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379 lines (339 loc) · 9.37 KB
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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.h" 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.h for every
* CONFIG_MY_OPTION encountered in any of the prerequisites.
*
* It will also filter out all the dependencies on *.ver. We need
* to make sure that the generated version checksum are globally up
* to date before even starting the recursive build, so it's too late
* at this point anyway.
*
* 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 <stdlib.h>
#include <stdio.h>
#include <ctype.h>
static void usage(void)
{
fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
exit(1);
}
/*
* Print out a dependency path from a symbol name
*/
static void print_dep(const char *m, int slen, const char *dir)
{
int c, prev_c = '/', i;
printf(" $(wildcard %s/", dir);
for (i = 0; i < slen; i++) {
c = m[i];
if (c == '_')
c = '/';
else
c = tolower(c);
if (c != '/' || prev_c != '/')
putchar(c);
prev_c = c;
}
printf(".h) \\\n");
}
struct item {
struct item *next;
unsigned int len;
unsigned int hash;
char name[0];
};
#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_dep(m, slen, "include/config");
}
/* 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 (*q && (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") ||
str_ends_with(s, len, ".ver");
}
/*
* 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;
printf("source_%s := %s\n\n",
target, m);
printf("deps_%s := \\\n", target);
}
is_first_dep = 0;
} else {
printf(" %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);
}
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("cmd_%s := %s\n\n", target, cmdline);
buf = read_file(depfile);
parse_dep_file(buf, target);
free(buf);
return 0;
}
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