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 = al->map->dso;
  56
  57         if (!dso)
  58                 return 0;
  59
  60         mod = dwfl_addrmodule(ui->dwfl, ip);
  61         if (mod) {
  62                 Dwarf_Addr s;
  63                 void **userdatap;
  64
  65                 dwfl_module_info(mod, &userdatap, &s, NULL, NULL, NULL, NULL, NULL);
  66                 *userdatap = dso;
  67                 if (s != al->map->start - al->map->pgoff)
  68                         mod = 0;
  69         }
  70
  71         if (!mod)
  72                 mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1,
  73                                       al->map->start - al->map->pgoff, false);
  74         if (!mod) {
  75                 char filename[PATH_MAX];
  76
  77                 if (dso__build_id_filename(dso, filename, sizeof(filename), false))
  78                         mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
  79                                               al->map->start - al->map->pgoff, false);
  80         }
  81
  82         return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
  83 }
  84
  85 static int report_module(u64 ip, struct unwind_info *ui)
  86 {
  87         struct addr_location al;
  88
  89         return __report_module(&al, ip, ui);
  90 }
  91
  92 /*
  93  * Store all entries within entries array,
  94  * we will process it after we finish unwind.
  95  */
  96 static int entry(u64 ip, struct unwind_info *ui)
  97
  98 {
  99         struct unwind_entry *e = &ui->entries[ui->idx++];
 100         struct addr_location al;
 101
 102         if (__report_module(&al, ip, ui))
 103                 return -1;
 104
 105         e->ip     = ip;
 106         e->ms.maps = al.maps;
 107         e->ms.map = al.map;
 108         e->ms.sym = al.sym;
 109
 110         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
 111                  al.sym ? al.sym->name : "''",
 112                  ip,
 113                  al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
 114         return 0;
 115 }
 116
 117 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
 118 {
 119         /* We want only single thread to be processed. */
 120         if (*thread_argp != NULL)
 121                 return 0;
 122
 123         *thread_argp = arg;
 124         return dwfl_pid(dwfl);
 125 }
 126
 127 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 128                           Dwarf_Word *data)
 129 {
 130         struct addr_location al;
 131         ssize_t size;
 132
 133         if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
 134                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 135                 return -1;
 136         }
 137
 138         if (!al.map->dso)
 139                 return -1;
 140
 141         size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
 142                                    addr, (u8 *) data, sizeof(*data));
 143
 144         return !(size == sizeof(*data));
 145 }
 146
 147 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
 148                         void *arg)
 149 {
 150         struct unwind_info *ui = arg;
 151         struct stack_dump *stack = &ui->sample->user_stack;
 152         u64 start, end;
 153         int offset;
 154         int ret;
 155
 156         ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
 157         if (ret)
 158                 return false;
 159
 160         end = start + stack->size;
 161
 162         /* Check overflow. */
 163         if (addr + sizeof(Dwarf_Word) < addr)
 164                 return false;
 165
 166         if (addr < start || addr + sizeof(Dwarf_Word) > end) {
 167                 ret = access_dso_mem(ui, addr, result);
 168                 if (ret) {
 169                         pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
 170                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 171                                 addr, start, end);
 172                         return false;
 173                 }
 174                 return true;
 175         }
 176
 177         offset  = addr - start;
 178         *result = *(Dwarf_Word *)&stack->data[offset];
 179         pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
 180                  addr, (unsigned long)*result, offset);
 181         return true;
 182 }
 183
 184 static const Dwfl_Thread_Callbacks callbacks = {
 185         .next_thread            = next_thread,
 186         .memory_read            = memory_read,
 187         .set_initial_registers  = libdw__arch_set_initial_registers,
 188 };
 189
 190 static int
 191 frame_callback(Dwfl_Frame *state, void *arg)
 192 {
 193         struct unwind_info *ui = arg;
 194         Dwarf_Addr pc;
 195         bool isactivation;
 196
 197         if (!dwfl_frame_pc(state, &pc, NULL)) {
 198                 pr_err("%s", dwfl_errmsg(-1));
 199                 return DWARF_CB_ABORT;
 200         }
 201
 202         // report the module before we query for isactivation
 203         report_module(pc, ui);
 204
 205         if (!dwfl_frame_pc(state, &pc, &isactivation)) {
 206                 pr_err("%s", dwfl_errmsg(-1));
 207                 return DWARF_CB_ABORT;
 208         }
 209
 210         if (!isactivation)
 211                 --pc;
 212
 213         return entry(pc, ui) || !(--ui->max_stack) ?
 214                DWARF_CB_ABORT : DWARF_CB_OK;
 215 }
 216
 217 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 218                         struct thread *thread,
 219                         struct perf_sample *data,
 220                         int max_stack)
 221 {
 222         struct unwind_info *ui, ui_buf = {
 223                 .sample         = data,
 224                 .thread         = thread,
 225                 .machine        = thread->maps->machine,
 226                 .cb             = cb,
 227                 .arg            = arg,
 228                 .max_stack      = max_stack,
 229         };
 230         Dwarf_Word ip;
 231         int err = -EINVAL, i;
 232
 233         if (!data->user_regs.regs)
 234                 return -EINVAL;
 235
 236         ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 237         if (!ui)
 238                 return -ENOMEM;
 239
 240         *ui = ui_buf;
 241
 242         ui->dwfl = dwfl_begin(&offline_callbacks);
 243         if (!ui->dwfl)
 244                 goto out;
 245
 246         err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
 247         if (err)
 248                 goto out;
 249
 250         err = report_module(ip, ui);
 251         if (err)
 252                 goto out;
 253
 254         err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
 255         if (err)
 256                 goto out;
 257
 258         err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
 259
 260         if (err && ui->max_stack != max_stack)
 261                 err = 0;
 262
 263         /*
 264          * Display what we got based on the order setup.
 265          */
 266         for (i = 0; i < ui->idx && !err; i++) {
 267                 int j = i;
 268
 269                 if (callchain_param.order == ORDER_CALLER)
 270                         j = ui->idx - i - 1;
 271
 272                 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 273         }
 274
 275  out:
 276         if (err)
 277                 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 278
 279         dwfl_end(ui->dwfl);
 280         free(ui);
 281         return 0;
 282 }