1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*
23 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29/*
30 * Shell Escape I/O Backend
31 *
32 * The MDB parser implements two forms of shell escapes: (1) traditional adb(1)
33 * style shell escapes of the form "!command", which simply allows the user to
34 * invoke a command (or shell pipeline) as if they had executed sh -c command
35 * and then return to the debugger, and (2) shell pipes of the form "dcmds !
36 * command", in which the output of one or more MDB dcmds is sent as standard
37 * input to a shell command (or shell pipeline).  Form (1) can be handled
38 * entirely from the parser by calling mdb_shell_exec (below); it simply
39 * forks the shell, executes the desired command, and waits for completion.
40 * Form (2) is slightly more complicated: we construct a UNIX pipe, fork
41 * the shell, and then built an fdio object out of the write end of the pipe.
42 * We then layer a shellio object (implemented below) and iob on top, and
43 * set mdb.m_out to point to this new iob.  The shellio is simply a pass-thru
44 * to the fdio, except that its io_close routine performs a waitpid for the
45 * forked child process.
46 */
47
48#include <sys/types.h>
49#include <sys/wait.h>
50#include <unistd.h>
51#include <errno.h>
52#include <stdlib.h>
53#include <fcntl.h>
54
55#include <mdb/mdb_shell.h>
56#include <mdb/mdb_lex.h>
57#include <mdb/mdb_err.h>
58#include <mdb/mdb_debug.h>
59#include <mdb/mdb_string.h>
60#include <mdb/mdb_frame.h>
61#include <mdb/mdb_io_impl.h>
62#include <mdb/mdb.h>
63
64#define	E_BADEXEC	127	/* Exit status for failed exec */
65
66/*
67 * We must manually walk the open file descriptors and set FD_CLOEXEC, because
68 * we need to be able to print an error if execlp() fails.  If mdb.m_err has
69 * been altered, then using closefrom() could close our output file descriptor,
70 * preventing us from displaying an error message.  Using FD_CLOEXEC ensures
71 * that the file descriptors are only closed if execlp() succeeds.
72 */
73/*ARGSUSED*/
74static int
75closefd_walk(void *unused, int fd)
76{
77	if (fd > 2)
78		(void) fcntl(fd, F_SETFD, FD_CLOEXEC);
79	return (0);
80}
81
82void
83mdb_shell_exec(char *cmd)
84{
85	int status;
86	pid_t pid;
87
88	if (access(mdb.m_shell, X_OK) == -1)
89		yyperror("cannot access %s", mdb.m_shell);
90
91	if ((pid = vfork()) == -1)
92		yyperror("failed to fork");
93
94	if (pid == 0) {
95		(void) fdwalk(closefd_walk, NULL);
96		(void) execlp(mdb.m_shell, strbasename(mdb.m_shell),
97		    "-c", cmd, NULL);
98
99		warn("failed to exec %s", mdb.m_shell);
100		_exit(E_BADEXEC);
101	}
102
103	do {
104		mdb_dprintf(MDB_DBG_SHELL, "waiting for PID %d\n", (int)pid);
105	} while (waitpid(pid, &status, 0) == -1 && errno == EINTR);
106
107	mdb_dprintf(MDB_DBG_SHELL, "waitpid %d -> 0x%x\n", (int)pid, status);
108	strfree(cmd);
109}
110
111/*
112 * This use of the io_unlink entry point is a little strange: we have stacked
113 * the shellio on top of the fdio, but before the shellio's close routine can
114 * wait for the child process, we need to close the UNIX pipe file descriptor
115 * in order to generate an EOF to terminate the child.  Since each io is
116 * unlinked from its iob before being popped by mdb_iob_destroy, we use the
117 * io_unlink entry point to release the underlying fdio (forcing its io_close
118 * routine to be called) and remove it from the iob's i/o stack out of order.
119 */
120
121/*ARGSUSED*/
122static void
123shellio_unlink(mdb_io_t *io, mdb_iob_t *iob)
124{
125	mdb_io_t *fdio = io->io_next;
126
127	ASSERT(iob->iob_iop == io);
128	ASSERT(fdio != NULL);
129
130	io->io_next = fdio->io_next;
131	fdio->io_next = NULL;
132	mdb_io_rele(fdio);
133}
134
135static void
136shellio_close(mdb_io_t *io)
137{
138	pid_t pid = (pid_t)(intptr_t)io->io_data;
139	int status;
140
141	do {
142		mdb_dprintf(MDB_DBG_SHELL, "waiting for PID %d\n", (int)pid);
143	} while (waitpid(pid, &status, 0) == -1 && errno == EINTR);
144
145	mdb_dprintf(MDB_DBG_SHELL, "waitpid %d -> 0x%x\n", (int)pid, status);
146}
147
148static const mdb_io_ops_t shellio_ops = {
149	no_io_read,
150	no_io_write,
151	no_io_seek,
152	no_io_ctl,
153	shellio_close,
154	no_io_name,
155	no_io_link,
156	shellio_unlink,
157	no_io_setattr,
158	no_io_suspend,
159	no_io_resume
160};
161
162void
163mdb_shell_pipe(char *cmd)
164{
165	uint_t iflag = mdb_iob_getflags(mdb.m_out) & MDB_IOB_INDENT;
166	mdb_iob_t *iob;
167	mdb_io_t *io;
168	int pfds[2];
169	pid_t pid;
170
171	if (access(mdb.m_shell, X_OK) == -1)
172		yyperror("cannot access %s", mdb.m_shell);
173
174	if (pipe(pfds) == -1)
175		yyperror("failed to open pipe");
176
177	iob = mdb_iob_create(mdb_fdio_create(pfds[1]), MDB_IOB_WRONLY | iflag);
178	mdb_iob_clrflags(iob, MDB_IOB_AUTOWRAP | MDB_IOB_INDENT);
179	mdb_iob_resize(iob, BUFSIZ, BUFSIZ);
180
181	if ((pid = vfork()) == -1) {
182		(void) close(pfds[0]);
183		(void) close(pfds[1]);
184		mdb_iob_destroy(iob);
185		yyperror("failed to fork");
186	}
187
188	if (pid == 0) {
189		(void) close(pfds[1]);
190		(void) close(STDIN_FILENO);
191		(void) dup2(pfds[0], STDIN_FILENO);
192
193		(void) fdwalk(closefd_walk, NULL);
194		(void) execlp(mdb.m_shell, strbasename(mdb.m_shell),
195		    "-c", cmd, NULL);
196
197		warn("failed to exec %s", mdb.m_shell);
198		_exit(E_BADEXEC);
199	}
200
201	(void) close(pfds[0]);
202	strfree(cmd);
203
204	io = mdb_alloc(sizeof (mdb_io_t), UM_SLEEP);
205
206	io->io_ops = &shellio_ops;
207	io->io_data = (void *)(intptr_t)pid;
208	io->io_next = NULL;
209	io->io_refcnt = 0;
210
211	mdb_iob_stack_push(&mdb.m_frame->f_ostk, mdb.m_out, yylineno);
212	mdb_iob_push_io(iob, io);
213	mdb.m_out = iob;
214}
215