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 					break;
97 				case ENOENT:
98 				case ESTALE:
99 				case ENOTDIR:
100 					/* Those errors indicate the file is missing or not executable
101 					   by us, in which case we want to just try the next path
102 					   directory.  */
103 				case ENODEV:
104 				case ETIMEDOUT:
105 					/* Some strange filesystems like AFS return even
106 					   stranger error numbers.  They cannot reasonably mean
107 					   anything else so ignore those, too.  */
108 				case ENOEXEC:
109 					/* We won't go searching for the shell
110 					 * if it is not executable - the Linux
111 					 * kernel already handles this enough,
112 					 * for us. */
113 					break;
114 
115 				default:
116 					/* Some other error means we found an executable file, but
117 					   something went wrong executing it; return the error to our
118 					   caller.  */
119 					return -errno;
120 			}
121 		} while (*p++ != '\0');
122 
123 		/* We tried every element and none of them worked.  */
124 		if (got_eacces)
125 			/* At least one failure was due to permissions, so report that
126 			   error.  */
127 			return -EACCES;
128 	}
129 
130 	/* Return the error from the last attempt (probably ENOENT).  */
131 	return -errno;
132 }
133 #ifdef TEST
main(int argc,char ** argv)134 int main(int argc, char**argv)
135 {
136 	char buf[PATH_MAX];
137 	int ret;
138 	argc--;
139 	if (!argc) {
140 		os_warn("Not enough arguments\n");
141 		return 1;
142 	}
143 	argv++;
144 	if (ret = execvp_noalloc(buf, argv[0], argv)) {
145 		errno = -ret;
146 		perror("execvp_noalloc");
147 	}
148 	return 0;
149 }
150 #endif
151