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 char filename[PATH_MAX]; 71 72 __symbol__join_symfs(filename, sizeof(filename), dso->long_name); 73 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1, 74 map__start(al->map) - map__pgoff(al->map), false); 75 } 76 if (!mod) { 77 char filename[PATH_MAX]; 78 79 if (dso__build_id_filename(dso, filename, sizeof(filename), false)) 80 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1, 81 map__start(al->map) - map__pgoff(al->map), false); 82 } 83 84 if (mod) { 85 void **userdatap; 86 87 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL); 88 *userdatap = dso; 89 } 90 91 return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1; 92 } 93 94 static int report_module(u64 ip, struct unwind_info *ui) 95 { 96 struct addr_location al; 97 int res; 98 99 addr_location__init(&al); 100 res = __report_module(&al, ip, ui); 101 addr_location__exit(&al); 102 return res; 103 } 104 105 /* 106 * Store all entries within entries array, 107 * we will process it after we finish unwind. 108 */ 109 static int entry(u64 ip, struct unwind_info *ui) 110 111 { 112 struct unwind_entry *e = &ui->entries[ui->idx++]; 113 struct addr_location al; 114 115 addr_location__init(&al); 116 if (__report_module(&al, ip, ui)) { 117 addr_location__exit(&al); 118 return -1; 119 } 120 121 e->ip = ip; 122 e->ms.maps = al.maps; 123 e->ms.map = al.map; 124 e->ms.sym = al.sym; 125 126 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 127 al.sym ? al.sym->name : "''", 128 ip, 129 al.map ? map__map_ip(al.map, ip) : (u64) 0); 130 addr_location__exit(&al); 131 return 0; 132 } 133 134 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp) 135 { 136 /* We want only single thread to be processed. */ 137 if (*thread_argp != NULL) 138 return 0; 139 140 *thread_argp = arg; 141 return dwfl_pid(dwfl); 142 } 143 144 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr, 145 Dwarf_Word *data) 146 { 147 struct addr_location al; 148 ssize_t size; 149 struct dso *dso; 150 151 addr_location__init(&al); 152 if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) { 153 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 154 goto out_fail; 155 } 156 dso = map__dso(al.map); 157 if (!dso) 158 goto out_fail; 159 160 size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data)); 161 162 addr_location__exit(&al); 163 return !(size == sizeof(*data)); 164 out_fail: 165 addr_location__exit(&al); 166 return -1; 167 } 168 169 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result, 170 void *arg) 171 { 172 struct unwind_info *ui = arg; 173 struct stack_dump *stack = &ui->sample->user_stack; 174 u64 start, end; 175 int offset; 176 int ret; 177 178 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP); 179 if (ret) 180 return false; 181 182 end = start + stack->size; 183 184 /* Check overflow. */ 185 if (addr + sizeof(Dwarf_Word) < addr) 186 return false; 187 188 if (addr < start || addr + sizeof(Dwarf_Word) > end) { 189 ret = access_dso_mem(ui, addr, result); 190 if (ret) { 191 pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range" 192 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 193 addr, start, end); 194 return false; 195 } 196 return true; 197 } 198 199 offset = addr - start; 200 *result = *(Dwarf_Word *)&stack->data[offset]; 201 pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n", 202 addr, (unsigned long)*result, offset); 203 return true; 204 } 205 206 static const Dwfl_Thread_Callbacks callbacks = { 207 .next_thread = next_thread, 208 .memory_read = memory_read, 209 .set_initial_registers = libdw__arch_set_initial_registers, 210 }; 211 212 static int 213 frame_callback(Dwfl_Frame *state, void *arg) 214 { 215 struct unwind_info *ui = arg; 216 Dwarf_Addr pc; 217 bool isactivation; 218 219 if (!dwfl_frame_pc(state, &pc, NULL)) { 220 if (!ui->best_effort) 221 pr_err("%s", dwfl_errmsg(-1)); 222 return DWARF_CB_ABORT; 223 } 224 225 // report the module before we query for isactivation 226 report_module(pc, ui); 227 228 if (!dwfl_frame_pc(state, &pc, &isactivation)) { 229 if (!ui->best_effort) 230 pr_err("%s", dwfl_errmsg(-1)); 231 return DWARF_CB_ABORT; 232 } 233 234 if (!isactivation) 235 --pc; 236 237 return entry(pc, ui) || !(--ui->max_stack) ? 238 DWARF_CB_ABORT : DWARF_CB_OK; 239 } 240 241 int unwind__get_entries(unwind_entry_cb_t cb, void *arg, 242 struct thread *thread, 243 struct perf_sample *data, 244 int max_stack, 245 bool best_effort) 246 { 247 struct unwind_info *ui, ui_buf = { 248 .sample = data, 249 .thread = thread, 250 .machine = RC_CHK_ACCESS(thread__maps(thread))->machine, 251 .cb = cb, 252 .arg = arg, 253 .max_stack = max_stack, 254 .best_effort = best_effort 255 }; 256 Dwarf_Word ip; 257 int err = -EINVAL, i; 258 259 if (!data->user_regs.regs) 260 return -EINVAL; 261 262 ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack); 263 if (!ui) 264 return -ENOMEM; 265 266 *ui = ui_buf; 267 268 ui->dwfl = dwfl_begin(&offline_callbacks); 269 if (!ui->dwfl) 270 goto out; 271 272 err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP); 273 if (err) 274 goto out; 275 276 err = report_module(ip, ui); 277 if (err) 278 goto out; 279 280 err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui); 281 if (err) 282 goto out; 283 284 err = dwfl_getthread_frames(ui->dwfl, thread__tid(thread), frame_callback, ui); 285 286 if (err && ui->max_stack != max_stack) 287 err = 0; 288 289 /* 290 * Display what we got based on the order setup. 291 */ 292 for (i = 0; i < ui->idx && !err; i++) { 293 int j = i; 294 295 if (callchain_param.order == ORDER_CALLER) 296 j = ui->idx - i - 1; 297 298 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0; 299 } 300 301 out: 302 if (err) 303 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1)); 304 305 dwfl_end(ui->dwfl); 306 free(ui); 307 return 0; 308 } 309