1// SPDX-License-Identifier: GPL-2.0
2/*
3 * KUnit function redirection (static stubbing) API.
4 *
5 * Copyright (C) 2022, Google LLC.
6 * Author: David Gow <davidgow@google.com>
7 */
8
9#include <kunit/test.h>
10#include <kunit/static_stub.h>
11#include "hooks-impl.h"
12
13
14/* Context for a static stub. This is stored in the resource data. */
15struct kunit_static_stub_ctx {
16	void *real_fn_addr;
17	void *replacement_addr;
18};
19
20static void __kunit_static_stub_resource_free(struct kunit_resource *res)
21{
22	kfree(res->data);
23}
24
25/* Matching function for kunit_find_resource(). match_data is real_fn_addr. */
26static bool __kunit_static_stub_resource_match(struct kunit *test,
27						struct kunit_resource *res,
28						void *match_real_fn_addr)
29{
30	/* This pointer is only valid if res is a static stub resource. */
31	struct kunit_static_stub_ctx *ctx = res->data;
32
33	/* Make sure the resource is a static stub resource. */
34	if (res->free != &__kunit_static_stub_resource_free)
35		return false;
36
37	return ctx->real_fn_addr == match_real_fn_addr;
38}
39
40/* Hook to return the address of the replacement function. */
41void *__kunit_get_static_stub_address_impl(struct kunit *test, void *real_fn_addr)
42{
43	struct kunit_resource *res;
44	struct kunit_static_stub_ctx *ctx;
45	void *replacement_addr;
46
47	res = kunit_find_resource(test,
48				  __kunit_static_stub_resource_match,
49				  real_fn_addr);
50
51	if (!res)
52		return NULL;
53
54	ctx = res->data;
55	replacement_addr = ctx->replacement_addr;
56	kunit_put_resource(res);
57	return replacement_addr;
58}
59
60void kunit_deactivate_static_stub(struct kunit *test, void *real_fn_addr)
61{
62	struct kunit_resource *res;
63
64	KUNIT_ASSERT_PTR_NE_MSG(test, real_fn_addr, NULL,
65				"Tried to deactivate a NULL stub.");
66
67	/* Look up the existing stub for this function. */
68	res = kunit_find_resource(test,
69				  __kunit_static_stub_resource_match,
70				  real_fn_addr);
71
72	/* Error out if the stub doesn't exist. */
73	KUNIT_ASSERT_PTR_NE_MSG(test, res, NULL,
74				"Tried to deactivate a nonexistent stub.");
75
76	/* Free the stub. We 'put' twice, as we got a reference
77	 * from kunit_find_resource()
78	 */
79	kunit_remove_resource(test, res);
80	kunit_put_resource(res);
81}
82EXPORT_SYMBOL_GPL(kunit_deactivate_static_stub);
83
84/* Helper function for kunit_activate_static_stub(). The macro does
85 * typechecking, so use it instead.
86 */
87void __kunit_activate_static_stub(struct kunit *test,
88				  void *real_fn_addr,
89				  void *replacement_addr)
90{
91	struct kunit_static_stub_ctx *ctx;
92	struct kunit_resource *res;
93
94	KUNIT_ASSERT_PTR_NE_MSG(test, real_fn_addr, NULL,
95				"Tried to activate a stub for function NULL");
96
97	/* If the replacement address is NULL, deactivate the stub. */
98	if (!replacement_addr) {
99		kunit_deactivate_static_stub(test, replacement_addr);
100		return;
101	}
102
103	/* Look up any existing stubs for this function, and replace them. */
104	res = kunit_find_resource(test,
105				  __kunit_static_stub_resource_match,
106				  real_fn_addr);
107	if (res) {
108		ctx = res->data;
109		ctx->replacement_addr = replacement_addr;
110
111		/* We got an extra reference from find_resource(), so put it. */
112		kunit_put_resource(res);
113	} else {
114		ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
115		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);
116		ctx->real_fn_addr = real_fn_addr;
117		ctx->replacement_addr = replacement_addr;
118		res = kunit_alloc_resource(test, NULL,
119				     &__kunit_static_stub_resource_free,
120				     GFP_KERNEL, ctx);
121	}
122}
123EXPORT_SYMBOL_GPL(__kunit_activate_static_stub);
124