exec.cpp revision 13ec1cf3da6f92defec62492a4a94ada4ee35aaf 
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
42extern "C" char** environ;
43
44enum ExecVariant { kIsExecL, kIsExecLE, kIsExecLP };
45
46static 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
72int 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
80int 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
88int 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
96int execv(const char* name, char* const* argv) {
97  return execve(name, argv, environ);
98}
99
100int execvp(const char* name, char* const* argv) {
101  return execvpe(name, argv, environ);
102}
103
104static 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
115int 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