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 (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25
26 /*
27 * Pipe I/O Backend
28 *
29 * In order to implement dcmd pipelines, we provide a pipe i/o backend that
30 * can be used to connect two mdb_iob structures (a read and write end).
31 * This backend is selected when mdb_iob_pipe is used to construct a pair of
32 * iobs. Each iob points at the same i/o backend (the pipe i/o), and the
33 * backend manages a circular fixed-size buffer which moves data between
34 * the reader and writer. The caller provides read and write-side service
35 * routines that are expected to perform context switching (see mdb_context.c).
36 * The pipe implementation is relatively simple: the writer calls any of the
37 * mdb_iob_* routines to fill the write-side iob, and when this iob needs to
38 * flush data to the underlying i/o, pio_write() below is called. This
39 * routine copies data into the pipe buffer until no more free space is
40 * available, and then calls the read-side service routine (presuming that
41 * when it returns, more free space will be available). On the read-side,
42 * pio_read() copies data up from the pipe buffer into the read-side iob.
43 * If pio_read() is called and the pipe buffer is empty, pio_read() calls
44 * the write-side service routine to force the writer to produce more data.
45 */
46
47 #include <sys/sysmacros.h>
48 #include <stropts.h>
49 #include <limits.h>
50
51 #include <mdb/mdb.h>
52 #include <mdb/mdb_modapi.h>
53 #include <mdb/mdb_debug.h>
54 #include <mdb/mdb_string.h>
55 #include <mdb/mdb_context.h>
56 #include <mdb/mdb_err.h>
57 #include <mdb/mdb_io_impl.h>
58 #include <mdb/mdb_frame.h>
59
60 typedef struct pipe_data {
61 mdb_iobsvc_f *pipe_rdsvc; /* Read-side service routine */
62 mdb_iob_t *pipe_rdiob; /* Read-side i/o buffer */
63 mdb_iobsvc_f *pipe_wrsvc; /* Write-side service routine */
64 mdb_iob_t *pipe_wriob; /* Write-side i/o buffer */
65 char pipe_buf[BUFSIZ]; /* Ring buffer for pipe contents */
66 mdb_iob_ctx_t pipe_ctx; /* Context data for service routines */
67 uint_t pipe_rdndx; /* Next byte index for reading */
68 uint_t pipe_wrndx; /* Next byte index for writing */
69 uint_t pipe_free; /* Free space for writing in bytes */
70 uint_t pipe_used; /* Used space for reading in bytes */
71 } pipe_data_t;
72
73
74 static ssize_t
pio_read(mdb_io_t * io,void * buf,size_t nbytes)75 pio_read(mdb_io_t *io, void *buf, size_t nbytes)
76 {
77 pipe_data_t *pd = io->io_data;
78 size_t n, nleft;
79
80 if (nbytes == 0)
81 return (0); /* return 0 for zero-length read */
82
83 for (nleft = nbytes; nleft == nbytes; nleft -= n) {
84 if (pd->pipe_used == 0) {
85 if (pd->pipe_wriob != NULL) {
86 pd->pipe_wrsvc(pd->pipe_rdiob,
87 pd->pipe_wriob, &pd->pipe_ctx);
88 }
89 if (pd->pipe_used == 0)
90 break;
91 }
92
93 n = MIN(pd->pipe_used, nleft);
94
95 if (BUFSIZ - pd->pipe_rdndx < n) {
96 /*
97 * Case 1: The amount to read overlaps the end of the
98 * circular buffer. 'n1' will be the amount to copy
99 * from the end of the buffer, and 'n2' will be the
100 * amount to copy from the beginning. Note that since
101 * n <= pipe_used, it is impossible to read past
102 * pipe_wrndx into undefined territory.
103 */
104 size_t n1 = BUFSIZ - pd->pipe_rdndx;
105 size_t n2 = n - n1;
106
107 ASSERT(n2 <= pd->pipe_wrndx);
108 bcopy(&pd->pipe_buf[pd->pipe_rdndx], buf, n1);
109 buf = (char *)buf + n1;
110 bcopy(&pd->pipe_buf[0], buf, n2);
111 buf = (char *)buf + n2;
112 } else {
113 /*
114 * Case 2: The easy case. Simply copy the data over
115 * to the buffer.
116 */
117 bcopy(&pd->pipe_buf[pd->pipe_rdndx], buf, n);
118 buf = (char *)buf + n;
119 }
120
121 pd->pipe_rdndx = (pd->pipe_rdndx + n) % BUFSIZ;
122 pd->pipe_free += n;
123 pd->pipe_used -= n;
124 }
125
126 /*
127 * If we have a writer, but pipe_wrsvc failed to produce any data,
128 * we return EAGAIN. If there is no writer, then return 0 for EOF.
129 */
130 if (nleft == nbytes) {
131 if (pd->pipe_wriob != NULL)
132 return (set_errno(EAGAIN));
133 else
134 return (0);
135 }
136
137 return (nbytes - nleft);
138 }
139
140 static ssize_t
pio_write(mdb_io_t * io,const void * buf,size_t nbytes)141 pio_write(mdb_io_t *io, const void *buf, size_t nbytes)
142 {
143 pipe_data_t *pd = io->io_data;
144 size_t n, nleft;
145
146 if (pd->pipe_rdiob == NULL)
147 return (set_errno(EPIPE)); /* fail with EPIPE if no reader */
148
149 for (nleft = nbytes; nleft != 0; nleft -= n) {
150 if (pd->pipe_free == 0) {
151 pd->pipe_rdsvc(pd->pipe_rdiob,
152 pd->pipe_wriob, &pd->pipe_ctx);
153 if (pd->pipe_free == 0)
154 break; /* if nothing consumed by reader, exit */
155 }
156
157 n = MIN(pd->pipe_free, nleft);
158
159 if (BUFSIZ - pd->pipe_wrndx < n) {
160 /*
161 * Case 1: The data will overlap the circular buffer
162 * boundary. In this case, 'n1' will be the number of
163 * bytes to put at the end of the buffer, and 'n2' will
164 * be the number of bytes to put at the beginning.
165 * Note that since n <= pipe_free, it is impossible to
166 * overlap rdndx with the initial data.
167 */
168 size_t n1 = BUFSIZ - pd->pipe_wrndx;
169 size_t n2 = n - n1;
170
171 ASSERT(n2 <= pd->pipe_rdndx);
172
173 bcopy(buf, &pd->pipe_buf[pd->pipe_wrndx], n1);
174 buf = (const char *)buf + n1;
175 bcopy(buf, &pd->pipe_buf[0], n2);
176 buf = (const char *)buf + n2;
177 } else {
178 /*
179 * Case 2: The easy case. Simply copy the data into
180 * the buffer.
181 */
182 bcopy(buf, &pd->pipe_buf[pd->pipe_wrndx], n);
183 buf = (const char *)buf + n;
184 }
185
186 pd->pipe_wrndx = (pd->pipe_wrndx + n) % BUFSIZ;
187 pd->pipe_free -= n;
188 pd->pipe_used += n;
189 }
190
191 if (nleft == nbytes && nbytes != 0)
192 return (set_errno(EAGAIN));
193
194 return (nbytes - nleft);
195 }
196
197 /*
198 * Provide support for STREAMS-style write-side flush ioctl. This can be
199 * used by the caller to force a context switch to the read-side.
200 */
201 static int
pio_ctl(mdb_io_t * io,int req,void * arg)202 pio_ctl(mdb_io_t *io, int req, void *arg)
203 {
204 pipe_data_t *pd = io->io_data;
205
206 if (io->io_next != NULL)
207 return (IOP_CTL(io->io_next, req, arg));
208
209 if (req != I_FLUSH || (intptr_t)arg != FLUSHW)
210 return (set_errno(ENOTSUP));
211
212 if (pd->pipe_used != 0)
213 pd->pipe_rdsvc(pd->pipe_rdiob, pd->pipe_wriob, &pd->pipe_ctx);
214
215 return (0);
216 }
217
218 static void
pio_close(mdb_io_t * io)219 pio_close(mdb_io_t *io)
220 {
221 mdb_free(io->io_data, sizeof (pipe_data_t));
222 }
223
224 /*ARGSUSED*/
225 static const char *
pio_name(mdb_io_t * io)226 pio_name(mdb_io_t *io)
227 {
228 return ("(pipeline)");
229 }
230
231 static void
pio_link(mdb_io_t * io,mdb_iob_t * iob)232 pio_link(mdb_io_t *io, mdb_iob_t *iob)
233 {
234 pipe_data_t *pd = io->io_data;
235
236 /*
237 * Here we take advantage of the IOP_LINK calls made to associate each
238 * i/o backend with its iob to determine our read and write iobs.
239 */
240 if (io->io_next == NULL) {
241 if (iob->iob_flags & MDB_IOB_RDONLY)
242 pd->pipe_rdiob = iob;
243 else
244 pd->pipe_wriob = iob;
245 } else
246 IOP_LINK(io->io_next, iob);
247 }
248
249 static void
pio_unlink(mdb_io_t * io,mdb_iob_t * iob)250 pio_unlink(mdb_io_t *io, mdb_iob_t *iob)
251 {
252 pipe_data_t *volatile pd = io->io_data;
253
254 /*
255 * The IOP_UNLINK call will be made when one of our associated iobs is
256 * destroyed. If the read-side iob is being destroyed, we simply set
257 * pipe_rdiob to NULL, forcing subsequent pio_write() calls to fail
258 * with EPIPE. Things are more complicated when the write-side is
259 * being destroyed. If this is the last close prior to destroying the
260 * pipe, we need to arrange for any in-transit data to be consumed by
261 * the reader. We first set pipe_wriob to NULL, which forces pio_read
262 * to return EOF when all in-transit data is consumed. We then call
263 * the read-service routine while there is still a reader and pipe_used
264 * is non-zero, indicating there is still data in the pipe.
265 */
266 if (io->io_next == NULL) {
267 if (pd->pipe_wriob == iob) {
268 pd->pipe_wriob = NULL; /* remove writer */
269
270 if (pd->pipe_used == 0 && pd->pipe_ctx.ctx_data == NULL)
271 return; /* no reader and nothing to read */
272
273 /*
274 * Note that we need to use a do-while construct here
275 * so that we resume the reader's context at *least*
276 * once. This forces it to read EOF and exit even if
277 * the pipeline is already completely flushed.
278 */
279 do {
280 if (pd->pipe_rdiob == NULL)
281 break;
282 if (mdb_iob_err(pd->pipe_rdiob) != 0) {
283 if (pd->pipe_ctx.ctx_wptr != NULL) {
284 mdb_frame_pop(
285 pd->pipe_ctx.ctx_wptr,
286 MDB_ERR_ABORT);
287 pd->pipe_ctx.ctx_wptr = NULL;
288 }
289 break; /* don't read if error bit set */
290 }
291 if (pd->pipe_ctx.ctx_data == NULL ||
292 setjmp(*mdb_context_getpcb(
293 pd->pipe_ctx.ctx_data)) == 0) {
294 pd->pipe_rdsvc(pd->pipe_rdiob,
295 pd->pipe_wriob, &pd->pipe_ctx);
296 }
297
298 } while (pd->pipe_used != 0);
299
300 if (pd->pipe_ctx.ctx_data != NULL) {
301 mdb_context_destroy(pd->pipe_ctx.ctx_data);
302 pd->pipe_ctx.ctx_data = NULL;
303 }
304
305 } else if (pd->pipe_rdiob == iob)
306 pd->pipe_rdiob = NULL; /* remove reader */
307 } else
308 IOP_UNLINK(io->io_next, iob);
309 }
310
311 static const mdb_io_ops_t pipeio_ops = {
312 .io_read = pio_read,
313 .io_write = pio_write,
314 .io_seek = no_io_seek,
315 .io_ctl = pio_ctl,
316 .io_close = pio_close,
317 .io_name = pio_name,
318 .io_link = pio_link,
319 .io_unlink = pio_unlink,
320 .io_setattr = no_io_setattr,
321 .io_suspend = no_io_suspend,
322 .io_resume = no_io_resume,
323 };
324
325 mdb_io_t *
mdb_pipeio_create(mdb_iobsvc_f * rdsvc,mdb_iobsvc_f * wrsvc)326 mdb_pipeio_create(mdb_iobsvc_f *rdsvc, mdb_iobsvc_f *wrsvc)
327 {
328 mdb_io_t *io = mdb_alloc(sizeof (mdb_io_t), UM_SLEEP);
329 pipe_data_t *pd = mdb_zalloc(sizeof (pipe_data_t), UM_SLEEP);
330
331 ASSERT(rdsvc != NULL && wrsvc != NULL);
332 pd->pipe_rdsvc = rdsvc;
333 pd->pipe_wrsvc = wrsvc;
334 pd->pipe_free = BUFSIZ;
335
336 io->io_ops = &pipeio_ops;
337 io->io_data = pd;
338 io->io_next = NULL;
339 io->io_refcnt = 0;
340
341 return (io);
342 }
343
344 int
mdb_iob_isapipe(mdb_iob_t * iob)345 mdb_iob_isapipe(mdb_iob_t *iob)
346 {
347 mdb_io_t *io;
348
349 for (io = iob->iob_iop; io != NULL; io = io->io_next) {
350 if (io->io_ops == &pipeio_ops)
351 return (1);
352 }
353
354 return (0);
355 }
356