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