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/config.h> which then again
  20  * includes <linux/autoconf.h>
  21  *
  22  * If the user re-runs make *config, linux/autoconf.h will be
  23  * regenerated.  make notices that and will rebuild every file which
  24  * includes autoconf.h, i.e. basically all files. This is extremely
  25  * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
  26  *
  27  * So we play the same trick that "mkdep" played before. We replace
  28  * the dependency on linux/autoconf.h by a dependency on every config
  29  * option which is mentioned in any of the listed prequisites.
  30  *
  31  * To be exact, split-include populates a tree in include/config/,
  32  * e.g. include/config/his/driver.h, which contains the #define/#undef
  33  * for the CONFIG_HIS_DRIVER option.
  34  *
  35  * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
  36  * which depend on "include/linux/config/his/driver.h" will be rebuilt,
  37  * so most likely only his driver ;-)
  38  *
  39  * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
  40  *
  41  * So to get dependencies right, there are two issues:
  42  * o if any of the files the compiler read changed, we need to rebuild
  43  * o if the command line given to the compile the file changed, we
  44  *   better rebuild as well.
  45  *
  46  * The former is handled by using the -MD output, the later by saving
  47  * the command line used to compile the old object and comparing it
  48  * to the one we would now use.
  49  *
  50  * Again, also this idea is pretty old and has been discussed on
  51  * kbuild-devel a long time ago. I don't have a sensibly working
  52  * internet connection right now, so I rather don't mention names
  53  * without double checking.
  54  *
  55  * This code here has been based partially based on mkdep.c, which
  56  * says the following about its history:
  57  *
  58  *   Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
  59  *   This is a C version of syncdep.pl by Werner Almesberger.
  60  *
  61  *
  62  * It is invoked as
  63  *
  64  *   fixdep <depfile> <target> <cmdline>
  65  *
  66  * and will read the dependency file <depfile>
  67  *
  68  * The transformed dependency snipped is written to stdout.
  69  *
  70  * It first generates a line
  71  *
  72  *   cmd_<target> = <cmdline>
  73  *
  74  * and then basically copies the .<target>.d file to stdout, in the
  75  * process filtering out the dependency on linux/autoconf.h and adding
  76  * dependencies on include/config/my/option.h for every
  77  * CONFIG_MY_OPTION encountered in any of the prequisites.
  78  *
  79  * It will also filter out all the dependencies on *.ver. We need
  80  * to make sure that the generated version checksum are globally up
  81  * to date before even starting the recursive build, so it's too late
  82  * at this point anyway.
  83  *
  84  * The algorithm to grep for "CONFIG_..." is bit unusual, but should
  85  * be fast ;-) 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 <sys/mman.h>
 108 #include <unistd.h>
 109 #include <fcntl.h>
 110 #include <string.h>
 111 #include <stdlib.h>
 112 #include <stdio.h>
 113 #include <limits.h>
 114 #include <ctype.h>
 115 #include <arpa/inet.h>
 116
 117 #define INT_CONF ntohl(0x434f4e46)
 118 #define INT_ONFI ntohl(0x4f4e4649)
 119 #define INT_NFIG ntohl(0x4e464947)
 120 #define INT_FIG_ ntohl(0x4649475f)
 121
 122 char *target;
 123 char *depfile;
 124 char *cmdline;
 125
 126 void usage(void)
 127
 128 {
 129         fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
 130         exit(1);
 131 }
 132
 133 void print_cmdline(void)
 134 {
 135         printf("cmd_%s := %s\n\n", target, cmdline);
 136 }
 137
 138 char * str_config  = NULL;
 139 int    size_config = 0;
 140 int    len_config  = 0;
 141
 142 /*
 143  * Grow the configuration string to a desired length.
 144  * Usually the first growth is plenty.
 145  */
 146 void grow_config(int len)
 147 {
 148         while (len_config + len > size_config) {
 149                 if (size_config == 0)
 150                         size_config = 2048;
 151                 str_config = realloc(str_config, size_config *= 2);
 152                 if (str_config == NULL)
 153                         { perror("fixdep:malloc"); exit(1); }
 154         }
 155 }
 156
 157
 158
 159 /*
 160  * Lookup a value in the configuration string.
 161  */
 162 int is_defined_config(const char * name, int len)
 163 {
 164         const char * pconfig;
 165         const char * plast = str_config + len_config - len;
 166         for ( pconfig = str_config + 1; pconfig < plast; pconfig++ ) {
 167                 if (pconfig[ -1] == '\n'
 168                 &&  pconfig[len] == '\n'
 169                 &&  !memcmp(pconfig, name, len))
 170                         return 1;
 171         }
 172         return 0;
 173 }
 174
 175 /*
 176  * Add a new value to the configuration string.
 177  */
 178 void define_config(const char * name, int len)
 179 {
 180         grow_config(len + 1);
 181
 182         memcpy(str_config+len_config, name, len);
 183         len_config += len;
 184         str_config[len_config++] = '\n';
 185 }
 186
 187 /*
 188  * Clear the set of configuration strings.
 189  */
 190 void clear_config(void)
 191 {
 192         len_config = 0;
 193         define_config("", 0);
 194 }
 195
 196 /*
 197  * Record the use of a CONFIG_* word.
 198  */
 199 void use_config(char *m, int slen)
 200 {
 201         char s[PATH_MAX];
 202         char *p;
 203
 204         if (is_defined_config(m, slen))
 205             return;
 206
 207         define_config(m, slen);
 208
 209         memcpy(s, m, slen); s[slen] = 0;
 210
 211         for (p = s; p < s + slen; p++) {
 212                 if (*p == '_')
 213                         *p = '/';
 214                 else
 215                         *p = tolower((unsigned char)*p);
 216         }
 217         printf("    $(wildcard include/config/%s.h) \\\n", s);
 218 }
 219
 220 void parse_config_file(signed char *map, size_t len)
 221 {
 222         int *end = (int *) (map + len);
 223         /* start at +1, so that p can never be < map */
 224         int *m   = (int *) map + 1;
 225         signed char *p, *q;
 226
 227         for (; m < end; m++) {
 228                 if (*m == INT_CONF) { p = (signed char *) m  ; goto conf; }
 229                 if (*m == INT_ONFI) { p = (signed char *) m-1; goto conf; }
 230                 if (*m == INT_NFIG) { p = (signed char *) m-2; goto conf; }
 231                 if (*m == INT_FIG_) { p = (signed char *) m-3; goto conf; }
 232                 continue;
 233         conf:
 234                 if (p > map + len - 7)
 235                         continue;
 236                 if (memcmp(p, "CONFIG_", 7))
 237                         continue;
 238                 for (q = p + 7; q < map + len; q++) {
 239                         if (!(isalnum(*q) || *q == '_'))
 240                                 goto found;
 241                 }
 242                 continue;
 243
 244         found:
 245                 use_config(p+7, q-p-7);
 246         }
 247 }
 248
 249 /* test is s ends in sub */
 250 int strrcmp(char *s, char *sub)
 251 {
 252         int slen = strlen(s);
 253         int sublen = strlen(sub);
 254
 255         if (sublen > slen)
 256                 return 1;
 257
 258         return memcmp(s + slen - sublen, sub, sublen);
 259 }
 260
 261 void do_config_file(char *filename)
 262 {
 263         struct stat st;
 264         int fd;
 265         void *map;
 266
 267         fd = open(filename, O_RDONLY);
 268         if (fd < 0) {
 269                 fprintf(stderr, "fixdep: ");
 270                 perror(filename);
 271                 exit(2);
 272         }
 273         fstat(fd, &st);
 274         if (st.st_size == 0) {
 275                 close(fd);
 276                 return;
 277         }
 278         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 279         if ((long) map == -1) {
 280                 perror("fixdep: mmap");
 281                 close(fd);
 282                 return;
 283         }
 284
 285         parse_config_file(map, st.st_size);
 286
 287         munmap(map, st.st_size);
 288
 289         close(fd);
 290 }
 291
 292 void parse_dep_file(void *map, size_t len)
 293 {
 294         signed char *m = map;
 295         signed char *end = m + len;
 296         signed char *p;
 297         char s[PATH_MAX];
 298
 299         p = strchr(m, ':');
 300         if (!p) {
 301                 fprintf(stderr, "fixdep: parse error\n");
 302                 exit(1);
 303         }
 304         memcpy(s, m, p-m); s[p-m] = 0;
 305         printf("deps_%s := \\\n", target);
 306         m = p+1;
 307
 308         clear_config();
 309
 310         while (m < end) {
 311                 while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
 312                         m++;
 313                 p = m;
 314                 while (p < end && *p != ' ') p++;
 315                 if (p == end) {
 316                         do p--; while (!isalnum(*p));
 317                         p++;
 318                 }
 319                 memcpy(s, m, p-m); s[p-m] = 0;
 320                 if (strrcmp(s, "include/linux/autoconf.h") &&
 321                     strrcmp(s, "arch/um/include/uml-config.h") &&
 322                     strrcmp(s, ".ver")) {
 323                         printf("  %s \\\n", s);
 324                         do_config_file(s);
 325                 }
 326                 m = p + 1;
 327         }
 328         printf("\n%s: $(deps_%s)\n\n", target, target);
 329         printf("$(deps_%s):\n", target);
 330 }
 331
 332 void print_deps(void)
 333 {
 334         struct stat st;
 335         int fd;
 336         void *map;
 337
 338         fd = open(depfile, O_RDONLY);
 339         if (fd < 0) {
 340                 fprintf(stderr, "fixdep: ");
 341                 perror(depfile);
 342                 exit(2);
 343         }
 344         fstat(fd, &st);
 345         if (st.st_size == 0) {
 346                 fprintf(stderr,"fixdep: %s is empty\n",depfile);
 347                 close(fd);
 348                 return;
 349         }
 350         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 351         if ((long) map == -1) {
 352                 perror("fixdep: mmap");
 353                 close(fd);
 354                 return;
 355         }
 356
 357         parse_dep_file(map, st.st_size);
 358
 359         munmap(map, st.st_size);
 360
 361         close(fd);
 362 }
 363
 364 void traps(void)
 365 {
 366         static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";
 367
 368         if (*(int *)test != INT_CONF) {
 369                 fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianess? %#x\n",
 370                         *(int *)test);
 371                 exit(2);
 372         }
 373 }
 374
 375 int main(int argc, char *argv[])
 376 {
 377         traps();
 378
 379         if (argc != 4)
 380                 usage();
 381
 382         depfile = argv[1];
 383         target = argv[2];
 384         cmdline = argv[3];
 385
 386         print_cmdline();
 387         print_deps();
 388
 389         return 0;
 390 }