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