> > So why do you want to use it here?  And how is is related to the rest
> > of the series?
> 
> To make it easier to test a wide range of architectures by not requiring a
> libc from the toolchain. It also avoids relying on a bunch of out-of-tree
> code (glibc) as part of the test. And there are existing kselftests which
> use it over glibc for their own reasons.
> 
> But using nolibc in test code is not necessary and nobody is forced to do so.
> 
> (Maybe a disclaimer that I'm one of the nolibc maintainers is in order)

Well, why do you even mix it up with this unrelated series then?

> To run kselftests we need the following things:
> a) A toolchain which can build userspace executables.

You'll need that for any userspace program, no matter what test
harness.

> b) Quite a bit of supporting userland, at least glibc, coreutils and bash.

Well, a libc you will need anyway.  Maybe nolibc is good enough for
some tests, but as you already stated not for very many.  The others
are just an artifcat of how you run tests.

> c) A rootfs assembled out of these.
> d) An efficient way to incrementally rebuild the test executables and rootfs.
> e) A way to put that rootfs into the system under test.

You don't need a rootfs.

> And for all of this there should be good in-tree tooling.

Absolutely.

> Moving to a pure userspace solution would preclude the usage of KUnit as far as
> I can see.

You've still failed why using kunit is the goal and not just something
that made your life easier archieving your goal.

> > Yes, kselftests suck as most people will agree. But the answer is not
> > to add a lot of kernel bloat to treat userspace integration tests
> > like kernel units tests.
> 
> I fail to understand how this test code is worse than the existing KUnit test
> code. This is not meant to test complex scenarios, but single system calls or
> specific UAPIs, which may depend on architecture features. For example timers,
> signals, vDSO, mm etc.

So now having another half-assed test framework is a good thing?

> > How about you just fix kselftests, preferably
> > by reusing well known and teststed userland code?
> 
> Is "well known and tested userland code" referring to glibc or testing
> frameworks? As mentioned above, glibc can be used just fine and the frameworks
> I know about are lacking.

Basically any kind of testing framework that has broad use.  It's not
like there aren't userland unit test frameworks if you really want to
use that.