John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 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 <elf.h> |
| 28 | #include <fcntl.h> |
| 29 | #include <setjmp.h> |
| 30 | #include <stdio.h> |
| 31 | #include <stdlib.h> |
| 32 | #include <string.h> |
| 33 | #include <unistd.h> |
| 34 | |
| 35 | static int fd_map; /* File descriptor for file being modified. */ |
| 36 | static int mmap_failed; /* Boolean flag. */ |
| 37 | static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */ |
| 38 | static char gpfx; /* prefix for global symbol name (sometimes '_') */ |
| 39 | static struct stat sb; /* Remember .st_size, etc. */ |
| 40 | static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */ |
| 41 | |
| 42 | /* setjmp() return values */ |
| 43 | enum { |
| 44 | SJ_SETJMP = 0, /* hardwired first return */ |
| 45 | SJ_FAIL, |
| 46 | SJ_SUCCEED |
| 47 | }; |
| 48 | |
| 49 | /* Per-file resource cleanup when multiple files. */ |
| 50 | static void |
| 51 | cleanup(void) |
| 52 | { |
| 53 | if (!mmap_failed) |
| 54 | munmap(ehdr_curr, sb.st_size); |
| 55 | else |
| 56 | free(ehdr_curr); |
| 57 | close(fd_map); |
| 58 | } |
| 59 | |
| 60 | static void __attribute__((noreturn)) |
| 61 | fail_file(void) |
| 62 | { |
| 63 | cleanup(); |
| 64 | longjmp(jmpenv, SJ_FAIL); |
| 65 | } |
| 66 | |
| 67 | static void __attribute__((noreturn)) |
| 68 | succeed_file(void) |
| 69 | { |
| 70 | cleanup(); |
| 71 | longjmp(jmpenv, SJ_SUCCEED); |
| 72 | } |
| 73 | |
| 74 | /* ulseek, uread, ...: Check return value for errors. */ |
| 75 | |
| 76 | static off_t |
| 77 | ulseek(int const fd, off_t const offset, int const whence) |
| 78 | { |
| 79 | off_t const w = lseek(fd, offset, whence); |
| 80 | if ((off_t)-1 == w) { |
| 81 | perror("lseek"); |
| 82 | fail_file(); |
| 83 | } |
| 84 | return w; |
| 85 | } |
| 86 | |
| 87 | static size_t |
| 88 | uread(int const fd, void *const buf, size_t const count) |
| 89 | { |
| 90 | size_t const n = read(fd, buf, count); |
| 91 | if (n != count) { |
| 92 | perror("read"); |
| 93 | fail_file(); |
| 94 | } |
| 95 | return n; |
| 96 | } |
| 97 | |
| 98 | static size_t |
| 99 | uwrite(int const fd, void const *const buf, size_t const count) |
| 100 | { |
| 101 | size_t const n = write(fd, buf, count); |
| 102 | if (n != count) { |
| 103 | perror("write"); |
| 104 | fail_file(); |
| 105 | } |
| 106 | return n; |
| 107 | } |
| 108 | |
| 109 | static void * |
| 110 | umalloc(size_t size) |
| 111 | { |
| 112 | void *const addr = malloc(size); |
| 113 | if (0 == addr) { |
| 114 | fprintf(stderr, "malloc failed: %zu bytes\n", size); |
| 115 | fail_file(); |
| 116 | } |
| 117 | return addr; |
| 118 | } |
| 119 | |
| 120 | /* |
| 121 | * Get the whole file as a programming convenience in order to avoid |
| 122 | * malloc+lseek+read+free of many pieces. If successful, then mmap |
| 123 | * avoids copying unused pieces; else just read the whole file. |
| 124 | * Open for both read and write; new info will be appended to the file. |
| 125 | * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr |
| 126 | * do not propagate to the file until an explicit overwrite at the last. |
| 127 | * This preserves most aspects of consistency (all except .st_size) |
| 128 | * for simultaneous readers of the file while we are appending to it. |
| 129 | * However, multiple writers still are bad. We choose not to use |
| 130 | * locking because it is expensive and the use case of kernel build |
| 131 | * makes multiple writers unlikely. |
| 132 | */ |
| 133 | static void *mmap_file(char const *fname) |
| 134 | { |
| 135 | void *addr; |
| 136 | |
| 137 | fd_map = open(fname, O_RDWR); |
| 138 | if (0 > fd_map || 0 > fstat(fd_map, &sb)) { |
| 139 | perror(fname); |
| 140 | fail_file(); |
| 141 | } |
| 142 | if (!S_ISREG(sb.st_mode)) { |
| 143 | fprintf(stderr, "not a regular file: %s\n", fname); |
| 144 | fail_file(); |
| 145 | } |
| 146 | addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, |
| 147 | fd_map, 0); |
| 148 | mmap_failed = 0; |
| 149 | if (MAP_FAILED == addr) { |
| 150 | mmap_failed = 1; |
| 151 | addr = umalloc(sb.st_size); |
| 152 | uread(fd_map, addr, sb.st_size); |
| 153 | } |
| 154 | return addr; |
| 155 | } |
| 156 | |
| 157 | /* w8rev, w8nat, ...: Handle endianness. */ |
| 158 | |
| 159 | static uint64_t w8rev(uint64_t const x) |
| 160 | { |
| 161 | return ((0xff & (x >> (0 * 8))) << (7 * 8)) |
| 162 | | ((0xff & (x >> (1 * 8))) << (6 * 8)) |
| 163 | | ((0xff & (x >> (2 * 8))) << (5 * 8)) |
| 164 | | ((0xff & (x >> (3 * 8))) << (4 * 8)) |
| 165 | | ((0xff & (x >> (4 * 8))) << (3 * 8)) |
| 166 | | ((0xff & (x >> (5 * 8))) << (2 * 8)) |
| 167 | | ((0xff & (x >> (6 * 8))) << (1 * 8)) |
| 168 | | ((0xff & (x >> (7 * 8))) << (0 * 8)); |
| 169 | } |
| 170 | |
| 171 | static uint32_t w4rev(uint32_t const x) |
| 172 | { |
| 173 | return ((0xff & (x >> (0 * 8))) << (3 * 8)) |
| 174 | | ((0xff & (x >> (1 * 8))) << (2 * 8)) |
| 175 | | ((0xff & (x >> (2 * 8))) << (1 * 8)) |
| 176 | | ((0xff & (x >> (3 * 8))) << (0 * 8)); |
| 177 | } |
| 178 | |
| 179 | static uint32_t w2rev(uint16_t const x) |
| 180 | { |
| 181 | return ((0xff & (x >> (0 * 8))) << (1 * 8)) |
| 182 | | ((0xff & (x >> (1 * 8))) << (0 * 8)); |
| 183 | } |
| 184 | |
| 185 | static uint64_t w8nat(uint64_t const x) |
| 186 | { |
| 187 | return x; |
| 188 | } |
| 189 | |
| 190 | static uint32_t w4nat(uint32_t const x) |
| 191 | { |
| 192 | return x; |
| 193 | } |
| 194 | |
| 195 | static uint32_t w2nat(uint16_t const x) |
| 196 | { |
| 197 | return x; |
| 198 | } |
| 199 | |
| 200 | static uint64_t (*w8)(uint64_t); |
| 201 | static uint32_t (*w)(uint32_t); |
| 202 | static uint32_t (*w2)(uint16_t); |
| 203 | |
| 204 | /* Names of the sections that could contain calls to mcount. */ |
| 205 | static int |
| 206 | is_mcounted_section_name(char const *const txtname) |
| 207 | { |
| 208 | return 0 == strcmp(".text", txtname) || |
| 209 | 0 == strcmp(".sched.text", txtname) || |
| 210 | 0 == strcmp(".spinlock.text", txtname) || |
| 211 | 0 == strcmp(".irqentry.text", txtname) || |
| 212 | 0 == strcmp(".text.unlikely", txtname); |
| 213 | } |
| 214 | |
Steven Rostedt | c28d507 | 2010-10-13 19:06:14 -0400 | [diff] [blame] | 215 | /* 32 bit and 64 bit are very similar */ |
| 216 | #include "recordmcount.h" |
| 217 | #define RECORD_MCOUNT_64 |
| 218 | #include "recordmcount.h" |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 219 | |
John Reiser | a2d4935 | 2010-10-27 18:59:07 +0800 | [diff] [blame^] | 220 | /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. |
| 221 | * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf |
| 222 | * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] |
| 223 | * to imply the order of the members; the spec does not say so. |
| 224 | * typedef unsigned char Elf64_Byte; |
| 225 | * fails on MIPS64 because their <elf.h> already has it! |
| 226 | */ |
| 227 | |
| 228 | typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ |
| 229 | |
| 230 | union mips_r_info { |
| 231 | Elf64_Xword r_info; |
| 232 | struct { |
| 233 | Elf64_Word r_sym; /* Symbol index. */ |
| 234 | myElf64_Byte r_ssym; /* Special symbol. */ |
| 235 | myElf64_Byte r_type3; /* Third relocation. */ |
| 236 | myElf64_Byte r_type2; /* Second relocation. */ |
| 237 | myElf64_Byte r_type; /* First relocation. */ |
| 238 | } r_mips; |
| 239 | }; |
| 240 | |
| 241 | static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) |
| 242 | { |
| 243 | return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); |
| 244 | } |
| 245 | |
| 246 | static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) |
| 247 | { |
| 248 | rp->r_info = ((union mips_r_info){ |
| 249 | .r_mips = { .r_sym = w(sym), .r_type = type } |
| 250 | }).r_info; |
| 251 | } |
| 252 | |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 253 | static void |
| 254 | do_file(char const *const fname) |
| 255 | { |
| 256 | Elf32_Ehdr *const ehdr = mmap_file(fname); |
| 257 | unsigned int reltype = 0; |
| 258 | |
| 259 | ehdr_curr = ehdr; |
| 260 | w = w4nat; |
| 261 | w2 = w2nat; |
| 262 | w8 = w8nat; |
| 263 | switch (ehdr->e_ident[EI_DATA]) { |
| 264 | static unsigned int const endian = 1; |
| 265 | default: { |
| 266 | fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", |
| 267 | ehdr->e_ident[EI_DATA], fname); |
| 268 | fail_file(); |
| 269 | } break; |
| 270 | case ELFDATA2LSB: { |
| 271 | if (1 != *(unsigned char const *)&endian) { |
| 272 | /* main() is big endian, file.o is little endian. */ |
| 273 | w = w4rev; |
| 274 | w2 = w2rev; |
| 275 | w8 = w8rev; |
| 276 | } |
| 277 | } break; |
| 278 | case ELFDATA2MSB: { |
| 279 | if (0 != *(unsigned char const *)&endian) { |
| 280 | /* main() is little endian, file.o is big endian. */ |
| 281 | w = w4rev; |
| 282 | w2 = w2rev; |
| 283 | w8 = w8rev; |
| 284 | } |
| 285 | } break; |
| 286 | } /* end switch */ |
| 287 | if (0 != memcmp(ELFMAG, ehdr->e_ident, SELFMAG) |
| 288 | || ET_REL != w2(ehdr->e_type) |
| 289 | || EV_CURRENT != ehdr->e_ident[EI_VERSION]) { |
| 290 | fprintf(stderr, "unrecognized ET_REL file %s\n", fname); |
| 291 | fail_file(); |
| 292 | } |
| 293 | |
| 294 | gpfx = 0; |
| 295 | switch (w2(ehdr->e_machine)) { |
| 296 | default: { |
| 297 | fprintf(stderr, "unrecognized e_machine %d %s\n", |
| 298 | w2(ehdr->e_machine), fname); |
| 299 | fail_file(); |
| 300 | } break; |
| 301 | case EM_386: reltype = R_386_32; break; |
| 302 | case EM_ARM: reltype = R_ARM_ABS32; break; |
| 303 | case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; |
John Reiser | a2d4935 | 2010-10-27 18:59:07 +0800 | [diff] [blame^] | 304 | case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break; |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 305 | case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; |
| 306 | case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; |
| 307 | case EM_S390: /* reltype: e_class */ gpfx = '_'; break; |
| 308 | case EM_SH: reltype = R_SH_DIR32; break; |
| 309 | case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; |
| 310 | case EM_X86_64: reltype = R_X86_64_64; break; |
| 311 | } /* end switch */ |
| 312 | |
| 313 | switch (ehdr->e_ident[EI_CLASS]) { |
| 314 | default: { |
| 315 | fprintf(stderr, "unrecognized ELF class %d %s\n", |
| 316 | ehdr->e_ident[EI_CLASS], fname); |
| 317 | fail_file(); |
| 318 | } break; |
| 319 | case ELFCLASS32: { |
| 320 | if (sizeof(Elf32_Ehdr) != w2(ehdr->e_ehsize) |
| 321 | || sizeof(Elf32_Shdr) != w2(ehdr->e_shentsize)) { |
| 322 | fprintf(stderr, |
| 323 | "unrecognized ET_REL file: %s\n", fname); |
| 324 | fail_file(); |
| 325 | } |
| 326 | if (EM_S390 == w2(ehdr->e_machine)) |
| 327 | reltype = R_390_32; |
John Reiser | a2d4935 | 2010-10-27 18:59:07 +0800 | [diff] [blame^] | 328 | if (EM_MIPS == w2(ehdr->e_machine)) |
| 329 | reltype = R_MIPS_32; |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 330 | do32(ehdr, fname, reltype); |
| 331 | } break; |
| 332 | case ELFCLASS64: { |
| 333 | Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; |
| 334 | if (sizeof(Elf64_Ehdr) != w2(ghdr->e_ehsize) |
| 335 | || sizeof(Elf64_Shdr) != w2(ghdr->e_shentsize)) { |
| 336 | fprintf(stderr, |
| 337 | "unrecognized ET_REL file: %s\n", fname); |
| 338 | fail_file(); |
| 339 | } |
| 340 | if (EM_S390 == w2(ghdr->e_machine)) |
| 341 | reltype = R_390_64; |
John Reiser | a2d4935 | 2010-10-27 18:59:07 +0800 | [diff] [blame^] | 342 | if (EM_MIPS == w2(ghdr->e_machine)) { |
| 343 | reltype = R_MIPS_64; |
| 344 | Elf64_r_sym = MIPS64_r_sym; |
| 345 | Elf64_r_info = MIPS64_r_info; |
| 346 | } |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 347 | do64(ghdr, fname, reltype); |
| 348 | } break; |
| 349 | } /* end switch */ |
| 350 | |
| 351 | cleanup(); |
| 352 | } |
| 353 | |
| 354 | int |
| 355 | main(int argc, char const *argv[]) |
| 356 | { |
Steven Rostedt | 4447586 | 2010-10-15 11:49:47 -0400 | [diff] [blame] | 357 | const char ftrace[] = "kernel/trace/ftrace.o"; |
| 358 | int ftrace_size = sizeof(ftrace) - 1; |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 359 | int n_error = 0; /* gcc-4.3.0 false positive complaint */ |
Steven Rostedt | 4447586 | 2010-10-15 11:49:47 -0400 | [diff] [blame] | 360 | |
| 361 | if (argc <= 1) { |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 362 | fprintf(stderr, "usage: recordmcount file.o...\n"); |
Steven Rostedt | 4447586 | 2010-10-15 11:49:47 -0400 | [diff] [blame] | 363 | return 0; |
| 364 | } |
| 365 | |
| 366 | /* Process each file in turn, allowing deep failure. */ |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 367 | for (--argc, ++argv; 0 < argc; --argc, ++argv) { |
| 368 | int const sjval = setjmp(jmpenv); |
Steven Rostedt | 4447586 | 2010-10-15 11:49:47 -0400 | [diff] [blame] | 369 | int len; |
| 370 | |
| 371 | /* |
| 372 | * The file kernel/trace/ftrace.o references the mcount |
| 373 | * function but does not call it. Since ftrace.o should |
| 374 | * not be traced anyway, we just skip it. |
| 375 | */ |
| 376 | len = strlen(argv[0]); |
| 377 | if (len >= ftrace_size && |
| 378 | strcmp(argv[0] + (len - ftrace_size), ftrace) == 0) |
| 379 | continue; |
| 380 | |
John Reiser | 81d3858 | 2010-10-13 15:12:54 -0400 | [diff] [blame] | 381 | switch (sjval) { |
| 382 | default: { |
| 383 | fprintf(stderr, "internal error: %s\n", argv[0]); |
| 384 | exit(1); |
| 385 | } break; |
| 386 | case SJ_SETJMP: { /* normal sequence */ |
| 387 | /* Avoid problems if early cleanup() */ |
| 388 | fd_map = -1; |
| 389 | ehdr_curr = NULL; |
| 390 | mmap_failed = 1; |
| 391 | do_file(argv[0]); |
| 392 | } break; |
| 393 | case SJ_FAIL: { /* error in do_file or below */ |
| 394 | ++n_error; |
| 395 | } break; |
| 396 | case SJ_SUCCEED: { /* premature success */ |
| 397 | /* do nothing */ |
| 398 | } break; |
| 399 | } /* end switch */ |
| 400 | } |
| 401 | return !!n_error; |
| 402 | } |
| 403 | |
| 404 | |