scripts/recordmcount.c

   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 }