tools/perf/util/unwind-libdw.c

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