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