1 /* 2 * recordmcount.c: construct a table of the locations of calls to 'mcount' 3 * so that ftrace can find them quickly. 4 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved. 5 * Licensed under the GNU General Public License, version 2 (GPLv2). 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 <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, uread, ...: Check return value for errors. */ 93 94 static off_t 95 ulseek(int const fd, 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 uread(int const fd, void *const buf, size_t const count) 117 { 118 size_t const n = read(fd, buf, count); 119 if (n != count) { 120 perror("read"); 121 fail_file(); 122 } 123 return n; 124 } 125 126 static size_t 127 uwrite(int const fd, void const *const buf, size_t const count) 128 { 129 size_t cnt = count; 130 off_t idx = 0; 131 132 file_updated = 1; 133 134 if (file_ptr + count >= file_end) { 135 off_t aoffset = (file_ptr + count) - file_end; 136 137 if (aoffset > file_append_size) { 138 file_append = realloc(file_append, aoffset); 139 file_append_size = aoffset; 140 } 141 if (!file_append) { 142 perror("write"); 143 fail_file(); 144 } 145 if (file_ptr < file_end) { 146 cnt = file_end - file_ptr; 147 } else { 148 cnt = 0; 149 idx = aoffset - count; 150 } 151 } 152 153 if (cnt) 154 memcpy(file_ptr, buf, cnt); 155 156 if (cnt < count) 157 memcpy(file_append + idx, buf + cnt, count - cnt); 158 159 file_ptr += count; 160 return count; 161 } 162 163 static void * 164 umalloc(size_t size) 165 { 166 void *const addr = malloc(size); 167 if (addr == 0) { 168 fprintf(stderr, "malloc failed: %zu bytes\n", size); 169 fail_file(); 170 } 171 return addr; 172 } 173 174 static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; 175 static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; 176 static unsigned char *ideal_nop; 177 178 static char rel_type_nop; 179 180 static int (*make_nop)(void *map, size_t const offset); 181 182 static int make_nop_x86(void *map, size_t const offset) 183 { 184 uint32_t *ptr; 185 unsigned char *op; 186 187 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ 188 ptr = map + offset; 189 if (*ptr != 0) 190 return -1; 191 192 op = map + offset - 1; 193 if (*op != 0xe8) 194 return -1; 195 196 /* convert to nop */ 197 ulseek(fd_map, offset - 1, SEEK_SET); 198 uwrite(fd_map, ideal_nop, 5); 199 return 0; 200 } 201 202 static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */ 203 static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */ 204 static unsigned char *ideal_nop4_arm; 205 206 static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */ 207 static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */ 208 static unsigned char *bl_mcount_arm; 209 210 static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */ 211 static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */ 212 static unsigned char *push_arm; 213 214 static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */ 215 static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */ 216 static unsigned char *ideal_nop2_thumb; 217 218 static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */ 219 static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */ 220 static unsigned char *push_bl_mcount_thumb; 221 222 static int make_nop_arm(void *map, size_t const offset) 223 { 224 char *ptr; 225 int cnt = 1; 226 int nop_size; 227 size_t off = offset; 228 229 ptr = map + offset; 230 if (memcmp(ptr, bl_mcount_arm, 4) == 0) { 231 if (memcmp(ptr - 4, push_arm, 4) == 0) { 232 off -= 4; 233 cnt = 2; 234 } 235 ideal_nop = ideal_nop4_arm; 236 nop_size = 4; 237 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) { 238 cnt = 3; 239 nop_size = 2; 240 off -= 2; 241 ideal_nop = ideal_nop2_thumb; 242 } else 243 return -1; 244 245 /* Convert to nop */ 246 ulseek(fd_map, off, SEEK_SET); 247 248 do { 249 uwrite(fd_map, ideal_nop, nop_size); 250 } while (--cnt > 0); 251 252 return 0; 253 } 254 255 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5}; 256 static int make_nop_arm64(void *map, size_t const offset) 257 { 258 uint32_t *ptr; 259 260 ptr = map + offset; 261 /* bl <_mcount> is 0x94000000 before relocation */ 262 if (*ptr != 0x94000000) 263 return -1; 264 265 /* Convert to nop */ 266 ulseek(fd_map, offset, SEEK_SET); 267 uwrite(fd_map, ideal_nop, 4); 268 return 0; 269 } 270 271 /* 272 * Get the whole file as a programming convenience in order to avoid 273 * malloc+lseek+read+free of many pieces. If successful, then mmap 274 * avoids copying unused pieces; else just read the whole file. 275 * Open for both read and write; new info will be appended to the file. 276 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr 277 * do not propagate to the file until an explicit overwrite at the last. 278 * This preserves most aspects of consistency (all except .st_size) 279 * for simultaneous readers of the file while we are appending to it. 280 * However, multiple writers still are bad. We choose not to use 281 * locking because it is expensive and the use case of kernel build 282 * makes multiple writers unlikely. 283 */ 284 static void *mmap_file(char const *fname) 285 { 286 fd_map = open(fname, O_RDONLY); 287 if (fd_map < 0 || fstat(fd_map, &sb) < 0) { 288 perror(fname); 289 fail_file(); 290 } 291 if (!S_ISREG(sb.st_mode)) { 292 fprintf(stderr, "not a regular file: %s\n", fname); 293 fail_file(); 294 } 295 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, 296 fd_map, 0); 297 mmap_failed = 0; 298 if (file_map == MAP_FAILED) { 299 mmap_failed = 1; 300 file_map = umalloc(sb.st_size); 301 uread(fd_map, file_map, sb.st_size); 302 } 303 close(fd_map); 304 305 file_end = file_map + sb.st_size; 306 307 return file_map; 308 } 309 310 static void write_file(const char *fname) 311 { 312 char tmp_file[strlen(fname) + 4]; 313 size_t n; 314 315 if (!file_updated) 316 return; 317 318 sprintf(tmp_file, "%s.rc", fname); 319 320 /* 321 * After reading the entire file into memory, delete it 322 * and write it back, to prevent weird side effects of modifying 323 * an object file in place. 324 */ 325 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode); 326 if (fd_map < 0) { 327 perror(fname); 328 fail_file(); 329 } 330 n = write(fd_map, file_map, sb.st_size); 331 if (n != sb.st_size) { 332 perror("write"); 333 fail_file(); 334 } 335 if (file_append_size) { 336 n = write(fd_map, file_append, file_append_size); 337 if (n != file_append_size) { 338 perror("write"); 339 fail_file(); 340 } 341 } 342 close(fd_map); 343 if (rename(tmp_file, fname) < 0) { 344 perror(fname); 345 fail_file(); 346 } 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 strcmp(".text", txtname) == 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 strcmp(".text.unlikely", txtname) == 0; 410 } 411 412 /* 32 bit and 64 bit are very similar */ 413 #include "recordmcount.h" 414 #define RECORD_MCOUNT_64 415 #include "recordmcount.h" 416 417 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. 418 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf 419 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] 420 * to imply the order of the members; the spec does not say so. 421 * typedef unsigned char Elf64_Byte; 422 * fails on MIPS64 because their <elf.h> already has it! 423 */ 424 425 typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ 426 427 union mips_r_info { 428 Elf64_Xword r_info; 429 struct { 430 Elf64_Word r_sym; /* Symbol index. */ 431 myElf64_Byte r_ssym; /* Special symbol. */ 432 myElf64_Byte r_type3; /* Third relocation. */ 433 myElf64_Byte r_type2; /* Second relocation. */ 434 myElf64_Byte r_type; /* First relocation. */ 435 } r_mips; 436 }; 437 438 static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) 439 { 440 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); 441 } 442 443 static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) 444 { 445 rp->r_info = ((union mips_r_info){ 446 .r_mips = { .r_sym = w(sym), .r_type = type } 447 }).r_info; 448 } 449 450 static void 451 do_file(char const *const fname) 452 { 453 Elf32_Ehdr *const ehdr = mmap_file(fname); 454 unsigned int reltype = 0; 455 456 w = w4nat; 457 w2 = w2nat; 458 w8 = w8nat; 459 switch (ehdr->e_ident[EI_DATA]) { 460 static unsigned int const endian = 1; 461 default: 462 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", 463 ehdr->e_ident[EI_DATA], fname); 464 fail_file(); 465 break; 466 case ELFDATA2LSB: 467 if (*(unsigned char const *)&endian != 1) { 468 /* main() is big endian, file.o is little endian. */ 469 w = w4rev; 470 w2 = w2rev; 471 w8 = w8rev; 472 } 473 ideal_nop4_arm = ideal_nop4_arm_le; 474 bl_mcount_arm = bl_mcount_arm_le; 475 push_arm = push_arm_le; 476 ideal_nop2_thumb = ideal_nop2_thumb_le; 477 push_bl_mcount_thumb = push_bl_mcount_thumb_le; 478 break; 479 case ELFDATA2MSB: 480 if (*(unsigned char const *)&endian != 0) { 481 /* main() is little endian, file.o is big endian. */ 482 w = w4rev; 483 w2 = w2rev; 484 w8 = w8rev; 485 } 486 ideal_nop4_arm = ideal_nop4_arm_be; 487 bl_mcount_arm = bl_mcount_arm_be; 488 push_arm = push_arm_be; 489 ideal_nop2_thumb = ideal_nop2_thumb_be; 490 push_bl_mcount_thumb = push_bl_mcount_thumb_be; 491 break; 492 } /* end switch */ 493 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 494 || w2(ehdr->e_type) != ET_REL 495 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) { 496 fprintf(stderr, "unrecognized ET_REL file %s\n", fname); 497 fail_file(); 498 } 499 500 gpfx = 0; 501 switch (w2(ehdr->e_machine)) { 502 default: 503 fprintf(stderr, "unrecognized e_machine %u %s\n", 504 w2(ehdr->e_machine), fname); 505 fail_file(); 506 break; 507 case EM_386: 508 reltype = R_386_32; 509 rel_type_nop = R_386_NONE; 510 make_nop = make_nop_x86; 511 ideal_nop = ideal_nop5_x86_32; 512 mcount_adjust_32 = -1; 513 break; 514 case EM_ARM: reltype = R_ARM_ABS32; 515 altmcount = "__gnu_mcount_nc"; 516 make_nop = make_nop_arm; 517 rel_type_nop = R_ARM_NONE; 518 break; 519 case EM_AARCH64: 520 reltype = R_AARCH64_ABS64; 521 make_nop = make_nop_arm64; 522 rel_type_nop = R_AARCH64_NONE; 523 ideal_nop = ideal_nop4_arm64; 524 gpfx = '_'; 525 break; 526 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; 527 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break; 528 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; 529 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; 530 case EM_S390: /* reltype: e_class */ gpfx = '_'; break; 531 case EM_SH: reltype = R_SH_DIR32; break; 532 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; 533 case EM_X86_64: 534 make_nop = make_nop_x86; 535 ideal_nop = ideal_nop5_x86_64; 536 reltype = R_X86_64_64; 537 rel_type_nop = R_X86_64_NONE; 538 mcount_adjust_64 = -1; 539 break; 540 } /* end switch */ 541 542 switch (ehdr->e_ident[EI_CLASS]) { 543 default: 544 fprintf(stderr, "unrecognized ELF class %d %s\n", 545 ehdr->e_ident[EI_CLASS], fname); 546 fail_file(); 547 break; 548 case ELFCLASS32: 549 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr) 550 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) { 551 fprintf(stderr, 552 "unrecognized ET_REL file: %s\n", fname); 553 fail_file(); 554 } 555 if (w2(ehdr->e_machine) == EM_MIPS) { 556 reltype = R_MIPS_32; 557 is_fake_mcount32 = MIPS32_is_fake_mcount; 558 } 559 do32(ehdr, fname, reltype); 560 break; 561 case ELFCLASS64: { 562 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; 563 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr) 564 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) { 565 fprintf(stderr, 566 "unrecognized ET_REL file: %s\n", fname); 567 fail_file(); 568 } 569 if (w2(ghdr->e_machine) == EM_S390) { 570 reltype = R_390_64; 571 mcount_adjust_64 = -14; 572 } 573 if (w2(ghdr->e_machine) == EM_MIPS) { 574 reltype = R_MIPS_64; 575 Elf64_r_sym = MIPS64_r_sym; 576 Elf64_r_info = MIPS64_r_info; 577 is_fake_mcount64 = MIPS64_is_fake_mcount; 578 } 579 do64(ghdr, fname, reltype); 580 break; 581 } 582 } /* end switch */ 583 584 write_file(fname); 585 cleanup(); 586 } 587 588 int 589 main(int argc, char *argv[]) 590 { 591 const char ftrace[] = "/ftrace.o"; 592 int ftrace_size = sizeof(ftrace) - 1; 593 int n_error = 0; /* gcc-4.3.0 false positive complaint */ 594 int c; 595 int i; 596 597 while ((c = getopt(argc, argv, "w")) >= 0) { 598 switch (c) { 599 case 'w': 600 warn_on_notrace_sect = 1; 601 break; 602 default: 603 fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); 604 return 0; 605 } 606 } 607 608 if ((argc - optind) < 1) { 609 fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); 610 return 0; 611 } 612 613 /* Process each file in turn, allowing deep failure. */ 614 for (i = optind; i < argc; i++) { 615 char *file = argv[i]; 616 int const sjval = setjmp(jmpenv); 617 int len; 618 619 /* 620 * The file kernel/trace/ftrace.o references the mcount 621 * function but does not call it. Since ftrace.o should 622 * not be traced anyway, we just skip it. 623 */ 624 len = strlen(file); 625 if (len >= ftrace_size && 626 strcmp(file + (len - ftrace_size), ftrace) == 0) 627 continue; 628 629 switch (sjval) { 630 default: 631 fprintf(stderr, "internal error: %s\n", file); 632 exit(1); 633 break; 634 case SJ_SETJMP: /* normal sequence */ 635 /* Avoid problems if early cleanup() */ 636 fd_map = -1; 637 mmap_failed = 1; 638 file_map = NULL; 639 file_ptr = NULL; 640 file_updated = 0; 641 do_file(file); 642 break; 643 case SJ_FAIL: /* error in do_file or below */ 644 fprintf(stderr, "%s: failed\n", file); 645 ++n_error; 646 break; 647 case SJ_SUCCEED: /* premature success */ 648 /* do nothing */ 649 break; 650 } /* end switch */ 651 } 652 return !!n_error; 653 } 654