// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright 2018-2019 IBM Corporation.
*/
#define __SANE_USERSPACE_TYPES__
#include <sys/types.h>
#include <stdint.h>
#include <malloc.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <sys/prctl.h>
#include "utils.h"
#include "../pmu/event.h"
extern void pattern_cache_loop(void);
extern void indirect_branch_loop(void);
static int do_count_loop(struct event *events, bool is_p9, s64 *miss_percent)
{
u64 pred, mpred;
prctl(PR_TASK_PERF_EVENTS_ENABLE);
if (is_p9)
pattern_cache_loop();
else
indirect_branch_loop();
prctl(PR_TASK_PERF_EVENTS_DISABLE);
event_read(&events[0]);
event_read(&events[1]);
// We could scale all the events by running/enabled but we're lazy
// As long as the PMU is uncontended they should all run
FAIL_IF(events[0].result.running != events[0].result.enabled);
FAIL_IF(events[1].result.running != events[1].result.enabled);
pred = events[0].result.value;
mpred = events[1].result.value;
if (is_p9) {
event_read(&events[2]);
event_read(&events[3]);
FAIL_IF(events[2].result.running != events[2].result.enabled);
FAIL_IF(events[3].result.running != events[3].result.enabled);
pred += events[2].result.value;
mpred += events[3].result.value;
}
*miss_percent = 100 * mpred / pred;
return 0;
}
static void setup_event(struct event *e, u64 config, char *name)
{
event_init_named(e, config, name);
e->attr.disabled = 1;
e->attr.exclude_kernel = 1;
e->attr.exclude_hv = 1;
e->attr.exclude_idle = 1;
}
enum spectre_v2_state {
VULNERABLE = 0,
UNKNOWN = 1, // Works with FAIL_IF()
NOT_AFFECTED,
BRANCH_SERIALISATION,
COUNT_CACHE_DISABLED,
COUNT_CACHE_FLUSH_SW,
COUNT_CACHE_FLUSH_HW,
BTB_FLUSH,
};
static enum spectre_v2_state get_sysfs_state(void)
{
enum spectre_v2_state state = UNKNOWN;
char buf[256];
int len;
memset(buf, 0, sizeof(buf));
FAIL_IF(read_sysfs_file("devices/system/cpu/vulnerabilities/spectre_v2", buf, sizeof(buf)));
// Make sure it's NULL terminated
buf[sizeof(buf) - 1] = '\0';
// Trim the trailing newline
len = strlen(buf);
FAIL_IF(len < 1);
buf[len - 1] = '\0';
printf("sysfs reports: '%s'\n", buf);
// Order matters
if (strstr(buf, "Vulnerable"))
state = VULNERABLE;
else if (strstr(buf, "Not affected"))
state = NOT_AFFECTED;
else if (strstr(buf, "Indirect branch serialisation (kernel only)"))
state = BRANCH_SERIALISATION;
else if (strstr(buf, "Indirect branch cache disabled"))
state = COUNT_CACHE_DISABLED;
else if (strstr(buf, "Software count cache flush (hardware accelerated)"))
state = COUNT_CACHE_FLUSH_HW;
else if (strstr(buf, "Software count cache flush"))
state = COUNT_CACHE_FLUSH_SW;
else if (strstr(buf, "Branch predictor state flush"))
state = BTB_FLUSH;
return state;
}
#define PM_BR_PRED_CCACHE 0x040a4 // P8 + P9
#define PM_BR_MPRED_CCACHE 0x040ac // P8 + P9
#define PM_BR_PRED_PCACHE 0x048a0 // P9 only
#define PM_BR_MPRED_PCACHE 0x048b0 // P9 only
int spectre_v2_test(void)
{
enum spectre_v2_state state;
struct event events[4];
s64 miss_percent;
bool is_p9;
// The PMU events we use only work on Power8 or later
SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_2_07));
state = get_sysfs_state();
if (state == UNKNOWN) {
printf("Error: couldn't determine spectre_v2 mitigation state?\n");
return -1;
}
memset(events, 0, sizeof(events));
setup_event(&events[0], PM_BR_PRED_CCACHE, "PM_BR_PRED_CCACHE");
setup_event(&events[1], PM_BR_MPRED_CCACHE, "PM_BR_MPRED_CCACHE");
FAIL_IF(event_open(&events[0]));
FAIL_IF(event_open_with_group(&events[1], events[0].fd) == -1);
is_p9 = ((mfspr(SPRN_PVR) >> 16) & 0xFFFF) == 0x4e;
if (is_p9) {
// Count pattern cache too
setup_event(&events[2], PM_BR_PRED_PCACHE, "PM_BR_PRED_PCACHE");
setup_event(&events[3], PM_BR_MPRED_PCACHE, "PM_BR_MPRED_PCACHE");
FAIL_IF(event_open_with_group(&events[2], events[0].fd) == -1);
FAIL_IF(event_open_with_group(&events[3], events[0].fd) == -1);
}
FAIL_IF(do_count_loop(events, is_p9, &miss_percent));
event_report_justified(&events[0], 18, 10);
event_report_justified(&events[1], 18, 10);
event_close(&events[0]);
event_close(&events[1]);
if (is_p9) {
event_report_justified(&events[2], 18, 10);
event_report_justified(&events[3], 18, 10);
event_close(&events[2]);
event_close(&events[3]);
}
printf("Miss percent %lld %%\n", miss_percent);
switch (state) {
case VULNERABLE:
case NOT_AFFECTED:
case COUNT_CACHE_FLUSH_SW:
case COUNT_CACHE_FLUSH_HW:
// These should all not affect userspace branch prediction
if (miss_percent > 15) {
if (miss_percent > 95) {
/*
* Such a mismatch may be caused by a system being unaware
* the count cache is disabled. This may be to enable
* guest migration between hosts with different settings.
* Return skip code to avoid detecting this as an error.
* We are not vulnerable and reporting otherwise, so
* missing such a mismatch is safe.
*/
printf("Branch misses > 95%% unexpected in this configuration.\n");
printf("Count cache likely disabled without Linux knowing.\n");
if (state == COUNT_CACHE_FLUSH_SW)
printf("WARNING: Kernel performing unnecessary flushes.\n");
return 4;
}
printf("Branch misses > 15%% unexpected in this configuration!\n");
printf("Possible mismatch between reported & actual mitigation\n");
return 1;
}
break;
case BRANCH_SERIALISATION:
// This seems to affect userspace branch prediction a bit?
if (miss_percent > 25) {
printf("Branch misses > 25%% unexpected in this configuration!\n");
printf("Possible mismatch between reported & actual mitigation\n");
return 1;
}
break;
case COUNT_CACHE_DISABLED:
if (miss_percent < 95) {
printf("Branch misses < 95%% unexpected in this configuration!\n");
printf("Possible mismatch between reported & actual mitigation\n");
return 1;
}
break;
case UNKNOWN:
case BTB_FLUSH:
printf("Not sure!\n");
return 1;
}
printf("OK - Measured branch prediction rates match reported spectre v2 mitigation.\n");
return 0;
}
int main(int argc, char *argv[])
{
return test_harness(spectre_v2_test, "spectre_v2");
}
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