1 /*-
2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include <sys/types.h>
31 #include <sys/uio.h>
32
33 #include <errno.h>
34 #include <limits.h>
35 #include <paths.h>
36 #include <stdarg.h>
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <string.h>
40 #include <unistd.h>
41
42 extern "C" char** environ;
43
44 enum ExecVariant { kIsExecL, kIsExecLE, kIsExecLP };
45
__execl(const char * name,const char * argv0,ExecVariant variant,va_list ap)46 static int __execl(const char* name, const char* argv0, ExecVariant variant, va_list ap) {
47 // Count the arguments.
48 va_list count_ap;
49 va_copy(count_ap, ap);
50 size_t n = 1;
51 while (va_arg(count_ap, char*) != nullptr) {
52 ++n;
53 }
54 va_end(count_ap);
55
56 // Construct the new argv.
57 char* argv[n + 1];
58 argv[0] = const_cast<char*>(argv0);
59 n = 1;
60 while ((argv[n] = va_arg(ap, char*)) != nullptr) {
61 ++n;
62 }
63
64 // Collect the argp too.
65 char** argp = (variant == kIsExecLE) ? va_arg(ap, char**) : environ;
66
67 va_end(ap);
68
69 return (variant == kIsExecLP) ? execvp(name, argv) : execve(name, argv, argp);
70 }
71
execl(const char * name,const char * arg,...)72 int execl(const char* name, const char* arg, ...) {
73 va_list ap;
74 va_start(ap, arg);
75 int result = __execl(name, arg, kIsExecL, ap);
76 va_end(ap);
77 return result;
78 }
79
execle(const char * name,const char * arg,...)80 int execle(const char* name, const char* arg, ...) {
81 va_list ap;
82 va_start(ap, arg);
83 int result = __execl(name, arg, kIsExecLE, ap);
84 va_end(ap);
85 return result;
86 }
87
execlp(const char * name,const char * arg,...)88 int execlp(const char* name, const char* arg, ...) {
89 va_list ap;
90 va_start(ap, arg);
91 int result = __execl(name, arg, kIsExecLP, ap);
92 va_end(ap);
93 return result;
94 }
95
execv(const char * name,char * const * argv)96 int execv(const char* name, char* const* argv) {
97 return execve(name, argv, environ);
98 }
99
execvp(const char * name,char * const * argv)100 int execvp(const char* name, char* const* argv) {
101 return execvpe(name, argv, environ);
102 }
103
__exec_as_script(const char * buf,char * const * argv,char * const * envp)104 static int __exec_as_script(const char* buf, char* const* argv, char* const* envp) {
105 size_t arg_count = 1;
106 while (argv[arg_count] != nullptr) ++arg_count;
107
108 const char* script_argv[arg_count + 2];
109 script_argv[0] = "sh";
110 script_argv[1] = buf;
111 memcpy(script_argv + 2, argv + 1, arg_count * sizeof(char*));
112 return execve(_PATH_BSHELL, const_cast<char**>(script_argv), envp);
113 }
114
execvpe(const char * name,char * const * argv,char * const * envp)115 int execvpe(const char* name, char* const* argv, char* const* envp) {
116 // Do not allow null name.
117 if (name == nullptr || *name == '\0') {
118 errno = ENOENT;
119 return -1;
120 }
121
122 // If it's an absolute or relative path name, it's easy.
123 if (strchr(name, '/') && execve(name, argv, envp) == -1) {
124 if (errno == ENOEXEC) return __exec_as_script(name, argv, envp);
125 return -1;
126 }
127
128 // Get the path we're searching.
129 const char* path = getenv("PATH");
130 if (path == nullptr) path = _PATH_DEFPATH;
131
132 // Make a writable copy.
133 size_t len = strlen(path) + 1;
134 char writable_path[len];
135 memcpy(writable_path, path, len);
136
137 bool saw_EACCES = false;
138
139 // Try each element of $PATH in turn...
140 char* strsep_buf = writable_path;
141 const char* dir;
142 while ((dir = strsep(&strsep_buf, ":"))) {
143 // It's a shell path: double, leading and trailing colons
144 // mean the current directory.
145 if (*dir == '\0') dir = const_cast<char*>(".");
146
147 size_t dir_len = strlen(dir);
148 size_t name_len = strlen(name);
149
150 char buf[dir_len + 1 + name_len + 1];
151 mempcpy(mempcpy(mempcpy(buf, dir, dir_len), "/", 1), name, name_len + 1);
152
153 execve(buf, argv, envp);
154 switch (errno) {
155 case EISDIR:
156 case ELOOP:
157 case ENAMETOOLONG:
158 case ENOENT:
159 case ENOTDIR:
160 break;
161 case ENOEXEC:
162 return __exec_as_script(buf, argv, envp);
163 case EACCES:
164 saw_EACCES = true;
165 break;
166 default:
167 return -1;
168 }
169 }
170 if (saw_EACCES) errno = EACCES;
171 return -1;
172 }
173