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