binder: Scaffolding for binder_alloc KUnit tests

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>
Acked-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20250714185321.2417234-5-ynaffit@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

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/

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>
@@ -5947,10 +5949,11 @@ 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,

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)
@@ -955,7 +957,7 @@ err_invalid_mm:
 			   failure_string, ret);
 	return ret;
 }
-
+EXPORT_SYMBOL_IF_KUNIT(binder_alloc_mmap_handler);
 
 void binder_alloc_deferred_release(struct binder_alloc *alloc)
 {
@@ -1024,6 +1026,7 @@ 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
@@ -1116,6 +1119,7 @@ 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
@@ -1223,8 +1227,8 @@ 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;
@@ -1233,6 +1237,7 @@ 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

drivers/android/binder_alloc.h

@@ -184,5 +184,11 @@ 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 */
 

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
+
 #endif /* _LINUX_BINDER_INTERNAL_H */

drivers/android/tests/.kunitconfig

@@ -0,0 +1,3 @@
+CONFIG_KUNIT=y
+CONFIG_ANDROID_BINDER_IPC=y
+CONFIG_ANDROID_BINDER_ALLOC_KUNIT_TEST=y

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

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");