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 #include <sys/types.h> 98 #include <sys/stat.h> 99 #include <unistd.h> 100 #include <fcntl.h> 101 #include <string.h> 102 #include <stdarg.h> 103 #include <stdlib.h> 104 #include <stdio.h> 105 #include <ctype.h> 106 107 static void usage(void) 108 { 109 fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n"); 110 exit(1); 111 } 112 113 /* 114 * In the intended usage of this program, the stdout is redirected to .*.cmd 115 * files. The return value of printf() and putchar() must be checked to catch 116 * any error, e.g. "No space left on device". 117 */ 118 static void xprintf(const char *format, ...) 119 { 120 va_list ap; 121 int ret; 122 123 va_start(ap, format); 124 ret = vprintf(format, ap); 125 if (ret < 0) { 126 perror("fixdep"); 127 exit(1); 128 } 129 va_end(ap); 130 } 131 132 static void xputchar(int c) 133 { 134 int ret; 135 136 ret = putchar(c); 137 if (ret == EOF) { 138 perror("fixdep"); 139 exit(1); 140 } 141 } 142 143 /* 144 * Print out a dependency path from a symbol name 145 */ 146 static void print_dep(const char *m, int slen, const char *dir) 147 { 148 int c, prev_c = '/', i; 149 150 xprintf(" $(wildcard %s/", dir); 151 for (i = 0; i < slen; i++) { 152 c = m[i]; 153 if (c == '_') 154 c = '/'; 155 else 156 c = tolower(c); 157 if (c != '/' || prev_c != '/') 158 xputchar(c); 159 prev_c = c; 160 } 161 xprintf(".h) \\\n"); 162 } 163 164 struct item { 165 struct item *next; 166 unsigned int len; 167 unsigned int hash; 168 char name[0]; 169 }; 170 171 #define HASHSZ 256 172 static struct item *hashtab[HASHSZ]; 173 174 static unsigned int strhash(const char *str, unsigned int sz) 175 { 176 /* fnv32 hash */ 177 unsigned int i, hash = 2166136261U; 178 179 for (i = 0; i < sz; i++) 180 hash = (hash ^ str[i]) * 0x01000193; 181 return hash; 182 } 183 184 /* 185 * Lookup a value in the configuration string. 186 */ 187 static int is_defined_config(const char *name, int len, unsigned int hash) 188 { 189 struct item *aux; 190 191 for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) { 192 if (aux->hash == hash && aux->len == len && 193 memcmp(aux->name, name, len) == 0) 194 return 1; 195 } 196 return 0; 197 } 198 199 /* 200 * Add a new value to the configuration string. 201 */ 202 static void define_config(const char *name, int len, unsigned int hash) 203 { 204 struct item *aux = malloc(sizeof(*aux) + len); 205 206 if (!aux) { 207 perror("fixdep:malloc"); 208 exit(1); 209 } 210 memcpy(aux->name, name, len); 211 aux->len = len; 212 aux->hash = hash; 213 aux->next = hashtab[hash % HASHSZ]; 214 hashtab[hash % HASHSZ] = aux; 215 } 216 217 /* 218 * Record the use of a CONFIG_* word. 219 */ 220 static void use_config(const char *m, int slen) 221 { 222 unsigned int hash = strhash(m, slen); 223 224 if (is_defined_config(m, slen, hash)) 225 return; 226 227 define_config(m, slen, hash); 228 print_dep(m, slen, "include/config"); 229 } 230 231 /* test if s ends in sub */ 232 static int str_ends_with(const char *s, int slen, const char *sub) 233 { 234 int sublen = strlen(sub); 235 236 if (sublen > slen) 237 return 0; 238 239 return !memcmp(s + slen - sublen, sub, sublen); 240 } 241 242 static void parse_config_file(const char *p) 243 { 244 const char *q, *r; 245 const char *start = p; 246 247 while ((p = strstr(p, "CONFIG_"))) { 248 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) { 249 p += 7; 250 continue; 251 } 252 p += 7; 253 q = p; 254 while (*q && (isalnum(*q) || *q == '_')) 255 q++; 256 if (str_ends_with(p, q - p, "_MODULE")) 257 r = q - 7; 258 else 259 r = q; 260 if (r > p) 261 use_config(p, r - p); 262 p = q; 263 } 264 } 265 266 static void *read_file(const char *filename) 267 { 268 struct stat st; 269 int fd; 270 char *buf; 271 272 fd = open(filename, O_RDONLY); 273 if (fd < 0) { 274 fprintf(stderr, "fixdep: error opening file: "); 275 perror(filename); 276 exit(2); 277 } 278 if (fstat(fd, &st) < 0) { 279 fprintf(stderr, "fixdep: error fstat'ing file: "); 280 perror(filename); 281 exit(2); 282 } 283 buf = malloc(st.st_size + 1); 284 if (!buf) { 285 perror("fixdep: malloc"); 286 exit(2); 287 } 288 if (read(fd, buf, st.st_size) != st.st_size) { 289 perror("fixdep: read"); 290 exit(2); 291 } 292 buf[st.st_size] = '\0'; 293 close(fd); 294 295 return buf; 296 } 297 298 /* Ignore certain dependencies */ 299 static int is_ignored_file(const char *s, int len) 300 { 301 return str_ends_with(s, len, "include/generated/autoconf.h") || 302 str_ends_with(s, len, "include/generated/autoksyms.h") || 303 str_ends_with(s, len, ".ver"); 304 } 305 306 /* 307 * Important: The below generated source_foo.o and deps_foo.o variable 308 * assignments are parsed not only by make, but also by the rather simple 309 * parser in scripts/mod/sumversion.c. 310 */ 311 static void parse_dep_file(char *m, const char *target) 312 { 313 char *p; 314 int is_last, is_target; 315 int saw_any_target = 0; 316 int is_first_dep = 0; 317 void *buf; 318 319 while (1) { 320 /* Skip any "white space" */ 321 while (*m == ' ' || *m == '\\' || *m == '\n') 322 m++; 323 324 if (!*m) 325 break; 326 327 /* Find next "white space" */ 328 p = m; 329 while (*p && *p != ' ' && *p != '\\' && *p != '\n') 330 p++; 331 is_last = (*p == '\0'); 332 /* Is the token we found a target name? */ 333 is_target = (*(p-1) == ':'); 334 /* Don't write any target names into the dependency file */ 335 if (is_target) { 336 /* The /next/ file is the first dependency */ 337 is_first_dep = 1; 338 } else if (!is_ignored_file(m, p - m)) { 339 *p = '\0'; 340 341 /* 342 * Do not list the source file as dependency, so that 343 * kbuild is not confused if a .c file is rewritten 344 * into .S or vice versa. Storing it in source_* is 345 * needed for modpost to compute srcversions. 346 */ 347 if (is_first_dep) { 348 /* 349 * If processing the concatenation of multiple 350 * dependency files, only process the first 351 * target name, which will be the original 352 * source name, and ignore any other target 353 * names, which will be intermediate temporary 354 * files. 355 */ 356 if (!saw_any_target) { 357 saw_any_target = 1; 358 xprintf("source_%s := %s\n\n", 359 target, m); 360 xprintf("deps_%s := \\\n", target); 361 } 362 is_first_dep = 0; 363 } else { 364 xprintf(" %s \\\n", m); 365 } 366 367 buf = read_file(m); 368 parse_config_file(buf); 369 free(buf); 370 } 371 372 if (is_last) 373 break; 374 375 /* 376 * Start searching for next token immediately after the first 377 * "whitespace" character that follows this token. 378 */ 379 m = p + 1; 380 } 381 382 if (!saw_any_target) { 383 fprintf(stderr, "fixdep: parse error; no targets found\n"); 384 exit(1); 385 } 386 387 xprintf("\n%s: $(deps_%s)\n\n", target, target); 388 xprintf("$(deps_%s):\n", target); 389 } 390 391 int main(int argc, char *argv[]) 392 { 393 const char *depfile, *target, *cmdline; 394 void *buf; 395 396 if (argc != 4) 397 usage(); 398 399 depfile = argv[1]; 400 target = argv[2]; 401 cmdline = argv[3]; 402 403 xprintf("cmd_%s := %s\n\n", target, cmdline); 404 405 buf = read_file(depfile); 406 parse_dep_file(buf, target); 407 free(buf); 408 409 return 0; 410 } 411