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.h" 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 * cmd_<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.h for every 78 * CONFIG_MY_OPTION encountered in any of the prerequisites. 79 * 80 * It will also filter out all the dependencies on *.ver. We need 81 * to make sure that the generated version checksum are globally up 82 * to date before even starting the recursive build, so it's too late 83 * at this point anyway. 84 * 85 * We don't even try to really parse the header files, but 86 * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will 87 * be picked up as well. It's not a problem with respect to 88 * correctness, since that can only give too many dependencies, thus 89 * we cannot miss a rebuild. Since people tend to not mention totally 90 * unrelated CONFIG_ options all over the place, it's not an 91 * efficiency problem either. 92 * 93 * (Note: it'd be easy to port over the complete mkdep state machine, 94 * but I don't think the added complexity is worth it) 95 */ 96 /* 97 * Note 2: if somebody writes HELLO_CONFIG_BOOM in a file, it will depend onto 98 * CONFIG_BOOM. This could seem a bug (not too hard to fix), but please do not 99 * fix it! Some UserModeLinux files (look at arch/um/) call CONFIG_BOOM as 100 * UML_CONFIG_BOOM, to avoid conflicts with /usr/include/linux/autoconf.h, 101 * through arch/um/include/uml-config.h; this fixdep "bug" makes sure that 102 * those files will have correct dependencies. 103 */ 104 105 #include <sys/types.h> 106 #include <sys/stat.h> 107 #include <unistd.h> 108 #include <fcntl.h> 109 #include <string.h> 110 #include <stdlib.h> 111 #include <stdio.h> 112 #include <ctype.h> 113 114 static void usage(void) 115 { 116 fprintf(stderr, "Usage: fixdep [-e] <depfile> <target> <cmdline>\n"); 117 fprintf(stderr, " -e insert extra dependencies given on stdin\n"); 118 exit(1); 119 } 120 121 /* 122 * Print out a dependency path from a symbol name 123 */ 124 static void print_config(const char *m, int slen) 125 { 126 int c, i; 127 128 printf(" $(wildcard include/config/"); 129 for (i = 0; i < slen; i++) { 130 c = m[i]; 131 if (c == '_') 132 c = '/'; 133 else 134 c = tolower(c); 135 putchar(c); 136 } 137 printf(".h) \\\n"); 138 } 139 140 static void do_extra_deps(void) 141 { 142 char buf[80]; 143 144 while (fgets(buf, sizeof(buf), stdin)) { 145 int len = strlen(buf); 146 147 if (len < 2 || buf[len - 1] != '\n') { 148 fprintf(stderr, "fixdep: bad data on stdin\n"); 149 exit(1); 150 } 151 print_config(buf, len - 1); 152 } 153 } 154 155 struct item { 156 struct item *next; 157 unsigned int len; 158 unsigned int hash; 159 char name[0]; 160 }; 161 162 #define HASHSZ 256 163 static struct item *hashtab[HASHSZ]; 164 165 static unsigned int strhash(const char *str, unsigned int sz) 166 { 167 /* fnv32 hash */ 168 unsigned int i, hash = 2166136261U; 169 170 for (i = 0; i < sz; i++) 171 hash = (hash ^ str[i]) * 0x01000193; 172 return hash; 173 } 174 175 /* 176 * Lookup a value in the configuration string. 177 */ 178 static int is_defined_config(const char *name, int len, unsigned int hash) 179 { 180 struct item *aux; 181 182 for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) { 183 if (aux->hash == hash && aux->len == len && 184 memcmp(aux->name, name, len) == 0) 185 return 1; 186 } 187 return 0; 188 } 189 190 /* 191 * Add a new value to the configuration string. 192 */ 193 static void define_config(const char *name, int len, unsigned int hash) 194 { 195 struct item *aux = malloc(sizeof(*aux) + len); 196 197 if (!aux) { 198 perror("fixdep:malloc"); 199 exit(1); 200 } 201 memcpy(aux->name, name, len); 202 aux->len = len; 203 aux->hash = hash; 204 aux->next = hashtab[hash % HASHSZ]; 205 hashtab[hash % HASHSZ] = aux; 206 } 207 208 /* 209 * Record the use of a CONFIG_* word. 210 */ 211 static void use_config(const char *m, int slen) 212 { 213 unsigned int hash = strhash(m, slen); 214 215 if (is_defined_config(m, slen, hash)) 216 return; 217 218 define_config(m, slen, hash); 219 print_config(m, slen); 220 } 221 222 /* test if s ends in sub */ 223 static int str_ends_with(const char *s, int slen, const char *sub) 224 { 225 int sublen = strlen(sub); 226 227 if (sublen > slen) 228 return 0; 229 230 return !memcmp(s + slen - sublen, sub, sublen); 231 } 232 233 static void parse_config_file(const char *p) 234 { 235 const char *q, *r; 236 237 while ((p = strstr(p, "CONFIG_"))) { 238 p += 7; 239 q = p; 240 while (*q && (isalnum(*q) || *q == '_')) 241 q++; 242 if (str_ends_with(p, q - p, "_MODULE")) 243 r = q - 7; 244 else 245 r = q; 246 if (r > p) 247 use_config(p, r - p); 248 p = q; 249 } 250 } 251 252 static void *read_file(const char *filename) 253 { 254 struct stat st; 255 int fd; 256 char *buf; 257 258 fd = open(filename, O_RDONLY); 259 if (fd < 0) { 260 fprintf(stderr, "fixdep: error opening file: "); 261 perror(filename); 262 exit(2); 263 } 264 if (fstat(fd, &st) < 0) { 265 fprintf(stderr, "fixdep: error fstat'ing file: "); 266 perror(filename); 267 exit(2); 268 } 269 buf = malloc(st.st_size + 1); 270 if (!buf) { 271 perror("fixdep: malloc"); 272 exit(2); 273 } 274 if (read(fd, buf, st.st_size) != st.st_size) { 275 perror("fixdep: read"); 276 exit(2); 277 } 278 buf[st.st_size] = '\0'; 279 close(fd); 280 281 return buf; 282 } 283 284 /* Ignore certain dependencies */ 285 static int is_ignored_file(const char *s, int len) 286 { 287 return str_ends_with(s, len, "include/generated/autoconf.h") || 288 str_ends_with(s, len, "include/generated/autoksyms.h") || 289 str_ends_with(s, len, "arch/um/include/uml-config.h") || 290 str_ends_with(s, len, "include/linux/kconfig.h") || 291 str_ends_with(s, len, ".ver"); 292 } 293 294 /* 295 * Important: The below generated source_foo.o and deps_foo.o variable 296 * assignments are parsed not only by make, but also by the rather simple 297 * parser in scripts/mod/sumversion.c. 298 */ 299 static void parse_dep_file(char *m, const char *target, int insert_extra_deps) 300 { 301 char *p; 302 int is_last, is_target; 303 int saw_any_target = 0; 304 int is_first_dep = 0; 305 void *buf; 306 307 while (1) { 308 /* Skip any "white space" */ 309 while (*m == ' ' || *m == '\\' || *m == '\n') 310 m++; 311 312 if (!*m) 313 break; 314 315 /* Find next "white space" */ 316 p = m; 317 while (*p && *p != ' ' && *p != '\\' && *p != '\n') 318 p++; 319 is_last = (*p == '\0'); 320 /* Is the token we found a target name? */ 321 is_target = (*(p-1) == ':'); 322 /* Don't write any target names into the dependency file */ 323 if (is_target) { 324 /* The /next/ file is the first dependency */ 325 is_first_dep = 1; 326 } else if (!is_ignored_file(m, p - m)) { 327 *p = '\0'; 328 329 /* 330 * Do not list the source file as dependency, so that 331 * kbuild is not confused if a .c file is rewritten 332 * into .S or vice versa. Storing it in source_* is 333 * needed for modpost to compute srcversions. 334 */ 335 if (is_first_dep) { 336 /* 337 * If processing the concatenation of multiple 338 * dependency files, only process the first 339 * target name, which will be the original 340 * source name, and ignore any other target 341 * names, which will be intermediate temporary 342 * files. 343 */ 344 if (!saw_any_target) { 345 saw_any_target = 1; 346 printf("source_%s := %s\n\n", 347 target, m); 348 printf("deps_%s := \\\n", target); 349 } 350 is_first_dep = 0; 351 } else { 352 printf(" %s \\\n", m); 353 } 354 355 buf = read_file(m); 356 parse_config_file(buf); 357 free(buf); 358 } 359 360 if (is_last) 361 break; 362 363 /* 364 * Start searching for next token immediately after the first 365 * "whitespace" character that follows this token. 366 */ 367 m = p + 1; 368 } 369 370 if (!saw_any_target) { 371 fprintf(stderr, "fixdep: parse error; no targets found\n"); 372 exit(1); 373 } 374 375 if (insert_extra_deps) 376 do_extra_deps(); 377 378 printf("\n%s: $(deps_%s)\n\n", target, target); 379 printf("$(deps_%s):\n", target); 380 } 381 382 int main(int argc, char *argv[]) 383 { 384 const char *depfile, *target, *cmdline; 385 int insert_extra_deps = 0; 386 void *buf; 387 388 if (argc == 5 && !strcmp(argv[1], "-e")) { 389 insert_extra_deps = 1; 390 argv++; 391 } else if (argc != 4) 392 usage(); 393 394 depfile = argv[1]; 395 target = argv[2]; 396 cmdline = argv[3]; 397 398 printf("cmd_%s := %s\n\n", target, cmdline); 399 400 buf = read_file(depfile); 401 parse_dep_file(buf, target, insert_extra_deps); 402 free(buf); 403 404 return 0; 405 } 406