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 #ifdef __linux__
7 #define _GNU_SOURCE 1
8 #endif
9 #include <sys/types.h>
10 #include <sys/param.h>
11 #include <dirent.h>
12 #include <unistd.h>
13 #include <stdlib.h>
14 #include <string.h>
15 #include <errno.h>
16 #include <stdio.h>
17 #include "qemu-common.h"
18
19 struct pathelem
20 {
21 /* Name of this, eg. lib */
22 char *name;
23 /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
24 char *pathname;
25 struct pathelem *parent;
26 /* Children */
27 unsigned int num_entries;
28 struct pathelem *entries[0];
29 };
30
31 static struct pathelem *base;
32
33 /* First N chars of S1 match S2, and S2 is N chars long. */
strneq(const char * s1,unsigned int n,const char * s2)34 static int strneq(const char *s1, unsigned int n, const char *s2)
35 {
36 unsigned int i;
37
38 for (i = 0; i < n; i++)
39 if (s1[i] != s2[i])
40 return 0;
41 return s2[i] == 0;
42 }
43
44 static struct pathelem *add_entry(struct pathelem *root, const char *name,
45 unsigned char type);
46
new_entry(const char * root,struct pathelem * parent,const char * name)47 static struct pathelem *new_entry(const char *root,
48 struct pathelem *parent,
49 const char *name)
50 {
51 struct pathelem *new = malloc(sizeof(*new));
52 new->name = strdup(name);
53 if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
54 printf("Cannot allocate memory\n");
55 exit(1);
56 }
57 new->num_entries = 0;
58 return new;
59 }
60
61 #define streq(a,b) (strcmp((a), (b)) == 0)
62
63 /* Not all systems provide this feature */
64 #if defined(DT_DIR) && defined(DT_UNKNOWN)
65 # define dirent_type(dirent) ((dirent)->d_type)
66 # define is_dir_maybe(type) ((type) == DT_DIR || (type) == DT_UNKNOWN)
67 #else
68 # define dirent_type(dirent) (1)
69 # define is_dir_maybe(type) (type)
70 #endif
71
add_dir_maybe(struct pathelem * path)72 static struct pathelem *add_dir_maybe(struct pathelem *path)
73 {
74 DIR *dir;
75
76 if ((dir = opendir(path->pathname)) != NULL) {
77 struct dirent *dirent;
78
79 while ((dirent = readdir(dir)) != NULL) {
80 if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
81 path = add_entry(path, dirent->d_name, dirent_type(dirent));
82 }
83 }
84 closedir(dir);
85 }
86 return path;
87 }
88
add_entry(struct pathelem * root,const char * name,unsigned char type)89 static struct pathelem *add_entry(struct pathelem *root, const char *name,
90 unsigned char type)
91 {
92 struct pathelem **e;
93
94 root->num_entries++;
95
96 root = realloc(root, sizeof(*root)
97 + sizeof(root->entries[0])*root->num_entries);
98 e = &root->entries[root->num_entries-1];
99
100 *e = new_entry(root->pathname, root, name);
101 if (is_dir_maybe(type)) {
102 *e = add_dir_maybe(*e);
103 }
104
105 return root;
106 }
107
108 /* This needs to be done after tree is stabilized (ie. no more reallocs!). */
set_parents(struct pathelem * child,struct pathelem * parent)109 static void set_parents(struct pathelem *child, struct pathelem *parent)
110 {
111 unsigned int i;
112
113 child->parent = parent;
114 for (i = 0; i < child->num_entries; i++)
115 set_parents(child->entries[i], child);
116 }
117
118 /* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
119 static const char *
follow_path(const struct pathelem * cursor,const char * name)120 follow_path(const struct pathelem *cursor, const char *name)
121 {
122 unsigned int i, namelen;
123
124 name += strspn(name, "/");
125 namelen = strcspn(name, "/");
126
127 if (namelen == 0)
128 return cursor->pathname;
129
130 if (strneq(name, namelen, ".."))
131 return follow_path(cursor->parent, name + namelen);
132
133 if (strneq(name, namelen, "."))
134 return follow_path(cursor, name + namelen);
135
136 for (i = 0; i < cursor->num_entries; i++)
137 if (strneq(name, namelen, cursor->entries[i]->name))
138 return follow_path(cursor->entries[i], name + namelen);
139
140 /* Not found */
141 return NULL;
142 }
143
init_paths(const char * prefix)144 void init_paths(const char *prefix)
145 {
146 char pref_buf[PATH_MAX];
147
148 if (prefix[0] == '\0' ||
149 !strcmp(prefix, "/"))
150 return;
151
152 if (prefix[0] != '/') {
153 char *cwd = getcwd(NULL, 0);
154 size_t pref_buf_len = sizeof(pref_buf);
155
156 if (!cwd)
157 abort();
158 pstrcpy(pref_buf, sizeof(pref_buf), cwd);
159 pstrcat(pref_buf, pref_buf_len, "/");
160 pstrcat(pref_buf, pref_buf_len, prefix);
161 free(cwd);
162 } else
163 pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
164
165 base = new_entry("", NULL, pref_buf);
166 base = add_dir_maybe(base);
167 if (base->num_entries == 0) {
168 free (base);
169 base = NULL;
170 } else {
171 set_parents(base, base);
172 }
173 }
174
175 /* Look for path in emulation dir, otherwise return name. */
path(const char * name)176 const char *path(const char *name)
177 {
178 /* Only do absolute paths: quick and dirty, but should mostly be OK.
179 Could do relative by tracking cwd. */
180 if (!base || !name || name[0] != '/')
181 return name;
182
183 return follow_path(base, name) ?: name;
184 }
185