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