1 /*
2 * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 /*
27 * jexec for J2SE
28 *
29 * jexec is used by the system to allow execution of JAR files.
30 * Essentially jexec needs to run java and
31 * needs to be a native ISA executable (not a shell script), although
32 * this native ISA executable requirement was a mistake that will be fixed.
33 * (<ISA> is sparc or i386 or amd64).
34 *
35 * When you execute a jar file, jexec is executed by the system as follows:
36 * /usr/java/jre/lib/<ISA>/jexec -jar JARFILENAME
37 * so this just needs to be turned into:
38 * /usr/java/jre/bin/java -jar JARFILENAME
39 *
40 * Solaris systems (new 7's and all 8's) will be looking for jexec at:
41 * /usr/java/jre/lib/<ISA>/jexec
42 * Older systems may need to add this to their /etc/system file:
43 * set javaexec:jexec="/usr/java/jre/lib/<ISA>/jexec"
44 * and reboot the machine for this to work.
45 *
46 * This source should be compiled as:
47 * cc -o jexec jexec.c
48 *
49 * And jexec should be placed at the following location of the installation:
50 * <INSTALLATIONDIR>/jre/lib/<ISA>/jexec (for Solaris)
51 * <INSTALLATIONDIR>/lib/jexec (for Linux)
52 *
53 * NOTE: Unless <INSTALLATIONDIR> is the "default" JDK on the system
54 * (i.e. /usr/java -> <INSTALLATIONDIR>), this jexec will not be
55 * found. The 1.2 java is only the default on Solaris 8 and
56 * on systems where the 1.2 packages were installed and no 1.1
57 * java was found.
58 *
59 * NOTE: You must use 1.2 jar to build your jar files. The system
60 * doesn't seem to pick up 1.1 jar files.
61 *
62 * NOTE: We don't need to set LD_LIBRARY_PATH here, even though we
63 * are running the actual java binary because the java binary will
64 * look for it's libraries through it's own runpath, which uses
65 * $ORIGIN.
66 *
67 * NOTE: This jexec should NOT have any special .so library needs because
68 * it appears that this executable will NOT get the $ORIGIN of jexec
69 * but the $ORIGIN of the jar file being executed. Be careful to keep
70 * this program simple and with no .so dependencies.
71 */
72
73 #include <stdlib.h>
74 #include <stdio.h>
75 #include <unistd.h>
76 #include <string.h>
77 #include <limits.h>
78 #include <errno.h>
79
80 static const int CRAZY_EXEC = ENOEXEC;
81 static const int BAD_MAGIC = ENOEXEC;
82
83 static const char * BAD_EXEC_MSG = "jexec failed";
84 static const char * CRAZY_EXEC_MSG = "missing args";
85 static const char * MISSING_JAVA_MSG = "can't locate java";
86 static const char * UNKNOWN_ERROR = "unknown error";
87
88 /* Define a constant that represents the number of directories to pop off the
89 * current location to find the java binary */
90 static const int RELATIVE_DEPTH = 3;
91
92 /* path to java after popping */
93 static const char * BIN_PATH = "/bin/java";
94
95 /* flag used when running JAR files */
96 static const char * JAR_FLAG = "-jar";
97
98 int main(int argc, const char * argv[]);
99 void errorExit(int error, const char * message);
100 int getJavaPath(const char * path, char * buf, int depth);
101
102 /*
103 * This is the main entry point. This program (jexec) will attempt to execute
104 * a JAR file by finding the Java program (java), relative to its own location.
105 * The exact location of the Java program depends on the platform, i.e.
106 *
107 * <INSTALLATIONDIR>/jre/lib/<ISA>/jexec (for Solaris)
108 * <INSTALLATIONDIR>/lib/jexec (for Linux JDK)
109 *
110 * Once the Java program is found, this program copies any remaining arguments
111 * into another array, which is then used to exec the Java program.
112 *
113 * On Linux this program does some additional steps. When copying the array of
114 * args, it is necessary to insert the "-jar" flag between arg[0], the program
115 * name, and the original arg[1], which is presumed to be a path to a JAR file.
116 * It is also necessary to verify that the original arg[1] really is a JAR file.
117 * (These steps are unnecessary on Solaris because they are taken care of by
118 * the kernel.)
119 */
120 int main(int argc, const char * argv[]) {
121 /* We need to exec the original arguments using java, instead of jexec.
122 * Also, for Linux, it is necessary to add the "-jar" argument between
123 * the new arg[0], and the old arg[1]. To do this we will create a new
124 * args array. */
125 char java[PATH_MAX + 1]; /* path to java binary */
126 const char ** nargv = NULL; /* new args array */
127 int nargc = 0; /* new args array count */
128 int argi = 0; /* index into old array */
129
130 /* Make sure we have something to work with */
131 if ((argc < 1) || (argv == NULL)) {
132 /* Shouldn't happen... */
133 errorExit(CRAZY_EXEC, CRAZY_EXEC_MSG);
134 }
135
136 /* Get the path to the java binary, which is in a known position relative
137 * to our current position, which is in argv[0]. */
138 if (getJavaPath(argv[argi++], java, RELATIVE_DEPTH) != 0) {
139 errorExit(errno, MISSING_JAVA_MSG);
140 }
141
142 nargv = (const char **) malloc((argc + 2) * (sizeof (const char *)));
143 nargv[nargc++] = java;
144
145 if (argc >= 2) {
146 const char * jarfile = argv[argi++];
147 const char * message = NULL;
148
149 /* the next argument is the path to the JAR file */
150 nargv[nargc++] = jarfile;
151 }
152
153 /* finally copy any remaining arguments */
154 while (argi < argc) {
155 nargv[nargc++] = argv[argi++];
156 }
157
158 /* finally add one last terminating null */
159 nargv[nargc++] = NULL;
160
161 /* It's time to exec the java binary with the new arguments. It
162 * is possible that we've reached this point without actually
163 * having a JAR file argument (i.e. if argc < 2), but we still
164 * want to exec the java binary, since that will take care of
165 * displaying the correct usage. */
166 execv(java, (char * const *) nargv);
167
168 /* If the exec worked, this process would have been replaced
169 * by the new process. So any code reached beyond this point
170 * implies an error in the exec. */
171 free(nargv);
172 errorExit(errno, BAD_EXEC_MSG);
173 return 0; // keep the compiler happy
174 }
175
176
177 /*
178 * Exit the application by setting errno, and writing a message.
179 *
180 * Parameters:
181 * error - errno is set to this value, and it is used to exit.
182 * message - the message to write.
183 */
184 void errorExit(int error, const char * message) {
185 if (error != 0) {
186 errno = error;
187 perror((message != NULL) ? message : UNKNOWN_ERROR);
188 }
189
190 exit((error == 0) ? 0 : 1);
191 }
192
193
194 /*
195 * Get the path to the java binary that should be relative to the current path.
196 *
197 * Parameters:
198 * path - the input path that the java binary that should be relative to.
199 * buf - a buffer of size PATH_MAX or greater that the java path is
200 * copied to.
201 * depth - the number of names to trim off the current path, including the
202 * name of this program.
203 *
204 * Returns:
205 * This function returns 0 on success; otherwise it returns the value of
206 * errno.
207 */
208 int getJavaPath(const char * path, char * buf, int depth) {
209 int result = 0;
210
211 /* Get the full path to this program. Depending on whether this is Solaris
212 * or Linux, this will be something like,
213 *
214 * <FOO>/jre/lib/<ISA>/jexec (for Solaris)
215 * <FOO>/lib/jexec (for Linux)
216 */
217 if (realpath(path, buf) != NULL) {
218 int count = 0;
219
220 /* Pop off the filename, and then subdirectories for each level of
221 * depth */
222 for (count = 0; count < depth; count++) {
223 *(strrchr(buf, '/')) = '\0';
224 }
225
226 /* Append the relative location of java, creating something like,
227 *
228 * <FOO>/jre/bin/java (for Solaris)
229 * <FOO>/bin/java (for Linux)
230 */
231 strcat(buf, BIN_PATH);
232 }
233 else {
234 /* Failed to get the path */
235 result = errno;
236 }
237
238 return (result);
239 }