qemu/path.c
Mike Frysinger 2296f194df user: speed up init_paths a bit
The current init_paths code will attempt to opendir() every single file it
finds.  This can obviously generated a huge number of syscalls with even a
moderately small sysroot that will fail.  Since the readdir() call provides
the file type in the struct itself, use it.  On my system, this prevents
over 1000 syscalls from being made at every invocation of a target binary,
and I only have a C library installed.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Riku Voipio <riku.voipio@nokia.com>
2011-02-09 10:33:54 +02:00

182 lines
4.7 KiB
C

/* Code to mangle pathnames into those matching a given prefix.
eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");
The assumption is that this area does not change.
*/
#include <sys/types.h>
#include <sys/param.h>
#include <dirent.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include "qemu-common.h"
struct pathelem
{
/* Name of this, eg. lib */
char *name;
/* Full path name, eg. /usr/gnemul/x86-linux/lib. */
char *pathname;
struct pathelem *parent;
/* Children */
unsigned int num_entries;
struct pathelem *entries[0];
};
static struct pathelem *base;
/* First N chars of S1 match S2, and S2 is N chars long. */
static int strneq(const char *s1, unsigned int n, const char *s2)
{
unsigned int i;
for (i = 0; i < n; i++)
if (s1[i] != s2[i])
return 0;
return s2[i] == 0;
}
static struct pathelem *add_entry(struct pathelem *root, const char *name,
unsigned char type);
static struct pathelem *new_entry(const char *root,
struct pathelem *parent,
const char *name)
{
struct pathelem *new = malloc(sizeof(*new));
new->name = strdup(name);
if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
printf("Cannot allocate memory\n");
exit(1);
}
new->num_entries = 0;
return new;
}
#define streq(a,b) (strcmp((a), (b)) == 0)
/* Not all systems provide this feature */
#if defined(DT_DIR) && defined(DT_UNKNOWN)
# define dirent_type(dirent) ((dirent)->d_type)
# define is_dir_maybe(type) ((type) == DT_DIR || (type) == DT_UNKNOWN)
#else
# define dirent_type(dirent) (1)
# define is_dir_maybe(type) (type)
#endif
static struct pathelem *add_dir_maybe(struct pathelem *path)
{
DIR *dir;
if ((dir = opendir(path->pathname)) != NULL) {
struct dirent *dirent;
while ((dirent = readdir(dir)) != NULL) {
if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
path = add_entry(path, dirent->d_name, dirent_type(dirent));
}
}
closedir(dir);
}
return path;
}
static struct pathelem *add_entry(struct pathelem *root, const char *name,
unsigned char type)
{
struct pathelem **e;
root->num_entries++;
root = realloc(root, sizeof(*root)
+ sizeof(root->entries[0])*root->num_entries);
e = &root->entries[root->num_entries-1];
*e = new_entry(root->pathname, root, name);
if (is_dir_maybe(type)) {
*e = add_dir_maybe(*e);
}
return root;
}
/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
static void set_parents(struct pathelem *child, struct pathelem *parent)
{
unsigned int i;
child->parent = parent;
for (i = 0; i < child->num_entries; i++)
set_parents(child->entries[i], child);
}
/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
static const char *
follow_path(const struct pathelem *cursor, const char *name)
{
unsigned int i, namelen;
name += strspn(name, "/");
namelen = strcspn(name, "/");
if (namelen == 0)
return cursor->pathname;
if (strneq(name, namelen, ".."))
return follow_path(cursor->parent, name + namelen);
if (strneq(name, namelen, "."))
return follow_path(cursor, name + namelen);
for (i = 0; i < cursor->num_entries; i++)
if (strneq(name, namelen, cursor->entries[i]->name))
return follow_path(cursor->entries[i], name + namelen);
/* Not found */
return NULL;
}
void init_paths(const char *prefix)
{
char pref_buf[PATH_MAX];
if (prefix[0] == '\0' ||
!strcmp(prefix, "/"))
return;
if (prefix[0] != '/') {
char *cwd = getcwd(NULL, 0);
size_t pref_buf_len = sizeof(pref_buf);
if (!cwd)
abort();
pstrcpy(pref_buf, sizeof(pref_buf), cwd);
pstrcat(pref_buf, pref_buf_len, "/");
pstrcat(pref_buf, pref_buf_len, prefix);
free(cwd);
} else
pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
base = new_entry("", NULL, pref_buf);
base = add_dir_maybe(base);
if (base->num_entries == 0) {
free (base);
base = NULL;
} else {
set_parents(base, base);
}
}
/* Look for path in emulation dir, otherwise return name. */
const char *path(const char *name)
{
/* Only do absolute paths: quick and dirty, but should mostly be OK.
Could do relative by tracking cwd. */
if (!base || !name || name[0] != '/')
return name;
return follow_path(base, name) ?: name;
}