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