scripts/basic/fixdep.c

   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 prequisites.
  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/linux/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 prequisites.
  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  * The algorithm to grep for "CONFIG_..." is bit unusual, but should
  86  * be fast ;-) We don't even try to really parse the header files, but
  87  * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
  88  * be picked up as well. It's not a problem with respect to
  89  * correctness, since that can only give too many dependencies, thus
  90  * we cannot miss a rebuild. Since people tend to not mention totally
  91  * unrelated CONFIG_ options all over the place, it's not an
  92  * efficiency problem either.
  93  *
  94  * (Note: it'd be easy to port over the complete mkdep state machine,
  95  *  but I don't think the added complexity is worth it)
  96  */
  97 /*
  98  * Note 2: if somebody writes HELLO_CONFIG_BOOM in a file, it will depend onto
  99  * CONFIG_BOOM. This could seem a bug (not too hard to fix), but please do not
 100  * fix it! Some UserModeLinux files (look at arch/um/) call CONFIG_BOOM as
 101  * UML_CONFIG_BOOM, to avoid conflicts with /usr/include/linux/autoconf.h,
 102  * through arch/um/include/uml-config.h; this fixdep "bug" makes sure that
 103  * those files will have correct dependencies.
 104  */
 105
 106 #include <sys/types.h>
 107 #include <sys/stat.h>
 108 #include <sys/mman.h>
 109 #include <unistd.h>
 110 #include <fcntl.h>
 111 #include <string.h>
 112 #include <stdlib.h>
 113 #include <stdio.h>
 114 #include <limits.h>
 115 #include <ctype.h>
 116 #include <arpa/inet.h>
 117
 118 #define INT_CONF ntohl(0x434f4e46)
 119 #define INT_ONFI ntohl(0x4f4e4649)
 120 #define INT_NFIG ntohl(0x4e464947)
 121 #define INT_FIG_ ntohl(0x4649475f)
 122
 123 char *target;
 124 char *depfile;
 125 char *cmdline;
 126
 127 static void usage(void)
 128 {
 129         fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
 130         exit(1);
 131 }
 132
 133 /*
 134  * Print out the commandline prefixed with cmd_<target filename> :=
 135  */
 136 static void print_cmdline(void)
 137 {
 138         printf("cmd_%s := %s\n\n", target, cmdline);
 139 }
 140
 141 struct item {
 142         struct item     *next;
 143         unsigned int    len;
 144         unsigned int    hash;
 145         char            name[0];
 146 };
 147
 148 #define HASHSZ 256
 149 static struct item *hashtab[HASHSZ];
 150
 151 static unsigned int strhash(const char *str, unsigned int sz)
 152 {
 153         /* fnv32 hash */
 154         unsigned int i, hash = 2166136261U;
 155
 156         for (i = 0; i < sz; i++)
 157                 hash = (hash ^ str[i]) * 0x01000193;
 158         return hash;
 159 }
 160
 161 /*
 162  * Lookup a value in the configuration string.
 163  */
 164 static int is_defined_config(const char *name, int len, unsigned int hash)
 165 {
 166         struct item *aux;
 167
 168         for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
 169                 if (aux->hash == hash && aux->len == len &&
 170                     memcmp(aux->name, name, len) == 0)
 171                         return 1;
 172         }
 173         return 0;
 174 }
 175
 176 /*
 177  * Add a new value to the configuration string.
 178  */
 179 static void define_config(const char *name, int len, unsigned int hash)
 180 {
 181         struct item *aux = malloc(sizeof(*aux) + len);
 182
 183         if (!aux) {
 184                 perror("fixdep:malloc");
 185                 exit(1);
 186         }
 187         memcpy(aux->name, name, len);
 188         aux->len = len;
 189         aux->hash = hash;
 190         aux->next = hashtab[hash % HASHSZ];
 191         hashtab[hash % HASHSZ] = aux;
 192 }
 193
 194 /*
 195  * Clear the set of configuration strings.
 196  */
 197 static void clear_config(void)
 198 {
 199         struct item *aux, *next;
 200         unsigned int i;
 201
 202         for (i = 0; i < HASHSZ; i++) {
 203                 for (aux = hashtab[i]; aux; aux = next) {
 204                         next = aux->next;
 205                         free(aux);
 206                 }
 207                 hashtab[i] = NULL;
 208         }
 209 }
 210
 211 /*
 212  * Record the use of a CONFIG_* word.
 213  */
 214 static void use_config(const char *m, int slen)
 215 {
 216         unsigned int hash = strhash(m, slen);
 217         int c, i;
 218
 219         if (is_defined_config(m, slen, hash))
 220             return;
 221
 222         define_config(m, slen, hash);
 223
 224         printf("    $(wildcard include/config/");
 225         for (i = 0; i < slen; i++) {
 226                 c = m[i];
 227                 if (c == '_')
 228                         c = '/';
 229                 else
 230                         c = tolower(c);
 231                 putchar(c);
 232         }
 233         printf(".h) \\\n");
 234 }
 235
 236 static void parse_config_file(const char *map, size_t len)
 237 {
 238         const int *end = (const int *) (map + len);
 239         /* start at +1, so that p can never be < map */
 240         const int *m   = (const int *) map + 1;
 241         const char *p, *q;
 242
 243         for (; m < end; m++) {
 244                 if (*m == INT_CONF) { p = (char *) m  ; goto conf; }
 245                 if (*m == INT_ONFI) { p = (char *) m-1; goto conf; }
 246                 if (*m == INT_NFIG) { p = (char *) m-2; goto conf; }
 247                 if (*m == INT_FIG_) { p = (char *) m-3; goto conf; }
 248                 continue;
 249         conf:
 250                 if (p > map + len - 7)
 251                         continue;
 252                 if (memcmp(p, "CONFIG_", 7))
 253                         continue;
 254                 for (q = p + 7; q < map + len; q++) {
 255                         if (!(isalnum(*q) || *q == '_'))
 256                                 goto found;
 257                 }
 258                 continue;
 259
 260         found:
 261                 if (!memcmp(q - 7, "_MODULE", 7))
 262                         q -= 7;
 263                 if( (q-p-7) < 0 )
 264                         continue;
 265                 use_config(p+7, q-p-7);
 266         }
 267 }
 268
 269 /* test is s ends in sub */
 270 static int strrcmp(char *s, char *sub)
 271 {
 272         int slen = strlen(s);
 273         int sublen = strlen(sub);
 274
 275         if (sublen > slen)
 276                 return 1;
 277
 278         return memcmp(s + slen - sublen, sub, sublen);
 279 }
 280
 281 static void do_config_file(const char *filename)
 282 {
 283         struct stat st;
 284         int fd;
 285         void *map;
 286
 287         fd = open(filename, O_RDONLY);
 288         if (fd < 0) {
 289                 fprintf(stderr, "fixdep: error opening config file: ");
 290                 perror(filename);
 291                 exit(2);
 292         }
 293         fstat(fd, &st);
 294         if (st.st_size == 0) {
 295                 close(fd);
 296                 return;
 297         }
 298         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 299         if ((long) map == -1) {
 300                 perror("fixdep: mmap");
 301                 close(fd);
 302                 return;
 303         }
 304
 305         parse_config_file(map, st.st_size);
 306
 307         munmap(map, st.st_size);
 308
 309         close(fd);
 310 }
 311
 312 static void parse_dep_file(void *map, size_t len)
 313 {
 314         char *m = map;
 315         char *end = m + len;
 316         char *p;
 317         char s[PATH_MAX];
 318         int first;
 319
 320         p = strchr(m, ':');
 321         if (!p) {
 322                 fprintf(stderr, "fixdep: parse error\n");
 323                 exit(1);
 324         }
 325         memcpy(s, m, p-m); s[p-m] = 0;
 326         printf("deps_%s := \\\n", target);
 327         m = p+1;
 328
 329         clear_config();
 330
 331         first = 1;
 332         while (m < end) {
 333                 while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
 334                         m++;
 335                 p = m;
 336                 while (p < end && *p != ' ') p++;
 337                 if (p == end) {
 338                         do p--; while (!isalnum(*p));
 339                         p++;
 340                 }
 341                 memcpy(s, m, p-m); s[p-m] = 0;
 342                 if (strrcmp(s, "include/generated/autoconf.h") &&
 343                     strrcmp(s, "arch/um/include/uml-config.h") &&
 344                     strrcmp(s, ".ver")) {
 345                         /*
 346                          * Do not output the first dependency (the
 347                          * source file), so that kbuild is not confused
 348                          * if a .c file is rewritten into .S or vice
 349                          * versa.
 350                          */
 351                         if (!first)
 352                                 printf("  %s \\\n", s);
 353                         do_config_file(s);
 354                 }
 355                 first = 0;
 356                 m = p + 1;
 357         }
 358         printf("\n%s: $(deps_%s)\n\n", target, target);
 359         printf("$(deps_%s):\n", target);
 360 }
 361
 362 static void print_deps(void)
 363 {
 364         struct stat st;
 365         int fd;
 366         void *map;
 367
 368         fd = open(depfile, O_RDONLY);
 369         if (fd < 0) {
 370                 fprintf(stderr, "fixdep: error opening depfile: ");
 371                 perror(depfile);
 372                 exit(2);
 373         }
 374         if (fstat(fd, &st) < 0) {
 375                 fprintf(stderr, "fixdep: error fstat'ing depfile: ");
 376                 perror(depfile);
 377                 exit(2);
 378         }
 379         if (st.st_size == 0) {
 380                 fprintf(stderr,"fixdep: %s is empty\n",depfile);
 381                 close(fd);
 382                 return;
 383         }
 384         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 385         if ((long) map == -1) {
 386                 perror("fixdep: mmap");
 387                 close(fd);
 388                 return;
 389         }
 390
 391         parse_dep_file(map, st.st_size);
 392
 393         munmap(map, st.st_size);
 394
 395         close(fd);
 396 }
 397
 398 static void traps(void)
 399 {
 400         static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";
 401         int *p = (int *)test;
 402
 403         if (*p != INT_CONF) {
 404                 fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianess? %#x\n",
 405                         *p);
 406                 exit(2);
 407         }
 408 }
 409
 410 int main(int argc, char *argv[])
 411 {
 412         traps();
 413
 414         if (argc != 4)
 415                 usage();
 416
 417         depfile = argv[1];
 418         target = argv[2];
 419         cmdline = argv[3];
 420
 421         print_cmdline();
 422         print_deps();
 423
 424         return 0;
 425 }