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