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