1/* Find path of executable.
2 Copyright (C) 1998-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <assert.h>
20#include <dl-dst.h>
21#include <fcntl.h>
22#include <ldsodefs.h>
23#include <sysdep.h>
24
25/* On Linux >= 2.1 systems which have the dcache implementation we can get
26 the path of the application from the /proc/self/exe symlink. Try this
27 first and fall back on the generic method if necessary. */
28
29const char *
30_dl_get_origin (void)
31{
32 char linkval[PATH_MAX];
33 char *result;
34 int len;
35
36 len = INTERNAL_SYSCALL_CALL (readlinkat, AT_FDCWD, "/proc/self/exe",
37 linkval, sizeof (linkval));
38 if (len > 0 && linkval[0] != '[')
39 {
40 /* We can use this value. */
41 assert (linkval[0] == '/');
42 while (len > 1 && linkval[len - 1] != '/')
43 --len;
44 result = (char *) malloc (len + 1);
45 if (result == NULL)
46 result = (char *) -1;
47 else if (len == 1)
48 memcpy (result, "/", 2);
49 else
50 *((char *) __mempcpy (result, linkval, len - 1)) = '\0';
51 }
52 else
53 {
54 result = (char *) -1;
55 /* We use the environment variable LD_ORIGIN_PATH. If it is set make
56 a copy and strip out trailing slashes. */
57 if (GLRO(dl_origin_path) != NULL)
58 {
59 size_t len = strlen (GLRO(dl_origin_path));
60 result = (char *) malloc (len + 1);
61 if (result == NULL)
62 result = (char *) -1;
63 else
64 {
65 char *cp = __mempcpy (result, GLRO(dl_origin_path), len);
66 while (cp > result + 1 && cp[-1] == '/')
67 --cp;
68 *cp = '\0';
69 }
70 }
71 }
72
73 return result;
74}
75