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  * 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 /*
 109  * In the intended usage of this program, the stdout is redirected to .*.cmd
 110  * files. The return value of printf() and putchar() must be checked to catch
 111  * any error, e.g. "No space left on device".
 112  */
 113 static void xprintf(const char *format, ...)
 114 {
 115         va_list ap;
 116         int ret;
 117
 118         va_start(ap, format);
 119         ret = vprintf(format, ap);
 120         if (ret < 0) {
 121                 perror("fixdep");
 122                 exit(1);
 123         }
 124         va_end(ap);
 125 }
 126
 127 static void xputchar(int c)
 128 {
 129         int ret;
 130
 131         ret = putchar(c);
 132         if (ret == EOF) {
 133                 perror("fixdep");
 134                 exit(1);
 135         }
 136 }
 137
 138 /*
 139  * Print out a dependency path from a symbol name
 140  */
 141 static void print_dep(const char *m, int slen, const char *dir)
 142 {
 143         int c, prev_c = '/', i;
 144
 145         xprintf("    $(wildcard %s/", dir);
 146         for (i = 0; i < slen; i++) {
 147                 c = m[i];
 148                 if (c == '_')
 149                         c = '/';
 150                 else
 151                         c = tolower(c);
 152                 if (c != '/' || prev_c != '/')
 153                         xputchar(c);
 154                 prev_c = c;
 155         }
 156         xprintf(".h) \\\n");
 157 }
 158
 159 struct item {
 160         struct item     *next;
 161         unsigned int    len;
 162         unsigned int    hash;
 163         char            name[0];
 164 };
 165
 166 #define HASHSZ 256
 167 static struct item *hashtab[HASHSZ];
 168
 169 static unsigned int strhash(const char *str, unsigned int sz)
 170 {
 171         /* fnv32 hash */
 172         unsigned int i, hash = 2166136261U;
 173
 174         for (i = 0; i < sz; i++)
 175                 hash = (hash ^ str[i]) * 0x01000193;
 176         return hash;
 177 }
 178
 179 /*
 180  * Lookup a value in the configuration string.
 181  */
 182 static int is_defined_config(const char *name, int len, unsigned int hash)
 183 {
 184         struct item *aux;
 185
 186         for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
 187                 if (aux->hash == hash && aux->len == len &&
 188                     memcmp(aux->name, name, len) == 0)
 189                         return 1;
 190         }
 191         return 0;
 192 }
 193
 194 /*
 195  * Add a new value to the configuration string.
 196  */
 197 static void define_config(const char *name, int len, unsigned int hash)
 198 {
 199         struct item *aux = malloc(sizeof(*aux) + len);
 200
 201         if (!aux) {
 202                 perror("fixdep:malloc");
 203                 exit(1);
 204         }
 205         memcpy(aux->name, name, len);
 206         aux->len = len;
 207         aux->hash = hash;
 208         aux->next = hashtab[hash % HASHSZ];
 209         hashtab[hash % HASHSZ] = aux;
 210 }
 211
 212 /*
 213  * Record the use of a CONFIG_* word.
 214  */
 215 static void use_config(const char *m, int slen)
 216 {
 217         unsigned int hash = strhash(m, slen);
 218
 219         if (is_defined_config(m, slen, hash))
 220             return;
 221
 222         define_config(m, slen, hash);
 223         print_dep(m, slen, "include/config");
 224 }
 225
 226 /* test if s ends in sub */
 227 static int str_ends_with(const char *s, int slen, const char *sub)
 228 {
 229         int sublen = strlen(sub);
 230
 231         if (sublen > slen)
 232                 return 0;
 233
 234         return !memcmp(s + slen - sublen, sub, sublen);
 235 }
 236
 237 static void parse_config_file(const char *p)
 238 {
 239         const char *q, *r;
 240         const char *start = p;
 241
 242         while ((p = strstr(p, "CONFIG_"))) {
 243                 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
 244                         p += 7;
 245                         continue;
 246                 }
 247                 p += 7;
 248                 q = p;
 249                 while (isalnum(*q) || *q == '_')
 250                         q++;
 251                 if (str_ends_with(p, q - p, "_MODULE"))
 252                         r = q - 7;
 253                 else
 254                         r = q;
 255                 if (r > p)
 256                         use_config(p, r - p);
 257                 p = q;
 258         }
 259 }
 260
 261 static void *read_file(const char *filename)
 262 {
 263         struct stat st;
 264         int fd;
 265         char *buf;
 266
 267         fd = open(filename, O_RDONLY);
 268         if (fd < 0) {
 269                 fprintf(stderr, "fixdep: error opening file: ");
 270                 perror(filename);
 271                 exit(2);
 272         }
 273         if (fstat(fd, &st) < 0) {
 274                 fprintf(stderr, "fixdep: error fstat'ing file: ");
 275                 perror(filename);
 276                 exit(2);
 277         }
 278         buf = malloc(st.st_size + 1);
 279         if (!buf) {
 280                 perror("fixdep: malloc");
 281                 exit(2);
 282         }
 283         if (read(fd, buf, st.st_size) != st.st_size) {
 284                 perror("fixdep: read");
 285                 exit(2);
 286         }
 287         buf[st.st_size] = '\0';
 288         close(fd);
 289
 290         return buf;
 291 }
 292
 293 /* Ignore certain dependencies */
 294 static int is_ignored_file(const char *s, int len)
 295 {
 296         return str_ends_with(s, len, "include/generated/autoconf.h") ||
 297                str_ends_with(s, len, "include/generated/autoksyms.h");
 298 }
 299
 300 /*
 301  * Important: The below generated source_foo.o and deps_foo.o variable
 302  * assignments are parsed not only by make, but also by the rather simple
 303  * parser in scripts/mod/sumversion.c.
 304  */
 305 static void parse_dep_file(char *m, const char *target)
 306 {
 307         char *p;
 308         int is_last, is_target;
 309         int saw_any_target = 0;
 310         int is_first_dep = 0;
 311         void *buf;
 312
 313         while (1) {
 314                 /* Skip any "white space" */
 315                 while (*m == ' ' || *m == '\\' || *m == '\n')
 316                         m++;
 317
 318                 if (!*m)
 319                         break;
 320
 321                 /* Find next "white space" */
 322                 p = m;
 323                 while (*p && *p != ' ' && *p != '\\' && *p != '\n')
 324                         p++;
 325                 is_last = (*p == '\0');
 326                 /* Is the token we found a target name? */
 327                 is_target = (*(p-1) == ':');
 328                 /* Don't write any target names into the dependency file */
 329                 if (is_target) {
 330                         /* The /next/ file is the first dependency */
 331                         is_first_dep = 1;
 332                 } else if (!is_ignored_file(m, p - m)) {
 333                         *p = '\0';
 334
 335                         /*
 336                          * Do not list the source file as dependency, so that
 337                          * kbuild is not confused if a .c file is rewritten
 338                          * into .S or vice versa. Storing it in source_* is
 339                          * needed for modpost to compute srcversions.
 340                          */
 341                         if (is_first_dep) {
 342                                 /*
 343                                  * If processing the concatenation of multiple
 344                                  * dependency files, only process the first
 345                                  * target name, which will be the original
 346                                  * source name, and ignore any other target
 347                                  * names, which will be intermediate temporary
 348                                  * files.
 349                                  */
 350                                 if (!saw_any_target) {
 351                                         saw_any_target = 1;
 352                                         xprintf("source_%s := %s\n\n",
 353                                                 target, m);
 354                                         xprintf("deps_%s := \\\n", target);
 355                                 }
 356                                 is_first_dep = 0;
 357                         } else {
 358                                 xprintf("  %s \\\n", m);
 359                         }
 360
 361                         buf = read_file(m);
 362                         parse_config_file(buf);
 363                         free(buf);
 364                 }
 365
 366                 if (is_last)
 367                         break;
 368
 369                 /*
 370                  * Start searching for next token immediately after the first
 371                  * "whitespace" character that follows this token.
 372                  */
 373                 m = p + 1;
 374         }
 375
 376         if (!saw_any_target) {
 377                 fprintf(stderr, "fixdep: parse error; no targets found\n");
 378                 exit(1);
 379         }
 380
 381         xprintf("\n%s: $(deps_%s)\n\n", target, target);
 382         xprintf("$(deps_%s):\n", target);
 383 }
 384
 385 int main(int argc, char *argv[])
 386 {
 387         const char *depfile, *target, *cmdline;
 388         void *buf;
 389
 390         if (argc != 4)
 391                 usage();
 392
 393         depfile = argv[1];
 394         target = argv[2];
 395         cmdline = argv[3];
 396
 397         xprintf("cmd_%s := %s\n\n", target, cmdline);
 398
 399         buf = read_file(depfile);
 400         parse_dep_file(buf, target);
 401         free(buf);
 402
 403         return 0;
 404 }