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