1 #include <stdlib.h>
2 #include <limits.h>
3 #include <sys/stat.h>
4 #include <fcntl.h>
5 #include <errno.h>
6 #include <unistd.h>
7 #include <string.h>
8 #include "syscall.h"
9
realpath(const char * restrict filename,char * restrict resolved)10 char *realpath(const char *restrict filename, char *restrict resolved)
11 {
12 int fd;
13 ssize_t r;
14 struct stat st1, st2;
15 char buf[15+3*sizeof(int)];
16 char tmp[PATH_MAX];
17
18 if (!filename) {
19 errno = EINVAL;
20 return 0;
21 }
22
23 fd = sys_open(filename, O_PATH|O_NONBLOCK|O_CLOEXEC);
24 if (fd < 0) return 0;
25 __procfdname(buf, fd);
26
27 r = readlink(buf, tmp, sizeof tmp - 1);
28 if (r < 0) goto err;
29 tmp[r] = 0;
30
31 fstat(fd, &st1);
32 r = stat(tmp, &st2);
33 if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) {
34 if (!r) errno = ELOOP;
35 goto err;
36 }
37
38 __syscall(SYS_close, fd);
39 return resolved ? strcpy(resolved, tmp) : strdup(tmp);
40 err:
41 __syscall(SYS_close, fd);
42 return 0;
43 }
44