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