| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * kallsyms.c: in-kernel printing of symbolic oopses and stack traces. |
| 4 | * |
| 5 | * Rewritten and vastly simplified by Rusty Russell for in-kernel |
| 6 | * module loader: |
| 7 | * Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation |
| 8 | * |
| 9 | * ChangeLog: |
| 10 | * |
| 11 | * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com> |
| 12 | * Changed the compression method from stem compression to "table lookup" |
| 13 | * compression (see scripts/kallsyms.c for a more complete description) |
| 14 | */ |
| 15 | #include <linux/kallsyms.h> |
| 16 | #include <linux/init.h> |
| 17 | #include <linux/seq_file.h> |
| 18 | #include <linux/fs.h> |
| 19 | #include <linux/kdb.h> |
| 20 | #include <linux/err.h> |
| 21 | #include <linux/proc_fs.h> |
| 22 | #include <linux/sched.h> /* for cond_resched */ |
| 23 | #include <linux/ctype.h> |
| 24 | #include <linux/slab.h> |
| 25 | #include <linux/filter.h> |
| 26 | #include <linux/ftrace.h> |
| 27 | #include <linux/kprobes.h> |
| 28 | #include <linux/build_bug.h> |
| 29 | #include <linux/compiler.h> |
| 30 | #include <linux/module.h> |
| 31 | #include <linux/kernel.h> |
| 32 | #include <linux/bsearch.h> |
| 33 | #include <linux/btf_ids.h> |
| 34 | |
| 35 | /* |
| 36 | * These will be re-linked against their real values |
| 37 | * during the second link stage. |
| 38 | */ |
| 39 | extern const unsigned long kallsyms_addresses[] __weak; |
| 40 | extern const int kallsyms_offsets[] __weak; |
| 41 | extern const u8 kallsyms_names[] __weak; |
| 42 | |
| 43 | /* |
| 44 | * Tell the compiler that the count isn't in the small data section if the arch |
| 45 | * has one (eg: FRV). |
| 46 | */ |
| 47 | extern const unsigned int kallsyms_num_syms |
| 48 | __section(".rodata") __attribute__((weak)); |
| 49 | |
| 50 | extern const unsigned long kallsyms_relative_base |
| 51 | __section(".rodata") __attribute__((weak)); |
| 52 | |
| 53 | extern const char kallsyms_token_table[] __weak; |
| 54 | extern const u16 kallsyms_token_index[] __weak; |
| 55 | |
| 56 | extern const unsigned int kallsyms_markers[] __weak; |
| 57 | |
| 58 | /* |
| 59 | * Expand a compressed symbol data into the resulting uncompressed string, |
| 60 | * if uncompressed string is too long (>= maxlen), it will be truncated, |
| 61 | * given the offset to where the symbol is in the compressed stream. |
| 62 | */ |
| 63 | static unsigned int kallsyms_expand_symbol(unsigned int off, |
| 64 | char *result, size_t maxlen) |
| 65 | { |
| 66 | int len, skipped_first = 0; |
| 67 | const char *tptr; |
| 68 | const u8 *data; |
| 69 | |
| 70 | /* Get the compressed symbol length from the first symbol byte. */ |
| 71 | data = &kallsyms_names[off]; |
| 72 | len = *data; |
| 73 | data++; |
| 74 | |
| 75 | /* |
| 76 | * Update the offset to return the offset for the next symbol on |
| 77 | * the compressed stream. |
| 78 | */ |
| 79 | off += len + 1; |
| 80 | |
| 81 | /* |
| 82 | * For every byte on the compressed symbol data, copy the table |
| 83 | * entry for that byte. |
| 84 | */ |
| 85 | while (len) { |
| 86 | tptr = &kallsyms_token_table[kallsyms_token_index[*data]]; |
| 87 | data++; |
| 88 | len--; |
| 89 | |
| 90 | while (*tptr) { |
| 91 | if (skipped_first) { |
| 92 | if (maxlen <= 1) |
| 93 | goto tail; |
| 94 | *result = *tptr; |
| 95 | result++; |
| 96 | maxlen--; |
| 97 | } else |
| 98 | skipped_first = 1; |
| 99 | tptr++; |
| 100 | } |
| 101 | } |
| 102 | |
| 103 | tail: |
| 104 | if (maxlen) |
| 105 | *result = '\0'; |
| 106 | |
| 107 | /* Return to offset to the next symbol. */ |
| 108 | return off; |
| 109 | } |
| 110 | |
| 111 | /* |
| 112 | * Get symbol type information. This is encoded as a single char at the |
| 113 | * beginning of the symbol name. |
| 114 | */ |
| 115 | static char kallsyms_get_symbol_type(unsigned int off) |
| 116 | { |
| 117 | /* |
| 118 | * Get just the first code, look it up in the token table, |
| 119 | * and return the first char from this token. |
| 120 | */ |
| 121 | return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]]; |
| 122 | } |
| 123 | |
| 124 | |
| 125 | /* |
| 126 | * Find the offset on the compressed stream given and index in the |
| 127 | * kallsyms array. |
| 128 | */ |
| 129 | static unsigned int get_symbol_offset(unsigned long pos) |
| 130 | { |
| 131 | const u8 *name; |
| 132 | int i; |
| 133 | |
| 134 | /* |
| 135 | * Use the closest marker we have. We have markers every 256 positions, |
| 136 | * so that should be close enough. |
| 137 | */ |
| 138 | name = &kallsyms_names[kallsyms_markers[pos >> 8]]; |
| 139 | |
| 140 | /* |
| 141 | * Sequentially scan all the symbols up to the point we're searching |
| 142 | * for. Every symbol is stored in a [<len>][<len> bytes of data] format, |
| 143 | * so we just need to add the len to the current pointer for every |
| 144 | * symbol we wish to skip. |
| 145 | */ |
| 146 | for (i = 0; i < (pos & 0xFF); i++) |
| 147 | name = name + (*name) + 1; |
| 148 | |
| 149 | return name - kallsyms_names; |
| 150 | } |
| 151 | |
| 152 | static unsigned long kallsyms_sym_address(int idx) |
| 153 | { |
| 154 | if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE)) |
| 155 | return kallsyms_addresses[idx]; |
| 156 | |
| 157 | /* values are unsigned offsets if --absolute-percpu is not in effect */ |
| 158 | if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU)) |
| 159 | return kallsyms_relative_base + (u32)kallsyms_offsets[idx]; |
| 160 | |
| 161 | /* ...otherwise, positive offsets are absolute values */ |
| 162 | if (kallsyms_offsets[idx] >= 0) |
| 163 | return kallsyms_offsets[idx]; |
| 164 | |
| 165 | /* ...and negative offsets are relative to kallsyms_relative_base - 1 */ |
| 166 | return kallsyms_relative_base - 1 - kallsyms_offsets[idx]; |
| 167 | } |
| 168 | |
| 169 | static bool cleanup_symbol_name(char *s) |
| 170 | { |
| 171 | char *res; |
| 172 | |
| 173 | if (!IS_ENABLED(CONFIG_LTO_CLANG)) |
| 174 | return false; |
| 175 | |
| 176 | /* |
| 177 | * LLVM appends various suffixes for local functions and variables that |
| 178 | * must be promoted to global scope as part of LTO. This can break |
| 179 | * hooking of static functions with kprobes. '.' is not a valid |
| 180 | * character in an identifier in C. Suffixes observed: |
| 181 | * - foo.llvm.[0-9a-f]+ |
| 182 | * - foo.[0-9a-f]+ |
| 183 | * - foo.[0-9a-f]+.cfi_jt |
| 184 | */ |
| 185 | res = strchr(s, '.'); |
| 186 | if (res) { |
| 187 | *res = '\0'; |
| 188 | return true; |
| 189 | } |
| 190 | |
| 191 | if (!IS_ENABLED(CONFIG_CFI_CLANG) || |
| 192 | !IS_ENABLED(CONFIG_LTO_CLANG_THIN) || |
| 193 | CONFIG_CLANG_VERSION >= 130000) |
| 194 | return false; |
| 195 | |
| 196 | /* |
| 197 | * Prior to LLVM 13, the following suffixes were observed when thinLTO |
| 198 | * and CFI are both enabled: |
| 199 | * - foo$[0-9]+ |
| 200 | */ |
| 201 | res = strrchr(s, '$'); |
| 202 | if (res) { |
| 203 | *res = '\0'; |
| 204 | return true; |
| 205 | } |
| 206 | |
| 207 | return false; |
| 208 | } |
| 209 | |
| 210 | /* Lookup the address for this symbol. Returns 0 if not found. */ |
| 211 | unsigned long kallsyms_lookup_name(const char *name) |
| 212 | { |
| 213 | char namebuf[KSYM_NAME_LEN]; |
| 214 | unsigned long i; |
| 215 | unsigned int off; |
| 216 | |
| 217 | /* Skip the search for empty string. */ |
| 218 | if (!*name) |
| 219 | return 0; |
| 220 | |
| 221 | for (i = 0, off = 0; i < kallsyms_num_syms; i++) { |
| 222 | off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); |
| 223 | |
| 224 | if (strcmp(namebuf, name) == 0) |
| 225 | return kallsyms_sym_address(i); |
| 226 | |
| 227 | if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0) |
| 228 | return kallsyms_sym_address(i); |
| 229 | } |
| 230 | return module_kallsyms_lookup_name(name); |
| 231 | } |
| 232 | |
| 233 | /* |
| 234 | * Iterate over all symbols in vmlinux. For symbols from modules use |
| 235 | * module_kallsyms_on_each_symbol instead. |
| 236 | */ |
| 237 | int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, |
| 238 | unsigned long), |
| 239 | void *data) |
| 240 | { |
| 241 | char namebuf[KSYM_NAME_LEN]; |
| 242 | unsigned long i; |
| 243 | unsigned int off; |
| 244 | int ret; |
| 245 | |
| 246 | for (i = 0, off = 0; i < kallsyms_num_syms; i++) { |
| 247 | off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf)); |
| 248 | ret = fn(data, namebuf, NULL, kallsyms_sym_address(i)); |
| 249 | if (ret != 0) |
| 250 | return ret; |
| 251 | cond_resched(); |
| 252 | } |
| 253 | return 0; |
| 254 | } |
| 255 | |
| 256 | static unsigned long get_symbol_pos(unsigned long addr, |
| 257 | unsigned long *symbolsize, |
| 258 | unsigned long *offset) |
| 259 | { |
| 260 | unsigned long symbol_start = 0, symbol_end = 0; |
| 261 | unsigned long i, low, high, mid; |
| 262 | |
| 263 | /* This kernel should never had been booted. */ |
| 264 | if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE)) |
| 265 | BUG_ON(!kallsyms_addresses); |
| 266 | else |
| 267 | BUG_ON(!kallsyms_offsets); |
| 268 | |
| 269 | /* Do a binary search on the sorted kallsyms_addresses array. */ |
| 270 | low = 0; |
| 271 | high = kallsyms_num_syms; |
| 272 | |
| 273 | while (high - low > 1) { |
| 274 | mid = low + (high - low) / 2; |
| 275 | if (kallsyms_sym_address(mid) <= addr) |
| 276 | low = mid; |
| 277 | else |
| 278 | high = mid; |
| 279 | } |
| 280 | |
| 281 | /* |
| 282 | * Search for the first aliased symbol. Aliased |
| 283 | * symbols are symbols with the same address. |
| 284 | */ |
| 285 | while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low)) |
| 286 | --low; |
| 287 | |
| 288 | symbol_start = kallsyms_sym_address(low); |
| 289 | |
| 290 | /* Search for next non-aliased symbol. */ |
| 291 | for (i = low + 1; i < kallsyms_num_syms; i++) { |
| 292 | if (kallsyms_sym_address(i) > symbol_start) { |
| 293 | symbol_end = kallsyms_sym_address(i); |
| 294 | break; |
| 295 | } |
| 296 | } |
| 297 | |
| 298 | /* If we found no next symbol, we use the end of the section. */ |
| 299 | if (!symbol_end) { |
| 300 | if (is_kernel_inittext(addr)) |
| 301 | symbol_end = (unsigned long)_einittext; |
| 302 | else if (IS_ENABLED(CONFIG_KALLSYMS_ALL)) |
| 303 | symbol_end = (unsigned long)_end; |
| 304 | else |
| 305 | symbol_end = (unsigned long)_etext; |
| 306 | } |
| 307 | |
| 308 | if (symbolsize) |
| 309 | *symbolsize = symbol_end - symbol_start; |
| 310 | if (offset) |
| 311 | *offset = addr - symbol_start; |
| 312 | |
| 313 | return low; |
| 314 | } |
| 315 | |
| 316 | /* |
| 317 | * Lookup an address but don't bother to find any names. |
| 318 | */ |
| 319 | int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize, |
| 320 | unsigned long *offset) |
| 321 | { |
| 322 | char namebuf[KSYM_NAME_LEN]; |
| 323 | |
| 324 | if (is_ksym_addr(addr)) { |
| 325 | get_symbol_pos(addr, symbolsize, offset); |
| 326 | return 1; |
| 327 | } |
| 328 | return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) || |
| 329 | !!__bpf_address_lookup(addr, symbolsize, offset, namebuf); |
| 330 | } |
| 331 | |
| 332 | static const char *kallsyms_lookup_buildid(unsigned long addr, |
| 333 | unsigned long *symbolsize, |
| 334 | unsigned long *offset, char **modname, |
| 335 | const unsigned char **modbuildid, char *namebuf) |
| 336 | { |
| 337 | const char *ret; |
| 338 | |
| 339 | namebuf[KSYM_NAME_LEN - 1] = 0; |
| 340 | namebuf[0] = 0; |
| 341 | |
| 342 | if (is_ksym_addr(addr)) { |
| 343 | unsigned long pos; |
| 344 | |
| 345 | pos = get_symbol_pos(addr, symbolsize, offset); |
| 346 | /* Grab name */ |
| 347 | kallsyms_expand_symbol(get_symbol_offset(pos), |
| 348 | namebuf, KSYM_NAME_LEN); |
| 349 | if (modname) |
| 350 | *modname = NULL; |
| 351 | if (modbuildid) |
| 352 | *modbuildid = NULL; |
| 353 | |
| 354 | ret = namebuf; |
| 355 | goto found; |
| 356 | } |
| 357 | |
| 358 | /* See if it's in a module or a BPF JITed image. */ |
| 359 | ret = module_address_lookup(addr, symbolsize, offset, |
| 360 | modname, modbuildid, namebuf); |
| 361 | if (!ret) |
| 362 | ret = bpf_address_lookup(addr, symbolsize, |
| 363 | offset, modname, namebuf); |
| 364 | |
| 365 | if (!ret) |
| 366 | ret = ftrace_mod_address_lookup(addr, symbolsize, |
| 367 | offset, modname, namebuf); |
| 368 | |
| 369 | found: |
| 370 | cleanup_symbol_name(namebuf); |
| 371 | return ret; |
| 372 | } |
| 373 | |
| 374 | /* |
| 375 | * Lookup an address |
| 376 | * - modname is set to NULL if it's in the kernel. |
| 377 | * - We guarantee that the returned name is valid until we reschedule even if. |
| 378 | * It resides in a module. |
| 379 | * - We also guarantee that modname will be valid until rescheduled. |
| 380 | */ |
| 381 | const char *kallsyms_lookup(unsigned long addr, |
| 382 | unsigned long *symbolsize, |
| 383 | unsigned long *offset, |
| 384 | char **modname, char *namebuf) |
| 385 | { |
| 386 | return kallsyms_lookup_buildid(addr, symbolsize, offset, modname, |
| 387 | NULL, namebuf); |
| 388 | } |
| 389 | |
| 390 | int lookup_symbol_name(unsigned long addr, char *symname) |
| 391 | { |
| 392 | int res; |
| 393 | |
| 394 | symname[0] = '\0'; |
| 395 | symname[KSYM_NAME_LEN - 1] = '\0'; |
| 396 | |
| 397 | if (is_ksym_addr(addr)) { |
| 398 | unsigned long pos; |
| 399 | |
| 400 | pos = get_symbol_pos(addr, NULL, NULL); |
| 401 | /* Grab name */ |
| 402 | kallsyms_expand_symbol(get_symbol_offset(pos), |
| 403 | symname, KSYM_NAME_LEN); |
| 404 | goto found; |
| 405 | } |
| 406 | /* See if it's in a module. */ |
| 407 | res = lookup_module_symbol_name(addr, symname); |
| 408 | if (res) |
| 409 | return res; |
| 410 | |
| 411 | found: |
| 412 | cleanup_symbol_name(symname); |
| 413 | return 0; |
| 414 | } |
| 415 | |
| 416 | int lookup_symbol_attrs(unsigned long addr, unsigned long *size, |
| 417 | unsigned long *offset, char *modname, char *name) |
| 418 | { |
| 419 | int res; |
| 420 | |
| 421 | name[0] = '\0'; |
| 422 | name[KSYM_NAME_LEN - 1] = '\0'; |
| 423 | |
| 424 | if (is_ksym_addr(addr)) { |
| 425 | unsigned long pos; |
| 426 | |
| 427 | pos = get_symbol_pos(addr, size, offset); |
| 428 | /* Grab name */ |
| 429 | kallsyms_expand_symbol(get_symbol_offset(pos), |
| 430 | name, KSYM_NAME_LEN); |
| 431 | modname[0] = '\0'; |
| 432 | goto found; |
| 433 | } |
| 434 | /* See if it's in a module. */ |
| 435 | res = lookup_module_symbol_attrs(addr, size, offset, modname, name); |
| 436 | if (res) |
| 437 | return res; |
| 438 | |
| 439 | found: |
| 440 | cleanup_symbol_name(name); |
| 441 | return 0; |
| 442 | } |
| 443 | |
| 444 | /* Look up a kernel symbol and return it in a text buffer. */ |
| 445 | static int __sprint_symbol(char *buffer, unsigned long address, |
| 446 | int symbol_offset, int add_offset, int add_buildid) |
| 447 | { |
| 448 | char *modname; |
| 449 | const unsigned char *buildid; |
| 450 | const char *name; |
| 451 | unsigned long offset, size; |
| 452 | int len; |
| 453 | |
| 454 | address += symbol_offset; |
| 455 | name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid, |
| 456 | buffer); |
| 457 | if (!name) |
| 458 | return sprintf(buffer, "0x%lx", address - symbol_offset); |
| 459 | |
| 460 | if (name != buffer) |
| 461 | strcpy(buffer, name); |
| 462 | len = strlen(buffer); |
| 463 | offset -= symbol_offset; |
| 464 | |
| 465 | if (add_offset) |
| 466 | len += sprintf(buffer + len, "+%#lx/%#lx", offset, size); |
| 467 | |
| 468 | if (modname) { |
| 469 | len += sprintf(buffer + len, " [%s", modname); |
| 470 | #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) |
| 471 | if (add_buildid && buildid) { |
| 472 | /* build ID should match length of sprintf */ |
| 473 | #if IS_ENABLED(CONFIG_MODULES) |
| 474 | static_assert(sizeof(typeof_member(struct module, build_id)) == 20); |
| 475 | #endif |
| 476 | len += sprintf(buffer + len, " %20phN", buildid); |
| 477 | } |
| 478 | #endif |
| 479 | len += sprintf(buffer + len, "]"); |
| 480 | } |
| 481 | |
| 482 | return len; |
| 483 | } |
| 484 | |
| 485 | /** |
| 486 | * sprint_symbol - Look up a kernel symbol and return it in a text buffer |
| 487 | * @buffer: buffer to be stored |
| 488 | * @address: address to lookup |
| 489 | * |
| 490 | * This function looks up a kernel symbol with @address and stores its name, |
| 491 | * offset, size and module name to @buffer if possible. If no symbol was found, |
| 492 | * just saves its @address as is. |
| 493 | * |
| 494 | * This function returns the number of bytes stored in @buffer. |
| 495 | */ |
| 496 | int sprint_symbol(char *buffer, unsigned long address) |
| 497 | { |
| 498 | return __sprint_symbol(buffer, address, 0, 1, 0); |
| 499 | } |
| 500 | EXPORT_SYMBOL_GPL(sprint_symbol); |
| 501 | |
| 502 | /** |
| 503 | * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer |
| 504 | * @buffer: buffer to be stored |
| 505 | * @address: address to lookup |
| 506 | * |
| 507 | * This function looks up a kernel symbol with @address and stores its name, |
| 508 | * offset, size, module name and module build ID to @buffer if possible. If no |
| 509 | * symbol was found, just saves its @address as is. |
| 510 | * |
| 511 | * This function returns the number of bytes stored in @buffer. |
| 512 | */ |
| 513 | int sprint_symbol_build_id(char *buffer, unsigned long address) |
| 514 | { |
| 515 | return __sprint_symbol(buffer, address, 0, 1, 1); |
| 516 | } |
| 517 | EXPORT_SYMBOL_GPL(sprint_symbol_build_id); |
| 518 | |
| 519 | /** |
| 520 | * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer |
| 521 | * @buffer: buffer to be stored |
| 522 | * @address: address to lookup |
| 523 | * |
| 524 | * This function looks up a kernel symbol with @address and stores its name |
| 525 | * and module name to @buffer if possible. If no symbol was found, just saves |
| 526 | * its @address as is. |
| 527 | * |
| 528 | * This function returns the number of bytes stored in @buffer. |
| 529 | */ |
| 530 | int sprint_symbol_no_offset(char *buffer, unsigned long address) |
| 531 | { |
| 532 | return __sprint_symbol(buffer, address, 0, 0, 0); |
| 533 | } |
| 534 | EXPORT_SYMBOL_GPL(sprint_symbol_no_offset); |
| 535 | |
| 536 | /** |
| 537 | * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer |
| 538 | * @buffer: buffer to be stored |
| 539 | * @address: address to lookup |
| 540 | * |
| 541 | * This function is for stack backtrace and does the same thing as |
| 542 | * sprint_symbol() but with modified/decreased @address. If there is a |
| 543 | * tail-call to the function marked "noreturn", gcc optimized out code after |
| 544 | * the call so that the stack-saved return address could point outside of the |
| 545 | * caller. This function ensures that kallsyms will find the original caller |
| 546 | * by decreasing @address. |
| 547 | * |
| 548 | * This function returns the number of bytes stored in @buffer. |
| 549 | */ |
| 550 | int sprint_backtrace(char *buffer, unsigned long address) |
| 551 | { |
| 552 | return __sprint_symbol(buffer, address, -1, 1, 0); |
| 553 | } |
| 554 | |
| 555 | /** |
| 556 | * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer |
| 557 | * @buffer: buffer to be stored |
| 558 | * @address: address to lookup |
| 559 | * |
| 560 | * This function is for stack backtrace and does the same thing as |
| 561 | * sprint_symbol() but with modified/decreased @address. If there is a |
| 562 | * tail-call to the function marked "noreturn", gcc optimized out code after |
| 563 | * the call so that the stack-saved return address could point outside of the |
| 564 | * caller. This function ensures that kallsyms will find the original caller |
| 565 | * by decreasing @address. This function also appends the module build ID to |
| 566 | * the @buffer if @address is within a kernel module. |
| 567 | * |
| 568 | * This function returns the number of bytes stored in @buffer. |
| 569 | */ |
| 570 | int sprint_backtrace_build_id(char *buffer, unsigned long address) |
| 571 | { |
| 572 | return __sprint_symbol(buffer, address, -1, 1, 1); |
| 573 | } |
| 574 | |
| 575 | /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */ |
| 576 | struct kallsym_iter { |
| 577 | loff_t pos; |
| 578 | loff_t pos_arch_end; |
| 579 | loff_t pos_mod_end; |
| 580 | loff_t pos_ftrace_mod_end; |
| 581 | loff_t pos_bpf_end; |
| 582 | unsigned long value; |
| 583 | unsigned int nameoff; /* If iterating in core kernel symbols. */ |
| 584 | char type; |
| 585 | char name[KSYM_NAME_LEN]; |
| 586 | char module_name[MODULE_NAME_LEN]; |
| 587 | int exported; |
| 588 | int show_value; |
| 589 | }; |
| 590 | |
| 591 | int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, |
| 592 | char *type, char *name) |
| 593 | { |
| 594 | return -EINVAL; |
| 595 | } |
| 596 | |
| 597 | static int get_ksymbol_arch(struct kallsym_iter *iter) |
| 598 | { |
| 599 | int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms, |
| 600 | &iter->value, &iter->type, |
| 601 | iter->name); |
| 602 | |
| 603 | if (ret < 0) { |
| 604 | iter->pos_arch_end = iter->pos; |
| 605 | return 0; |
| 606 | } |
| 607 | |
| 608 | return 1; |
| 609 | } |
| 610 | |
| 611 | static int get_ksymbol_mod(struct kallsym_iter *iter) |
| 612 | { |
| 613 | int ret = module_get_kallsym(iter->pos - iter->pos_arch_end, |
| 614 | &iter->value, &iter->type, |
| 615 | iter->name, iter->module_name, |
| 616 | &iter->exported); |
| 617 | if (ret < 0) { |
| 618 | iter->pos_mod_end = iter->pos; |
| 619 | return 0; |
| 620 | } |
| 621 | |
| 622 | return 1; |
| 623 | } |
| 624 | |
| 625 | /* |
| 626 | * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace |
| 627 | * purposes. In that case "__builtin__ftrace" is used as a module name, even |
| 628 | * though "__builtin__ftrace" is not a module. |
| 629 | */ |
| 630 | static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter) |
| 631 | { |
| 632 | int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end, |
| 633 | &iter->value, &iter->type, |
| 634 | iter->name, iter->module_name, |
| 635 | &iter->exported); |
| 636 | if (ret < 0) { |
| 637 | iter->pos_ftrace_mod_end = iter->pos; |
| 638 | return 0; |
| 639 | } |
| 640 | |
| 641 | return 1; |
| 642 | } |
| 643 | |
| 644 | static int get_ksymbol_bpf(struct kallsym_iter *iter) |
| 645 | { |
| 646 | int ret; |
| 647 | |
| 648 | strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN); |
| 649 | iter->exported = 0; |
| 650 | ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end, |
| 651 | &iter->value, &iter->type, |
| 652 | iter->name); |
| 653 | if (ret < 0) { |
| 654 | iter->pos_bpf_end = iter->pos; |
| 655 | return 0; |
| 656 | } |
| 657 | |
| 658 | return 1; |
| 659 | } |
| 660 | |
| 661 | /* |
| 662 | * This uses "__builtin__kprobes" as a module name for symbols for pages |
| 663 | * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a |
| 664 | * module. |
| 665 | */ |
| 666 | static int get_ksymbol_kprobe(struct kallsym_iter *iter) |
| 667 | { |
| 668 | strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN); |
| 669 | iter->exported = 0; |
| 670 | return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end, |
| 671 | &iter->value, &iter->type, |
| 672 | iter->name) < 0 ? 0 : 1; |
| 673 | } |
| 674 | |
| 675 | /* Returns space to next name. */ |
| 676 | static unsigned long get_ksymbol_core(struct kallsym_iter *iter) |
| 677 | { |
| 678 | unsigned off = iter->nameoff; |
| 679 | |
| 680 | iter->module_name[0] = '\0'; |
| 681 | iter->value = kallsyms_sym_address(iter->pos); |
| 682 | |
| 683 | iter->type = kallsyms_get_symbol_type(off); |
| 684 | |
| 685 | off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name)); |
| 686 | |
| 687 | return off - iter->nameoff; |
| 688 | } |
| 689 | |
| 690 | static void reset_iter(struct kallsym_iter *iter, loff_t new_pos) |
| 691 | { |
| 692 | iter->name[0] = '\0'; |
| 693 | iter->nameoff = get_symbol_offset(new_pos); |
| 694 | iter->pos = new_pos; |
| 695 | if (new_pos == 0) { |
| 696 | iter->pos_arch_end = 0; |
| 697 | iter->pos_mod_end = 0; |
| 698 | iter->pos_ftrace_mod_end = 0; |
| 699 | iter->pos_bpf_end = 0; |
| 700 | } |
| 701 | } |
| 702 | |
| 703 | /* |
| 704 | * The end position (last + 1) of each additional kallsyms section is recorded |
| 705 | * in iter->pos_..._end as each section is added, and so can be used to |
| 706 | * determine which get_ksymbol_...() function to call next. |
| 707 | */ |
| 708 | static int update_iter_mod(struct kallsym_iter *iter, loff_t pos) |
| 709 | { |
| 710 | iter->pos = pos; |
| 711 | |
| 712 | if ((!iter->pos_arch_end || iter->pos_arch_end > pos) && |
| 713 | get_ksymbol_arch(iter)) |
| 714 | return 1; |
| 715 | |
| 716 | if ((!iter->pos_mod_end || iter->pos_mod_end > pos) && |
| 717 | get_ksymbol_mod(iter)) |
| 718 | return 1; |
| 719 | |
| 720 | if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) && |
| 721 | get_ksymbol_ftrace_mod(iter)) |
| 722 | return 1; |
| 723 | |
| 724 | if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) && |
| 725 | get_ksymbol_bpf(iter)) |
| 726 | return 1; |
| 727 | |
| 728 | return get_ksymbol_kprobe(iter); |
| 729 | } |
| 730 | |
| 731 | /* Returns false if pos at or past end of file. */ |
| 732 | static int update_iter(struct kallsym_iter *iter, loff_t pos) |
| 733 | { |
| 734 | /* Module symbols can be accessed randomly. */ |
| 735 | if (pos >= kallsyms_num_syms) |
| 736 | return update_iter_mod(iter, pos); |
| 737 | |
| 738 | /* If we're not on the desired position, reset to new position. */ |
| 739 | if (pos != iter->pos) |
| 740 | reset_iter(iter, pos); |
| 741 | |
| 742 | iter->nameoff += get_ksymbol_core(iter); |
| 743 | iter->pos++; |
| 744 | |
| 745 | return 1; |
| 746 | } |
| 747 | |
| 748 | static void *s_next(struct seq_file *m, void *p, loff_t *pos) |
| 749 | { |
| 750 | (*pos)++; |
| 751 | |
| 752 | if (!update_iter(m->private, *pos)) |
| 753 | return NULL; |
| 754 | return p; |
| 755 | } |
| 756 | |
| 757 | static void *s_start(struct seq_file *m, loff_t *pos) |
| 758 | { |
| 759 | if (!update_iter(m->private, *pos)) |
| 760 | return NULL; |
| 761 | return m->private; |
| 762 | } |
| 763 | |
| 764 | static void s_stop(struct seq_file *m, void *p) |
| 765 | { |
| 766 | } |
| 767 | |
| 768 | static int s_show(struct seq_file *m, void *p) |
| 769 | { |
| 770 | void *value; |
| 771 | struct kallsym_iter *iter = m->private; |
| 772 | |
| 773 | /* Some debugging symbols have no name. Ignore them. */ |
| 774 | if (!iter->name[0]) |
| 775 | return 0; |
| 776 | |
| 777 | value = iter->show_value ? (void *)iter->value : NULL; |
| 778 | |
| 779 | if (iter->module_name[0]) { |
| 780 | char type; |
| 781 | |
| 782 | /* |
| 783 | * Label it "global" if it is exported, |
| 784 | * "local" if not exported. |
| 785 | */ |
| 786 | type = iter->exported ? toupper(iter->type) : |
| 787 | tolower(iter->type); |
| 788 | seq_printf(m, "%px %c %s\t[%s]\n", value, |
| 789 | type, iter->name, iter->module_name); |
| 790 | } else |
| 791 | seq_printf(m, "%px %c %s\n", value, |
| 792 | iter->type, iter->name); |
| 793 | return 0; |
| 794 | } |
| 795 | |
| 796 | static const struct seq_operations kallsyms_op = { |
| 797 | .start = s_start, |
| 798 | .next = s_next, |
| 799 | .stop = s_stop, |
| 800 | .show = s_show |
| 801 | }; |
| 802 | |
| 803 | #ifdef CONFIG_BPF_SYSCALL |
| 804 | |
| 805 | struct bpf_iter__ksym { |
| 806 | __bpf_md_ptr(struct bpf_iter_meta *, meta); |
| 807 | __bpf_md_ptr(struct kallsym_iter *, ksym); |
| 808 | }; |
| 809 | |
| 810 | static int ksym_prog_seq_show(struct seq_file *m, bool in_stop) |
| 811 | { |
| 812 | struct bpf_iter__ksym ctx; |
| 813 | struct bpf_iter_meta meta; |
| 814 | struct bpf_prog *prog; |
| 815 | |
| 816 | meta.seq = m; |
| 817 | prog = bpf_iter_get_info(&meta, in_stop); |
| 818 | if (!prog) |
| 819 | return 0; |
| 820 | |
| 821 | ctx.meta = &meta; |
| 822 | ctx.ksym = m ? m->private : NULL; |
| 823 | return bpf_iter_run_prog(prog, &ctx); |
| 824 | } |
| 825 | |
| 826 | static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p) |
| 827 | { |
| 828 | return ksym_prog_seq_show(m, false); |
| 829 | } |
| 830 | |
| 831 | static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p) |
| 832 | { |
| 833 | if (!p) |
| 834 | (void) ksym_prog_seq_show(m, true); |
| 835 | else |
| 836 | s_stop(m, p); |
| 837 | } |
| 838 | |
| 839 | static const struct seq_operations bpf_iter_ksym_ops = { |
| 840 | .start = s_start, |
| 841 | .next = s_next, |
| 842 | .stop = bpf_iter_ksym_seq_stop, |
| 843 | .show = bpf_iter_ksym_seq_show, |
| 844 | }; |
| 845 | |
| 846 | static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux) |
| 847 | { |
| 848 | struct kallsym_iter *iter = priv_data; |
| 849 | |
| 850 | reset_iter(iter, 0); |
| 851 | |
| 852 | /* cache here as in kallsyms_open() case; use current process |
| 853 | * credentials to tell BPF iterators if values should be shown. |
| 854 | */ |
| 855 | iter->show_value = kallsyms_show_value(current_cred()); |
| 856 | |
| 857 | return 0; |
| 858 | } |
| 859 | |
| 860 | DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym) |
| 861 | |
| 862 | static const struct bpf_iter_seq_info ksym_iter_seq_info = { |
| 863 | .seq_ops = &bpf_iter_ksym_ops, |
| 864 | .init_seq_private = bpf_iter_ksym_init, |
| 865 | .fini_seq_private = NULL, |
| 866 | .seq_priv_size = sizeof(struct kallsym_iter), |
| 867 | }; |
| 868 | |
| 869 | static struct bpf_iter_reg ksym_iter_reg_info = { |
| 870 | .target = "ksym", |
| 871 | .feature = BPF_ITER_RESCHED, |
| 872 | .ctx_arg_info_size = 1, |
| 873 | .ctx_arg_info = { |
| 874 | { offsetof(struct bpf_iter__ksym, ksym), |
| 875 | PTR_TO_BTF_ID_OR_NULL }, |
| 876 | }, |
| 877 | .seq_info = &ksym_iter_seq_info, |
| 878 | }; |
| 879 | |
| 880 | BTF_ID_LIST(btf_ksym_iter_id) |
| 881 | BTF_ID(struct, kallsym_iter) |
| 882 | |
| 883 | static int __init bpf_ksym_iter_register(void) |
| 884 | { |
| 885 | ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id; |
| 886 | return bpf_iter_reg_target(&ksym_iter_reg_info); |
| 887 | } |
| 888 | |
| 889 | late_initcall(bpf_ksym_iter_register); |
| 890 | |
| 891 | #endif /* CONFIG_BPF_SYSCALL */ |
| 892 | |
| 893 | static inline int kallsyms_for_perf(void) |
| 894 | { |
| 895 | #ifdef CONFIG_PERF_EVENTS |
| 896 | extern int sysctl_perf_event_paranoid; |
| 897 | if (sysctl_perf_event_paranoid <= 1) |
| 898 | return 1; |
| 899 | #endif |
| 900 | return 0; |
| 901 | } |
| 902 | |
| 903 | /* |
| 904 | * We show kallsyms information even to normal users if we've enabled |
| 905 | * kernel profiling and are explicitly not paranoid (so kptr_restrict |
| 906 | * is clear, and sysctl_perf_event_paranoid isn't set). |
| 907 | * |
| 908 | * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to |
| 909 | * block even that). |
| 910 | */ |
| 911 | bool kallsyms_show_value(const struct cred *cred) |
| 912 | { |
| 913 | switch (kptr_restrict) { |
| 914 | case 0: |
| 915 | if (kallsyms_for_perf()) |
| 916 | return true; |
| 917 | fallthrough; |
| 918 | case 1: |
| 919 | if (security_capable(cred, &init_user_ns, CAP_SYSLOG, |
| 920 | CAP_OPT_NOAUDIT) == 0) |
| 921 | return true; |
| 922 | fallthrough; |
| 923 | default: |
| 924 | return false; |
| 925 | } |
| 926 | } |
| 927 | |
| 928 | static int kallsyms_open(struct inode *inode, struct file *file) |
| 929 | { |
| 930 | /* |
| 931 | * We keep iterator in m->private, since normal case is to |
| 932 | * s_start from where we left off, so we avoid doing |
| 933 | * using get_symbol_offset for every symbol. |
| 934 | */ |
| 935 | struct kallsym_iter *iter; |
| 936 | iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter)); |
| 937 | if (!iter) |
| 938 | return -ENOMEM; |
| 939 | reset_iter(iter, 0); |
| 940 | |
| 941 | /* |
| 942 | * Instead of checking this on every s_show() call, cache |
| 943 | * the result here at open time. |
| 944 | */ |
| 945 | iter->show_value = kallsyms_show_value(file->f_cred); |
| 946 | return 0; |
| 947 | } |
| 948 | |
| 949 | #ifdef CONFIG_KGDB_KDB |
| 950 | const char *kdb_walk_kallsyms(loff_t *pos) |
| 951 | { |
| 952 | static struct kallsym_iter kdb_walk_kallsyms_iter; |
| 953 | if (*pos == 0) { |
| 954 | memset(&kdb_walk_kallsyms_iter, 0, |
| 955 | sizeof(kdb_walk_kallsyms_iter)); |
| 956 | reset_iter(&kdb_walk_kallsyms_iter, 0); |
| 957 | } |
| 958 | while (1) { |
| 959 | if (!update_iter(&kdb_walk_kallsyms_iter, *pos)) |
| 960 | return NULL; |
| 961 | ++*pos; |
| 962 | /* Some debugging symbols have no name. Ignore them. */ |
| 963 | if (kdb_walk_kallsyms_iter.name[0]) |
| 964 | return kdb_walk_kallsyms_iter.name; |
| 965 | } |
| 966 | } |
| 967 | #endif /* CONFIG_KGDB_KDB */ |
| 968 | |
| 969 | static const struct proc_ops kallsyms_proc_ops = { |
| 970 | .proc_open = kallsyms_open, |
| 971 | .proc_read = seq_read, |
| 972 | .proc_lseek = seq_lseek, |
| 973 | .proc_release = seq_release_private, |
| 974 | }; |
| 975 | |
| 976 | static int __init kallsyms_init(void) |
| 977 | { |
| 978 | proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); |
| 979 | return 0; |
| 980 | } |
| 981 | device_initcall(kallsyms_init); |