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 <[email protected]> 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:[email protected]>. 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 static void usage(void) 103 { 104 fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n"); 105 exit(1); 106 } 107 108 struct item { 109 struct item *next; 110 unsigned int len; 111 unsigned int hash; 112 char name[]; 113 }; 114 115 #define HASHSZ 256 116 static struct item *config_hashtab[HASHSZ], *file_hashtab[HASHSZ]; 117 118 static unsigned int strhash(const char *str, unsigned int sz) 119 { 120 /* fnv32 hash */ 121 unsigned int i, hash = 2166136261U; 122 123 for (i = 0; i < sz; i++) 124 hash = (hash ^ str[i]) * 0x01000193; 125 return hash; 126 } 127 128 /* 129 * Add a new value to the configuration string. 130 */ 131 static void add_to_hashtable(const char *name, int len, unsigned int hash, 132 struct item *hashtab[]) 133 { 134 struct item *aux = malloc(sizeof(*aux) + len); 135 136 if (!aux) { 137 perror("fixdep:malloc"); 138 exit(1); 139 } 140 memcpy(aux->name, name, len); 141 aux->len = len; 142 aux->hash = hash; 143 aux->next = hashtab[hash % HASHSZ]; 144 hashtab[hash % HASHSZ] = aux; 145 } 146 147 /* 148 * Lookup a string in the hash table. If found, just return true. 149 * If not, add it to the hashtable and return false. 150 */ 151 static bool in_hashtable(const char *name, int len, struct item *hashtab[]) 152 { 153 struct item *aux; 154 unsigned int hash = strhash(name, len); 155 156 for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) { 157 if (aux->hash == hash && aux->len == len && 158 memcmp(aux->name, name, len) == 0) 159 return true; 160 } 161 162 add_to_hashtable(name, len, hash, hashtab); 163 164 return false; 165 } 166 167 /* 168 * Record the use of a CONFIG_* word. 169 */ 170 static void use_config(const char *m, int slen) 171 { 172 if (in_hashtable(m, slen, config_hashtab)) 173 return; 174 175 /* Print out a dependency path from a symbol name. */ 176 printf(" $(wildcard include/config/%.*s) \\\n", slen, m); 177 } 178 179 /* test if s ends in sub */ 180 static int str_ends_with(const char *s, int slen, const char *sub) 181 { 182 int sublen = strlen(sub); 183 184 if (sublen > slen) 185 return 0; 186 187 return !memcmp(s + slen - sublen, sub, sublen); 188 } 189 190 static void parse_config_file(const char *p) 191 { 192 const char *q, *r; 193 const char *start = p; 194 195 while ((p = strstr(p, "CONFIG_"))) { 196 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) { 197 p += 7; 198 continue; 199 } 200 p += 7; 201 q = p; 202 while (isalnum(*q) || *q == '_') 203 q++; 204 if (str_ends_with(p, q - p, "_MODULE")) 205 r = q - 7; 206 else 207 r = q; 208 if (r > p) 209 use_config(p, r - p); 210 p = q; 211 } 212 } 213 214 static void *read_file(const char *filename) 215 { 216 struct stat st; 217 int fd; 218 char *buf; 219 220 fd = open(filename, O_RDONLY); 221 if (fd < 0) { 222 fprintf(stderr, "fixdep: error opening file: "); 223 perror(filename); 224 exit(2); 225 } 226 if (fstat(fd, &st) < 0) { 227 fprintf(stderr, "fixdep: error fstat'ing file: "); 228 perror(filename); 229 exit(2); 230 } 231 buf = malloc(st.st_size + 1); 232 if (!buf) { 233 perror("fixdep: malloc"); 234 exit(2); 235 } 236 if (read(fd, buf, st.st_size) != st.st_size) { 237 perror("fixdep: read"); 238 exit(2); 239 } 240 buf[st.st_size] = '\0'; 241 close(fd); 242 243 return buf; 244 } 245 246 /* Ignore certain dependencies */ 247 static int is_ignored_file(const char *s, int len) 248 { 249 return str_ends_with(s, len, "include/generated/autoconf.h") || 250 str_ends_with(s, len, "include/generated/autoksyms.h"); 251 } 252 253 /* 254 * Important: The below generated source_foo.o and deps_foo.o variable 255 * assignments are parsed not only by make, but also by the rather simple 256 * parser in scripts/mod/sumversion.c. 257 */ 258 static void parse_dep_file(char *p, const char *target) 259 { 260 bool saw_any_target = false; 261 bool is_target = true; 262 bool is_source = false; 263 bool need_parse; 264 char *q, saved_c; 265 266 while (*p) { 267 /* handle some special characters first. */ 268 switch (*p) { 269 case '#': 270 /* 271 * skip comments. 272 * rustc may emit comments to dep-info. 273 */ 274 p++; 275 while (*p != '\0' && *p != '\n') { 276 /* 277 * escaped newlines continue the comment across 278 * multiple lines. 279 */ 280 if (*p == '\\') 281 p++; 282 p++; 283 } 284 continue; 285 case ' ': 286 case '\t': 287 /* skip whitespaces */ 288 p++; 289 continue; 290 case '\\': 291 /* 292 * backslash/newline combinations continue the 293 * statement. Skip it just like a whitespace. 294 */ 295 if (*(p + 1) == '\n') { 296 p += 2; 297 continue; 298 } 299 break; 300 case '\n': 301 /* 302 * Makefiles use a line-based syntax, where the newline 303 * is the end of a statement. After seeing a newline, 304 * we expect the next token is a target. 305 */ 306 p++; 307 is_target = true; 308 continue; 309 case ':': 310 /* 311 * assume the first dependency after a colon as the 312 * source file. 313 */ 314 p++; 315 is_target = false; 316 is_source = true; 317 continue; 318 } 319 320 /* find the end of the token */ 321 q = p; 322 while (*q != ' ' && *q != '\t' && *q != '\n' && *q != '#' && *q != ':') { 323 if (*q == '\\') { 324 /* 325 * backslash/newline combinations work like as 326 * a whitespace, so this is the end of token. 327 */ 328 if (*(q + 1) == '\n') 329 break; 330 331 /* escaped special characters */ 332 if (*(q + 1) == '#' || *(q + 1) == ':') { 333 memmove(p + 1, p, q - p); 334 p++; 335 } 336 337 q++; 338 } 339 340 if (*q == '\0') 341 break; 342 q++; 343 } 344 345 /* Just discard the target */ 346 if (is_target) { 347 p = q; 348 continue; 349 } 350 351 saved_c = *q; 352 *q = '\0'; 353 need_parse = false; 354 355 /* 356 * Do not list the source file as dependency, so that kbuild is 357 * not confused if a .c file is rewritten into .S or vice versa. 358 * Storing it in source_* is needed for modpost to compute 359 * srcversions. 360 */ 361 if (is_source) { 362 /* 363 * The DT build rule concatenates multiple dep files. 364 * When processing them, only process the first source 365 * name, which will be the original one, and ignore any 366 * other source names, which will be intermediate 367 * temporary files. 368 * 369 * rustc emits the same dependency list for each 370 * emission type. It is enough to list the source name 371 * just once. 372 */ 373 if (!saw_any_target) { 374 saw_any_target = true; 375 printf("source_%s := %s\n\n", target, p); 376 printf("deps_%s := \\\n", target); 377 need_parse = true; 378 } 379 } else if (!is_ignored_file(p, q - p) && 380 !in_hashtable(p, q - p, file_hashtab)) { 381 printf(" %s \\\n", p); 382 need_parse = true; 383 } 384 385 if (need_parse) { 386 void *buf; 387 388 buf = read_file(p); 389 parse_config_file(buf); 390 free(buf); 391 } 392 393 is_source = false; 394 *q = saved_c; 395 p = q; 396 } 397 398 if (!saw_any_target) { 399 fprintf(stderr, "fixdep: parse error; no targets found\n"); 400 exit(1); 401 } 402 403 printf("\n%s: $(deps_%s)\n\n", target, target); 404 printf("$(deps_%s):\n", target); 405 } 406 407 int main(int argc, char *argv[]) 408 { 409 const char *depfile, *target, *cmdline; 410 void *buf; 411 412 if (argc != 4) 413 usage(); 414 415 depfile = argv[1]; 416 target = argv[2]; 417 cmdline = argv[3]; 418 419 printf("savedcmd_%s := %s\n\n", target, cmdline); 420 421 buf = read_file(depfile); 422 parse_dep_file(buf, target); 423 free(buf); 424 425 fflush(stdout); 426 427 /* 428 * In the intended usage, the stdout is redirected to .*.cmd files. 429 * Call ferror() to catch errors such as "No space left on device". 430 */ 431 if (ferror(stdout)) { 432 fprintf(stderr, "fixdep: not all data was written to the output\n"); 433 exit(1); 434 } 435 436 return 0; 437 } 438