1// SPDX-License-Identifier: GPL-2.0
2/*
3 * KUnit test for hw_breakpoint constraints accounting logic.
4 *
5 * Copyright (C) 2022, Google LLC.
6 */
7
8#include <kunit/test.h>
9#include <linux/cpumask.h>
10#include <linux/hw_breakpoint.h>
11#include <linux/kthread.h>
12#include <linux/perf_event.h>
13#include <asm/hw_breakpoint.h>
14
15#define TEST_REQUIRES_BP_SLOTS(test, slots) \
16 do { \
17 if ((slots) > get_test_bp_slots()) { \
18 kunit_skip((test), "Requires breakpoint slots: %d > %d", slots, \
19 get_test_bp_slots()); \
20 } \
21 } while (0)
22
23#define TEST_EXPECT_NOSPC(expr) KUNIT_EXPECT_EQ(test, -ENOSPC, PTR_ERR(expr))
24
25#define MAX_TEST_BREAKPOINTS 512
26
27static char break_vars[MAX_TEST_BREAKPOINTS];
28static struct perf_event *test_bps[MAX_TEST_BREAKPOINTS];
29static struct task_struct *__other_task;
30
31static struct perf_event *register_test_bp(int cpu, struct task_struct *tsk, int idx)
32{
33 struct perf_event_attr attr = {};
34
35 if (WARN_ON(idx < 0 || idx >= MAX_TEST_BREAKPOINTS))
36 return NULL;
37
38 hw_breakpoint_init(attr: &attr);
39 attr.bp_addr = (unsigned long)&break_vars[idx];
40 attr.bp_len = HW_BREAKPOINT_LEN_1;
41 attr.bp_type = HW_BREAKPOINT_RW;
42 return perf_event_create_kernel_counter(attr: &attr, cpu, task: tsk, NULL, NULL);
43}
44
45static void unregister_test_bp(struct perf_event **bp)
46{
47 if (WARN_ON(IS_ERR(*bp)))
48 return;
49 if (WARN_ON(!*bp))
50 return;
51 unregister_hw_breakpoint(bp: *bp);
52 *bp = NULL;
53}
54
55static int get_test_bp_slots(void)
56{
57 static int slots;
58
59 if (!slots)
60 slots = hw_breakpoint_slots(TYPE_DATA);
61
62 return slots;
63}
64
65static void fill_one_bp_slot(struct kunit *test, int *id, int cpu, struct task_struct *tsk)
66{
67 struct perf_event *bp = register_test_bp(cpu, tsk, idx: *id);
68
69 KUNIT_ASSERT_NOT_NULL(test, bp);
70 KUNIT_ASSERT_FALSE(test, IS_ERR(bp));
71 KUNIT_ASSERT_NULL(test, test_bps[*id]);
72 test_bps[(*id)++] = bp;
73}
74
75/*
76 * Fills up the given @cpu/@tsk with breakpoints, only leaving @skip slots free.
77 *
78 * Returns true if this can be called again, continuing at @id.
79 */
80static bool fill_bp_slots(struct kunit *test, int *id, int cpu, struct task_struct *tsk, int skip)
81{
82 for (int i = 0; i < get_test_bp_slots() - skip; ++i)
83 fill_one_bp_slot(test, id, cpu, tsk);
84
85 return *id + get_test_bp_slots() <= MAX_TEST_BREAKPOINTS;
86}
87
88static int dummy_kthread(void *arg)
89{
90 return 0;
91}
92
93static struct task_struct *get_other_task(struct kunit *test)
94{
95 struct task_struct *tsk;
96
97 if (__other_task)
98 return __other_task;
99
100 tsk = kthread_create(dummy_kthread, NULL, "hw_breakpoint_dummy_task");
101 KUNIT_ASSERT_FALSE(test, IS_ERR(tsk));
102 __other_task = tsk;
103 return __other_task;
104}
105
106static int get_test_cpu(int num)
107{
108 int cpu;
109
110 WARN_ON(num < 0);
111
112 for_each_online_cpu(cpu) {
113 if (num-- <= 0)
114 break;
115 }
116
117 return cpu;
118}
119
120/* ===== Test cases ===== */
121
122static void test_one_cpu(struct kunit *test)
123{
124 int idx = 0;
125
126 fill_bp_slots(test, id: &idx, cpu: get_test_cpu(num: 0), NULL, skip: 0);
127 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
128 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
129}
130
131static void test_many_cpus(struct kunit *test)
132{
133 int idx = 0;
134 int cpu;
135
136 /* Test that CPUs are independent. */
137 for_each_online_cpu(cpu) {
138 bool do_continue = fill_bp_slots(test, id: &idx, cpu, NULL, skip: 0);
139
140 TEST_EXPECT_NOSPC(register_test_bp(cpu, NULL, idx));
141 if (!do_continue)
142 break;
143 }
144}
145
146static void test_one_task_on_all_cpus(struct kunit *test)
147{
148 int idx = 0;
149
150 fill_bp_slots(test, id: &idx, cpu: -1, current, skip: 0);
151 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
152 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
153 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
154 /* Remove one and adding back CPU-target should work. */
155 unregister_test_bp(bp: &test_bps[0]);
156 fill_one_bp_slot(test, id: &idx, cpu: get_test_cpu(num: 0), NULL);
157}
158
159static void test_two_tasks_on_all_cpus(struct kunit *test)
160{
161 int idx = 0;
162
163 /* Test that tasks are independent. */
164 fill_bp_slots(test, id: &idx, cpu: -1, current, skip: 0);
165 fill_bp_slots(test, id: &idx, cpu: -1, tsk: get_other_task(test), skip: 0);
166
167 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
168 TEST_EXPECT_NOSPC(register_test_bp(-1, get_other_task(test), idx));
169 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
170 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), get_other_task(test), idx));
171 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
172 /* Remove one from first task and adding back CPU-target should not work. */
173 unregister_test_bp(bp: &test_bps[0]);
174 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
175}
176
177static void test_one_task_on_one_cpu(struct kunit *test)
178{
179 int idx = 0;
180
181 fill_bp_slots(test, id: &idx, cpu: get_test_cpu(num: 0), current, skip: 0);
182 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
183 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
184 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
185 /*
186 * Remove one and adding back CPU-target should work; this case is
187 * special vs. above because the task's constraints are CPU-dependent.
188 */
189 unregister_test_bp(bp: &test_bps[0]);
190 fill_one_bp_slot(test, id: &idx, cpu: get_test_cpu(num: 0), NULL);
191}
192
193static void test_one_task_mixed(struct kunit *test)
194{
195 int idx = 0;
196
197 TEST_REQUIRES_BP_SLOTS(test, 3);
198
199 fill_one_bp_slot(test, id: &idx, cpu: get_test_cpu(num: 0), current);
200 fill_bp_slots(test, id: &idx, cpu: -1, current, skip: 1);
201 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
202 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
203 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
204
205 /* Transition from CPU-dependent pinned count to CPU-independent. */
206 unregister_test_bp(bp: &test_bps[0]);
207 unregister_test_bp(bp: &test_bps[1]);
208 fill_one_bp_slot(test, id: &idx, cpu: get_test_cpu(num: 0), NULL);
209 fill_one_bp_slot(test, id: &idx, cpu: get_test_cpu(num: 0), NULL);
210 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
211}
212
213static void test_two_tasks_on_one_cpu(struct kunit *test)
214{
215 int idx = 0;
216
217 fill_bp_slots(test, id: &idx, cpu: get_test_cpu(num: 0), current, skip: 0);
218 fill_bp_slots(test, id: &idx, cpu: get_test_cpu(num: 0), tsk: get_other_task(test), skip: 0);
219
220 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
221 TEST_EXPECT_NOSPC(register_test_bp(-1, get_other_task(test), idx));
222 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
223 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), get_other_task(test), idx));
224 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
225 /* Can still create breakpoints on some other CPU. */
226 fill_bp_slots(test, id: &idx, cpu: get_test_cpu(num: 1), NULL, skip: 0);
227}
228
229static void test_two_tasks_on_one_all_cpus(struct kunit *test)
230{
231 int idx = 0;
232
233 fill_bp_slots(test, id: &idx, cpu: get_test_cpu(num: 0), current, skip: 0);
234 fill_bp_slots(test, id: &idx, cpu: -1, tsk: get_other_task(test), skip: 0);
235
236 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
237 TEST_EXPECT_NOSPC(register_test_bp(-1, get_other_task(test), idx));
238 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
239 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), get_other_task(test), idx));
240 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
241 /* Cannot create breakpoints on some other CPU either. */
242 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(1), NULL, idx));
243}
244
245static void test_task_on_all_and_one_cpu(struct kunit *test)
246{
247 int tsk_on_cpu_idx, cpu_idx;
248 int idx = 0;
249
250 TEST_REQUIRES_BP_SLOTS(test, 3);
251
252 fill_bp_slots(test, id: &idx, cpu: -1, current, skip: 2);
253 /* Transitioning from only all CPU breakpoints to mixed. */
254 tsk_on_cpu_idx = idx;
255 fill_one_bp_slot(test, id: &idx, cpu: get_test_cpu(num: 0), current);
256 fill_one_bp_slot(test, id: &idx, cpu: -1, current);
257
258 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
259 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
260 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
261
262 /* We should still be able to use up another CPU's slots. */
263 cpu_idx = idx;
264 fill_one_bp_slot(test, id: &idx, cpu: get_test_cpu(num: 1), NULL);
265 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(1), NULL, idx));
266
267 /* Transitioning back to task target on all CPUs. */
268 unregister_test_bp(bp: &test_bps[tsk_on_cpu_idx]);
269 /* Still have a CPU target breakpoint in get_test_cpu(1). */
270 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
271 /* Remove it and try again. */
272 unregister_test_bp(bp: &test_bps[cpu_idx]);
273 fill_one_bp_slot(test, id: &idx, cpu: -1, current);
274
275 TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
276 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
277 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
278 TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(1), NULL, idx));
279}
280
281static struct kunit_case hw_breakpoint_test_cases[] = {
282 KUNIT_CASE(test_one_cpu),
283 KUNIT_CASE(test_many_cpus),
284 KUNIT_CASE(test_one_task_on_all_cpus),
285 KUNIT_CASE(test_two_tasks_on_all_cpus),
286 KUNIT_CASE(test_one_task_on_one_cpu),
287 KUNIT_CASE(test_one_task_mixed),
288 KUNIT_CASE(test_two_tasks_on_one_cpu),
289 KUNIT_CASE(test_two_tasks_on_one_all_cpus),
290 KUNIT_CASE(test_task_on_all_and_one_cpu),
291 {},
292};
293
294static int test_init(struct kunit *test)
295{
296 /* Most test cases want 2 distinct CPUs. */
297 if (num_online_cpus() < 2)
298 kunit_skip(test, "not enough cpus");
299
300 /* Want the system to not use breakpoints elsewhere. */
301 if (hw_breakpoint_is_used())
302 kunit_skip(test, "hw breakpoint already in use");
303
304 return 0;
305}
306
307static void test_exit(struct kunit *test)
308{
309 for (int i = 0; i < MAX_TEST_BREAKPOINTS; ++i) {
310 if (test_bps[i])
311 unregister_test_bp(bp: &test_bps[i]);
312 }
313
314 if (__other_task) {
315 kthread_stop(k: __other_task);
316 __other_task = NULL;
317 }
318
319 /* Verify that internal state agrees that no breakpoints are in use. */
320 KUNIT_EXPECT_FALSE(test, hw_breakpoint_is_used());
321}
322
323static struct kunit_suite hw_breakpoint_test_suite = {
324 .name = "hw_breakpoint",
325 .test_cases = hw_breakpoint_test_cases,
326 .init = test_init,
327 .exit = test_exit,
328};
329
330kunit_test_suites(&hw_breakpoint_test_suite);
331
332MODULE_AUTHOR("Marco Elver <elver@google.com>");
333

source code of linux/kernel/events/hw_breakpoint_test.c