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