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+/*
+ * "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
+ *
+ * savedcmd_<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 <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <ctype.h>
+
+static void usage(void)
+{
+ fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
+ exit(1);
+}
+
+struct item {
+ struct item *next;
+ unsigned int len;
+ unsigned int hash;
+ char name[];
+};
+
+#define HASHSZ 256
+static struct item *config_hashtab[HASHSZ], *file_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;
+}
+
+/*
+ * Add a new value to the configuration string.
+ */
+static void add_to_hashtable(const char *name, int len, unsigned int hash,
+ struct item *hashtab[])
+{
+ 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;
+}
+
+/*
+ * Lookup a string in the hash table. If found, just return true.
+ * If not, add it to the hashtable and return false.
+ */
+static bool in_hashtable(const char *name, int len, struct item *hashtab[])
+{
+ struct item *aux;
+ unsigned int hash = strhash(name, len);
+
+ for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
+ if (aux->hash == hash && aux->len == len &&
+ memcmp(aux->name, name, len) == 0)
+ return true;
+ }
+
+ add_to_hashtable(name, len, hash, hashtab);
+
+ return false;
+}
+
+/*
+ * Record the use of a CONFIG_* word.
+ */
+static void use_config(const char *m, int slen)
+{
+ if (in_hashtable(m, slen, config_hashtab))
+ return;
+
+ /* Print out a dependency path from a symbol name. */
+ printf(" $(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");
+}
+
+/* Do not parse these files */
+static int is_no_parse_file(const char *s, int len)
+{
+ /* rustc may list binary files in dep-info */
+ return str_ends_with(s, len, ".rlib") ||
+ str_ends_with(s, len, ".rmeta") ||
+ str_ends_with(s, len, ".so");
+}
+
+/*
+ * 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 *p, const char *target)
+{
+ bool saw_any_target = false;
+ bool is_target = true;
+ bool is_source = false;
+ bool need_parse;
+ char *q, saved_c;
+
+ while (*p) {
+ /* handle some special characters first. */
+ switch (*p) {
+ case '#':
+ /*
+ * skip comments.
+ * rustc may emit comments to dep-info.
+ */
+ p++;
+ while (*p != '\0' && *p != '\n') {
+ /*
+ * escaped newlines continue the comment across
+ * multiple lines.
+ */
+ if (*p == '\\')
+ p++;
+ p++;
+ }
+ continue;
+ case ' ':
+ case '\t':
+ /* skip whitespaces */
+ p++;
+ continue;
+ case '\\':
+ /*
+ * backslash/newline combinations continue the
+ * statement. Skip it just like a whitespace.
+ */
+ if (*(p + 1) == '\n') {
+ p += 2;
+ continue;
+ }
+ break;
+ case '\n':
+ /*
+ * Makefiles use a line-based syntax, where the newline
+ * is the end of a statement. After seeing a newline,
+ * we expect the next token is a target.
+ */
+ p++;
+ is_target = true;
+ continue;
+ case ':':
+ /*
+ * assume the first dependency after a colon as the
+ * source file.
+ */
+ p++;
+ is_target = false;
+ is_source = true;
+ continue;
+ }
+
+ /* find the end of the token */
+ q = p;
+ while (*q != ' ' && *q != '\t' && *q != '\n' && *q != '#' && *q != ':') {
+ if (*q == '\\') {
+ /*
+ * backslash/newline combinations work like as
+ * a whitespace, so this is the end of token.
+ */
+ if (*(q + 1) == '\n')
+ break;
+
+ /* escaped special characters */
+ if (*(q + 1) == '#' || *(q + 1) == ':') {
+ memmove(p + 1, p, q - p);
+ p++;
+ }
+
+ q++;
+ }
+
+ if (*q == '\0')
+ break;
+ q++;
+ }
+
+ /* Just discard the target */
+ if (is_target) {
+ p = q;
+ continue;
+ }
+
+ saved_c = *q;
+ *q = '\0';
+ need_parse = false;
+
+ /*
+ * 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_source) {
+ /*
+ * The DT build rule concatenates multiple dep files.
+ * When processing them, only process the first source
+ * name, which will be the original one, and ignore any
+ * other source names, which will be intermediate
+ * temporary files.
+ *
+ * rustc emits the same dependency list for each
+ * emission type. It is enough to list the source name
+ * just once.
+ */
+ if (!saw_any_target) {
+ saw_any_target = true;
+ printf("source_%s := %s\n\n", target, p);
+ printf("deps_%s := \\\n", target);
+ need_parse = true;
+ }
+ } else if (!is_ignored_file(p, q - p) &&
+ !in_hashtable(p, q - p, file_hashtab)) {
+ printf(" %s \\\n", p);
+ need_parse = true;
+ }
+
+ if (need_parse && !is_no_parse_file(p, q - p)) {
+ void *buf;
+
+ buf = read_file(p);
+ parse_config_file(buf);
+ free(buf);
+ }
+
+ is_source = false;
+ *q = saved_c;
+ p = q;
+ }
+
+ if (!saw_any_target) {
+ fprintf(stderr, "fixdep: parse error; no targets found\n");
+ exit(1);
+ }
+
+ printf("\n%s: $(deps_%s)\n\n", target, target);
+ printf("$(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];
+
+ printf("savedcmd_%s := %s\n\n", target, cmdline);
+
+ buf = read_file(depfile);
+ parse_dep_file(buf, target);
+ free(buf);
+
+ fflush(stdout);
+
+ /*
+ * In the intended usage, the stdout is redirected to .*.cmd files.
+ * Call ferror() to catch errors such as "No space left on device".
+ */
+ if (ferror(stdout)) {
+ fprintf(stderr, "fixdep: not all data was written to the output\n");
+ exit(1);
+ }
+
+ return 0;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-29 09:38:27 +0000