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