tools/perf/tests/dwarf-unwind.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/compiler.h>
   3 #include <linux/types.h>
   4 #include <linux/zalloc.h>
   5 #include <inttypes.h>
   6 #include <limits.h>
   7 #include <unistd.h>
   8 #include "tests.h"
   9 #include "debug.h"
  10 #include "machine.h"
  11 #include "event.h"
  12 #include "../util/unwind.h"
  13 #include "perf_regs.h"
  14 #include "map.h"
  15 #include "symbol.h"
  16 #include "thread.h"
  17 #include "callchain.h"
  18 #include "util/synthetic-events.h"
  19
  20 /* For bsearch. We try to unwind functions in shared object. */
  21 #include <stdlib.h>
  22
  23 /*
  24  * The test will assert frames are on the stack but tail call optimizations lose
  25  * the frame of the caller. Clang can disable this optimization on a called
  26  * function but GCC currently (11/2020) lacks this attribute. The barrier is
  27  * used to inhibit tail calls in these cases.
  28  */
  29 #ifdef __has_attribute
  30 #if __has_attribute(disable_tail_calls)
  31 #define NO_TAIL_CALL_ATTRIBUTE __attribute__((disable_tail_calls))
  32 #define NO_TAIL_CALL_BARRIER
  33 #endif
  34 #endif
  35 #ifndef NO_TAIL_CALL_ATTRIBUTE
  36 #define NO_TAIL_CALL_ATTRIBUTE
  37 #define NO_TAIL_CALL_BARRIER __asm__ __volatile__("" : : : "memory");
  38 #endif
  39
  40 static int mmap_handler(const struct perf_tool *tool __maybe_unused,
  41                         union perf_event *event,
  42                         struct perf_sample *sample,
  43                         struct machine *machine)
  44 {
  45         return machine__process_mmap2_event(machine, event, sample);
  46 }
  47
  48 static int init_live_machine(struct machine *machine)
  49 {
  50         union perf_event event;
  51         pid_t pid = getpid();
  52
  53         memset(&event, 0, sizeof(event));
  54         return perf_event__synthesize_mmap_events(NULL, &event, pid, pid,
  55                                                   mmap_handler, machine, true);
  56 }
  57
  58 /*
  59  * We need to keep these functions global, despite the
  60  * fact that they are used only locally in this object,
  61  * in order to keep them around even if the binary is
  62  * stripped. If they are gone, the unwind check for
  63  * symbol fails.
  64  */
  65 int test_dwarf_unwind__thread(struct thread *thread);
  66 int test_dwarf_unwind__compare(void *p1, void *p2);
  67 int test_dwarf_unwind__krava_3(struct thread *thread);
  68 int test_dwarf_unwind__krava_2(struct thread *thread);
  69 int test_dwarf_unwind__krava_1(struct thread *thread);
  70 int test__dwarf_unwind(struct test_suite *test, int subtest);
  71
  72 #define MAX_STACK 8
  73
  74 static int unwind_entry(struct unwind_entry *entry, void *arg)
  75 {
  76         unsigned long *cnt = (unsigned long *) arg;
  77         char *symbol = entry->ms.sym ? entry->ms.sym->name : NULL;
  78         static const char *funcs[MAX_STACK] = {
  79                 "test__arch_unwind_sample",
  80                 "test_dwarf_unwind__thread",
  81                 "test_dwarf_unwind__compare",
  82                 "bsearch",
  83                 "test_dwarf_unwind__krava_3",
  84                 "test_dwarf_unwind__krava_2",
  85                 "test_dwarf_unwind__krava_1",
  86                 "test__dwarf_unwind"
  87         };
  88         /*
  89          * The funcs[MAX_STACK] array index, based on the
  90          * callchain order setup.
  91          */
  92         int idx = callchain_param.order == ORDER_CALLER ?
  93                   MAX_STACK - *cnt - 1 : *cnt;
  94
  95         if (*cnt >= MAX_STACK) {
  96                 pr_debug("failed: crossed the max stack value %d\n", MAX_STACK);
  97                 return -1;
  98         }
  99
 100         if (!symbol) {
 101                 pr_debug("failed: got unresolved address 0x%" PRIx64 "\n",
 102                          entry->ip);
 103                 return -1;
 104         }
 105
 106         (*cnt)++;
 107         pr_debug("got: %s 0x%" PRIx64 ", expecting %s\n",
 108                  symbol, entry->ip, funcs[idx]);
 109         return strcmp((const char *) symbol, funcs[idx]);
 110 }
 111
 112 NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__thread(struct thread *thread)
 113 {
 114         struct perf_sample sample;
 115         unsigned long cnt = 0;
 116         int err = -1;
 117
 118         memset(&sample, 0, sizeof(sample));
 119
 120         if (test__arch_unwind_sample(&sample, thread)) {
 121                 pr_debug("failed to get unwind sample\n");
 122                 goto out;
 123         }
 124
 125         err = unwind__get_entries(unwind_entry, &cnt, thread,
 126                                   &sample, MAX_STACK, false);
 127         if (err)
 128                 pr_debug("unwind failed\n");
 129         else if (cnt != MAX_STACK) {
 130                 pr_debug("got wrong number of stack entries %lu != %d\n",
 131                          cnt, MAX_STACK);
 132                 err = -1;
 133         }
 134
 135  out:
 136         zfree(&sample.user_stack.data);
 137         zfree(&sample.user_regs.regs);
 138         return err;
 139 }
 140
 141 static int global_unwind_retval = -INT_MAX;
 142
 143 NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__compare(void *p1, void *p2)
 144 {
 145         /* Any possible value should be 'thread' */
 146         struct thread *thread = *(struct thread **)p1;
 147
 148         if (global_unwind_retval == -INT_MAX) {
 149                 /* Call unwinder twice for both callchain orders. */
 150                 callchain_param.order = ORDER_CALLER;
 151
 152                 global_unwind_retval = test_dwarf_unwind__thread(thread);
 153                 if (!global_unwind_retval) {
 154                         callchain_param.order = ORDER_CALLEE;
 155                         global_unwind_retval = test_dwarf_unwind__thread(thread);
 156                 }
 157         }
 158
 159         return p1 - p2;
 160 }
 161
 162 NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_3(struct thread *thread)
 163 {
 164         struct thread *array[2] = {thread, thread};
 165         void *fp = &bsearch;
 166         /*
 167          * make _bsearch a volatile function pointer to
 168          * prevent potential optimization, which may expand
 169          * bsearch and call compare directly from this function,
 170          * instead of libc shared object.
 171          */
 172         void *(*volatile _bsearch)(void *, void *, size_t,
 173                         size_t, int (*)(void *, void *));
 174
 175         _bsearch = fp;
 176         _bsearch(array, &thread, 2, sizeof(struct thread **),
 177                  test_dwarf_unwind__compare);
 178         return global_unwind_retval;
 179 }
 180
 181 NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_2(struct thread *thread)
 182 {
 183         int ret;
 184
 185         ret =  test_dwarf_unwind__krava_3(thread);
 186         NO_TAIL_CALL_BARRIER;
 187         return ret;
 188 }
 189
 190 NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_1(struct thread *thread)
 191 {
 192         int ret;
 193
 194         ret =  test_dwarf_unwind__krava_2(thread);
 195         NO_TAIL_CALL_BARRIER;
 196         return ret;
 197 }
 198
 199 noinline int test__dwarf_unwind(struct test_suite *test __maybe_unused,
 200                                 int subtest __maybe_unused)
 201 {
 202         struct machine *machine;
 203         struct thread *thread;
 204         int err = -1;
 205
 206         machine = machine__new_host();
 207         if (!machine) {
 208                 pr_err("Could not get machine\n");
 209                 return -1;
 210         }
 211
 212         if (machine__create_kernel_maps(machine)) {
 213                 pr_err("Failed to create kernel maps\n");
 214                 return -1;
 215         }
 216
 217         callchain_param.record_mode = CALLCHAIN_DWARF;
 218         dwarf_callchain_users = true;
 219
 220         if (init_live_machine(machine)) {
 221                 pr_err("Could not init machine\n");
 222                 goto out;
 223         }
 224
 225         if (verbose > 1)
 226                 machine__fprintf(machine, stderr);
 227
 228         thread = machine__find_thread(machine, getpid(), getpid());
 229         if (!thread) {
 230                 pr_err("Could not get thread\n");
 231                 goto out;
 232         }
 233
 234         err = test_dwarf_unwind__krava_1(thread);
 235         thread__put(thread);
 236
 237  out:
 238         machine__delete(machine);
 239         return err;
 240 }
 241
 242 DEFINE_SUITE("Test dwarf unwind", dwarf_unwind);