root / path.c @ d7582078
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/* Code to mangle pathnames into those matching a given prefix.
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eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");
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The assumption is that this area does not change.
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*/
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#include <sys/types.h> |
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#include <sys/param.h> |
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#include <dirent.h> |
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#include <unistd.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#include <errno.h> |
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#include <stdio.h> |
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#include "qemu-common.h" |
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struct pathelem
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{ |
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/* Name of this, eg. lib */
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char *name;
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/* Full path name, eg. /usr/gnemul/x86-linux/lib. */
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char *pathname;
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struct pathelem *parent;
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/* Children */
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unsigned int num_entries; |
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struct pathelem *entries[0]; |
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}; |
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static struct pathelem *base; |
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/* First N chars of S1 match S2, and S2 is N chars long. */
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static int strneq(const char *s1, unsigned int n, const char *s2) |
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{ |
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unsigned int i; |
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for (i = 0; i < n; i++) |
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if (s1[i] != s2[i])
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return 0; |
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return s2[i] == 0; |
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} |
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static struct pathelem *add_entry(struct pathelem *root, const char *name, |
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unsigned char type); |
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static struct pathelem *new_entry(const char *root, |
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struct pathelem *parent,
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const char *name) |
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{ |
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struct pathelem *new = malloc(sizeof(*new)); |
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new->name = strdup(name); |
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if (asprintf(&new->pathname, "%s/%s", root, name) == -1) { |
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printf("Cannot allocate memory\n");
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exit(1);
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} |
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new->num_entries = 0;
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return new;
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} |
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#define streq(a,b) (strcmp((a), (b)) == 0) |
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/* Not all systems provide this feature */
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#if defined(DT_DIR) && defined(DT_UNKNOWN)
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# define dirent_type(dirent) ((dirent)->d_type)
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# define is_dir_maybe(type) ((type) == DT_DIR || (type) == DT_UNKNOWN)
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#else
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# define dirent_type(dirent) (1) |
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# define is_dir_maybe(type) (type)
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#endif
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static struct pathelem *add_dir_maybe(struct pathelem *path) |
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{ |
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DIR *dir; |
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if ((dir = opendir(path->pathname)) != NULL) { |
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struct dirent *dirent;
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while ((dirent = readdir(dir)) != NULL) { |
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if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){ |
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path = add_entry(path, dirent->d_name, dirent_type(dirent)); |
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} |
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} |
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closedir(dir); |
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} |
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return path;
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} |
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static struct pathelem *add_entry(struct pathelem *root, const char *name, |
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unsigned char type) |
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{ |
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struct pathelem **e;
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root->num_entries++; |
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root = realloc(root, sizeof(*root)
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+ sizeof(root->entries[0])*root->num_entries); |
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e = &root->entries[root->num_entries-1];
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*e = new_entry(root->pathname, root, name); |
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if (is_dir_maybe(type)) {
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*e = add_dir_maybe(*e); |
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} |
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return root;
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} |
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/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
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static void set_parents(struct pathelem *child, struct pathelem *parent) |
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{ |
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unsigned int i; |
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child->parent = parent; |
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for (i = 0; i < child->num_entries; i++) |
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set_parents(child->entries[i], child); |
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} |
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/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
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static const char * |
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follow_path(const struct pathelem *cursor, const char *name) |
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{ |
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unsigned int i, namelen; |
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name += strspn(name, "/");
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namelen = strcspn(name, "/");
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if (namelen == 0) |
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return cursor->pathname;
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if (strneq(name, namelen, "..")) |
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return follow_path(cursor->parent, name + namelen);
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if (strneq(name, namelen, ".")) |
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return follow_path(cursor, name + namelen);
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for (i = 0; i < cursor->num_entries; i++) |
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if (strneq(name, namelen, cursor->entries[i]->name))
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return follow_path(cursor->entries[i], name + namelen);
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/* Not found */
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return NULL; |
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} |
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void init_paths(const char *prefix) |
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{ |
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char pref_buf[PATH_MAX];
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if (prefix[0] == '\0' || |
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!strcmp(prefix, "/"))
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return;
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if (prefix[0] != '/') { |
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char *cwd = getcwd(NULL, 0); |
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size_t pref_buf_len = sizeof(pref_buf);
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if (!cwd)
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abort(); |
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pstrcpy(pref_buf, sizeof(pref_buf), cwd);
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pstrcat(pref_buf, pref_buf_len, "/");
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pstrcat(pref_buf, pref_buf_len, prefix); |
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free(cwd); |
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} else
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pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1); |
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base = new_entry("", NULL, pref_buf); |
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base = add_dir_maybe(base); |
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if (base->num_entries == 0) { |
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free (base); |
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base = NULL;
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} else {
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set_parents(base, base); |
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} |
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} |
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/* Look for path in emulation dir, otherwise return name. */
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const char *path(const char *name) |
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{ |
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/* Only do absolute paths: quick and dirty, but should mostly be OK.
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Could do relative by tracking cwd. */
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if (!base || !name || name[0] != '/') |
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return name;
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return follow_path(base, name) ?: name;
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} |