tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2021 Facebook */
   3 #include <test_progs.h>
   4 #include "get_branch_snapshot.skel.h"
   5
   6 static int *pfd_array;
   7 static int cpu_cnt;
   8
   9 static bool is_hypervisor(void)
  10 {
  11         char *line = NULL;
  12         bool ret = false;
  13         size_t len;
  14         FILE *fp;
  15
  16         fp = fopen("/proc/cpuinfo", "r");
  17         if (!fp)
  18                 return false;
  19
  20         while (getline(&line, &len, fp) != -1) {
  21                 if (!strncmp(line, "flags", 5)) {
  22                         if (strstr(line, "hypervisor") != NULL)
  23                                 ret = true;
  24                         break;
  25                 }
  26         }
  27
  28         free(line);
  29         fclose(fp);
  30         return ret;
  31 }
  32
  33 static int create_perf_events(void)
  34 {
  35         struct perf_event_attr attr = {0};
  36         int cpu;
  37
  38         /* create perf event */
  39         attr.size = sizeof(attr);
  40         attr.type = PERF_TYPE_HARDWARE;
  41         attr.config = PERF_COUNT_HW_CPU_CYCLES;
  42         attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
  43         attr.branch_sample_type = PERF_SAMPLE_BRANCH_KERNEL |
  44                 PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY;
  45
  46         cpu_cnt = libbpf_num_possible_cpus();
  47         pfd_array = malloc(sizeof(int) * cpu_cnt);
  48         if (!pfd_array) {
  49                 cpu_cnt = 0;
  50                 return 1;
  51         }
  52
  53         for (cpu = 0; cpu < cpu_cnt; cpu++) {
  54                 pfd_array[cpu] = syscall(__NR_perf_event_open, &attr,
  55                                          -1, cpu, -1, PERF_FLAG_FD_CLOEXEC);
  56                 if (pfd_array[cpu] < 0)
  57                         break;
  58         }
  59
  60         return cpu == 0;
  61 }
  62
  63 static void close_perf_events(void)
  64 {
  65         int cpu, fd;
  66
  67         for (cpu = 0; cpu < cpu_cnt; cpu++) {
  68                 fd = pfd_array[cpu];
  69                 if (fd < 0)
  70                         break;
  71                 close(fd);
  72         }
  73         free(pfd_array);
  74 }
  75
  76 void serial_test_get_branch_snapshot(void)
  77 {
  78         struct get_branch_snapshot *skel = NULL;
  79         int err;
  80
  81         /* Skip the test before we fix LBR snapshot for hypervisor. */
  82         if (is_hypervisor()) {
  83                 test__skip();
  84                 return;
  85         }
  86
  87         if (create_perf_events()) {
  88                 test__skip();  /* system doesn't support LBR */
  89                 goto cleanup;
  90         }
  91
  92         skel = get_branch_snapshot__open_and_load();
  93         if (!ASSERT_OK_PTR(skel, "get_branch_snapshot__open_and_load"))
  94                 goto cleanup;
  95
  96         err = kallsyms_find("bpf_testmod_loop_test", &skel->bss->address_low);
  97         if (!ASSERT_OK(err, "kallsyms_find"))
  98                 goto cleanup;
  99
 100         /* Just a guess for the end of this function, as module functions
 101          * in /proc/kallsyms could come in any order.
 102          */
 103         skel->bss->address_high = skel->bss->address_low + 128;
 104
 105         err = get_branch_snapshot__attach(skel);
 106         if (!ASSERT_OK(err, "get_branch_snapshot__attach"))
 107                 goto cleanup;
 108
 109         trigger_module_test_read(100);
 110
 111         if (skel->bss->total_entries < 16) {
 112                 /* too few entries for the hit/waste test */
 113                 test__skip();
 114                 goto cleanup;
 115         }
 116
 117         ASSERT_GT(skel->bss->test1_hits, 6, "find_looptest_in_lbr");
 118
 119         /* Given we stop LBR in software, we will waste a few entries.
 120          * But we should try to waste as few as possible entries. We are at
 121          * about 7 on x86_64 systems.
 122          * Add a check for < 10 so that we get heads-up when something
 123          * changes and wastes too many entries.
 124          */
 125         ASSERT_LT(skel->bss->wasted_entries, 10, "check_wasted_entries");
 126
 127 cleanup:
 128         get_branch_snapshot__destroy(skel);
 129         close_perf_events();
 130 }