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 int spectre_v2_test(void)
129 {
130 enum spectre_v2_state state;
131 struct event events[4];
132 s64 miss_percent;
133 bool is_p9;
134
135 // The PMU events we use only work on Power8 or later
136 SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_2_07));
137
138 state = get_sysfs_state();
139 if (state == UNKNOWN) {
140 printf("Error: couldn't determine spectre_v2 mitigation state?\n");
141 return -1;
142 }
143
144 memset(events, 0, sizeof(events));
145
146 setup_event(&events[0], PM_BR_PRED_CCACHE, "PM_BR_PRED_CCACHE");
147 setup_event(&events[1], PM_BR_MPRED_CCACHE, "PM_BR_MPRED_CCACHE");
148 FAIL_IF(event_open(&events[0]));
149 FAIL_IF(event_open_with_group(&events[1], events[0].fd) == -1);
150
151 is_p9 = ((mfspr(SPRN_PVR) >> 16) & 0xFFFF) == 0x4e;
152
153 if (is_p9) {
154 // Count pattern cache too
155 setup_event(&events[2], PM_BR_PRED_PCACHE, "PM_BR_PRED_PCACHE");
156 setup_event(&events[3], PM_BR_MPRED_PCACHE, "PM_BR_MPRED_PCACHE");
157
158 FAIL_IF(event_open_with_group(&events[2], events[0].fd) == -1);
159 FAIL_IF(event_open_with_group(&events[3], events[0].fd) == -1);
160 }
161
162 FAIL_IF(do_count_loop(events, is_p9, &miss_percent));
163
164 event_report_justified(&events[0], 18, 10);
165 event_report_justified(&events[1], 18, 10);
166 event_close(&events[0]);
167 event_close(&events[1]);
168
169 if (is_p9) {
170 event_report_justified(&events[2], 18, 10);
171 event_report_justified(&events[3], 18, 10);
172 event_close(&events[2]);
173 event_close(&events[3]);
174 }
175
176 printf("Miss percent %lld %%\n", miss_percent);
177
178 switch (state) {
179 case VULNERABLE:
180 case NOT_AFFECTED:
181 case COUNT_CACHE_FLUSH_SW:
182 case COUNT_CACHE_FLUSH_HW:
183 // These should all not affect userspace branch prediction
184 if (miss_percent > 15) {
185 if (miss_percent > 95) {
186 /*
187 * Such a mismatch may be caused by a system being unaware
188 * the count cache is disabled. This may be to enable
189 * guest migration between hosts with different settings.
190 * Return skip code to avoid detecting this as an error.
191 * We are not vulnerable and reporting otherwise, so
192 * missing such a mismatch is safe.
193 */
194 printf("Branch misses > 95%% unexpected in this configuration.\n");
195 printf("Count cache likely disabled without Linux knowing.\n");
196 if (state == COUNT_CACHE_FLUSH_SW)
197 printf("WARNING: Kernel performing unnecessary flushes.\n");
198 return 4;
199 }
200 printf("Branch misses > 15%% unexpected in this configuration!\n");
201 printf("Possible mismatch between reported & actual mitigation\n");
202
203 return 1;
204 }
205 break;
206 case BRANCH_SERIALISATION:
207 // This seems to affect userspace branch prediction a bit?
208 if (miss_percent > 25) {
209 printf("Branch misses > 25%% unexpected in this configuration!\n");
210 printf("Possible mismatch between reported & actual mitigation\n");
211 return 1;
212 }
213 break;
214 case COUNT_CACHE_DISABLED:
215 if (miss_percent < 95) {
216 printf("Branch misses < 95%% unexpected in this configuration!\n");
217 printf("Possible mismatch between reported & actual mitigation\n");
218 return 1;
219 }
220 break;
221 case UNKNOWN:
222 case BTB_FLUSH:
223 printf("Not sure!\n");
224 return 1;
225 }
226
227 printf("OK - Measured branch prediction rates match reported spectre v2 mitigation.\n");
228
229 return 0;
230 }
231
232 int main(int argc, char *argv[])
233 {
234 return test_harness(spectre_v2_test, "spectre_v2");
235 }
236
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