1 // SPDX-License-Identifier: GPL-2.0+
2 
3 /*
4  * Copyright 2018-2019 IBM Corporation.
5  */
6 
7 #define __SANE_USERSPACE_TYPES__
8 
9 #include <sys/types.h>
10 #include <stdint.h>
11 #include <malloc.h>
12 #include <unistd.h>
13 #include <stdlib.h>
14 #include <string.h>
15 #include <stdio.h>
16 #include <sys/prctl.h>
17 #include "utils.h"
18 
19 #include "../pmu/event.h"
20 
21 
22 extern void pattern_cache_loop(void);
23 extern void indirect_branch_loop(void);
24 
25 static int do_count_loop(struct event *events, bool is_p9, s64 *miss_percent)
26 {
27 	u64 pred, mpred;
28 
29 	prctl(PR_TASK_PERF_EVENTS_ENABLE);
30 
31 	if (is_p9)
32 		pattern_cache_loop();
33 	else
34 		indirect_branch_loop();
35 
36 	prctl(PR_TASK_PERF_EVENTS_DISABLE);
37 
38 	event_read(&events[0]);
39 	event_read(&events[1]);
40 
41 	// We could scale all the events by running/enabled but we're lazy
42 	// As long as the PMU is uncontended they should all run
43 	FAIL_IF(events[0].result.running != events[0].result.enabled);
44 	FAIL_IF(events[1].result.running != events[1].result.enabled);
45 
46 	pred =  events[0].result.value;
47 	mpred = events[1].result.value;
48 
49 	if (is_p9) {
50 		event_read(&events[2]);
51 		event_read(&events[3]);
52 		FAIL_IF(events[2].result.running != events[2].result.enabled);
53 		FAIL_IF(events[3].result.running != events[3].result.enabled);
54 
55 		pred  += events[2].result.value;
56 		mpred += events[3].result.value;
57 	}
58 
59 	*miss_percent = 100 * mpred / pred;
60 
61 	return 0;
62 }
63 
64 static void setup_event(struct event *e, u64 config, char *name)
65 {
66 	event_init_named(e, config, name);
67 
68 	e->attr.disabled = 1;
69 	e->attr.exclude_kernel = 1;
70 	e->attr.exclude_hv = 1;
71 	e->attr.exclude_idle = 1;
72 }
73 
74 enum spectre_v2_state {
75 	VULNERABLE = 0,
76 	UNKNOWN = 1,		// Works with FAIL_IF()
77 	NOT_AFFECTED,
78 	BRANCH_SERIALISATION,
79 	COUNT_CACHE_DISABLED,
80 	COUNT_CACHE_FLUSH_SW,
81 	COUNT_CACHE_FLUSH_HW,
82 	BTB_FLUSH,
83 };
84 
85 static enum spectre_v2_state get_sysfs_state(void)
86 {
87 	enum spectre_v2_state state = UNKNOWN;
88 	char buf[256];
89 	int len;
90 
91 	memset(buf, 0, sizeof(buf));
92 	FAIL_IF(read_sysfs_file("devices/system/cpu/vulnerabilities/spectre_v2", buf, sizeof(buf)));
93 
94 	// Make sure it's NULL terminated
95 	buf[sizeof(buf) - 1] = '\0';
96 
97 	// Trim the trailing newline
98 	len = strlen(buf);
99 	FAIL_IF(len < 1);
100 	buf[len - 1] = '\0';
101 
102 	printf("sysfs reports: '%s'\n", buf);
103 
104 	// Order matters
105 	if (strstr(buf, "Vulnerable"))
106 		state = VULNERABLE;
107 	else if (strstr(buf, "Not affected"))
108 		state = NOT_AFFECTED;
109 	else if (strstr(buf, "Indirect branch serialisation (kernel only)"))
110 		state = BRANCH_SERIALISATION;
111 	else if (strstr(buf, "Indirect branch cache disabled"))
112 		state = COUNT_CACHE_DISABLED;
113 	else if (strstr(buf, "Software count cache flush (hardware accelerated)"))
114 		state = COUNT_CACHE_FLUSH_HW;
115 	else if (strstr(buf, "Software count cache flush"))
116 		state = COUNT_CACHE_FLUSH_SW;
117 	else if (strstr(buf, "Branch predictor state flush"))
118 		state = BTB_FLUSH;
119 
120 	return state;
121 }
122 
123 #define PM_BR_PRED_CCACHE	0x040a4	// P8 + P9
124 #define PM_BR_MPRED_CCACHE	0x040ac	// P8 + P9
125 #define PM_BR_PRED_PCACHE	0x048a0	// P9 only
126 #define PM_BR_MPRED_PCACHE	0x048b0	// P9 only
127 
128 #define SPRN_PVR 287
129 
130 int spectre_v2_test(void)
131 {
132 	enum spectre_v2_state state;
133 	struct event events[4];
134 	s64 miss_percent;
135 	bool is_p9;
136 
137 	// The PMU events we use only work on Power8 or later
138 	SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_2_07));
139 
140 	state = get_sysfs_state();
141 	if (state == UNKNOWN) {
142 		printf("Error: couldn't determine spectre_v2 mitigation state?\n");
143 		return -1;
144 	}
145 
146 	memset(events, 0, sizeof(events));
147 
148 	setup_event(&events[0], PM_BR_PRED_CCACHE,  "PM_BR_PRED_CCACHE");
149 	setup_event(&events[1], PM_BR_MPRED_CCACHE, "PM_BR_MPRED_CCACHE");
150 	FAIL_IF(event_open(&events[0]));
151 	FAIL_IF(event_open_with_group(&events[1], events[0].fd) == -1);
152 
153 	is_p9 = ((mfspr(SPRN_PVR) >>  16) & 0xFFFF) == 0x4e;
154 
155 	if (is_p9) {
156 		// Count pattern cache too
157 		setup_event(&events[2], PM_BR_PRED_PCACHE,  "PM_BR_PRED_PCACHE");
158 		setup_event(&events[3], PM_BR_MPRED_PCACHE, "PM_BR_MPRED_PCACHE");
159 
160 		FAIL_IF(event_open_with_group(&events[2], events[0].fd) == -1);
161 		FAIL_IF(event_open_with_group(&events[3], events[0].fd) == -1);
162 	}
163 
164 	FAIL_IF(do_count_loop(events, is_p9, &miss_percent));
165 
166 	event_report_justified(&events[0], 18, 10);
167 	event_report_justified(&events[1], 18, 10);
168 	event_close(&events[0]);
169 	event_close(&events[1]);
170 
171 	if (is_p9) {
172 		event_report_justified(&events[2], 18, 10);
173 		event_report_justified(&events[3], 18, 10);
174 		event_close(&events[2]);
175 		event_close(&events[3]);
176 	}
177 
178 	printf("Miss percent %lld %%\n", miss_percent);
179 
180 	switch (state) {
181 	case VULNERABLE:
182 	case NOT_AFFECTED:
183 	case COUNT_CACHE_FLUSH_SW:
184 	case COUNT_CACHE_FLUSH_HW:
185 		// These should all not affect userspace branch prediction
186 		if (miss_percent > 15) {
187 			printf("Branch misses > 15%% unexpected in this configuration!\n");
188 			printf("Possible mis-match between reported & actual mitigation\n");
189 			/*
190 			 * Such a mismatch may be caused by a guest system
191 			 * reporting as vulnerable when the host is mitigated.
192 			 * Return skip code to avoid detecting this as an error.
193 			 * We are not vulnerable and reporting otherwise, so
194 			 * missing such a mismatch is safe.
195 			 */
196 			if (state == VULNERABLE)
197 				return 4;
198 
199 			return 1;
200 		}
201 		break;
202 	case BRANCH_SERIALISATION:
203 		// This seems to affect userspace branch prediction a bit?
204 		if (miss_percent > 25) {
205 			printf("Branch misses > 25%% unexpected in this configuration!\n");
206 			printf("Possible mis-match between reported & actual mitigation\n");
207 			return 1;
208 		}
209 		break;
210 	case COUNT_CACHE_DISABLED:
211 		if (miss_percent < 95) {
212 			printf("Branch misses < 20%% unexpected in this configuration!\n");
213 			printf("Possible mis-match between reported & actual mitigation\n");
214 			return 1;
215 		}
216 		break;
217 	case UNKNOWN:
218 	case BTB_FLUSH:
219 		printf("Not sure!\n");
220 		return 1;
221 	}
222 
223 	printf("OK - Measured branch prediction rates match reported spectre v2 mitigation.\n");
224 
225 	return 0;
226 }
227 
228 int main(int argc, char *argv[])
229 {
230 	return test_harness(spectre_v2_test, "spectre_v2");
231 }
232