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 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 }