1/* Find path of executable.
2 Copyright (C) 1998-2022 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 <stdlib.h>
21#include <string.h>
22#include <unistd.h>
23#include <fcntl.h>
24#include <sys/param.h>
25#include <ldsodefs.h>
26#include <sysdep.h>
27
28#include <dl-dst.h>
29
30/* On Linux >= 2.1 systems which have the dcache implementation we can get
31 the path of the application from the /proc/self/exe symlink. Try this
32 first and fall back on the generic method if necessary. */
33
34const char *
35_dl_get_origin (void)
36{
37 char linkval[PATH_MAX];
38 char *result;
39 int len;
40
41 len = INTERNAL_SYSCALL_CALL (readlinkat, AT_FDCWD, "/proc/self/exe",
42 linkval, sizeof (linkval));
43 if (! INTERNAL_SYSCALL_ERROR_P (len) && len > 0 && linkval[0] != '[')
44 {
45 /* We can use this value. */
46 assert (linkval[0] == '/');
47 while (len > 1 && linkval[len - 1] != '/')
48 --len;
49 result = (char *) malloc (len + 1);
50 if (result == NULL)
51 result = (char *) -1;
52 else if (len == 1)
53 memcpy (result, "/", 2);
54 else
55 *((char *) __mempcpy (result, linkval, len - 1)) = '\0';
56 }
57 else
58 {
59 result = (char *) -1;
60 /* We use the environment variable LD_ORIGIN_PATH. If it is set make
61 a copy and strip out trailing slashes. */
62 if (GLRO(dl_origin_path) != NULL)
63 {
64 size_t len = strlen (GLRO(dl_origin_path));
65 result = (char *) malloc (len + 1);
66 if (result == NULL)
67 result = (char *) -1;
68 else
69 {
70 char *cp = __mempcpy (result, GLRO(dl_origin_path), len);
71 while (cp > result + 1 && cp[-1] == '/')
72 --cp;
73 *cp = '\0';
74 }
75 }
76 }
77
78 return result;
79}
80

source code of glibc/sysdeps/unix/sysv/linux/generic/dl-origin.c