text: /*
   * "Optimize" a list of dependencies as spit out by gcc -MD
   * for the kernel build
   * ===========================================================================
   *
   * Author       Kai Germaschewski
   * Copyright    2002 by Kai Germaschewski  <kai.germaschewski@gmx.de>
   *
   * This software may be used and distributed according to the terms
   * of the GNU General Public License, incorporated herein by reference.
   *
   *
   * Introduction:
   *
   * gcc produces a very nice and correct list of dependencies which
   * tells make when to remake a file.
   *
   * To use this list as-is however has the drawback that virtually
   * every file in the kernel includes autoconf.h.
   *
   * If the user re-runs make *config, autoconf.h will be
   * regenerated.  make notices that and will rebuild every file which
   * includes autoconf.h, i.e. basically all files. This is extremely
   * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
   *
   * So we play the same trick that "mkdep" played before. We replace
   * the dependency on autoconf.h by a dependency on every config
   * option which is mentioned in any of the listed prerequisites.
   *
   * kconfig populates a tree in include/config/ with an empty file
   * for each config symbol and when the configuration is updated
   * the files representing changed config options are touched
   * which then let make pick up the changes and the files that use
   * the config symbols are rebuilt.
   *
   * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
   * which depend on "include/config/HIS_DRIVER" will be rebuilt,
   * so most likely only his driver ;-)
   *
   * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
   *
   * So to get dependencies right, there are two issues:
   * o if any of the files the compiler read changed, we need to rebuild
   * o if the command line given to the compile the file changed, we
   *   better rebuild as well.
   *
   * The former is handled by using the -MD output, the later by saving
   * the command line used to compile the old object and comparing it
   * to the one we would now use.
   *
   * Again, also this idea is pretty old and has been discussed on
   * kbuild-devel a long time ago. I don't have a sensibly working
   * internet connection right now, so I rather don't mention names
   * without double checking.
   *
   * This code here has been based partially based on mkdep.c, which
   * says the following about its history:
   *
   *   Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
   *   This is a C version of syncdep.pl by Werner Almesberger.
   *
   *
   * It is invoked as
   *
   *   fixdep <depfile> <target> <cmdline>
   *
   * and will read the dependency file <depfile>
   *
   * The transformed dependency snipped is written to stdout.
   *
   * It first generates a line
   *
   *   cmd_<target> = <cmdline>
   *
   * and then basically copies the .<target>.d file to stdout, in the
   * process filtering out the dependency on autoconf.h and adding
   * dependencies on include/config/MY_OPTION for every
   * CONFIG_MY_OPTION encountered in any of the prerequisites.
   *
   * We don't even try to really parse the header files, but
   * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
   * be picked up as well. It's not a problem with respect to
   * correctness, since that can only give too many dependencies, thus
   * we cannot miss a rebuild. Since people tend to not mention totally
   * unrelated CONFIG_ options all over the place, it's not an
   * efficiency problem either.
   *
   * (Note: it'd be easy to port over the complete mkdep state machine,
   *  but I don't think the added complexity is worth it)
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <string.h>
  #include <stdarg.h>
  #include <stdlib.h>
  #include <stdio.h>
  #include <ctype.h>
  
  static void usage(void)
  {
  	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
  	exit(1);
  }
  
  /*
   * In the intended usage of this program, the stdout is redirected to .*.cmd
   * files. The return value of printf() must be checked to catch any error,
   * e.g. "No space left on device".
   */
  static void xprintf(const char *format, ...)
  {
  	va_list ap;
  	int ret;
  
  	va_start(ap, format);
  	ret = vprintf(format, ap);
  	if (ret < 0) {
  		perror("fixdep");
  		exit(1);
  	}
  	va_end(ap);
  }
  
  struct item {
  	struct item	*next;
  	unsigned int	len;
  	unsigned int	hash;
  	char		name[];
  };
  
  #define HASHSZ 256
  static struct item *hashtab[HASHSZ];
  
  static unsigned int strhash(const char *str, unsigned int sz)
  {
  	/* fnv32 hash */
  	unsigned int i, hash = 2166136261U;
  
  	for (i = 0; i < sz; i++)
  		hash = (hash ^ str[i]) * 0x01000193;
  	return hash;
  }
  
  /*
   * Lookup a value in the configuration string.
   */
  static int is_defined_config(const char *name, int len, unsigned int hash)
  {
  	struct item *aux;
  
  	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
  		if (aux->hash == hash && aux->len == len &&
  		    memcmp(aux->name, name, len) == 0)
  			return 1;
  	}
  	return 0;
  }
  
  /*
   * Add a new value to the configuration string.
   */
  static void define_config(const char *name, int len, unsigned int hash)
  {
  	struct item *aux = malloc(sizeof(*aux) + len);
  
  	if (!aux) {
  		perror("fixdep:malloc");
  		exit(1);
  	}
  	memcpy(aux->name, name, len);
  	aux->len = len;
  	aux->hash = hash;
  	aux->next = hashtab[hash % HASHSZ];
  	hashtab[hash % HASHSZ] = aux;
  }
  
  /*
   * Record the use of a CONFIG_* word.
   */
  static void use_config(const char *m, int slen)
  {
  	unsigned int hash = strhash(m, slen);
  
  	if (is_defined_config(m, slen, hash))
  	    return;
  
  	define_config(m, slen, hash);
  	/* Print out a dependency path from a symbol name. */
  	xprintf("    $(wildcard include/config/%.*s) \\\n", slen, m);
  }
  
  /* test if s ends in sub */
  static int str_ends_with(const char *s, int slen, const char *sub)
  {
  	int sublen = strlen(sub);
  
  	if (sublen > slen)
  		return 0;
  
  	return !memcmp(s + slen - sublen, sub, sublen);
  }
  
  static void parse_config_file(const char *p)
  {
  	const char *q, *r;
  	const char *start = p;
  
  	while ((p = strstr(p, "CONFIG_"))) {
  		if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
  			p += 7;
  			continue;
  		}
  		p += 7;
  		q = p;
  		while (isalnum(*q) || *q == '_')
  			q++;
  		if (str_ends_with(p, q - p, "_MODULE"))
  			r = q - 7;
  		else
  			r = q;
  		if (r > p)
  			use_config(p, r - p);
  		p = q;
  	}
  }
  
  static void *read_file(const char *filename)
  {
  	struct stat st;
  	int fd;
  	char *buf;
  
  	fd = open(filename, O_RDONLY);
  	if (fd < 0) {
  		fprintf(stderr, "fixdep: error opening file: ");
  		perror(filename);
  		exit(2);
  	}
  	if (fstat(fd, &st) < 0) {
  		fprintf(stderr, "fixdep: error fstat'ing file: ");
  		perror(filename);
  		exit(2);
  	}
  	buf = malloc(st.st_size + 1);
  	if (!buf) {
  		perror("fixdep: malloc");
  		exit(2);
  	}
  	if (read(fd, buf, st.st_size) != st.st_size) {
  		perror("fixdep: read");
  		exit(2);
  	}
  	buf[st.st_size] = '\0';
  	close(fd);
  
  	return buf;
  }
  
  /* Ignore certain dependencies */
  static int is_ignored_file(const char *s, int len)
  {
  	return str_ends_with(s, len, "include/generated/autoconf.h") ||
  	       str_ends_with(s, len, "include/generated/autoksyms.h");
  }
  
  /*
   * Important: The below generated source_foo.o and deps_foo.o variable
   * assignments are parsed not only by make, but also by the rather simple
   * parser in scripts/mod/sumversion.c.
   */
  static void parse_dep_file(char *m, const char *target)
  {
  	char *p;
  	int is_last, is_target;
  	int saw_any_target = 0;
  	int is_first_dep = 0;
  	void *buf;
  
  	while (1) {
  		/* Skip any "white space" */
  		while (*m == ' ' || *m == '\\' || *m == '\n')
  			m++;
  
  		if (!*m)
  			break;
  
  		/* Find next "white space" */
  		p = m;
  		while (*p && *p != ' ' && *p != '\\' && *p != '\n')
  			p++;
  		is_last = (*p == '\0');
  		/* Is the token we found a target name? */
  		is_target = (*(p-1) == ':');
  		/* Don't write any target names into the dependency file */
  		if (is_target) {
  			/* The /next/ file is the first dependency */
  			is_first_dep = 1;
  		} else if (!is_ignored_file(m, p - m)) {
  			*p = '\0';
  
  			/*
  			 * Do not list the source file as dependency, so that
  			 * kbuild is not confused if a .c file is rewritten
  			 * into .S or vice versa. Storing it in source_* is
  			 * needed for modpost to compute srcversions.
  			 */
  			if (is_first_dep) {
  				/*
  				 * If processing the concatenation of multiple
  				 * dependency files, only process the first
  				 * target name, which will be the original
  				 * source name, and ignore any other target
  				 * names, which will be intermediate temporary
  				 * files.
  				 */
  				if (!saw_any_target) {
  					saw_any_target = 1;
  					xprintf("source_%s := %s\n\n",
  						target, m);
  					xprintf("deps_%s := \\\n", target);
  				}
  				is_first_dep = 0;
  			} else {
  				xprintf("  %s \\\n", m);
  			}
  
  			buf = read_file(m);
  			parse_config_file(buf);
  			free(buf);
  		}
  
  		if (is_last)
  			break;
  
  		/*
  		 * Start searching for next token immediately after the first
  		 * "whitespace" character that follows this token.
  		 */
  		m = p + 1;
  	}
  
  	if (!saw_any_target) {
  		fprintf(stderr, "fixdep: parse error; no targets found\n");
  		exit(1);
  	}
  
  	xprintf("\n%s: $(deps_%s)\n\n", target, target);
  	xprintf("$(deps_%s):\n", target);
  }
  
  int main(int argc, char *argv[])
  {
  	const char *depfile, *target, *cmdline;
  	void *buf;
  
  	if (argc != 4)
  		usage();
  
  	depfile = argv[1];
  	target = argv[2];
  	cmdline = argv[3];
  
  	xprintf("cmd_%s := %s\n\n", target, cmdline);
  
  	buf = read_file(depfile);
  	parse_dep_file(buf, target);
  	free(buf);
  
  	return 0;
  }
  