xref: /openbmc/qemu/util/path.c (revision 14a650ec)
1 /* Code to mangle pathnames into those matching a given prefix.
2    eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");
3 
4    The assumption is that this area does not change.
5 */
6 #include <sys/types.h>
7 #include <sys/param.h>
8 #include <dirent.h>
9 #include <unistd.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <errno.h>
13 #include <stdio.h>
14 #include "qemu-common.h"
15 
16 struct pathelem
17 {
18     /* Name of this, eg. lib */
19     char *name;
20     /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
21     char *pathname;
22     struct pathelem *parent;
23     /* Children */
24     unsigned int num_entries;
25     struct pathelem *entries[0];
26 };
27 
28 static struct pathelem *base;
29 
30 /* First N chars of S1 match S2, and S2 is N chars long. */
31 static int strneq(const char *s1, unsigned int n, const char *s2)
32 {
33     unsigned int i;
34 
35     for (i = 0; i < n; i++)
36         if (s1[i] != s2[i])
37             return 0;
38     return s2[i] == 0;
39 }
40 
41 static struct pathelem *add_entry(struct pathelem *root, const char *name,
42                                   unsigned type);
43 
44 static struct pathelem *new_entry(const char *root,
45                                   struct pathelem *parent,
46                                   const char *name)
47 {
48     struct pathelem *new = malloc(sizeof(*new));
49     new->name = strdup(name);
50     new->pathname = g_strdup_printf("%s/%s", root, name);
51     new->num_entries = 0;
52     return new;
53 }
54 
55 #define streq(a,b) (strcmp((a), (b)) == 0)
56 
57 /* Not all systems provide this feature */
58 #if defined(DT_DIR) && defined(DT_UNKNOWN) && defined(DT_LNK)
59 # define dirent_type(dirent) ((dirent)->d_type)
60 # define is_dir_maybe(type) \
61     ((type) == DT_DIR || (type) == DT_UNKNOWN || (type) == DT_LNK)
62 #else
63 # define dirent_type(dirent) (1)
64 # define is_dir_maybe(type)  (type)
65 #endif
66 
67 static struct pathelem *add_dir_maybe(struct pathelem *path)
68 {
69     DIR *dir;
70 
71     if ((dir = opendir(path->pathname)) != NULL) {
72         struct dirent *dirent;
73 
74         while ((dirent = readdir(dir)) != NULL) {
75             if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
76                 path = add_entry(path, dirent->d_name, dirent_type(dirent));
77             }
78         }
79         closedir(dir);
80     }
81     return path;
82 }
83 
84 static struct pathelem *add_entry(struct pathelem *root, const char *name,
85                                   unsigned type)
86 {
87     struct pathelem **e;
88 
89     root->num_entries++;
90 
91     root = realloc(root, sizeof(*root)
92                    + sizeof(root->entries[0])*root->num_entries);
93     e = &root->entries[root->num_entries-1];
94 
95     *e = new_entry(root->pathname, root, name);
96     if (is_dir_maybe(type)) {
97         *e = add_dir_maybe(*e);
98     }
99 
100     return root;
101 }
102 
103 /* This needs to be done after tree is stabilized (ie. no more reallocs!). */
104 static void set_parents(struct pathelem *child, struct pathelem *parent)
105 {
106     unsigned int i;
107 
108     child->parent = parent;
109     for (i = 0; i < child->num_entries; i++)
110         set_parents(child->entries[i], child);
111 }
112 
113 /* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
114 static const char *
115 follow_path(const struct pathelem *cursor, const char *name)
116 {
117     unsigned int i, namelen;
118 
119     name += strspn(name, "/");
120     namelen = strcspn(name, "/");
121 
122     if (namelen == 0)
123         return cursor->pathname;
124 
125     if (strneq(name, namelen, ".."))
126         return follow_path(cursor->parent, name + namelen);
127 
128     if (strneq(name, namelen, "."))
129         return follow_path(cursor, name + namelen);
130 
131     for (i = 0; i < cursor->num_entries; i++)
132         if (strneq(name, namelen, cursor->entries[i]->name))
133             return follow_path(cursor->entries[i], name + namelen);
134 
135     /* Not found */
136     return NULL;
137 }
138 
139 void init_paths(const char *prefix)
140 {
141     char pref_buf[PATH_MAX];
142 
143     if (prefix[0] == '\0' ||
144         !strcmp(prefix, "/"))
145         return;
146 
147     if (prefix[0] != '/') {
148         char *cwd = getcwd(NULL, 0);
149         size_t pref_buf_len = sizeof(pref_buf);
150 
151         if (!cwd)
152             abort();
153         pstrcpy(pref_buf, sizeof(pref_buf), cwd);
154         pstrcat(pref_buf, pref_buf_len, "/");
155         pstrcat(pref_buf, pref_buf_len, prefix);
156         free(cwd);
157     } else
158         pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
159 
160     base = new_entry("", NULL, pref_buf);
161     base = add_dir_maybe(base);
162     if (base->num_entries == 0) {
163         free (base);
164         base = NULL;
165     } else {
166         set_parents(base, base);
167     }
168 }
169 
170 /* Look for path in emulation dir, otherwise return name. */
171 const char *path(const char *name)
172 {
173     /* Only do absolute paths: quick and dirty, but should mostly be OK.
174        Could do relative by tracking cwd. */
175     if (!base || !name || name[0] != '/')
176         return name;
177 
178     return follow_path(base, name) ?: name;
179 }
180