1 /* 2 * "Optimize" a list of dependencies as spit out by gcc -MD 3 * for the kernel build 4 * =========================================================================== 5 * 6 * Author Kai Germaschewski 7 * Copyright 2002 by Kai Germaschewski <kai.germaschewski@gmx.de> 8 * 9 * This software may be used and distributed according to the terms 10 * of the GNU General Public License, incorporated herein by reference. 11 * 12 * 13 * Introduction: 14 * 15 * gcc produces a very nice and correct list of dependencies which 16 * tells make when to remake a file. 17 * 18 * To use this list as-is however has the drawback that virtually 19 * every file in the kernel includes autoconf.h. 20 * 21 * If the user re-runs make *config, autoconf.h will be 22 * regenerated. make notices that and will rebuild every file which 23 * includes autoconf.h, i.e. basically all files. This is extremely 24 * annoying if the user just changed CONFIG_HIS_DRIVER from n to m. 25 * 26 * So we play the same trick that "mkdep" played before. We replace 27 * the dependency on autoconf.h by a dependency on every config 28 * option which is mentioned in any of the listed prerequisites. 29 * 30 * kconfig populates a tree in include/config/ with an empty file 31 * for each config symbol and when the configuration is updated 32 * the files representing changed config options are touched 33 * which then let make pick up the changes and the files that use 34 * the config symbols are rebuilt. 35 * 36 * So if the user changes his CONFIG_HIS_DRIVER option, only the objects 37 * which depend on "include/config/HIS_DRIVER" will be rebuilt, 38 * so most likely only his driver ;-) 39 * 40 * The idea above dates, by the way, back to Michael E Chastain, AFAIK. 41 * 42 * So to get dependencies right, there are two issues: 43 * o if any of the files the compiler read changed, we need to rebuild 44 * o if the command line given to the compile the file changed, we 45 * better rebuild as well. 46 * 47 * The former is handled by using the -MD output, the later by saving 48 * the command line used to compile the old object and comparing it 49 * to the one we would now use. 50 * 51 * Again, also this idea is pretty old and has been discussed on 52 * kbuild-devel a long time ago. I don't have a sensibly working 53 * internet connection right now, so I rather don't mention names 54 * without double checking. 55 * 56 * This code here has been based partially based on mkdep.c, which 57 * says the following about its history: 58 * 59 * Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>. 60 * This is a C version of syncdep.pl by Werner Almesberger. 61 * 62 * 63 * It is invoked as 64 * 65 * fixdep <depfile> <target> <cmdline> 66 * 67 * and will read the dependency file <depfile> 68 * 69 * The transformed dependency snipped is written to stdout. 70 * 71 * It first generates a line 72 * 73 * savedcmd_<target> = <cmdline> 74 * 75 * and then basically copies the .<target>.d file to stdout, in the 76 * process filtering out the dependency on autoconf.h and adding 77 * dependencies on include/config/MY_OPTION for every 78 * CONFIG_MY_OPTION encountered in any of the prerequisites. 79 * 80 * We don't even try to really parse the header files, but 81 * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will 82 * be picked up as well. It's not a problem with respect to 83 * correctness, since that can only give too many dependencies, thus 84 * we cannot miss a rebuild. Since people tend to not mention totally 85 * unrelated CONFIG_ options all over the place, it's not an 86 * efficiency problem either. 87 * 88 * (Note: it'd be easy to port over the complete mkdep state machine, 89 * but I don't think the added complexity is worth it) 90 */ 91 92 #include <sys/types.h> 93 #include <sys/stat.h> 94 #include <unistd.h> 95 #include <fcntl.h> 96 #include <string.h> 97 #include <stdbool.h> 98 #include <stdlib.h> 99 #include <stdio.h> 100 #include <ctype.h> 101 102 #include <xalloc.h> 103 104 static void usage(void) 105 { 106 fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n"); 107 exit(1); 108 } 109 110 struct item { 111 struct item *next; 112 unsigned int len; 113 unsigned int hash; 114 char name[]; 115 }; 116 117 #define HASHSZ 256 118 static struct item *config_hashtab[HASHSZ], *file_hashtab[HASHSZ]; 119 120 static unsigned int strhash(const char *str, unsigned int sz) 121 { 122 /* fnv32 hash */ 123 unsigned int i, hash = 2166136261U; 124 125 for (i = 0; i < sz; i++) 126 hash = (hash ^ str[i]) * 0x01000193; 127 return hash; 128 } 129 130 /* 131 * Add a new value to the configuration string. 132 */ 133 static void add_to_hashtable(const char *name, int len, unsigned int hash, 134 struct item *hashtab[]) 135 { 136 struct item *aux; 137 138 aux = xmalloc(sizeof(*aux) + len); 139 memcpy(aux->name, name, len); 140 aux->len = len; 141 aux->hash = hash; 142 aux->next = hashtab[hash % HASHSZ]; 143 hashtab[hash % HASHSZ] = aux; 144 } 145 146 /* 147 * Lookup a string in the hash table. If found, just return true. 148 * If not, add it to the hashtable and return false. 149 */ 150 static bool in_hashtable(const char *name, int len, struct item *hashtab[]) 151 { 152 struct item *aux; 153 unsigned int hash = strhash(name, len); 154 155 for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) { 156 if (aux->hash == hash && aux->len == len && 157 memcmp(aux->name, name, len) == 0) 158 return true; 159 } 160 161 add_to_hashtable(name, len, hash, hashtab); 162 163 return false; 164 } 165 166 /* 167 * Record the use of a CONFIG_* word. 168 */ 169 static void use_config(const char *m, int slen) 170 { 171 if (in_hashtable(m, slen, config_hashtab)) 172 return; 173 174 /* Print out a dependency path from a symbol name. */ 175 printf(" $(wildcard include/config/%.*s) \\\n", slen, m); 176 } 177 178 /* test if s ends in sub */ 179 static int str_ends_with(const char *s, int slen, const char *sub) 180 { 181 int sublen = strlen(sub); 182 183 if (sublen > slen) 184 return 0; 185 186 return !memcmp(s + slen - sublen, sub, sublen); 187 } 188 189 static void parse_config_file(const char *p) 190 { 191 const char *q, *r; 192 const char *start = p; 193 194 while ((p = strstr(p, "CONFIG_"))) { 195 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) { 196 p += 7; 197 continue; 198 } 199 p += 7; 200 q = p; 201 while (isalnum(*q) || *q == '_') 202 q++; 203 if (str_ends_with(p, q - p, "_MODULE")) 204 r = q - 7; 205 else 206 r = q; 207 if (r > p) 208 use_config(p, r - p); 209 p = q; 210 } 211 } 212 213 static void *read_file(const char *filename) 214 { 215 struct stat st; 216 int fd; 217 char *buf; 218 219 fd = open(filename, O_RDONLY); 220 if (fd < 0) { 221 fprintf(stderr, "fixdep: error opening file: "); 222 perror(filename); 223 exit(2); 224 } 225 if (fstat(fd, &st) < 0) { 226 fprintf(stderr, "fixdep: error fstat'ing file: "); 227 perror(filename); 228 exit(2); 229 } 230 buf = xmalloc(st.st_size + 1); 231 if (read(fd, buf, st.st_size) != st.st_size) { 232 perror("fixdep: read"); 233 exit(2); 234 } 235 buf[st.st_size] = '\0'; 236 close(fd); 237 238 return buf; 239 } 240 241 /* Ignore certain dependencies */ 242 static int is_ignored_file(const char *s, int len) 243 { 244 return str_ends_with(s, len, "include/generated/autoconf.h"); 245 } 246 247 /* Do not parse these files */ 248 static int is_no_parse_file(const char *s, int len) 249 { 250 /* rustc may list binary files in dep-info */ 251 return str_ends_with(s, len, ".rlib") || 252 str_ends_with(s, len, ".rmeta") || 253 str_ends_with(s, len, ".so"); 254 } 255 256 /* 257 * Important: The below generated source_foo.o and deps_foo.o variable 258 * assignments are parsed not only by make, but also by the rather simple 259 * parser in scripts/mod/sumversion.c. 260 */ 261 static void parse_dep_file(char *p, const char *target) 262 { 263 bool saw_any_target = false; 264 bool is_target = true; 265 bool is_source = false; 266 bool need_parse; 267 char *q, saved_c; 268 269 while (*p) { 270 /* handle some special characters first. */ 271 switch (*p) { 272 case '#': 273 /* 274 * skip comments. 275 * rustc may emit comments to dep-info. 276 */ 277 p++; 278 while (*p != '\0' && *p != '\n') { 279 /* 280 * escaped newlines continue the comment across 281 * multiple lines. 282 */ 283 if (*p == '\\') 284 p++; 285 p++; 286 } 287 continue; 288 case ' ': 289 case '\t': 290 /* skip whitespaces */ 291 p++; 292 continue; 293 case '\\': 294 /* 295 * backslash/newline combinations continue the 296 * statement. Skip it just like a whitespace. 297 */ 298 if (*(p + 1) == '\n') { 299 p += 2; 300 continue; 301 } 302 break; 303 case '\n': 304 /* 305 * Makefiles use a line-based syntax, where the newline 306 * is the end of a statement. After seeing a newline, 307 * we expect the next token is a target. 308 */ 309 p++; 310 is_target = true; 311 continue; 312 case ':': 313 /* 314 * assume the first dependency after a colon as the 315 * source file. 316 */ 317 p++; 318 is_target = false; 319 is_source = true; 320 continue; 321 } 322 323 /* find the end of the token */ 324 q = p; 325 while (*q != ' ' && *q != '\t' && *q != '\n' && *q != '#' && *q != ':') { 326 if (*q == '\\') { 327 /* 328 * backslash/newline combinations work like as 329 * a whitespace, so this is the end of token. 330 */ 331 if (*(q + 1) == '\n') 332 break; 333 334 /* escaped special characters */ 335 if (*(q + 1) == '#' || *(q + 1) == ':') { 336 memmove(p + 1, p, q - p); 337 p++; 338 } 339 340 q++; 341 } 342 343 if (*q == '\0') 344 break; 345 q++; 346 } 347 348 /* Just discard the target */ 349 if (is_target) { 350 p = q; 351 continue; 352 } 353 354 saved_c = *q; 355 *q = '\0'; 356 need_parse = false; 357 358 /* 359 * Do not list the source file as dependency, so that kbuild is 360 * not confused if a .c file is rewritten into .S or vice versa. 361 * Storing it in source_* is needed for modpost to compute 362 * srcversions. 363 */ 364 if (is_source) { 365 /* 366 * The DT build rule concatenates multiple dep files. 367 * When processing them, only process the first source 368 * name, which will be the original one, and ignore any 369 * other source names, which will be intermediate 370 * temporary files. 371 * 372 * rustc emits the same dependency list for each 373 * emission type. It is enough to list the source name 374 * just once. 375 */ 376 if (!saw_any_target) { 377 saw_any_target = true; 378 printf("source_%s := %s\n\n", target, p); 379 printf("deps_%s := \\\n", target); 380 need_parse = true; 381 } 382 } else if (!is_ignored_file(p, q - p) && 383 !in_hashtable(p, q - p, file_hashtab)) { 384 printf(" %s \\\n", p); 385 need_parse = true; 386 } 387 388 if (need_parse && !is_no_parse_file(p, q - p)) { 389 void *buf; 390 391 buf = read_file(p); 392 parse_config_file(buf); 393 free(buf); 394 } 395 396 is_source = false; 397 *q = saved_c; 398 p = q; 399 } 400 401 if (!saw_any_target) { 402 fprintf(stderr, "fixdep: parse error; no targets found\n"); 403 exit(1); 404 } 405 406 printf("\n%s: $(deps_%s)\n\n", target, target); 407 printf("$(deps_%s):\n", target); 408 } 409 410 int main(int argc, char *argv[]) 411 { 412 const char *depfile, *target, *cmdline; 413 void *buf; 414 415 if (argc != 4) 416 usage(); 417 418 depfile = argv[1]; 419 target = argv[2]; 420 cmdline = argv[3]; 421 422 printf("savedcmd_%s := %s\n\n", target, cmdline); 423 424 buf = read_file(depfile); 425 parse_dep_file(buf, target); 426 free(buf); 427 428 fflush(stdout); 429 430 /* 431 * In the intended usage, the stdout is redirected to .*.cmd files. 432 * Call ferror() to catch errors such as "No space left on device". 433 */ 434 if (ferror(stdout)) { 435 fprintf(stderr, "fixdep: not all data was written to the output\n"); 436 exit(1); 437 } 438 439 return 0; 440 } 441