Re: [PATCH v3 4/6] binder: Scaffolding for binder_alloc KUnit tests

On Mon, Jul 14, 2025 at 11:53:17AM -0700, Tiffany Yang wrote:

Add setup and teardown for testing binder allocator code with KUnit. Include minimal test cases to verify that tests are initialized correctly.

Tested-by: Rae Moar rmoar@google.com Signed-off-by: Tiffany Yang ynaffit@google.com

---

v2:

• Added tested-by tag

v3:

• Split kunit lib change into separate change

---

drivers/android/Kconfig | 11 ++ drivers/android/Makefile | 1 + drivers/android/binder.c | 5 +- drivers/android/binder_alloc.c | 15 +- drivers/android/binder_alloc.h | 6 + drivers/android/binder_internal.h | 4 + drivers/android/tests/.kunitconfig | 3 + drivers/android/tests/Makefile | 3 + drivers/android/tests/binder_alloc_kunit.c | 166 +++++++++++++++++++++ 9 files changed, 208 insertions(+), 6 deletions(-) create mode 100644 drivers/android/tests/.kunitconfig create mode 100644 drivers/android/tests/Makefile create mode 100644 drivers/android/tests/binder_alloc_kunit.c

diff --git a/drivers/android/Kconfig b/drivers/android/Kconfig index 07aa8ae0a058..b1bc7183366c 100644 --- a/drivers/android/Kconfig +++ b/drivers/android/Kconfig @@ -47,4 +47,15 @@ config ANDROID_BINDER_IPC_SELFTEST exhaustively with combinations of various buffer sizes and alignments. +config ANDROID_BINDER_ALLOC_KUNIT_TEST

• tristate "KUnit Tests for Android Binder Alloc" if !KUNIT_ALL_TESTS
• depends on ANDROID_BINDER_IPC && KUNIT
• default KUNIT_ALL_TESTS
• help

•  This feature builds the binder alloc KUnit tests.
  

•  Each test case runs using a pared-down binder_alloc struct and
  

•  test-specific freelist, which allows this KUnit module to be loaded
  

•  for testing without interfering with a running system.
  

endmenu diff --git a/drivers/android/Makefile b/drivers/android/Makefile index c9d3d0c99c25..74d02a335d4e 100644 --- a/drivers/android/Makefile +++ b/drivers/android/Makefile @@ -4,3 +4,4 @@ ccflags-y += -I$(src) # needed for trace events obj-$(CONFIG_ANDROID_BINDERFS) += binderfs.o obj-$(CONFIG_ANDROID_BINDER_IPC) += binder.o binder_alloc.o obj-$(CONFIG_ANDROID_BINDER_IPC_SELFTEST) += binder_alloc_selftest.o +obj-$(CONFIG_ANDROID_BINDER_ALLOC_KUNIT_TEST) += tests/ diff --git a/drivers/android/binder.c b/drivers/android/binder.c index c463ca4a8fff..9dfe90c284fc 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -68,6 +68,8 @@ #include <linux/sizes.h> #include <linux/ktime.h> +#include <kunit/visibility.h>

#include <uapi/linux/android/binder.h> #include <linux/cacheflush.h> @@ -5956,10 +5958,11 @@ static void binder_vma_close(struct vm_area_struct *vma) binder_alloc_vma_close(&proc->alloc); } -static vm_fault_t binder_vm_fault(struct vm_fault *vmf) +VISIBLE_IF_KUNIT vm_fault_t binder_vm_fault(struct vm_fault *vmf) { return VM_FAULT_SIGBUS; } +EXPORT_SYMBOL_IF_KUNIT(binder_vm_fault); static const struct vm_operations_struct binder_vm_ops = { .open = binder_vma_open, diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 2e89f9127883..c79e5c6721f0 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -23,6 +23,7 @@ #include <linux/uaccess.h> #include <linux/highmem.h> #include <linux/sizes.h> +#include <kunit/visibility.h> #include "binder_alloc.h" #include "binder_trace.h" @@ -57,13 +58,14 @@ static struct binder_buffer *binder_buffer_prev(struct binder_buffer *buffer) return list_entry(buffer->entry.prev, struct binder_buffer, entry); } -static size_t binder_alloc_buffer_size(struct binder_alloc *alloc,

• 		       struct binder_buffer *buffer)
  

+VISIBLE_IF_KUNIT size_t binder_alloc_buffer_size(struct binder_alloc *alloc,

• 				 struct binder_buffer *buffer)
  

{ if (list_is_last(&buffer->entry, &alloc->buffers)) return alloc->vm_start + alloc->buffer_size - buffer->user_data; return binder_buffer_next(buffer)->user_data - buffer->user_data; } +EXPORT_SYMBOL_IF_KUNIT(binder_alloc_buffer_size); static void binder_insert_free_buffer(struct binder_alloc *alloc, struct binder_buffer *new_buffer) @@ -959,7 +961,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, failure_string, ret); return ret; }

+EXPORT_SYMBOL_IF_KUNIT(binder_alloc_mmap_handler); void binder_alloc_deferred_release(struct binder_alloc *alloc) { @@ -1028,6 +1030,7 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc) "%s: %d buffers %d, pages %d\n", __func__, alloc->pid, buffers, page_count); } +EXPORT_SYMBOL_IF_KUNIT(binder_alloc_deferred_release); /**

• binder_alloc_print_allocated() - print buffer info

@@ -1122,6 +1125,7 @@ void binder_alloc_vma_close(struct binder_alloc *alloc) { binder_alloc_set_mapped(alloc, false); } +EXPORT_SYMBOL_IF_KUNIT(binder_alloc_vma_close); /**

• binder_alloc_free_page() - shrinker callback to free pages

@@ -1229,8 +1233,8 @@ binder_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) static struct shrinker *binder_shrinker; -static void __binder_alloc_init(struct binder_alloc *alloc,

• 		struct list_lru *freelist)
  

+VISIBLE_IF_KUNIT void __binder_alloc_init(struct binder_alloc *alloc,

• 			  struct list_lru *freelist)
  

{ alloc->pid = current->group_leader->pid; alloc->mm = current->mm; @@ -1239,6 +1243,7 @@ static void __binder_alloc_init(struct binder_alloc *alloc, INIT_LIST_HEAD(&alloc->buffers); alloc->freelist = freelist; } +EXPORT_SYMBOL_IF_KUNIT(__binder_alloc_init); /**

• binder_alloc_init() - called by binder_open() for per-proc initialization

diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h index aa05a9df1360..dc8dce2469a7 100644 --- a/drivers/android/binder_alloc.h +++ b/drivers/android/binder_alloc.h @@ -188,5 +188,11 @@ int binder_alloc_copy_from_buffer(struct binder_alloc *alloc, binder_size_t buffer_offset, size_t bytes); +#if IS_ENABLED(CONFIG_KUNIT) +void __binder_alloc_init(struct binder_alloc *alloc, struct list_lru *freelist); +size_t binder_alloc_buffer_size(struct binder_alloc *alloc,

• 		struct binder_buffer *buffer);
  

+#endif

#endif /* _LINUX_BINDER_ALLOC_H */ diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h index 1ba5caf1d88d..b5d3014fb4dc 100644 --- a/drivers/android/binder_internal.h +++ b/drivers/android/binder_internal.h @@ -592,4 +592,8 @@ void binder_add_device(struct binder_device *device); */ void binder_remove_device(struct binder_device *device); +#if IS_ENABLED(CONFIG_KUNIT) +vm_fault_t binder_vm_fault(struct vm_fault *vmf); +#endif

I'm used to the "#ifdef CONFIG_..." idiom, but looking at the tree, I see that "#if IS_ENANLED(CONFIG...)" is relatively common too. I don't think there is a function difference, so I leave the style choice up to you! ;)

#endif /* _LINUX_BINDER_INTERNAL_H */ diff --git a/drivers/android/tests/.kunitconfig b/drivers/android/tests/.kunitconfig new file mode 100644 index 000000000000..a73601231049 --- /dev/null +++ b/drivers/android/tests/.kunitconfig @@ -0,0 +1,3 @@ +CONFIG_KUNIT=y +CONFIG_ANDROID_BINDER_IPC=y +CONFIG_ANDROID_BINDER_ALLOC_KUNIT_TEST=y diff --git a/drivers/android/tests/Makefile b/drivers/android/tests/Makefile new file mode 100644 index 000000000000..6780967e573b --- /dev/null +++ b/drivers/android/tests/Makefile @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0-only

+obj-$(CONFIG_ANDROID_BINDER_ALLOC_KUNIT_TEST) += binder_alloc_kunit.o diff --git a/drivers/android/tests/binder_alloc_kunit.c b/drivers/android/tests/binder_alloc_kunit.c new file mode 100644 index 000000000000..4b68b5687d33 --- /dev/null +++ b/drivers/android/tests/binder_alloc_kunit.c @@ -0,0 +1,166 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Test cases for binder allocator code
• */

+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <kunit/test.h> +#include <linux/anon_inodes.h> +#include <linux/err.h> +#include <linux/file.h> +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/mman.h> +#include <linux/sizes.h>

+#include "../binder_alloc.h" +#include "../binder_internal.h"

+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");

+#define BINDER_MMAP_SIZE SZ_128K

+struct binder_alloc_test {

• struct binder_alloc alloc;
• struct list_lru binder_test_freelist;
• struct file *filp;
• unsigned long mmap_uaddr;

+};

+static void binder_alloc_test_init_freelist(struct kunit *test) +{

• struct binder_alloc_test *priv = test->priv;
• KUNIT_EXPECT_PTR_EQ(test, priv->alloc.freelist,

• 	    &priv->binder_test_freelist);
  

+}

+static void binder_alloc_test_mmap(struct kunit *test) +{

• struct binder_alloc_test *priv = test->priv;
• struct binder_alloc *alloc = &priv->alloc;
• struct binder_buffer *buf;
• struct rb_node *n;
• KUNIT_EXPECT_EQ(test, alloc->mapped, true);
• KUNIT_EXPECT_EQ(test, alloc->buffer_size, BINDER_MMAP_SIZE);
• n = rb_first(&alloc->allocated_buffers);
• KUNIT_EXPECT_PTR_EQ(test, n, NULL);
• n = rb_first(&alloc->free_buffers);
• buf = rb_entry(n, struct binder_buffer, rb_node);
• KUNIT_EXPECT_EQ(test, binder_alloc_buffer_size(alloc, buf),

• 	BINDER_MMAP_SIZE);
  

• KUNIT_EXPECT_TRUE(test, list_is_last(&buf->entry, &alloc->buffers));

+}

+/* ===== End test cases ===== */

+static void binder_alloc_test_vma_close(struct vm_area_struct *vma) +{

• struct binder_alloc *alloc = vma->vm_private_data;
• binder_alloc_vma_close(alloc);

+}

+static const struct vm_operations_struct binder_alloc_test_vm_ops = {

• .close = binder_alloc_test_vma_close,
• .fault = binder_vm_fault,

+};

+static int binder_alloc_test_mmap_handler(struct file *filp,

• 			  struct vm_area_struct *vma)
  

+{

• struct binder_alloc *alloc = filp->private_data;
• vm_flags_mod(vma, VM_DONTCOPY | VM_MIXEDMAP, VM_MAYWRITE);
• vma->vm_ops = &binder_alloc_test_vm_ops;
• vma->vm_private_data = alloc;
• return binder_alloc_mmap_handler(alloc, vma);

+}

+static const struct file_operations binder_alloc_test_fops = {

• .mmap = binder_alloc_test_mmap_handler,

+};

+static int binder_alloc_test_init(struct kunit *test) +{

• struct binder_alloc_test *priv;
• int ret;
• priv = kunit_kzalloc(test, sizeof(*priv), GFP_KERNEL);
• if (!priv)

• return -ENOMEM;
  

• test->priv = priv;
• ret = list_lru_init(&priv->binder_test_freelist);
• if (ret) {

• kunit_err(test, "Failed to initialize test freelist\n");
  

• return ret;
  

• }
• /* __binder_alloc_init requires mm to be attached */
• ret = kunit_attach_mm();
• if (ret) {

• kunit_err(test, "Failed to attach mm\n");
  

• return ret;
  

• }
• __binder_alloc_init(&priv->alloc, &priv->binder_test_freelist);
• priv->filp = anon_inode_getfile("binder_alloc_kunit",

• 			&binder_alloc_test_fops, &priv->alloc,
  

• 			O_RDWR | O_CLOEXEC);
  

• if (IS_ERR_OR_NULL(priv->filp)) {

• kunit_err(test, "Failed to open binder alloc test driver file\n");
  

• return priv->filp ? PTR_ERR(priv->filp) : -ENOMEM;
  

• }
• priv->mmap_uaddr = kunit_vm_mmap(test, priv->filp, 0, BINDER_MMAP_SIZE,

• 			 PROT_READ, MAP_PRIVATE | MAP_NORESERVE,
  

• 			 0);
  

• if (!priv->mmap_uaddr) {

• kunit_err(test, "Could not map the test's transaction memory\n");
  

• return -ENOMEM;
  

• }
• return 0;

+}

+static void binder_alloc_test_exit(struct kunit *test) +{

• struct binder_alloc_test *priv = test->priv;
• /* Close the backing file to make sure binder_alloc_vma_close runs */
• if (!IS_ERR_OR_NULL(priv->filp))

• fput(priv->filp);
  

• if (priv->alloc.mm)

• binder_alloc_deferred_release(&priv->alloc);
  

• /* Make sure freelist is empty */
• KUNIT_EXPECT_EQ(test, list_lru_count(&priv->binder_test_freelist), 0);
• list_lru_destroy(&priv->binder_test_freelist);

+}

+static struct kunit_case binder_alloc_test_cases[] = {

• KUNIT_CASE(binder_alloc_test_init_freelist),
• KUNIT_CASE(binder_alloc_test_mmap),
• {}

+};

+static struct kunit_suite binder_alloc_test_suite = {

• .name = "binder_alloc",
• .test_cases = binder_alloc_test_cases,
• .init = binder_alloc_test_init,
• .exit = binder_alloc_test_exit,

+};

+kunit_test_suite(binder_alloc_test_suite);

+MODULE_AUTHOR("Tiffany Yang ynaffit@google.com"); +MODULE_DESCRIPTION("Binder Alloc KUnit tests"); +MODULE_LICENSE("GPL");

Reviewed-by: Kees Cook kees@kernel.org