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