1 /* Copyright (C) 2006 by Paolo Giarrusso - modified from glibc' execvp.c.
2 Original copyright notice follows:
3
4 Copyright (C) 1991,92,1995-99,2002,2004 Free Software Foundation, Inc.
5 This file is part of the GNU C Library.
6
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
11
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
16
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, write to the Free
19 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
20 02111-1307 USA. */
21 #include <unistd.h>
22
23 #include <stdbool.h>
24 #include <stdlib.h>
25 #include <string.h>
26 #include <errno.h>
27 #include <limits.h>
28
29 #ifndef TEST
30 #include "um_malloc.h"
31 #else
32 #include <stdio.h>
33 #define um_kmalloc malloc
34 #endif
35 #include "os.h"
36
37 /* Execute FILE, searching in the `PATH' environment variable if it contains
38 no slashes, with arguments ARGV and environment from `environ'. */
execvp_noalloc(char * buf,const char * file,char * const argv[])39 int execvp_noalloc(char *buf, const char *file, char *const argv[])
40 {
41 if (*file == '\0') {
42 return -ENOENT;
43 }
44
45 if (strchr (file, '/') != NULL) {
46 /* Don't search when it contains a slash. */
47 execv(file, argv);
48 } else {
49 int got_eacces;
50 size_t len, pathlen;
51 char *name, *p;
52 char *path = getenv("PATH");
53 if (path == NULL)
54 path = ":/bin:/usr/bin";
55
56 len = strlen(file) + 1;
57 pathlen = strlen(path);
58 /* Copy the file name at the top. */
59 name = memcpy(buf + pathlen + 1, file, len);
60 /* And add the slash. */
61 *--name = '/';
62
63 got_eacces = 0;
64 p = path;
65 do {
66 char *startp;
67
68 path = p;
69 //Let's avoid this GNU extension.
70 //p = strchrnul (path, ':');
71 p = strchr(path, ':');
72 if (!p)
73 p = strchr(path, '\0');
74
75 if (p == path)
76 /* Two adjacent colons, or a colon at the beginning or the end
77 of `PATH' means to search the current directory. */
78 startp = name + 1;
79 else
80 startp = memcpy(name - (p - path), path, p - path);
81
82 /* Try to execute this name. If it works, execv will not return. */
83 execv(startp, argv);
84
85 /*
86 if (errno == ENOEXEC) {
87 }
88 */
89
90 switch (errno) {
91 case EACCES:
92 /* Record the we got a `Permission denied' error. If we end
93 up finding no executable we can use, we want to diagnose
94 that we did find one but were denied access. */
95 got_eacces = 1;
96 case ENOENT:
97 case ESTALE:
98 case ENOTDIR:
99 /* Those errors indicate the file is missing or not executable
100 by us, in which case we want to just try the next path
101 directory. */
102 case ENODEV:
103 case ETIMEDOUT:
104 /* Some strange filesystems like AFS return even
105 stranger error numbers. They cannot reasonably mean
106 anything else so ignore those, too. */
107 case ENOEXEC:
108 /* We won't go searching for the shell
109 * if it is not executable - the Linux
110 * kernel already handles this enough,
111 * for us. */
112 break;
113
114 default:
115 /* Some other error means we found an executable file, but
116 something went wrong executing it; return the error to our
117 caller. */
118 return -errno;
119 }
120 } while (*p++ != '\0');
121
122 /* We tried every element and none of them worked. */
123 if (got_eacces)
124 /* At least one failure was due to permissions, so report that
125 error. */
126 return -EACCES;
127 }
128
129 /* Return the error from the last attempt (probably ENOENT). */
130 return -errno;
131 }
132 #ifdef TEST
main(int argc,char ** argv)133 int main(int argc, char**argv)
134 {
135 char buf[PATH_MAX];
136 int ret;
137 argc--;
138 if (!argc) {
139 fprintf(stderr, "Not enough arguments\n");
140 return 1;
141 }
142 argv++;
143 if (ret = execvp_noalloc(buf, argv[0], argv)) {
144 errno = -ret;
145 perror("execvp_noalloc");
146 }
147 return 0;
148 }
149 #endif
150