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                 char filename[PATH_MAX];
  71
  72                 __symbol__join_symfs(filename, sizeof(filename), dso->long_name);
  73                 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
  74                                       map__start(al->map) - map__pgoff(al->map), false);
  75         }
  76         if (!mod) {
  77                 char filename[PATH_MAX];
  78
  79                 if (dso__build_id_filename(dso, filename, sizeof(filename), false))
  80                         mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
  81                                               map__start(al->map) - map__pgoff(al->map), false);
  82         }
  83
  84         if (mod) {
  85                 void **userdatap;
  86
  87                 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL);
  88                 *userdatap = dso;
  89         }
  90
  91         return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
  92 }
  93
  94 static int report_module(u64 ip, struct unwind_info *ui)
  95 {
  96         struct addr_location al;
  97         int res;
  98
  99         addr_location__init(&al);
 100         res = __report_module(&al, ip, ui);
 101         addr_location__exit(&al);
 102         return res;
 103 }
 104
 105 /*
 106  * Store all entries within entries array,
 107  * we will process it after we finish unwind.
 108  */
 109 static int entry(u64 ip, struct unwind_info *ui)
 110
 111 {
 112         struct unwind_entry *e = &ui->entries[ui->idx++];
 113         struct addr_location al;
 114
 115         addr_location__init(&al);
 116         if (__report_module(&al, ip, ui)) {
 117                 addr_location__exit(&al);
 118                 return -1;
 119         }
 120
 121         e->ip     = ip;
 122         e->ms.maps = al.maps;
 123         e->ms.map = al.map;
 124         e->ms.sym = al.sym;
 125
 126         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
 127                  al.sym ? al.sym->name : "''",
 128                  ip,
 129                  al.map ? map__map_ip(al.map, ip) : (u64) 0);
 130         addr_location__exit(&al);
 131         return 0;
 132 }
 133
 134 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
 135 {
 136         /* We want only single thread to be processed. */
 137         if (*thread_argp != NULL)
 138                 return 0;
 139
 140         *thread_argp = arg;
 141         return dwfl_pid(dwfl);
 142 }
 143
 144 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 145                           Dwarf_Word *data)
 146 {
 147         struct addr_location al;
 148         ssize_t size;
 149         struct dso *dso;
 150
 151         addr_location__init(&al);
 152         if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
 153                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 154                 goto out_fail;
 155         }
 156         dso = map__dso(al.map);
 157         if (!dso)
 158                 goto out_fail;
 159
 160         size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data));
 161
 162         addr_location__exit(&al);
 163         return !(size == sizeof(*data));
 164 out_fail:
 165         addr_location__exit(&al);
 166         return -1;
 167 }
 168
 169 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
 170                         void *arg)
 171 {
 172         struct unwind_info *ui = arg;
 173         struct stack_dump *stack = &ui->sample->user_stack;
 174         u64 start, end;
 175         int offset;
 176         int ret;
 177
 178         ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
 179         if (ret)
 180                 return false;
 181
 182         end = start + stack->size;
 183
 184         /* Check overflow. */
 185         if (addr + sizeof(Dwarf_Word) < addr)
 186                 return false;
 187
 188         if (addr < start || addr + sizeof(Dwarf_Word) > end) {
 189                 ret = access_dso_mem(ui, addr, result);
 190                 if (ret) {
 191                         pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
 192                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 193                                 addr, start, end);
 194                         return false;
 195                 }
 196                 return true;
 197         }
 198
 199         offset  = addr - start;
 200         *result = *(Dwarf_Word *)&stack->data[offset];
 201         pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
 202                  addr, (unsigned long)*result, offset);
 203         return true;
 204 }
 205
 206 static const Dwfl_Thread_Callbacks callbacks = {
 207         .next_thread            = next_thread,
 208         .memory_read            = memory_read,
 209         .set_initial_registers  = libdw__arch_set_initial_registers,
 210 };
 211
 212 static int
 213 frame_callback(Dwfl_Frame *state, void *arg)
 214 {
 215         struct unwind_info *ui = arg;
 216         Dwarf_Addr pc;
 217         bool isactivation;
 218
 219         if (!dwfl_frame_pc(state, &pc, NULL)) {
 220                 if (!ui->best_effort)
 221                         pr_err("%s", dwfl_errmsg(-1));
 222                 return DWARF_CB_ABORT;
 223         }
 224
 225         // report the module before we query for isactivation
 226         report_module(pc, ui);
 227
 228         if (!dwfl_frame_pc(state, &pc, &isactivation)) {
 229                 if (!ui->best_effort)
 230                         pr_err("%s", dwfl_errmsg(-1));
 231                 return DWARF_CB_ABORT;
 232         }
 233
 234         if (!isactivation)
 235                 --pc;
 236
 237         return entry(pc, ui) || !(--ui->max_stack) ?
 238                DWARF_CB_ABORT : DWARF_CB_OK;
 239 }
 240
 241 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 242                         struct thread *thread,
 243                         struct perf_sample *data,
 244                         int max_stack,
 245                         bool best_effort)
 246 {
 247         struct unwind_info *ui, ui_buf = {
 248                 .sample         = data,
 249                 .thread         = thread,
 250                 .machine        = RC_CHK_ACCESS(thread__maps(thread))->machine,
 251                 .cb             = cb,
 252                 .arg            = arg,
 253                 .max_stack      = max_stack,
 254                 .best_effort    = best_effort
 255         };
 256         Dwarf_Word ip;
 257         int err = -EINVAL, i;
 258
 259         if (!data->user_regs.regs)
 260                 return -EINVAL;
 261
 262         ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 263         if (!ui)
 264                 return -ENOMEM;
 265
 266         *ui = ui_buf;
 267
 268         ui->dwfl = dwfl_begin(&offline_callbacks);
 269         if (!ui->dwfl)
 270                 goto out;
 271
 272         err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
 273         if (err)
 274                 goto out;
 275
 276         err = report_module(ip, ui);
 277         if (err)
 278                 goto out;
 279
 280         err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui);
 281         if (err)
 282                 goto out;
 283
 284         err = dwfl_getthread_frames(ui->dwfl, thread__tid(thread), frame_callback, ui);
 285
 286         if (err && ui->max_stack != max_stack)
 287                 err = 0;
 288
 289         /*
 290          * Display what we got based on the order setup.
 291          */
 292         for (i = 0; i < ui->idx && !err; i++) {
 293                 int j = i;
 294
 295                 if (callchain_param.order == ORDER_CALLER)
 296                         j = ui->idx - i - 1;
 297
 298                 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 299         }
 300
 301  out:
 302         if (err)
 303                 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 304
 305         dwfl_end(ui->dwfl);
 306         free(ui);
 307         return 0;
 308 }