Re: [PATCH v3 4/6] binder: Scaffolding for binder_alloc KUnit tests
From: Tiffany Yang
Date: Wed Jul 16 2025 - 18:29:01 EST
Kees Cook <kees@xxxxxxxxxx> writes:
...
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! ;)
IIRC, I had tried using the #ifdef to inject test-specific code in some
places, but that created issues when we were loading KUnit as a module
because it causes the built-in code to be built as though the
"CONFIG_..." is undefined. Consequently, I started using IS_ENABLED by
default, but I'm not sure if it's strictly necessary for exposing
functions with a header file since I'd assume "CONFIG_..." will be
defined when we're building the module?
+
#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@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Binder Alloc KUnit tests");
+MODULE_LICENSE("GPL");
Reviewed-by: Kees Cook <kees@xxxxxxxxxx>
--
Tiffany Y. Yang