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