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 * 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 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 <stdarg.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 *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 * Lookup a value in the configuration string. 130 */ 131 static int is_defined_config(const char *name, int len, unsigned int hash) 132 { 133 struct item *aux; 134 135 for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) { 136 if (aux->hash == hash && aux->len == len && 137 memcmp(aux->name, name, len) == 0) 138 return 1; 139 } 140 return 0; 141 } 142 143 /* 144 * Add a new value to the configuration string. 145 */ 146 static void define_config(const char *name, int len, unsigned int hash) 147 { 148 struct item *aux = malloc(sizeof(*aux) + len); 149 150 if (!aux) { 151 perror("fixdep:malloc"); 152 exit(1); 153 } 154 memcpy(aux->name, name, len); 155 aux->len = len; 156 aux->hash = hash; 157 aux->next = hashtab[hash % HASHSZ]; 158 hashtab[hash % HASHSZ] = aux; 159 } 160 161 /* 162 * Record the use of a CONFIG_* word. 163 */ 164 static void use_config(const char *m, int slen) 165 { 166 unsigned int hash = strhash(m, slen); 167 168 if (is_defined_config(m, slen, hash)) 169 return; 170 171 define_config(m, slen, hash); 172 /* Print out a dependency path from a symbol name. */ 173 printf(" $(wildcard include/config/%.*s) \\\n", slen, m); 174 } 175 176 /* test if s ends in sub */ 177 static int str_ends_with(const char *s, int slen, const char *sub) 178 { 179 int sublen = strlen(sub); 180 181 if (sublen > slen) 182 return 0; 183 184 return !memcmp(s + slen - sublen, sub, sublen); 185 } 186 187 static void parse_config_file(const char *p) 188 { 189 const char *q, *r; 190 const char *start = p; 191 192 while ((p = strstr(p, "CONFIG_"))) { 193 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) { 194 p += 7; 195 continue; 196 } 197 p += 7; 198 q = p; 199 while (isalnum(*q) || *q == '_') 200 q++; 201 if (str_ends_with(p, q - p, "_MODULE")) 202 r = q - 7; 203 else 204 r = q; 205 if (r > p) 206 use_config(p, r - p); 207 p = q; 208 } 209 } 210 211 static void *read_file(const char *filename) 212 { 213 struct stat st; 214 int fd; 215 char *buf; 216 217 fd = open(filename, O_RDONLY); 218 if (fd < 0) { 219 fprintf(stderr, "fixdep: error opening file: "); 220 perror(filename); 221 exit(2); 222 } 223 if (fstat(fd, &st) < 0) { 224 fprintf(stderr, "fixdep: error fstat'ing file: "); 225 perror(filename); 226 exit(2); 227 } 228 buf = malloc(st.st_size + 1); 229 if (!buf) { 230 perror("fixdep: malloc"); 231 exit(2); 232 } 233 if (read(fd, buf, st.st_size) != st.st_size) { 234 perror("fixdep: read"); 235 exit(2); 236 } 237 buf[st.st_size] = '\0'; 238 close(fd); 239 240 return buf; 241 } 242 243 /* Ignore certain dependencies */ 244 static int is_ignored_file(const char *s, int len) 245 { 246 return str_ends_with(s, len, "include/generated/autoconf.h") || 247 str_ends_with(s, len, "include/generated/autoksyms.h"); 248 } 249 250 /* 251 * Important: The below generated source_foo.o and deps_foo.o variable 252 * assignments are parsed not only by make, but also by the rather simple 253 * parser in scripts/mod/sumversion.c. 254 */ 255 static void parse_dep_file(char *m, const char *target) 256 { 257 char *p; 258 int is_last, is_target; 259 int saw_any_target = 0; 260 int is_first_dep = 0; 261 void *buf; 262 263 while (1) { 264 /* Skip any "white space" */ 265 while (*m == ' ' || *m == '\\' || *m == '\n') 266 m++; 267 268 if (!*m) 269 break; 270 271 /* Find next "white space" */ 272 p = m; 273 while (*p && *p != ' ' && *p != '\\' && *p != '\n') 274 p++; 275 is_last = (*p == '\0'); 276 /* Is the token we found a target name? */ 277 is_target = (*(p-1) == ':'); 278 /* Don't write any target names into the dependency file */ 279 if (is_target) { 280 /* The /next/ file is the first dependency */ 281 is_first_dep = 1; 282 } else if (!is_ignored_file(m, p - m)) { 283 *p = '\0'; 284 285 /* 286 * Do not list the source file as dependency, so that 287 * kbuild is not confused if a .c file is rewritten 288 * into .S or vice versa. Storing it in source_* is 289 * needed for modpost to compute srcversions. 290 */ 291 if (is_first_dep) { 292 /* 293 * If processing the concatenation of multiple 294 * dependency files, only process the first 295 * target name, which will be the original 296 * source name, and ignore any other target 297 * names, which will be intermediate temporary 298 * files. 299 */ 300 if (!saw_any_target) { 301 saw_any_target = 1; 302 printf("source_%s := %s\n\n", 303 target, m); 304 printf("deps_%s := \\\n", target); 305 } 306 is_first_dep = 0; 307 } else { 308 printf(" %s \\\n", m); 309 } 310 311 buf = read_file(m); 312 parse_config_file(buf); 313 free(buf); 314 } 315 316 if (is_last) 317 break; 318 319 /* 320 * Start searching for next token immediately after the first 321 * "whitespace" character that follows this token. 322 */ 323 m = p + 1; 324 } 325 326 if (!saw_any_target) { 327 fprintf(stderr, "fixdep: parse error; no targets found\n"); 328 exit(1); 329 } 330 331 printf("\n%s: $(deps_%s)\n\n", target, target); 332 printf("$(deps_%s):\n", target); 333 } 334 335 int main(int argc, char *argv[]) 336 { 337 const char *depfile, *target, *cmdline; 338 void *buf; 339 340 if (argc != 4) 341 usage(); 342 343 depfile = argv[1]; 344 target = argv[2]; 345 cmdline = argv[3]; 346 347 printf("cmd_%s := %s\n\n", target, cmdline); 348 349 buf = read_file(depfile); 350 parse_dep_file(buf, target); 351 free(buf); 352 353 fflush(stdout); 354 355 /* 356 * In the intended usage, the stdout is redirected to .*.cmd files. 357 * Call ferror() to catch errors such as "No space left on device". 358 */ 359 if (ferror(stdout)) { 360 fprintf(stderr, "fixdep: not all data was written to the output\n"); 361 exit(1); 362 } 363 364 return 0; 365 } 366