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 <linux/autoconf.h>.
  20  *
  21  * If the user re-runs make *config, linux/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 linux/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 linux/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 char * str_config  = NULL;
 142 int    size_config = 0;
 143 int    len_config  = 0;
 144
 145 /*
 146  * Grow the configuration string to a desired length.
 147  * Usually the first growth is plenty.
 148  */
 149 static void grow_config(int len)
 150 {
 151         while (len_config + len > size_config) {
 152                 if (size_config == 0)
 153                         size_config = 2048;
 154                 str_config = realloc(str_config, size_config *= 2);
 155                 if (str_config == NULL)
 156                         { perror("fixdep:malloc"); exit(1); }
 157         }
 158 }
 159
 160
 161
 162 /*
 163  * Lookup a value in the configuration string.
 164  */
 165 static int is_defined_config(const char * name, int len)
 166 {
 167         const char * pconfig;
 168         const char * plast = str_config + len_config - len;
 169         for ( pconfig = str_config + 1; pconfig < plast; pconfig++ ) {
 170                 if (pconfig[ -1] == '\n'
 171                 &&  pconfig[len] == '\n'
 172                 &&  !memcmp(pconfig, name, len))
 173                         return 1;
 174         }
 175         return 0;
 176 }
 177
 178 /*
 179  * Add a new value to the configuration string.
 180  */
 181 static void define_config(const char * name, int len)
 182 {
 183         grow_config(len + 1);
 184
 185         memcpy(str_config+len_config, name, len);
 186         len_config += len;
 187         str_config[len_config++] = '\n';
 188 }
 189
 190 /*
 191  * Clear the set of configuration strings.
 192  */
 193 static void clear_config(void)
 194 {
 195         len_config = 0;
 196         define_config("", 0);
 197 }
 198
 199 /*
 200  * Record the use of a CONFIG_* word.
 201  */
 202 static void use_config(char *m, int slen)
 203 {
 204         char s[PATH_MAX];
 205         char *p;
 206
 207         if (is_defined_config(m, slen))
 208             return;
 209
 210         define_config(m, slen);
 211
 212         memcpy(s, m, slen); s[slen] = 0;
 213
 214         for (p = s; p < s + slen; p++) {
 215                 if (*p == '_')
 216                         *p = '/';
 217                 else
 218                         *p = tolower((int)*p);
 219         }
 220         printf("    $(wildcard include/config/%s.h) \\\n", s);
 221 }
 222
 223 static void parse_config_file(char *map, size_t len)
 224 {
 225         int *end = (int *) (map + len);
 226         /* start at +1, so that p can never be < map */
 227         int *m   = (int *) map + 1;
 228         char *p, *q;
 229
 230         for (; m < end; m++) {
 231                 if (*m == INT_CONF) { p = (char *) m  ; goto conf; }
 232                 if (*m == INT_ONFI) { p = (char *) m-1; goto conf; }
 233                 if (*m == INT_NFIG) { p = (char *) m-2; goto conf; }
 234                 if (*m == INT_FIG_) { p = (char *) m-3; goto conf; }
 235                 continue;
 236         conf:
 237                 if (p > map + len - 7)
 238                         continue;
 239                 if (memcmp(p, "CONFIG_", 7))
 240                         continue;
 241                 for (q = p + 7; q < map + len; q++) {
 242                         if (!(isalnum(*q) || *q == '_'))
 243                                 goto found;
 244                 }
 245                 continue;
 246
 247         found:
 248                 if (!memcmp(q - 7, "_MODULE", 7))
 249                         q -= 7;
 250                 if( (q-p-7) < 0 )
 251                         continue;
 252                 use_config(p+7, q-p-7);
 253         }
 254 }
 255
 256 /* test is s ends in sub */
 257 static int strrcmp(char *s, char *sub)
 258 {
 259         int slen = strlen(s);
 260         int sublen = strlen(sub);
 261
 262         if (sublen > slen)
 263                 return 1;
 264
 265         return memcmp(s + slen - sublen, sub, sublen);
 266 }
 267
 268 static void do_config_file(char *filename)
 269 {
 270         struct stat st;
 271         int fd;
 272         void *map;
 273
 274         fd = open(filename, O_RDONLY);
 275         if (fd < 0) {
 276                 fprintf(stderr, "fixdep: ");
 277                 perror(filename);
 278                 exit(2);
 279         }
 280         fstat(fd, &st);
 281         if (st.st_size == 0) {
 282                 close(fd);
 283                 return;
 284         }
 285         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 286         if ((long) map == -1) {
 287                 perror("fixdep: mmap");
 288                 close(fd);
 289                 return;
 290         }
 291
 292         parse_config_file(map, st.st_size);
 293
 294         munmap(map, st.st_size);
 295
 296         close(fd);
 297 }
 298
 299 static void parse_dep_file(void *map, size_t len)
 300 {
 301         char *m = map;
 302         char *end = m + len;
 303         char *p;
 304         char s[PATH_MAX];
 305
 306         p = strchr(m, ':');
 307         if (!p) {
 308                 fprintf(stderr, "fixdep: parse error\n");
 309                 exit(1);
 310         }
 311         memcpy(s, m, p-m); s[p-m] = 0;
 312         printf("deps_%s := \\\n", target);
 313         m = p+1;
 314
 315         clear_config();
 316
 317         while (m < end) {
 318                 while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
 319                         m++;
 320                 p = m;
 321                 while (p < end && *p != ' ') p++;
 322                 if (p == end) {
 323                         do p--; while (!isalnum(*p));
 324                         p++;
 325                 }
 326                 memcpy(s, m, p-m); s[p-m] = 0;
 327                 if (strrcmp(s, "include/linux/autoconf.h") &&
 328                     strrcmp(s, "arch/um/include/uml-config.h") &&
 329                     strrcmp(s, ".ver")) {
 330                         printf("  %s \\\n", s);
 331                         do_config_file(s);
 332                 }
 333                 m = p + 1;
 334         }
 335         printf("\n%s: $(deps_%s)\n\n", target, target);
 336         printf("$(deps_%s):\n", target);
 337 }
 338
 339 static void print_deps(void)
 340 {
 341         struct stat st;
 342         int fd;
 343         void *map;
 344
 345         fd = open(depfile, O_RDONLY);
 346         if (fd < 0) {
 347                 fprintf(stderr, "fixdep: ");
 348                 perror(depfile);
 349                 exit(2);
 350         }
 351         fstat(fd, &st);
 352         if (st.st_size == 0) {
 353                 fprintf(stderr,"fixdep: %s is empty\n",depfile);
 354                 close(fd);
 355                 return;
 356         }
 357         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 358         if ((long) map == -1) {
 359                 perror("fixdep: mmap");
 360                 close(fd);
 361                 return;
 362         }
 363
 364         parse_dep_file(map, st.st_size);
 365
 366         munmap(map, st.st_size);
 367
 368         close(fd);
 369 }
 370
 371 static void traps(void)
 372 {
 373         static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";
 374         int *p = (int *)test;
 375
 376         if (*p != INT_CONF) {
 377                 fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianess? %#x\n",
 378                         *p);
 379                 exit(2);
 380         }
 381 }
 382
 383 int main(int argc, char *argv[])
 384 {
 385         traps();
 386
 387         if (argc != 4)
 388                 usage();
 389
 390         depfile = argv[1];
 391         target = argv[2];
 392         cmdline = argv[3];
 393
 394         print_cmdline();
 395         print_deps();
 396
 397         return 0;
 398 }