xref: /titanic_44/usr/src/cmd/mdb/common/mdb/mdb_tdb.c (revision 3f7d54a6b84904c8f4d8daa4c7b577bede7df8b9)
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 (c) 2000-2001 by Sun Microsystems, Inc.
24  * All rights reserved.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 /*
30  * libthread_db (tdb) cache
31  *
32  * In order to properly debug multi-threaded programs, the proc target must be
33  * able to query and modify information such as a thread's register set using
34  * either the native LWP services provided by libproc (if the process is not
35  * linked with libthread), or using the services provided by libthread_db (if
36  * the process is linked with libthread).  Additionally, a process may begin
37  * life as a single-threaded process and then later dlopen() libthread, so we
38  * must be prepared to switch modes on-the-fly.  There are also two possible
39  * libthread implementations (one in /usr/lib and one in /usr/lib/lwp) so we
40  * cannot link mdb against libthread_db directly; instead, we must dlopen the
41  * appropriate libthread_db on-the-fly based on which libthread.so the victim
42  * process has open.  Finally, mdb is designed so that multiple targets can be
43  * active simultaneously, so we could even have *both* libthread_db's open at
44  * the same time.  This might happen if you were looking at two multi-threaded
45  * user processes inside of a crash dump, one using /usr/lib/libthread.so and
46  * the other using /usr/lib/lwp/libthread.so.  To meet these requirements, we
47  * implement a libthread_db "cache" in this file.  The proc target calls
48  * mdb_tdb_load() with the pathname of a libthread_db to load, and if it is
49  * not already open, we dlopen() it, look up the symbols we need to reference,
50  * and fill in an ops vector which we return to the caller.  Once an object is
51  * loaded, we don't bother unloading it unless the entire cache is explicitly
52  * flushed.  This mechanism also has the nice property that we don't bother
53  * loading libthread_db until we need it, so the debugger starts up faster.
54  */
55 
56 #include <mdb/mdb_tdb.h>
57 #include <mdb/mdb_modapi.h>
58 #include <mdb/mdb_err.h>
59 
60 #include <strings.h>
61 #include <unistd.h>
62 #include <dlfcn.h>
63 #include <link.h>
64 
65 static mdb_tdb_lib_t *tdb_list;
66 
67 static td_err_e
68 tdb_notsup()
69 {
70 	return (TD_NOCAPAB); /* return thread_db code for not supported */
71 }
72 
73 const mdb_tdb_ops_t *
74 mdb_tdb_load(const char *path)
75 {
76 	td_err_e (*tdb_init)(void);
77 	mdb_tdb_lib_t *t;
78 	td_err_e err;
79 	void *hdl;
80 
81 	/*
82 	 * Search through the existing cache of thread_db libraries and see if
83 	 * we have this one loaded already.  If so, just return its ops vector.
84 	 */
85 	for (t = tdb_list; t != NULL; t = t->tdb_next) {
86 		if (strcmp(path, t->tdb_pathname) == 0)
87 			break;
88 	}
89 
90 	if (t != NULL)
91 		return (&t->tdb_ops);
92 
93 	/*
94 	 * Otherwise dlmopen the new library, look up its td_init() function,
95 	 * and call it.  If any of this fails, we return NULL for failure.
96 	 */
97 	if (access(path, F_OK) == -1)
98 		return (NULL);
99 
100 	if ((hdl = dlmopen(LM_ID_BASE, path, RTLD_LAZY | RTLD_LOCAL)) == NULL) {
101 		(void) set_errno(EMDB_RTLD);
102 		return (NULL);
103 	}
104 
105 	if ((tdb_init = (td_err_e (*)(void))dlsym(hdl, "td_init")) == NULL) {
106 		(void) dlclose(hdl);
107 		(void) set_errno(tdb_to_errno(TD_NOCAPAB));
108 		return (NULL);
109 	}
110 
111 	if ((err = tdb_init()) != TD_OK) {
112 		(void) dlclose(hdl);
113 		(void) set_errno(tdb_to_errno(err));
114 		return (NULL);
115 	}
116 
117 	/*
118 	 * If td_init() succeeds, we can't fail from here on.  Allocate a new
119 	 * library entry and add it to our linked list.
120 	 */
121 	t = mdb_alloc(sizeof (mdb_tdb_lib_t), UM_SLEEP);
122 
123 	(void) strncpy(t->tdb_pathname, path, MAXPATHLEN);
124 	t->tdb_pathname[MAXPATHLEN - 1] = '\0';
125 	t->tdb_handle = hdl;
126 	t->tdb_next = tdb_list;
127 	tdb_list = t;
128 
129 	/*
130 	 * For each function we need to call in the thread_db library, look it
131 	 * up using dlsym().  If we find it, add it to the ops vector.  If not,
132 	 * put the address of our default function (see above) in that slot.
133 	 */
134 
135 	t->tdb_ops.td_ta_new = (td_err_e (*)())dlsym(hdl, "td_ta_new");
136 	if (t->tdb_ops.td_ta_new == NULL)
137 		t->tdb_ops.td_ta_new = (td_err_e (*)())tdb_notsup;
138 
139 	t->tdb_ops.td_ta_delete = (td_err_e (*)())dlsym(hdl, "td_ta_delete");
140 	if (t->tdb_ops.td_ta_delete == NULL)
141 		t->tdb_ops.td_ta_delete = (td_err_e (*)())tdb_notsup;
142 
143 	t->tdb_ops.td_ta_thr_iter = (td_err_e (*)())
144 	    dlsym(hdl, "td_ta_thr_iter");
145 	if (t->tdb_ops.td_ta_thr_iter == NULL)
146 		t->tdb_ops.td_ta_thr_iter = (td_err_e (*)())tdb_notsup;
147 
148 	t->tdb_ops.td_ta_map_id2thr = (td_err_e (*)())
149 	    dlsym(hdl, "td_ta_map_id2thr");
150 	if (t->tdb_ops.td_ta_map_id2thr == NULL)
151 		t->tdb_ops.td_ta_map_id2thr = (td_err_e (*)())tdb_notsup;
152 
153 	t->tdb_ops.td_ta_map_lwp2thr = (td_err_e (*)())
154 	    dlsym(hdl, "td_ta_map_lwp2thr");
155 	if (t->tdb_ops.td_ta_map_lwp2thr == NULL)
156 		t->tdb_ops.td_ta_map_lwp2thr = (td_err_e (*)())tdb_notsup;
157 
158 	t->tdb_ops.td_thr_get_info = (td_err_e (*)())
159 	    dlsym(hdl, "td_thr_get_info");
160 	if (t->tdb_ops.td_thr_get_info == NULL)
161 		t->tdb_ops.td_thr_get_info = (td_err_e (*)())tdb_notsup;
162 
163 	t->tdb_ops.td_thr_getgregs = (td_err_e (*)())
164 	    dlsym(hdl, "td_thr_getgregs");
165 	if (t->tdb_ops.td_thr_getgregs == NULL)
166 		t->tdb_ops.td_thr_getgregs = (td_err_e (*)())tdb_notsup;
167 
168 	t->tdb_ops.td_thr_setgregs = (td_err_e (*)())
169 	    dlsym(hdl, "td_thr_setgregs");
170 	if (t->tdb_ops.td_thr_setgregs == NULL)
171 		t->tdb_ops.td_thr_setgregs = (td_err_e (*)())tdb_notsup;
172 
173 	t->tdb_ops.td_thr_getfpregs = (td_err_e (*)())
174 	    dlsym(hdl, "td_thr_getfpregs");
175 	if (t->tdb_ops.td_thr_getfpregs == NULL)
176 		t->tdb_ops.td_thr_getfpregs = (td_err_e (*)())tdb_notsup;
177 
178 	t->tdb_ops.td_thr_setfpregs = (td_err_e (*)())
179 	    dlsym(hdl, "td_thr_setfpregs");
180 	if (t->tdb_ops.td_thr_setfpregs == NULL)
181 		t->tdb_ops.td_thr_setfpregs = (td_err_e (*)())tdb_notsup;
182 
183 	t->tdb_ops.td_thr_tlsbase = (td_err_e (*)())
184 	    dlsym(hdl, "td_thr_tlsbase");
185 	if (t->tdb_ops.td_thr_tlsbase == NULL)
186 		t->tdb_ops.td_thr_tlsbase = (td_err_e (*)())tdb_notsup;
187 
188 #ifdef __sparc
189 	t->tdb_ops.td_thr_getxregs = (td_err_e (*)())
190 	    dlsym(hdl, "td_thr_getxregs");
191 	if (t->tdb_ops.td_thr_getxregs == NULL)
192 		t->tdb_ops.td_thr_getxregs = (td_err_e (*)())tdb_notsup;
193 
194 	t->tdb_ops.td_thr_setxregs = (td_err_e (*)())
195 	    dlsym(hdl, "td_thr_setxregs");
196 	if (t->tdb_ops.td_thr_setxregs == NULL)
197 		t->tdb_ops.td_thr_setxregs = (td_err_e (*)())tdb_notsup;
198 #endif	/* __sparc */
199 
200 	return (&t->tdb_ops);
201 }
202 
203 void
204 mdb_tdb_flush(void)
205 {
206 	mdb_tdb_lib_t *t, *u;
207 
208 	for (t = tdb_list; t != NULL; t = u) {
209 		u = t->tdb_next;
210 		(void) dlclose(t->tdb_handle);
211 		mdb_free(t, sizeof (mdb_tdb_lib_t));
212 	}
213 
214 	tdb_list = NULL;
215 }
216