1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * recordmcount.c: construct a table of the locations of calls to 'mcount' 4 * so that ftrace can find them quickly. 5 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved. 6 * 7 * Restructured to fit Linux format, as well as other updates: 8 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc. 9 */ 10 11 /* 12 * Strategy: alter the .o file in-place. 13 * 14 * Append a new STRTAB that has the new section names, followed by a new array 15 * ElfXX_Shdr[] that has the new section headers, followed by the section 16 * contents for __mcount_loc and its relocations. The old shstrtab strings, 17 * and the old ElfXX_Shdr[] array, remain as "garbage" (commonly, a couple 18 * kilobytes.) Subsequent processing by /bin/ld (or the kernel module loader) 19 * will ignore the garbage regions, because they are not designated by the 20 * new .e_shoff nor the new ElfXX_Shdr[]. [In order to remove the garbage, 21 * then use "ld -r" to create a new file that omits the garbage.] 22 */ 23 24 #include <sys/types.h> 25 #include <sys/mman.h> 26 #include <sys/stat.h> 27 #include <getopt.h> 28 #include <elf.h> 29 #include <fcntl.h> 30 #include <stdio.h> 31 #include <stdlib.h> 32 #include <string.h> 33 #include <unistd.h> 34 35 #ifndef EM_AARCH64 36 #define EM_AARCH64 183 37 #define R_AARCH64_NONE 0 38 #define R_AARCH64_ABS64 257 39 #endif 40 41 #define R_ARM_PC24 1 42 #define R_ARM_THM_CALL 10 43 #define R_ARM_CALL 28 44 45 #define R_AARCH64_CALL26 283 46 47 static int fd_map; /* File descriptor for file being modified. */ 48 static int mmap_failed; /* Boolean flag. */ 49 static char gpfx; /* prefix for global symbol name (sometimes '_') */ 50 static struct stat sb; /* Remember .st_size, etc. */ 51 static const char *altmcount; /* alternate mcount symbol name */ 52 static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */ 53 static void *file_map; /* pointer of the mapped file */ 54 static void *file_end; /* pointer to the end of the mapped file */ 55 static int file_updated; /* flag to state file was changed */ 56 static void *file_ptr; /* current file pointer location */ 57 58 static void *file_append; /* added to the end of the file */ 59 static size_t file_append_size; /* how much is added to end of file */ 60 61 /* Per-file resource cleanup when multiple files. */ 62 static void file_append_cleanup(void) 63 { 64 free(file_append); 65 file_append = NULL; 66 file_append_size = 0; 67 file_updated = 0; 68 } 69 70 static void mmap_cleanup(void) 71 { 72 if (!mmap_failed) 73 munmap(file_map, sb.st_size); 74 else 75 free(file_map); 76 file_map = NULL; 77 } 78 79 /* ulseek, uwrite, ...: Check return value for errors. */ 80 81 static off_t ulseek(off_t const offset, int const whence) 82 { 83 switch (whence) { 84 case SEEK_SET: 85 file_ptr = file_map + offset; 86 break; 87 case SEEK_CUR: 88 file_ptr += offset; 89 break; 90 case SEEK_END: 91 file_ptr = file_map + (sb.st_size - offset); 92 break; 93 } 94 if (file_ptr < file_map) { 95 fprintf(stderr, "lseek: seek before file\n"); 96 return -1; 97 } 98 return file_ptr - file_map; 99 } 100 101 static ssize_t uwrite(void const *const buf, size_t const count) 102 { 103 size_t cnt = count; 104 off_t idx = 0; 105 106 file_updated = 1; 107 108 if (file_ptr + count >= file_end) { 109 off_t aoffset = (file_ptr + count) - file_end; 110 111 if (aoffset > file_append_size) { 112 file_append = realloc(file_append, aoffset); 113 file_append_size = aoffset; 114 } 115 if (!file_append) { 116 perror("write"); 117 file_append_cleanup(); 118 mmap_cleanup(); 119 return -1; 120 } 121 if (file_ptr < file_end) { 122 cnt = file_end - file_ptr; 123 } else { 124 cnt = 0; 125 idx = aoffset - count; 126 } 127 } 128 129 if (cnt) 130 memcpy(file_ptr, buf, cnt); 131 132 if (cnt < count) 133 memcpy(file_append + idx, buf + cnt, count - cnt); 134 135 file_ptr += count; 136 return count; 137 } 138 139 static void * umalloc(size_t size) 140 { 141 void *const addr = malloc(size); 142 if (addr == 0) { 143 fprintf(stderr, "malloc failed: %zu bytes\n", size); 144 file_append_cleanup(); 145 mmap_cleanup(); 146 return NULL; 147 } 148 return addr; 149 } 150 151 /* 152 * Get the whole file as a programming convenience in order to avoid 153 * malloc+lseek+read+free of many pieces. If successful, then mmap 154 * avoids copying unused pieces; else just read the whole file. 155 * Open for both read and write; new info will be appended to the file. 156 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr 157 * do not propagate to the file until an explicit overwrite at the last. 158 * This preserves most aspects of consistency (all except .st_size) 159 * for simultaneous readers of the file while we are appending to it. 160 * However, multiple writers still are bad. We choose not to use 161 * locking because it is expensive and the use case of kernel build 162 * makes multiple writers unlikely. 163 */ 164 static void *mmap_file(char const *fname) 165 { 166 /* Avoid problems if early cleanup() */ 167 fd_map = -1; 168 mmap_failed = 1; 169 file_map = NULL; 170 file_ptr = NULL; 171 file_updated = 0; 172 sb.st_size = 0; 173 174 fd_map = open(fname, O_RDONLY); 175 if (fd_map < 0) { 176 perror(fname); 177 return NULL; 178 } 179 if (fstat(fd_map, &sb) < 0) { 180 perror(fname); 181 goto out; 182 } 183 if (!S_ISREG(sb.st_mode)) { 184 fprintf(stderr, "not a regular file: %s\n", fname); 185 goto out; 186 } 187 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, 188 fd_map, 0); 189 if (file_map == MAP_FAILED) { 190 mmap_failed = 1; 191 file_map = umalloc(sb.st_size); 192 if (!file_map) { 193 perror(fname); 194 goto out; 195 } 196 if (read(fd_map, file_map, sb.st_size) != sb.st_size) { 197 perror(fname); 198 free(file_map); 199 file_map = NULL; 200 goto out; 201 } 202 } else 203 mmap_failed = 0; 204 out: 205 close(fd_map); 206 fd_map = -1; 207 208 file_end = file_map + sb.st_size; 209 210 return file_map; 211 } 212 213 214 static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; 215 static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; 216 static unsigned char *ideal_nop; 217 218 static char rel_type_nop; 219 220 static int (*make_nop)(void *map, size_t const offset); 221 222 static int make_nop_x86(void *map, size_t const offset) 223 { 224 uint32_t *ptr; 225 unsigned char *op; 226 227 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ 228 ptr = map + offset; 229 if (*ptr != 0) 230 return -1; 231 232 op = map + offset - 1; 233 if (*op != 0xe8) 234 return -1; 235 236 /* convert to nop */ 237 if (ulseek(offset - 1, SEEK_SET) < 0) 238 return -1; 239 if (uwrite(ideal_nop, 5) < 0) 240 return -1; 241 return 0; 242 } 243 244 static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */ 245 static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */ 246 static unsigned char *ideal_nop4_arm; 247 248 static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */ 249 static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */ 250 static unsigned char *bl_mcount_arm; 251 252 static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */ 253 static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */ 254 static unsigned char *push_arm; 255 256 static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */ 257 static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */ 258 static unsigned char *ideal_nop2_thumb; 259 260 static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */ 261 static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */ 262 static unsigned char *push_bl_mcount_thumb; 263 264 static int make_nop_arm(void *map, size_t const offset) 265 { 266 char *ptr; 267 int cnt = 1; 268 int nop_size; 269 size_t off = offset; 270 271 ptr = map + offset; 272 if (memcmp(ptr, bl_mcount_arm, 4) == 0) { 273 if (memcmp(ptr - 4, push_arm, 4) == 0) { 274 off -= 4; 275 cnt = 2; 276 } 277 ideal_nop = ideal_nop4_arm; 278 nop_size = 4; 279 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) { 280 cnt = 3; 281 nop_size = 2; 282 off -= 2; 283 ideal_nop = ideal_nop2_thumb; 284 } else 285 return -1; 286 287 /* Convert to nop */ 288 if (ulseek(off, SEEK_SET) < 0) 289 return -1; 290 291 do { 292 if (uwrite(ideal_nop, nop_size) < 0) 293 return -1; 294 } while (--cnt > 0); 295 296 return 0; 297 } 298 299 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5}; 300 static int make_nop_arm64(void *map, size_t const offset) 301 { 302 uint32_t *ptr; 303 304 ptr = map + offset; 305 /* bl <_mcount> is 0x94000000 before relocation */ 306 if (*ptr != 0x94000000) 307 return -1; 308 309 /* Convert to nop */ 310 if (ulseek(offset, SEEK_SET) < 0) 311 return -1; 312 if (uwrite(ideal_nop, 4) < 0) 313 return -1; 314 return 0; 315 } 316 317 static int write_file(const char *fname) 318 { 319 char tmp_file[strlen(fname) + 4]; 320 size_t n; 321 322 if (!file_updated) 323 return 0; 324 325 sprintf(tmp_file, "%s.rc", fname); 326 327 /* 328 * After reading the entire file into memory, delete it 329 * and write it back, to prevent weird side effects of modifying 330 * an object file in place. 331 */ 332 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode); 333 if (fd_map < 0) { 334 perror(fname); 335 return -1; 336 } 337 n = write(fd_map, file_map, sb.st_size); 338 if (n != sb.st_size) { 339 perror("write"); 340 close(fd_map); 341 return -1; 342 } 343 if (file_append_size) { 344 n = write(fd_map, file_append, file_append_size); 345 if (n != file_append_size) { 346 perror("write"); 347 close(fd_map); 348 return -1; 349 } 350 } 351 close(fd_map); 352 if (rename(tmp_file, fname) < 0) { 353 perror(fname); 354 return -1; 355 } 356 return 0; 357 } 358 359 /* w8rev, w8nat, ...: Handle endianness. */ 360 361 static uint64_t w8rev(uint64_t const x) 362 { 363 return ((0xff & (x >> (0 * 8))) << (7 * 8)) 364 | ((0xff & (x >> (1 * 8))) << (6 * 8)) 365 | ((0xff & (x >> (2 * 8))) << (5 * 8)) 366 | ((0xff & (x >> (3 * 8))) << (4 * 8)) 367 | ((0xff & (x >> (4 * 8))) << (3 * 8)) 368 | ((0xff & (x >> (5 * 8))) << (2 * 8)) 369 | ((0xff & (x >> (6 * 8))) << (1 * 8)) 370 | ((0xff & (x >> (7 * 8))) << (0 * 8)); 371 } 372 373 static uint32_t w4rev(uint32_t const x) 374 { 375 return ((0xff & (x >> (0 * 8))) << (3 * 8)) 376 | ((0xff & (x >> (1 * 8))) << (2 * 8)) 377 | ((0xff & (x >> (2 * 8))) << (1 * 8)) 378 | ((0xff & (x >> (3 * 8))) << (0 * 8)); 379 } 380 381 static uint32_t w2rev(uint16_t const x) 382 { 383 return ((0xff & (x >> (0 * 8))) << (1 * 8)) 384 | ((0xff & (x >> (1 * 8))) << (0 * 8)); 385 } 386 387 static uint64_t w8nat(uint64_t const x) 388 { 389 return x; 390 } 391 392 static uint32_t w4nat(uint32_t const x) 393 { 394 return x; 395 } 396 397 static uint32_t w2nat(uint16_t const x) 398 { 399 return x; 400 } 401 402 static uint64_t (*w8)(uint64_t); 403 static uint32_t (*w)(uint32_t); 404 static uint32_t (*w2)(uint16_t); 405 406 /* Names of the sections that could contain calls to mcount. */ 407 static int is_mcounted_section_name(char const *const txtname) 408 { 409 return strncmp(".text", txtname, 5) == 0 || 410 strcmp(".init.text", txtname) == 0 || 411 strcmp(".ref.text", txtname) == 0 || 412 strcmp(".sched.text", txtname) == 0 || 413 strcmp(".spinlock.text", txtname) == 0 || 414 strcmp(".irqentry.text", txtname) == 0 || 415 strcmp(".softirqentry.text", txtname) == 0 || 416 strcmp(".kprobes.text", txtname) == 0 || 417 strcmp(".cpuidle.text", txtname) == 0; 418 } 419 420 static char const *already_has_rel_mcount = "success"; /* our work here is done! */ 421 422 /* 32 bit and 64 bit are very similar */ 423 #include "recordmcount.h" 424 #define RECORD_MCOUNT_64 425 #include "recordmcount.h" 426 427 static int arm_is_fake_mcount(Elf32_Rel const *rp) 428 { 429 switch (ELF32_R_TYPE(w(rp->r_info))) { 430 case R_ARM_THM_CALL: 431 case R_ARM_CALL: 432 case R_ARM_PC24: 433 return 0; 434 } 435 436 return 1; 437 } 438 439 static int arm64_is_fake_mcount(Elf64_Rel const *rp) 440 { 441 return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26; 442 } 443 444 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. 445 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf 446 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] 447 * to imply the order of the members; the spec does not say so. 448 * typedef unsigned char Elf64_Byte; 449 * fails on MIPS64 because their <elf.h> already has it! 450 */ 451 452 typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ 453 454 union mips_r_info { 455 Elf64_Xword r_info; 456 struct { 457 Elf64_Word r_sym; /* Symbol index. */ 458 myElf64_Byte r_ssym; /* Special symbol. */ 459 myElf64_Byte r_type3; /* Third relocation. */ 460 myElf64_Byte r_type2; /* Second relocation. */ 461 myElf64_Byte r_type; /* First relocation. */ 462 } r_mips; 463 }; 464 465 static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) 466 { 467 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); 468 } 469 470 static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) 471 { 472 rp->r_info = ((union mips_r_info){ 473 .r_mips = { .r_sym = w(sym), .r_type = type } 474 }).r_info; 475 } 476 477 static int do_file(char const *const fname) 478 { 479 unsigned int reltype = 0; 480 Elf32_Ehdr *ehdr; 481 int rc = -1; 482 483 ehdr = mmap_file(fname); 484 if (!ehdr) 485 goto out; 486 487 w = w4nat; 488 w2 = w2nat; 489 w8 = w8nat; 490 switch (ehdr->e_ident[EI_DATA]) { 491 static unsigned int const endian = 1; 492 default: 493 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", 494 ehdr->e_ident[EI_DATA], fname); 495 goto out; 496 case ELFDATA2LSB: 497 if (*(unsigned char const *)&endian != 1) { 498 /* main() is big endian, file.o is little endian. */ 499 w = w4rev; 500 w2 = w2rev; 501 w8 = w8rev; 502 } 503 ideal_nop4_arm = ideal_nop4_arm_le; 504 bl_mcount_arm = bl_mcount_arm_le; 505 push_arm = push_arm_le; 506 ideal_nop2_thumb = ideal_nop2_thumb_le; 507 push_bl_mcount_thumb = push_bl_mcount_thumb_le; 508 break; 509 case ELFDATA2MSB: 510 if (*(unsigned char const *)&endian != 0) { 511 /* main() is little endian, file.o is big endian. */ 512 w = w4rev; 513 w2 = w2rev; 514 w8 = w8rev; 515 } 516 ideal_nop4_arm = ideal_nop4_arm_be; 517 bl_mcount_arm = bl_mcount_arm_be; 518 push_arm = push_arm_be; 519 ideal_nop2_thumb = ideal_nop2_thumb_be; 520 push_bl_mcount_thumb = push_bl_mcount_thumb_be; 521 break; 522 } /* end switch */ 523 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 524 w2(ehdr->e_type) != ET_REL || 525 ehdr->e_ident[EI_VERSION] != EV_CURRENT) { 526 fprintf(stderr, "unrecognized ET_REL file %s\n", fname); 527 goto out; 528 } 529 530 gpfx = '_'; 531 switch (w2(ehdr->e_machine)) { 532 default: 533 fprintf(stderr, "unrecognized e_machine %u %s\n", 534 w2(ehdr->e_machine), fname); 535 goto out; 536 case EM_386: 537 reltype = R_386_32; 538 rel_type_nop = R_386_NONE; 539 make_nop = make_nop_x86; 540 ideal_nop = ideal_nop5_x86_32; 541 mcount_adjust_32 = -1; 542 gpfx = 0; 543 break; 544 case EM_ARM: 545 reltype = R_ARM_ABS32; 546 altmcount = "__gnu_mcount_nc"; 547 make_nop = make_nop_arm; 548 rel_type_nop = R_ARM_NONE; 549 is_fake_mcount32 = arm_is_fake_mcount; 550 gpfx = 0; 551 break; 552 case EM_AARCH64: 553 reltype = R_AARCH64_ABS64; 554 make_nop = make_nop_arm64; 555 rel_type_nop = R_AARCH64_NONE; 556 ideal_nop = ideal_nop4_arm64; 557 is_fake_mcount64 = arm64_is_fake_mcount; 558 break; 559 case EM_IA_64: reltype = R_IA64_IMM64; break; 560 case EM_MIPS: /* reltype: e_class */ break; 561 case EM_PPC: reltype = R_PPC_ADDR32; break; 562 case EM_PPC64: reltype = R_PPC64_ADDR64; break; 563 case EM_S390: /* reltype: e_class */ break; 564 case EM_SH: reltype = R_SH_DIR32; gpfx = 0; break; 565 case EM_SPARCV9: reltype = R_SPARC_64; break; 566 case EM_X86_64: 567 make_nop = make_nop_x86; 568 ideal_nop = ideal_nop5_x86_64; 569 reltype = R_X86_64_64; 570 rel_type_nop = R_X86_64_NONE; 571 mcount_adjust_64 = -1; 572 gpfx = 0; 573 break; 574 } /* end switch */ 575 576 switch (ehdr->e_ident[EI_CLASS]) { 577 default: 578 fprintf(stderr, "unrecognized ELF class %d %s\n", 579 ehdr->e_ident[EI_CLASS], fname); 580 goto out; 581 case ELFCLASS32: 582 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr) 583 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) { 584 fprintf(stderr, 585 "unrecognized ET_REL file: %s\n", fname); 586 goto out; 587 } 588 if (w2(ehdr->e_machine) == EM_MIPS) { 589 reltype = R_MIPS_32; 590 is_fake_mcount32 = MIPS32_is_fake_mcount; 591 } 592 if (do32(ehdr, fname, reltype) < 0) 593 goto out; 594 break; 595 case ELFCLASS64: { 596 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; 597 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr) 598 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) { 599 fprintf(stderr, 600 "unrecognized ET_REL file: %s\n", fname); 601 goto out; 602 } 603 if (w2(ghdr->e_machine) == EM_S390) { 604 reltype = R_390_64; 605 mcount_adjust_64 = -14; 606 } 607 if (w2(ghdr->e_machine) == EM_MIPS) { 608 reltype = R_MIPS_64; 609 Elf64_r_sym = MIPS64_r_sym; 610 Elf64_r_info = MIPS64_r_info; 611 is_fake_mcount64 = MIPS64_is_fake_mcount; 612 } 613 if (do64(ghdr, fname, reltype) < 0) 614 goto out; 615 break; 616 } 617 } /* end switch */ 618 619 rc = write_file(fname); 620 out: 621 file_append_cleanup(); 622 mmap_cleanup(); 623 return rc; 624 } 625 626 int main(int argc, char *argv[]) 627 { 628 const char ftrace[] = "/ftrace.o"; 629 int ftrace_size = sizeof(ftrace) - 1; 630 int n_error = 0; /* gcc-4.3.0 false positive complaint */ 631 int c; 632 int i; 633 634 while ((c = getopt(argc, argv, "w")) >= 0) { 635 switch (c) { 636 case 'w': 637 warn_on_notrace_sect = 1; 638 break; 639 default: 640 fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); 641 return 0; 642 } 643 } 644 645 if ((argc - optind) < 1) { 646 fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); 647 return 0; 648 } 649 650 /* Process each file in turn, allowing deep failure. */ 651 for (i = optind; i < argc; i++) { 652 char *file = argv[i]; 653 int len; 654 655 /* 656 * The file kernel/trace/ftrace.o references the mcount 657 * function but does not call it. Since ftrace.o should 658 * not be traced anyway, we just skip it. 659 */ 660 len = strlen(file); 661 if (len >= ftrace_size && 662 strcmp(file + (len - ftrace_size), ftrace) == 0) 663 continue; 664 665 if (do_file(file)) { 666 fprintf(stderr, "%s: failed\n", file); 667 ++n_error; 668 } 669 } 670 return !!n_error; 671 } 672