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 #include "util/env.h"
  21
  22 static char *debuginfo_path;
  23
  24 static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata,
  25                             const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused,
  26                             const char *file_name, const char *debuglink_file __maybe_unused,
  27                             GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name)
  28 {
  29         const struct dso *dso = *userdata;
  30
  31         assert(dso);
  32         if (dso->symsrc_filename && strcmp (file_name, dso->symsrc_filename))
  33                 *debuginfo_file_name = strdup(dso->symsrc_filename);
  34         return -1;
  35 }
  36
  37 static const Dwfl_Callbacks offline_callbacks = {
  38         .find_debuginfo         = __find_debuginfo,
  39         .debuginfo_path         = &debuginfo_path,
  40         .section_address        = dwfl_offline_section_address,
  41         // .find_elf is not set as we use dwfl_report_elf() instead.
  42 };
  43
  44 static int __report_module(struct addr_location *al, u64 ip,
  45                             struct unwind_info *ui)
  46 {
  47         Dwfl_Module *mod;
  48         struct dso *dso = NULL;
  49         Dwarf_Addr base;
  50         /*
  51          * Some callers will use al->sym, so we can't just use the
  52          * cheaper thread__find_map() here.
  53          */
  54         thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
  55
  56         if (al->map)
  57                 dso = map__dso(al->map);
  58
  59         if (!dso)
  60                 return 0;
  61
  62         /*
  63          * The generated JIT DSO files only map the code segment without
  64          * ELF headers.  Since JIT codes used to be packed in a memory
  65          * segment, calculating the base address using pgoff falls into
  66          * a different code in another DSO.  So just use the map->start
  67          * directly to pick the correct one.
  68          */
  69         if (!strncmp(dso->long_name, "/tmp/jitted-", 12))
  70                 base = map__start(al->map);
  71         else
  72                 base = map__start(al->map) - map__pgoff(al->map);
  73
  74         mod = dwfl_addrmodule(ui->dwfl, ip);
  75         if (mod) {
  76                 Dwarf_Addr s;
  77
  78                 dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
  79                 if (s != base)
  80                         mod = NULL;
  81         }
  82
  83         if (!mod) {
  84                 char filename[PATH_MAX];
  85
  86                 __symbol__join_symfs(filename, sizeof(filename), dso->long_name);
  87                 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
  88                                       base, false);
  89         }
  90         if (!mod) {
  91                 char filename[PATH_MAX];
  92
  93                 if (dso__build_id_filename(dso, filename, sizeof(filename), false))
  94                         mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
  95                                               base, false);
  96         }
  97
  98         if (mod) {
  99                 void **userdatap;
 100
 101                 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL);
 102                 *userdatap = dso;
 103         }
 104
 105         return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
 106 }
 107
 108 static int report_module(u64 ip, struct unwind_info *ui)
 109 {
 110         struct addr_location al;
 111         int res;
 112
 113         addr_location__init(&al);
 114         res = __report_module(&al, ip, ui);
 115         addr_location__exit(&al);
 116         return res;
 117 }
 118
 119 /*
 120  * Store all entries within entries array,
 121  * we will process it after we finish unwind.
 122  */
 123 static int entry(u64 ip, struct unwind_info *ui)
 124
 125 {
 126         struct unwind_entry *e = &ui->entries[ui->idx++];
 127         struct addr_location al;
 128
 129         addr_location__init(&al);
 130         if (__report_module(&al, ip, ui)) {
 131                 addr_location__exit(&al);
 132                 return -1;
 133         }
 134
 135         e->ip     = ip;
 136         e->ms.maps = al.maps;
 137         e->ms.map = al.map;
 138         e->ms.sym = al.sym;
 139
 140         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
 141                  al.sym ? al.sym->name : "''",
 142                  ip,
 143                  al.map ? map__map_ip(al.map, ip) : (u64) 0);
 144         addr_location__exit(&al);
 145         return 0;
 146 }
 147
 148 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
 149 {
 150         /* We want only single thread to be processed. */
 151         if (*thread_argp != NULL)
 152                 return 0;
 153
 154         *thread_argp = arg;
 155         return dwfl_pid(dwfl);
 156 }
 157
 158 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 159                           Dwarf_Word *data)
 160 {
 161         struct addr_location al;
 162         ssize_t size;
 163         struct dso *dso;
 164
 165         addr_location__init(&al);
 166         if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
 167                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 168                 goto out_fail;
 169         }
 170         dso = map__dso(al.map);
 171         if (!dso)
 172                 goto out_fail;
 173
 174         size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data));
 175
 176         addr_location__exit(&al);
 177         return !(size == sizeof(*data));
 178 out_fail:
 179         addr_location__exit(&al);
 180         return -1;
 181 }
 182
 183 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
 184                         void *arg)
 185 {
 186         struct unwind_info *ui = arg;
 187         const char *arch = perf_env__arch(ui->machine->env);
 188         struct stack_dump *stack = &ui->sample->user_stack;
 189         u64 start, end;
 190         int offset;
 191         int ret;
 192
 193         ret = perf_reg_value(&start, &ui->sample->user_regs,
 194                              perf_arch_reg_sp(arch));
 195         if (ret)
 196                 return false;
 197
 198         end = start + stack->size;
 199
 200         /* Check overflow. */
 201         if (addr + sizeof(Dwarf_Word) < addr)
 202                 return false;
 203
 204         if (addr < start || addr + sizeof(Dwarf_Word) > end) {
 205                 ret = access_dso_mem(ui, addr, result);
 206                 if (ret) {
 207                         pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
 208                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 209                                 addr, start, end);
 210                         return false;
 211                 }
 212                 return true;
 213         }
 214
 215         offset  = addr - start;
 216         *result = *(Dwarf_Word *)&stack->data[offset];
 217         pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
 218                  addr, (unsigned long)*result, offset);
 219         return true;
 220 }
 221
 222 static const Dwfl_Thread_Callbacks callbacks = {
 223         .next_thread            = next_thread,
 224         .memory_read            = memory_read,
 225         .set_initial_registers  = libdw__arch_set_initial_registers,
 226 };
 227
 228 static int
 229 frame_callback(Dwfl_Frame *state, void *arg)
 230 {
 231         struct unwind_info *ui = arg;
 232         Dwarf_Addr pc;
 233         bool isactivation;
 234
 235         if (!dwfl_frame_pc(state, &pc, NULL)) {
 236                 if (!ui->best_effort)
 237                         pr_err("%s", dwfl_errmsg(-1));
 238                 return DWARF_CB_ABORT;
 239         }
 240
 241         // report the module before we query for isactivation
 242         report_module(pc, ui);
 243
 244         if (!dwfl_frame_pc(state, &pc, &isactivation)) {
 245                 if (!ui->best_effort)
 246                         pr_err("%s", dwfl_errmsg(-1));
 247                 return DWARF_CB_ABORT;
 248         }
 249
 250         if (!isactivation)
 251                 --pc;
 252
 253         return entry(pc, ui) || !(--ui->max_stack) ?
 254                DWARF_CB_ABORT : DWARF_CB_OK;
 255 }
 256
 257 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 258                         struct thread *thread,
 259                         struct perf_sample *data,
 260                         int max_stack,
 261                         bool best_effort)
 262 {
 263         struct unwind_info *ui, ui_buf = {
 264                 .sample         = data,
 265                 .thread         = thread,
 266                 .machine        = maps__machine((thread__maps(thread))),
 267                 .cb             = cb,
 268                 .arg            = arg,
 269                 .max_stack      = max_stack,
 270                 .best_effort    = best_effort
 271         };
 272         const char *arch = perf_env__arch(ui_buf.machine->env);
 273         Dwarf_Word ip;
 274         int err = -EINVAL, i;
 275
 276         if (!data->user_regs.regs)
 277                 return -EINVAL;
 278
 279         ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 280         if (!ui)
 281                 return -ENOMEM;
 282
 283         *ui = ui_buf;
 284
 285         ui->dwfl = dwfl_begin(&offline_callbacks);
 286         if (!ui->dwfl)
 287                 goto out;
 288
 289         err = perf_reg_value(&ip, &data->user_regs, perf_arch_reg_ip(arch));
 290         if (err)
 291                 goto out;
 292
 293         err = report_module(ip, ui);
 294         if (err)
 295                 goto out;
 296
 297         err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui);
 298         if (err)
 299                 goto out;
 300
 301         err = dwfl_getthread_frames(ui->dwfl, thread__tid(thread), frame_callback, ui);
 302
 303         if (err && ui->max_stack != max_stack)
 304                 err = 0;
 305
 306         /*
 307          * Display what we got based on the order setup.
 308          */
 309         for (i = 0; i < ui->idx && !err; i++) {
 310                 int j = i;
 311
 312                 if (callchain_param.order == ORDER_CALLER)
 313                         j = ui->idx - i - 1;
 314
 315                 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 316         }
 317
 318  out:
 319         if (err)
 320                 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 321
 322         dwfl_end(ui->dwfl);
 323         free(ui);
 324         return 0;
 325 }