1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/compiler.h> 3 #include <elfutils/libdw.h> 4 #include <elfutils/libdwfl.h> 5 #include <inttypes.h> 6 #include <errno.h> 7 #include "debug.h" 8 #include "dso.h" 9 #include "unwind.h" 10 #include "unwind-libdw.h" 11 #include "machine.h" 12 #include "map.h" 13 #include "symbol.h" 14 #include "thread.h" 15 #include <linux/types.h> 16 #include <linux/zalloc.h> 17 #include "event.h" 18 #include "perf_regs.h" 19 #include "callchain.h" 20 21 static char *debuginfo_path; 22 23 static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata, 24 const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused, 25 const char *file_name, const char *debuglink_file __maybe_unused, 26 GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name) 27 { 28 const struct dso *dso = *userdata; 29 30 assert(dso); 31 if (dso->symsrc_filename && strcmp (file_name, dso->symsrc_filename)) 32 *debuginfo_file_name = strdup(dso->symsrc_filename); 33 return -1; 34 } 35 36 static const Dwfl_Callbacks offline_callbacks = { 37 .find_debuginfo = __find_debuginfo, 38 .debuginfo_path = &debuginfo_path, 39 .section_address = dwfl_offline_section_address, 40 // .find_elf is not set as we use dwfl_report_elf() instead. 41 }; 42 43 static int __report_module(struct addr_location *al, u64 ip, 44 struct unwind_info *ui) 45 { 46 Dwfl_Module *mod; 47 struct dso *dso = NULL; 48 /* 49 * Some callers will use al->sym, so we can't just use the 50 * cheaper thread__find_map() here. 51 */ 52 thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al); 53 54 if (al->map) 55 dso = map__dso(al->map); 56 57 if (!dso) 58 return 0; 59 60 mod = dwfl_addrmodule(ui->dwfl, ip); 61 if (mod) { 62 Dwarf_Addr s; 63 64 dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL); 65 if (s != map__start(al->map) - map__pgoff(al->map)) 66 mod = 0; 67 } 68 69 if (!mod) 70 mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1, 71 map__start(al->map) - map__pgoff(al->map), false); 72 if (!mod) { 73 char filename[PATH_MAX]; 74 75 if (dso__build_id_filename(dso, filename, sizeof(filename), false)) 76 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1, 77 map__start(al->map) - map__pgoff(al->map), false); 78 } 79 80 if (mod) { 81 void **userdatap; 82 83 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL); 84 *userdatap = dso; 85 } 86 87 return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1; 88 } 89 90 static int report_module(u64 ip, struct unwind_info *ui) 91 { 92 struct addr_location al; 93 int res; 94 95 addr_location__init(&al); 96 res = __report_module(&al, ip, ui); 97 addr_location__exit(&al); 98 return res; 99 } 100 101 /* 102 * Store all entries within entries array, 103 * we will process it after we finish unwind. 104 */ 105 static int entry(u64 ip, struct unwind_info *ui) 106 107 { 108 struct unwind_entry *e = &ui->entries[ui->idx++]; 109 struct addr_location al; 110 111 addr_location__init(&al); 112 if (__report_module(&al, ip, ui)) { 113 addr_location__exit(&al); 114 return -1; 115 } 116 117 e->ip = ip; 118 e->ms.maps = al.maps; 119 e->ms.map = al.map; 120 e->ms.sym = al.sym; 121 122 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 123 al.sym ? al.sym->name : "''", 124 ip, 125 al.map ? map__map_ip(al.map, ip) : (u64) 0); 126 addr_location__exit(&al); 127 return 0; 128 } 129 130 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp) 131 { 132 /* We want only single thread to be processed. */ 133 if (*thread_argp != NULL) 134 return 0; 135 136 *thread_argp = arg; 137 return dwfl_pid(dwfl); 138 } 139 140 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr, 141 Dwarf_Word *data) 142 { 143 struct addr_location al; 144 ssize_t size; 145 struct dso *dso; 146 147 addr_location__init(&al); 148 if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) { 149 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 150 goto out_fail; 151 } 152 dso = map__dso(al.map); 153 if (!dso) 154 goto out_fail; 155 156 size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data)); 157 158 addr_location__exit(&al); 159 return !(size == sizeof(*data)); 160 out_fail: 161 addr_location__exit(&al); 162 return -1; 163 } 164 165 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result, 166 void *arg) 167 { 168 struct unwind_info *ui = arg; 169 struct stack_dump *stack = &ui->sample->user_stack; 170 u64 start, end; 171 int offset; 172 int ret; 173 174 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP); 175 if (ret) 176 return false; 177 178 end = start + stack->size; 179 180 /* Check overflow. */ 181 if (addr + sizeof(Dwarf_Word) < addr) 182 return false; 183 184 if (addr < start || addr + sizeof(Dwarf_Word) > end) { 185 ret = access_dso_mem(ui, addr, result); 186 if (ret) { 187 pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range" 188 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 189 addr, start, end); 190 return false; 191 } 192 return true; 193 } 194 195 offset = addr - start; 196 *result = *(Dwarf_Word *)&stack->data[offset]; 197 pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n", 198 addr, (unsigned long)*result, offset); 199 return true; 200 } 201 202 static const Dwfl_Thread_Callbacks callbacks = { 203 .next_thread = next_thread, 204 .memory_read = memory_read, 205 .set_initial_registers = libdw__arch_set_initial_registers, 206 }; 207 208 static int 209 frame_callback(Dwfl_Frame *state, void *arg) 210 { 211 struct unwind_info *ui = arg; 212 Dwarf_Addr pc; 213 bool isactivation; 214 215 if (!dwfl_frame_pc(state, &pc, NULL)) { 216 if (!ui->best_effort) 217 pr_err("%s", dwfl_errmsg(-1)); 218 return DWARF_CB_ABORT; 219 } 220 221 // report the module before we query for isactivation 222 report_module(pc, ui); 223 224 if (!dwfl_frame_pc(state, &pc, &isactivation)) { 225 if (!ui->best_effort) 226 pr_err("%s", dwfl_errmsg(-1)); 227 return DWARF_CB_ABORT; 228 } 229 230 if (!isactivation) 231 --pc; 232 233 return entry(pc, ui) || !(--ui->max_stack) ? 234 DWARF_CB_ABORT : DWARF_CB_OK; 235 } 236 237 int unwind__get_entries(unwind_entry_cb_t cb, void *arg, 238 struct thread *thread, 239 struct perf_sample *data, 240 int max_stack, 241 bool best_effort) 242 { 243 struct unwind_info *ui, ui_buf = { 244 .sample = data, 245 .thread = thread, 246 .machine = RC_CHK_ACCESS(thread__maps(thread))->machine, 247 .cb = cb, 248 .arg = arg, 249 .max_stack = max_stack, 250 .best_effort = best_effort 251 }; 252 Dwarf_Word ip; 253 int err = -EINVAL, i; 254 255 if (!data->user_regs.regs) 256 return -EINVAL; 257 258 ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack); 259 if (!ui) 260 return -ENOMEM; 261 262 *ui = ui_buf; 263 264 ui->dwfl = dwfl_begin(&offline_callbacks); 265 if (!ui->dwfl) 266 goto out; 267 268 err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP); 269 if (err) 270 goto out; 271 272 err = report_module(ip, ui); 273 if (err) 274 goto out; 275 276 err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui); 277 if (err) 278 goto out; 279 280 err = dwfl_getthread_frames(ui->dwfl, thread__tid(thread), frame_callback, ui); 281 282 if (err && ui->max_stack != max_stack) 283 err = 0; 284 285 /* 286 * Display what we got based on the order setup. 287 */ 288 for (i = 0; i < ui->idx && !err; i++) { 289 int j = i; 290 291 if (callchain_param.order == ORDER_CALLER) 292 j = ui->idx - i - 1; 293 294 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0; 295 } 296 297 out: 298 if (err) 299 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1)); 300 301 dwfl_end(ui->dwfl); 302 free(ui); 303 return 0; 304 } 305