tools/perf/util/unwind-libdw.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/compiler.h>
   3 #include <elfutils/libdw.h>
   4 #include <elfutils/libdwfl.h>
   5 #include <inttypes.h>
   6 #include <errno.h>
   7 #include "debug.h"
   8 #include "dso.h"
   9 #include "unwind.h"
  10 #include "unwind-libdw.h"
  11 #include "machine.h"
  12 #include "map.h"
  13 #include "symbol.h"
  14 #include "thread.h"
  15 #include <linux/types.h>
  16 #include <linux/zalloc.h>
  17 #include "event.h"
  18 #include "perf_regs.h"
  19 #include "callchain.h"
  20
  21 static char *debuginfo_path;
  22
  23 static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata,
  24                             const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused,
  25                             const char *file_name, const char *debuglink_file __maybe_unused,
  26                             GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name)
  27 {
  28         const struct dso *dso = *userdata;
  29
  30         assert(dso);
  31         if (dso->symsrc_filename && strcmp (file_name, dso->symsrc_filename))
  32                 *debuginfo_file_name = strdup(dso->symsrc_filename);
  33         return -1;
  34 }
  35
  36 static const Dwfl_Callbacks offline_callbacks = {
  37         .find_debuginfo         = __find_debuginfo,
  38         .debuginfo_path         = &debuginfo_path,
  39         .section_address        = dwfl_offline_section_address,
  40         // .find_elf is not set as we use dwfl_report_elf() instead.
  41 };
  42
  43 static int __report_module(struct addr_location *al, u64 ip,
  44                             struct unwind_info *ui)
  45 {
  46         Dwfl_Module *mod;
  47         struct dso *dso = NULL;
  48         /*
  49          * Some callers will use al->sym, so we can't just use the
  50          * cheaper thread__find_map() here.
  51          */
  52         thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
  53
  54         if (al->map)
  55                 dso = map__dso(al->map);
  56
  57         if (!dso)
  58                 return 0;
  59
  60         mod = dwfl_addrmodule(ui->dwfl, ip);
  61         if (mod) {
  62                 Dwarf_Addr s;
  63
  64                 dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
  65                 if (s != map__start(al->map) - map__pgoff(al->map))
  66                         mod = 0;
  67         }
  68
  69         if (!mod)
  70                 mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1,
  71                                       map__start(al->map) - map__pgoff(al->map), false);
  72         if (!mod) {
  73                 char filename[PATH_MAX];
  74
  75                 if (dso__build_id_filename(dso, filename, sizeof(filename), false))
  76                         mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
  77                                               map__start(al->map) - map__pgoff(al->map), false);
  78         }
  79
  80         if (mod) {
  81                 void **userdatap;
  82
  83                 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL);
  84                 *userdatap = dso;
  85         }
  86
  87         return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
  88 }
  89
  90 static int report_module(u64 ip, struct unwind_info *ui)
  91 {
  92         struct addr_location al;
  93
  94         return __report_module(&al, ip, ui);
  95 }
  96
  97 /*
  98  * Store all entries within entries array,
  99  * we will process it after we finish unwind.
 100  */
 101 static int entry(u64 ip, struct unwind_info *ui)
 102
 103 {
 104         struct unwind_entry *e = &ui->entries[ui->idx++];
 105         struct addr_location al;
 106
 107         if (__report_module(&al, ip, ui))
 108                 return -1;
 109
 110         e->ip     = ip;
 111         e->ms.maps = al.maps;
 112         e->ms.map = al.map;
 113         e->ms.sym = al.sym;
 114
 115         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
 116                  al.sym ? al.sym->name : "''",
 117                  ip,
 118                  al.map ? map__map_ip(al.map, ip) : (u64) 0);
 119         return 0;
 120 }
 121
 122 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
 123 {
 124         /* We want only single thread to be processed. */
 125         if (*thread_argp != NULL)
 126                 return 0;
 127
 128         *thread_argp = arg;
 129         return dwfl_pid(dwfl);
 130 }
 131
 132 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 133                           Dwarf_Word *data)
 134 {
 135         struct addr_location al;
 136         ssize_t size;
 137         struct dso *dso;
 138
 139         if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
 140                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 141                 return -1;
 142         }
 143         dso = map__dso(al.map);
 144         if (!dso)
 145                 return -1;
 146
 147         size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data));
 148
 149         return !(size == sizeof(*data));
 150 }
 151
 152 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
 153                         void *arg)
 154 {
 155         struct unwind_info *ui = arg;
 156         struct stack_dump *stack = &ui->sample->user_stack;
 157         u64 start, end;
 158         int offset;
 159         int ret;
 160
 161         ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
 162         if (ret)
 163                 return false;
 164
 165         end = start + stack->size;
 166
 167         /* Check overflow. */
 168         if (addr + sizeof(Dwarf_Word) < addr)
 169                 return false;
 170
 171         if (addr < start || addr + sizeof(Dwarf_Word) > end) {
 172                 ret = access_dso_mem(ui, addr, result);
 173                 if (ret) {
 174                         pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
 175                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 176                                 addr, start, end);
 177                         return false;
 178                 }
 179                 return true;
 180         }
 181
 182         offset  = addr - start;
 183         *result = *(Dwarf_Word *)&stack->data[offset];
 184         pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
 185                  addr, (unsigned long)*result, offset);
 186         return true;
 187 }
 188
 189 static const Dwfl_Thread_Callbacks callbacks = {
 190         .next_thread            = next_thread,
 191         .memory_read            = memory_read,
 192         .set_initial_registers  = libdw__arch_set_initial_registers,
 193 };
 194
 195 static int
 196 frame_callback(Dwfl_Frame *state, void *arg)
 197 {
 198         struct unwind_info *ui = arg;
 199         Dwarf_Addr pc;
 200         bool isactivation;
 201
 202         if (!dwfl_frame_pc(state, &pc, NULL)) {
 203                 if (!ui->best_effort)
 204                         pr_err("%s", dwfl_errmsg(-1));
 205                 return DWARF_CB_ABORT;
 206         }
 207
 208         // report the module before we query for isactivation
 209         report_module(pc, ui);
 210
 211         if (!dwfl_frame_pc(state, &pc, &isactivation)) {
 212                 if (!ui->best_effort)
 213                         pr_err("%s", dwfl_errmsg(-1));
 214                 return DWARF_CB_ABORT;
 215         }
 216
 217         if (!isactivation)
 218                 --pc;
 219
 220         return entry(pc, ui) || !(--ui->max_stack) ?
 221                DWARF_CB_ABORT : DWARF_CB_OK;
 222 }
 223
 224 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 225                         struct thread *thread,
 226                         struct perf_sample *data,
 227                         int max_stack,
 228                         bool best_effort)
 229 {
 230         struct unwind_info *ui, ui_buf = {
 231                 .sample         = data,
 232                 .thread         = thread,
 233                 .machine        = RC_CHK_ACCESS(thread->maps)->machine,
 234                 .cb             = cb,
 235                 .arg            = arg,
 236                 .max_stack      = max_stack,
 237                 .best_effort    = best_effort
 238         };
 239         Dwarf_Word ip;
 240         int err = -EINVAL, i;
 241
 242         if (!data->user_regs.regs)
 243                 return -EINVAL;
 244
 245         ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 246         if (!ui)
 247                 return -ENOMEM;
 248
 249         *ui = ui_buf;
 250
 251         ui->dwfl = dwfl_begin(&offline_callbacks);
 252         if (!ui->dwfl)
 253                 goto out;
 254
 255         err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
 256         if (err)
 257                 goto out;
 258
 259         err = report_module(ip, ui);
 260         if (err)
 261                 goto out;
 262
 263         err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
 264         if (err)
 265                 goto out;
 266
 267         err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
 268
 269         if (err && ui->max_stack != max_stack)
 270                 err = 0;
 271
 272         /*
 273          * Display what we got based on the order setup.
 274          */
 275         for (i = 0; i < ui->idx && !err; i++) {
 276                 int j = i;
 277
 278                 if (callchain_param.order == ORDER_CALLER)
 279                         j = ui->idx - i - 1;
 280
 281                 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 282         }
 283
 284  out:
 285         if (err)
 286                 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 287
 288         dwfl_end(ui->dwfl);
 289         free(ui);
 290         return 0;
 291 }