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                 mod = dwfl_report_elf(ui->dwfl, dso->short_name,
  44                                       dso->long_name, -1, al->map->start,
  45                                       false);
  46
  47         return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
  48 }
  49
  50 static int report_module(u64 ip, struct unwind_info *ui)
  51 {
  52         struct addr_location al;
  53
  54         return __report_module(&al, ip, ui);
  55 }
  56
  57 /*
  58  * Store all entries within entries array,
  59  * we will process it after we finish unwind.
  60  */
  61 static int entry(u64 ip, struct unwind_info *ui)
  62
  63 {
  64         struct unwind_entry *e = &ui->entries[ui->idx++];
  65         struct addr_location al;
  66
  67         if (__report_module(&al, ip, ui))
  68                 return -1;
  69
  70         e->ip  = al.addr;
  71         e->map = al.map;
  72         e->sym = al.sym;
  73
  74         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
  75                  al.sym ? al.sym->name : "''",
  76                  ip,
  77                  al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
  78         return 0;
  79 }
  80
  81 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
  82 {
  83         /* We want only single thread to be processed. */
  84         if (*thread_argp != NULL)
  85                 return 0;
  86
  87         *thread_argp = arg;
  88         return dwfl_pid(dwfl);
  89 }
  90
  91 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
  92                           Dwarf_Word *data)
  93 {
  94         struct addr_location al;
  95         ssize_t size;
  96
  97         thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
  98                               MAP__FUNCTION, addr, &al);
  99         if (!al.map) {
 100                 /*
 101                  * We've seen cases (softice) where DWARF unwinder went
 102                  * through non executable mmaps, which we need to lookup
 103                  * in MAP__VARIABLE tree.
 104                  */
 105                 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
 106                                       MAP__VARIABLE, addr, &al);
 107         }
 108
 109         if (!al.map) {
 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
 172         if (!dwfl_frame_pc(state, &pc, NULL)) {
 173                 pr_err("%s", dwfl_errmsg(-1));
 174                 return DWARF_CB_ABORT;
 175         }
 176
 177         return entry(pc, ui) || !(--ui->max_stack) ?
 178                DWARF_CB_ABORT : DWARF_CB_OK;
 179 }
 180
 181 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 182                         struct thread *thread,
 183                         struct perf_sample *data,
 184                         int max_stack)
 185 {
 186         struct unwind_info *ui, ui_buf = {
 187                 .sample         = data,
 188                 .thread         = thread,
 189                 .machine        = thread->mg->machine,
 190                 .cb             = cb,
 191                 .arg            = arg,
 192                 .max_stack      = max_stack,
 193         };
 194         Dwarf_Word ip;
 195         int err = -EINVAL, i;
 196
 197         if (!data->user_regs.regs)
 198                 return -EINVAL;
 199
 200         ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 201         if (!ui)
 202                 return -ENOMEM;
 203
 204         *ui = ui_buf;
 205
 206         ui->dwfl = dwfl_begin(&offline_callbacks);
 207         if (!ui->dwfl)
 208                 goto out;
 209
 210         err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
 211         if (err)
 212                 goto out;
 213
 214         err = report_module(ip, ui);
 215         if (err)
 216                 goto out;
 217
 218         if (!dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui))
 219                 goto out;
 220
 221         err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
 222
 223         if (err && !ui->max_stack)
 224                 err = 0;
 225
 226         /*
 227          * Display what we got based on the order setup.
 228          */
 229         for (i = 0; i < ui->idx && !err; i++) {
 230                 int j = i;
 231
 232                 if (callchain_param.order == ORDER_CALLER)
 233                         j = ui->idx - i - 1;
 234
 235                 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 236         }
 237
 238  out:
 239         if (err)
 240                 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 241
 242         dwfl_end(ui->dwfl);
 243         free(ui);
 244         return 0;
 245 }