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 /* 37 * glibc synced up and added the metag number but didn't add the relocations. 38 * Work around this in a crude manner for now. 39 */ 40 #ifndef EM_METAG 41 #define EM_METAG 174 42 #endif 43 #ifndef R_METAG_ADDR32 44 #define R_METAG_ADDR32 2 45 #endif 46 #ifndef R_METAG_NONE 47 #define R_METAG_NONE 3 48 #endif 49 50 #ifndef EM_AARCH64 51 #define EM_AARCH64 183 52 #define R_AARCH64_NONE 0 53 #define R_AARCH64_ABS64 257 54 #endif 55 56 static int fd_map; /* File descriptor for file being modified. */ 57 static int mmap_failed; /* Boolean flag. */ 58 static char gpfx; /* prefix for global symbol name (sometimes '_') */ 59 static struct stat sb; /* Remember .st_size, etc. */ 60 static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */ 61 static const char *altmcount; /* alternate mcount symbol name */ 62 static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */ 63 static void *file_map; /* pointer of the mapped file */ 64 static void *file_end; /* pointer to the end of the mapped file */ 65 static int file_updated; /* flag to state file was changed */ 66 static void *file_ptr; /* current file pointer location */ 67 static void *file_append; /* added to the end of the file */ 68 static size_t file_append_size; /* how much is added to end of file */ 69 70 /* setjmp() return values */ 71 enum { 72 SJ_SETJMP = 0, /* hardwired first return */ 73 SJ_FAIL, 74 SJ_SUCCEED 75 }; 76 77 /* Per-file resource cleanup when multiple files. */ 78 static void 79 cleanup(void) 80 { 81 if (!mmap_failed) 82 munmap(file_map, sb.st_size); 83 else 84 free(file_map); 85 file_map = NULL; 86 free(file_append); 87 file_append = NULL; 88 file_append_size = 0; 89 file_updated = 0; 90 } 91 92 static void __attribute__((noreturn)) 93 fail_file(void) 94 { 95 cleanup(); 96 longjmp(jmpenv, SJ_FAIL); 97 } 98 99 static void __attribute__((noreturn)) 100 succeed_file(void) 101 { 102 cleanup(); 103 longjmp(jmpenv, SJ_SUCCEED); 104 } 105 106 /* ulseek, uread, ...: Check return value for errors. */ 107 108 static off_t 109 ulseek(int const fd, off_t const offset, int const whence) 110 { 111 switch (whence) { 112 case SEEK_SET: 113 file_ptr = file_map + offset; 114 break; 115 case SEEK_CUR: 116 file_ptr += offset; 117 break; 118 case SEEK_END: 119 file_ptr = file_map + (sb.st_size - offset); 120 break; 121 } 122 if (file_ptr < file_map) { 123 fprintf(stderr, "lseek: seek before file\n"); 124 fail_file(); 125 } 126 return file_ptr - file_map; 127 } 128 129 static size_t 130 uread(int const fd, void *const buf, size_t const count) 131 { 132 size_t const n = read(fd, buf, count); 133 if (n != count) { 134 perror("read"); 135 fail_file(); 136 } 137 return n; 138 } 139 140 static size_t 141 uwrite(int const fd, void const *const buf, size_t const count) 142 { 143 size_t cnt = count; 144 off_t idx = 0; 145 146 file_updated = 1; 147 148 if (file_ptr + count >= file_end) { 149 off_t aoffset = (file_ptr + count) - file_end; 150 151 if (aoffset > file_append_size) { 152 file_append = realloc(file_append, aoffset); 153 file_append_size = aoffset; 154 } 155 if (!file_append) { 156 perror("write"); 157 fail_file(); 158 } 159 if (file_ptr < file_end) { 160 cnt = file_end - file_ptr; 161 } else { 162 cnt = 0; 163 idx = aoffset - count; 164 } 165 } 166 167 if (cnt) 168 memcpy(file_ptr, buf, cnt); 169 170 if (cnt < count) 171 memcpy(file_append + idx, buf + cnt, count - cnt); 172 173 file_ptr += count; 174 return count; 175 } 176 177 static void * 178 umalloc(size_t size) 179 { 180 void *const addr = malloc(size); 181 if (addr == 0) { 182 fprintf(stderr, "malloc failed: %zu bytes\n", size); 183 fail_file(); 184 } 185 return addr; 186 } 187 188 static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; 189 static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; 190 static unsigned char *ideal_nop; 191 192 static char rel_type_nop; 193 194 static int (*make_nop)(void *map, size_t const offset); 195 196 static int make_nop_x86(void *map, size_t const offset) 197 { 198 uint32_t *ptr; 199 unsigned char *op; 200 201 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ 202 ptr = map + offset; 203 if (*ptr != 0) 204 return -1; 205 206 op = map + offset - 1; 207 if (*op != 0xe8) 208 return -1; 209 210 /* convert to nop */ 211 ulseek(fd_map, offset - 1, SEEK_SET); 212 uwrite(fd_map, ideal_nop, 5); 213 return 0; 214 } 215 216 static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */ 217 static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */ 218 static unsigned char *ideal_nop4_arm; 219 220 static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */ 221 static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */ 222 static unsigned char *bl_mcount_arm; 223 224 static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */ 225 static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */ 226 static unsigned char *push_arm; 227 228 static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */ 229 static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */ 230 static unsigned char *ideal_nop2_thumb; 231 232 static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */ 233 static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */ 234 static unsigned char *push_bl_mcount_thumb; 235 236 static int make_nop_arm(void *map, size_t const offset) 237 { 238 char *ptr; 239 int cnt = 1; 240 int nop_size; 241 size_t off = offset; 242 243 ptr = map + offset; 244 if (memcmp(ptr, bl_mcount_arm, 4) == 0) { 245 if (memcmp(ptr - 4, push_arm, 4) == 0) { 246 off -= 4; 247 cnt = 2; 248 } 249 ideal_nop = ideal_nop4_arm; 250 nop_size = 4; 251 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) { 252 cnt = 3; 253 nop_size = 2; 254 off -= 2; 255 ideal_nop = ideal_nop2_thumb; 256 } else 257 return -1; 258 259 /* Convert to nop */ 260 ulseek(fd_map, off, SEEK_SET); 261 262 do { 263 uwrite(fd_map, ideal_nop, nop_size); 264 } while (--cnt > 0); 265 266 return 0; 267 } 268 269 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5}; 270 static int make_nop_arm64(void *map, size_t const offset) 271 { 272 uint32_t *ptr; 273 274 ptr = map + offset; 275 /* bl <_mcount> is 0x94000000 before relocation */ 276 if (*ptr != 0x94000000) 277 return -1; 278 279 /* Convert to nop */ 280 ulseek(fd_map, offset, SEEK_SET); 281 uwrite(fd_map, ideal_nop, 4); 282 return 0; 283 } 284 285 /* 286 * Get the whole file as a programming convenience in order to avoid 287 * malloc+lseek+read+free of many pieces. If successful, then mmap 288 * avoids copying unused pieces; else just read the whole file. 289 * Open for both read and write; new info will be appended to the file. 290 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr 291 * do not propagate to the file until an explicit overwrite at the last. 292 * This preserves most aspects of consistency (all except .st_size) 293 * for simultaneous readers of the file while we are appending to it. 294 * However, multiple writers still are bad. We choose not to use 295 * locking because it is expensive and the use case of kernel build 296 * makes multiple writers unlikely. 297 */ 298 static void *mmap_file(char const *fname) 299 { 300 fd_map = open(fname, O_RDONLY); 301 if (fd_map < 0 || fstat(fd_map, &sb) < 0) { 302 perror(fname); 303 fail_file(); 304 } 305 if (!S_ISREG(sb.st_mode)) { 306 fprintf(stderr, "not a regular file: %s\n", fname); 307 fail_file(); 308 } 309 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, 310 fd_map, 0); 311 mmap_failed = 0; 312 if (file_map == MAP_FAILED) { 313 mmap_failed = 1; 314 file_map = umalloc(sb.st_size); 315 uread(fd_map, file_map, sb.st_size); 316 } 317 close(fd_map); 318 319 file_end = file_map + sb.st_size; 320 321 return file_map; 322 } 323 324 static void write_file(const char *fname) 325 { 326 char tmp_file[strlen(fname) + 4]; 327 size_t n; 328 329 if (!file_updated) 330 return; 331 332 sprintf(tmp_file, "%s.rc", fname); 333 334 /* 335 * After reading the entire file into memory, delete it 336 * and write it back, to prevent weird side effects of modifying 337 * an object file in place. 338 */ 339 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode); 340 if (fd_map < 0) { 341 perror(fname); 342 fail_file(); 343 } 344 n = write(fd_map, file_map, sb.st_size); 345 if (n != sb.st_size) { 346 perror("write"); 347 fail_file(); 348 } 349 if (file_append_size) { 350 n = write(fd_map, file_append, file_append_size); 351 if (n != file_append_size) { 352 perror("write"); 353 fail_file(); 354 } 355 } 356 close(fd_map); 357 if (rename(tmp_file, fname) < 0) { 358 perror(fname); 359 fail_file(); 360 } 361 } 362 363 /* w8rev, w8nat, ...: Handle endianness. */ 364 365 static uint64_t w8rev(uint64_t const x) 366 { 367 return ((0xff & (x >> (0 * 8))) << (7 * 8)) 368 | ((0xff & (x >> (1 * 8))) << (6 * 8)) 369 | ((0xff & (x >> (2 * 8))) << (5 * 8)) 370 | ((0xff & (x >> (3 * 8))) << (4 * 8)) 371 | ((0xff & (x >> (4 * 8))) << (3 * 8)) 372 | ((0xff & (x >> (5 * 8))) << (2 * 8)) 373 | ((0xff & (x >> (6 * 8))) << (1 * 8)) 374 | ((0xff & (x >> (7 * 8))) << (0 * 8)); 375 } 376 377 static uint32_t w4rev(uint32_t const x) 378 { 379 return ((0xff & (x >> (0 * 8))) << (3 * 8)) 380 | ((0xff & (x >> (1 * 8))) << (2 * 8)) 381 | ((0xff & (x >> (2 * 8))) << (1 * 8)) 382 | ((0xff & (x >> (3 * 8))) << (0 * 8)); 383 } 384 385 static uint32_t w2rev(uint16_t const x) 386 { 387 return ((0xff & (x >> (0 * 8))) << (1 * 8)) 388 | ((0xff & (x >> (1 * 8))) << (0 * 8)); 389 } 390 391 static uint64_t w8nat(uint64_t const x) 392 { 393 return x; 394 } 395 396 static uint32_t w4nat(uint32_t const x) 397 { 398 return x; 399 } 400 401 static uint32_t w2nat(uint16_t const x) 402 { 403 return x; 404 } 405 406 static uint64_t (*w8)(uint64_t); 407 static uint32_t (*w)(uint32_t); 408 static uint32_t (*w2)(uint16_t); 409 410 /* Names of the sections that could contain calls to mcount. */ 411 static int 412 is_mcounted_section_name(char const *const txtname) 413 { 414 return strcmp(".text", txtname) == 0 || 415 strcmp(".ref.text", txtname) == 0 || 416 strcmp(".sched.text", txtname) == 0 || 417 strcmp(".spinlock.text", txtname) == 0 || 418 strcmp(".irqentry.text", txtname) == 0 || 419 strcmp(".softirqentry.text", txtname) == 0 || 420 strcmp(".kprobes.text", txtname) == 0 || 421 strcmp(".cpuidle.text", txtname) == 0 || 422 strcmp(".text.unlikely", txtname) == 0; 423 } 424 425 /* 32 bit and 64 bit are very similar */ 426 #include "recordmcount.h" 427 #define RECORD_MCOUNT_64 428 #include "recordmcount.h" 429 430 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. 431 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf 432 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] 433 * to imply the order of the members; the spec does not say so. 434 * typedef unsigned char Elf64_Byte; 435 * fails on MIPS64 because their <elf.h> already has it! 436 */ 437 438 typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ 439 440 union mips_r_info { 441 Elf64_Xword r_info; 442 struct { 443 Elf64_Word r_sym; /* Symbol index. */ 444 myElf64_Byte r_ssym; /* Special symbol. */ 445 myElf64_Byte r_type3; /* Third relocation. */ 446 myElf64_Byte r_type2; /* Second relocation. */ 447 myElf64_Byte r_type; /* First relocation. */ 448 } r_mips; 449 }; 450 451 static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) 452 { 453 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); 454 } 455 456 static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) 457 { 458 rp->r_info = ((union mips_r_info){ 459 .r_mips = { .r_sym = w(sym), .r_type = type } 460 }).r_info; 461 } 462 463 static void 464 do_file(char const *const fname) 465 { 466 Elf32_Ehdr *const ehdr = mmap_file(fname); 467 unsigned int reltype = 0; 468 469 w = w4nat; 470 w2 = w2nat; 471 w8 = w8nat; 472 switch (ehdr->e_ident[EI_DATA]) { 473 static unsigned int const endian = 1; 474 default: 475 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", 476 ehdr->e_ident[EI_DATA], fname); 477 fail_file(); 478 break; 479 case ELFDATA2LSB: 480 if (*(unsigned char const *)&endian != 1) { 481 /* main() is big endian, file.o is little endian. */ 482 w = w4rev; 483 w2 = w2rev; 484 w8 = w8rev; 485 } 486 ideal_nop4_arm = ideal_nop4_arm_le; 487 bl_mcount_arm = bl_mcount_arm_le; 488 push_arm = push_arm_le; 489 ideal_nop2_thumb = ideal_nop2_thumb_le; 490 push_bl_mcount_thumb = push_bl_mcount_thumb_le; 491 break; 492 case ELFDATA2MSB: 493 if (*(unsigned char const *)&endian != 0) { 494 /* main() is little endian, file.o is big endian. */ 495 w = w4rev; 496 w2 = w2rev; 497 w8 = w8rev; 498 } 499 ideal_nop4_arm = ideal_nop4_arm_be; 500 bl_mcount_arm = bl_mcount_arm_be; 501 push_arm = push_arm_be; 502 ideal_nop2_thumb = ideal_nop2_thumb_be; 503 push_bl_mcount_thumb = push_bl_mcount_thumb_be; 504 break; 505 } /* end switch */ 506 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 507 || w2(ehdr->e_type) != ET_REL 508 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) { 509 fprintf(stderr, "unrecognized ET_REL file %s\n", fname); 510 fail_file(); 511 } 512 513 gpfx = 0; 514 switch (w2(ehdr->e_machine)) { 515 default: 516 fprintf(stderr, "unrecognized e_machine %d %s\n", 517 w2(ehdr->e_machine), fname); 518 fail_file(); 519 break; 520 case EM_386: 521 reltype = R_386_32; 522 rel_type_nop = R_386_NONE; 523 make_nop = make_nop_x86; 524 ideal_nop = ideal_nop5_x86_32; 525 mcount_adjust_32 = -1; 526 break; 527 case EM_ARM: reltype = R_ARM_ABS32; 528 altmcount = "__gnu_mcount_nc"; 529 make_nop = make_nop_arm; 530 rel_type_nop = R_ARM_NONE; 531 break; 532 case EM_AARCH64: 533 reltype = R_AARCH64_ABS64; 534 make_nop = make_nop_arm64; 535 rel_type_nop = R_AARCH64_NONE; 536 ideal_nop = ideal_nop4_arm64; 537 gpfx = '_'; 538 break; 539 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; 540 case EM_METAG: reltype = R_METAG_ADDR32; 541 altmcount = "_mcount_wrapper"; 542 rel_type_nop = R_METAG_NONE; 543 /* We happen to have the same requirement as MIPS */ 544 is_fake_mcount32 = MIPS32_is_fake_mcount; 545 break; 546 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break; 547 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; 548 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; 549 case EM_S390: /* reltype: e_class */ gpfx = '_'; break; 550 case EM_SH: reltype = R_SH_DIR32; break; 551 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; 552 case EM_X86_64: 553 make_nop = make_nop_x86; 554 ideal_nop = ideal_nop5_x86_64; 555 reltype = R_X86_64_64; 556 rel_type_nop = R_X86_64_NONE; 557 mcount_adjust_64 = -1; 558 break; 559 } /* end switch */ 560 561 switch (ehdr->e_ident[EI_CLASS]) { 562 default: 563 fprintf(stderr, "unrecognized ELF class %d %s\n", 564 ehdr->e_ident[EI_CLASS], fname); 565 fail_file(); 566 break; 567 case ELFCLASS32: 568 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr) 569 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) { 570 fprintf(stderr, 571 "unrecognized ET_REL file: %s\n", fname); 572 fail_file(); 573 } 574 if (w2(ehdr->e_machine) == EM_MIPS) { 575 reltype = R_MIPS_32; 576 is_fake_mcount32 = MIPS32_is_fake_mcount; 577 } 578 do32(ehdr, fname, reltype); 579 break; 580 case ELFCLASS64: { 581 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; 582 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr) 583 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) { 584 fprintf(stderr, 585 "unrecognized ET_REL file: %s\n", fname); 586 fail_file(); 587 } 588 if (w2(ghdr->e_machine) == EM_S390) { 589 reltype = R_390_64; 590 mcount_adjust_64 = -14; 591 } 592 if (w2(ghdr->e_machine) == EM_MIPS) { 593 reltype = R_MIPS_64; 594 Elf64_r_sym = MIPS64_r_sym; 595 Elf64_r_info = MIPS64_r_info; 596 is_fake_mcount64 = MIPS64_is_fake_mcount; 597 } 598 do64(ghdr, fname, reltype); 599 break; 600 } 601 } /* end switch */ 602 603 write_file(fname); 604 cleanup(); 605 } 606 607 int 608 main(int argc, char *argv[]) 609 { 610 const char ftrace[] = "/ftrace.o"; 611 int ftrace_size = sizeof(ftrace) - 1; 612 int n_error = 0; /* gcc-4.3.0 false positive complaint */ 613 int c; 614 int i; 615 616 while ((c = getopt(argc, argv, "w")) >= 0) { 617 switch (c) { 618 case 'w': 619 warn_on_notrace_sect = 1; 620 break; 621 default: 622 fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); 623 return 0; 624 } 625 } 626 627 if ((argc - optind) < 1) { 628 fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); 629 return 0; 630 } 631 632 /* Process each file in turn, allowing deep failure. */ 633 for (i = optind; i < argc; i++) { 634 char *file = argv[i]; 635 int const sjval = setjmp(jmpenv); 636 int len; 637 638 /* 639 * The file kernel/trace/ftrace.o references the mcount 640 * function but does not call it. Since ftrace.o should 641 * not be traced anyway, we just skip it. 642 */ 643 len = strlen(file); 644 if (len >= ftrace_size && 645 strcmp(file + (len - ftrace_size), ftrace) == 0) 646 continue; 647 648 switch (sjval) { 649 default: 650 fprintf(stderr, "internal error: %s\n", file); 651 exit(1); 652 break; 653 case SJ_SETJMP: /* normal sequence */ 654 /* Avoid problems if early cleanup() */ 655 fd_map = -1; 656 mmap_failed = 1; 657 file_map = NULL; 658 file_ptr = NULL; 659 file_updated = 0; 660 do_file(file); 661 break; 662 case SJ_FAIL: /* error in do_file or below */ 663 fprintf(stderr, "%s: failed\n", file); 664 ++n_error; 665 break; 666 case SJ_SUCCEED: /* premature success */ 667 /* do nothing */ 668 break; 669 } /* end switch */ 670 } 671 return !!n_error; 672 } 673