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#pragma ident	"%Z%%M%	%I%	%E% SMI"
27
28/*
29 * Pipe I/O Backend
30 *
31 * In order to implement dcmd pipelines, we provide a pipe i/o backend that
32 * can be used to connect two mdb_iob structures (a read and write end).
33 * This backend is selected when mdb_iob_pipe is used to construct a pair of
34 * iobs.  Each iob points at the same i/o backend (the pipe i/o), and the
35 * backend manages a circular fixed-size buffer which moves data between
36 * the reader and writer.  The caller provides read and write-side service
37 * routines that are expected to perform context switching (see mdb_context.c).
38 * The pipe implementation is relatively simple: the writer calls any of the
39 * mdb_iob_* routines to fill the write-side iob, and when this iob needs to
40 * flush data to the underlying i/o, pio_write() below is called.  This
41 * routine copies data into the pipe buffer until no more free space is
42 * available, and then calls the read-side service routine (presuming that
43 * when it returns, more free space will be available).  On the read-side,
44 * pio_read() copies data up from the pipe buffer into the read-side iob.
45 * If pio_read() is called and the pipe buffer is empty, pio_read() calls
46 * the write-side service routine to force the writer to produce more data.
47 */
48
49#include <sys/sysmacros.h>
50#include <stropts.h>
51#include <limits.h>
52
53#include <mdb/mdb.h>
54#include <mdb/mdb_modapi.h>
55#include <mdb/mdb_debug.h>
56#include <mdb/mdb_string.h>
57#include <mdb/mdb_context.h>
58#include <mdb/mdb_err.h>
59#include <mdb/mdb_io_impl.h>
60#include <mdb/mdb_frame.h>
61
62typedef struct pipe_data {
63	mdb_iobsvc_f *pipe_rdsvc;	/* Read-side service routine */
64	mdb_iob_t *pipe_rdiob;		/* Read-side i/o buffer */
65	mdb_iobsvc_f *pipe_wrsvc;	/* Write-side service routine */
66	mdb_iob_t *pipe_wriob;		/* Write-side i/o buffer */
67	char pipe_buf[BUFSIZ];		/* Ring buffer for pipe contents */
68	mdb_iob_ctx_t pipe_ctx;		/* Context data for service routines */
69	uint_t pipe_rdndx;		/* Next byte index for reading */
70	uint_t pipe_wrndx;		/* Next byte index for writing */
71	uint_t pipe_free;		/* Free space for writing in bytes */
72	uint_t pipe_used;		/* Used space for reading in bytes */
73} pipe_data_t;
74
75
76static ssize_t
77pio_read(mdb_io_t *io, void *buf, size_t nbytes)
78{
79	pipe_data_t *pd = io->io_data;
80	size_t n, nleft;
81
82	if (nbytes == 0)
83		return (0); /* return 0 for zero-length read */
84
85	for (nleft = nbytes; nleft == nbytes; nleft -= n) {
86		if (pd->pipe_used == 0) {
87			if (pd->pipe_wriob != NULL) {
88				pd->pipe_wrsvc(pd->pipe_rdiob,
89				    pd->pipe_wriob, &pd->pipe_ctx);
90			}
91			if (pd->pipe_used == 0)
92				break;
93		}
94
95		n = MIN(pd->pipe_used, nleft);
96
97		if (BUFSIZ - pd->pipe_rdndx < n) {
98			/*
99			 * Case 1: The amount to read overlaps the end of the
100			 * circular buffer.  'n1' will be the amount to copy
101			 * from the end of the buffer, and 'n2' will be the
102			 * amount to copy from the beginning.  Note that since
103			 * n <= pipe_used, it is impossible to read past
104			 * pipe_wrndx into undefined territory.
105			 */
106			size_t n1 = BUFSIZ - pd->pipe_rdndx;
107			size_t n2 = n - n1;
108
109			ASSERT(n2 <= pd->pipe_wrndx);
110			bcopy(&pd->pipe_buf[pd->pipe_rdndx], buf, n1);
111			buf = (char *)buf + n1;
112			bcopy(&pd->pipe_buf[0], buf, n2);
113			buf = (char *)buf + n2;
114		} else {
115			/*
116			 * Case 2: The easy case.  Simply copy the data over
117			 * to the buffer.
118			 */
119			bcopy(&pd->pipe_buf[pd->pipe_rdndx], buf, n);
120			buf = (char *)buf + n;
121		}
122
123		pd->pipe_rdndx = (pd->pipe_rdndx + n) % BUFSIZ;
124		pd->pipe_free += n;
125		pd->pipe_used -= n;
126	}
127
128	/*
129	 * If we have a writer, but pipe_wrsvc failed to produce any data,
130	 * we return EAGAIN.  If there is no writer, then return 0 for EOF.
131	 */
132	if (nleft == nbytes) {
133		if (pd->pipe_wriob != NULL)
134			return (set_errno(EAGAIN));
135		else
136			return (0);
137	}
138
139	return (nbytes - nleft);
140}
141
142static ssize_t
143pio_write(mdb_io_t *io, const void *buf, size_t nbytes)
144{
145	pipe_data_t *pd = io->io_data;
146	size_t n, nleft;
147
148	if (pd->pipe_rdiob == NULL)
149		return (set_errno(EPIPE)); /* fail with EPIPE if no reader */
150
151	for (nleft = nbytes; nleft != 0; nleft -= n) {
152		if (pd->pipe_free == 0) {
153			pd->pipe_rdsvc(pd->pipe_rdiob,
154			    pd->pipe_wriob, &pd->pipe_ctx);
155			if (pd->pipe_free == 0)
156				break; /* if nothing consumed by reader, exit */
157		}
158
159		n = MIN(pd->pipe_free, nleft);
160
161		if (BUFSIZ - pd->pipe_wrndx < n) {
162			/*
163			 * Case 1: The data will overlap the circular buffer
164			 * boundary. In this case, 'n1' will be the number of
165			 * bytes to put at the end of the buffer, and 'n2' will
166			 * be the number of bytes to put at the beginning.
167			 * Note that since n <= pipe_free, it is impossible to
168			 * overlap rdndx with the initial data.
169			 */
170			size_t n1 = BUFSIZ - pd->pipe_wrndx;
171			size_t n2 = n - n1;
172
173			ASSERT(n2 <= pd->pipe_rdndx);
174
175			bcopy(buf, &pd->pipe_buf[pd->pipe_wrndx], n1);
176			buf = (const char *)buf + n1;
177			bcopy(buf, &pd->pipe_buf[0], n2);
178			buf = (const char *)buf + n2;
179		} else {
180			/*
181			 * Case 2: The easy case.  Simply copy the data into
182			 * the buffer.
183			 */
184			bcopy(buf, &pd->pipe_buf[pd->pipe_wrndx], n);
185			buf = (const char *)buf + n;
186		}
187
188		pd->pipe_wrndx = (pd->pipe_wrndx + n) % BUFSIZ;
189		pd->pipe_free -= n;
190		pd->pipe_used += n;
191	}
192
193	if (nleft == nbytes && nbytes != 0)
194		return (set_errno(EAGAIN));
195
196	return (nbytes - nleft);
197}
198
199/*
200 * Provide support for STREAMS-style write-side flush ioctl.  This can be
201 * used by the caller to force a context switch to the read-side.
202 */
203static int
204pio_ctl(mdb_io_t *io, int req, void *arg)
205{
206	pipe_data_t *pd = io->io_data;
207
208	if (io->io_next != NULL)
209		return (IOP_CTL(io->io_next, req, arg));
210
211	if (req != I_FLUSH || (intptr_t)arg != FLUSHW)
212		return (set_errno(ENOTSUP));
213
214	if (pd->pipe_used != 0)
215		pd->pipe_rdsvc(pd->pipe_rdiob, pd->pipe_wriob, &pd->pipe_ctx);
216
217	return (0);
218}
219
220static void
221pio_close(mdb_io_t *io)
222{
223	mdb_free(io->io_data, sizeof (pipe_data_t));
224}
225
226/*ARGSUSED*/
227static const char *
228pio_name(mdb_io_t *io)
229{
230	return ("(pipeline)");
231}
232
233static void
234pio_link(mdb_io_t *io, mdb_iob_t *iob)
235{
236	pipe_data_t *pd = io->io_data;
237
238	/*
239	 * Here we take advantage of the IOP_LINK calls made to associate each
240	 * i/o backend with its iob to determine our read and write iobs.
241	 */
242	if (io->io_next == NULL) {
243		if (iob->iob_flags & MDB_IOB_RDONLY)
244			pd->pipe_rdiob = iob;
245		else
246			pd->pipe_wriob = iob;
247	} else
248		IOP_LINK(io->io_next, iob);
249}
250
251static void
252pio_unlink(mdb_io_t *io, mdb_iob_t *iob)
253{
254	pipe_data_t *volatile pd = io->io_data;
255
256	/*
257	 * The IOP_UNLINK call will be made when one of our associated iobs is
258	 * destroyed.  If the read-side iob is being destroyed, we simply set
259	 * pipe_rdiob to NULL, forcing subsequent pio_write() calls to fail
260	 * with EPIPE.  Things are more complicated when the write-side is
261	 * being destroyed.  If this is the last close prior to destroying the
262	 * pipe, we need to arrange for any in-transit data to be consumed by
263	 * the reader.  We first set pipe_wriob to NULL, which forces pio_read
264	 * to return EOF when all in-transit data is consumed.  We then call
265	 * the read-service routine while there is still a reader and pipe_used
266	 * is non-zero, indicating there is still data in the pipe.
267	 */
268	if (io->io_next == NULL) {
269		if (pd->pipe_wriob == iob) {
270			pd->pipe_wriob = NULL;	/* remove writer */
271
272			if (pd->pipe_used == 0 && pd->pipe_ctx.ctx_data == NULL)
273				return;	/* no reader and nothing to read */
274
275			/*
276			 * Note that we need to use a do-while construct here
277			 * so that we resume the reader's context at *least*
278			 * once.  This forces it to read EOF and exit even if
279			 * the pipeline is already completely flushed.
280			 */
281			do {
282				if (pd->pipe_rdiob == NULL)
283					break;
284				if (mdb_iob_err(pd->pipe_rdiob) != 0) {
285					if (pd->pipe_ctx.ctx_wptr != NULL) {
286						mdb_frame_pop(
287						    pd->pipe_ctx.ctx_wptr,
288						    MDB_ERR_ABORT);
289						pd->pipe_ctx.ctx_wptr = NULL;
290					}
291					break; /* don't read if error bit set */
292				}
293				if (pd->pipe_ctx.ctx_data == NULL ||
294				    setjmp(*mdb_context_getpcb(
295				    pd->pipe_ctx.ctx_data)) == 0) {
296					pd->pipe_rdsvc(pd->pipe_rdiob,
297					    pd->pipe_wriob, &pd->pipe_ctx);
298				}
299
300			} while (pd->pipe_used != 0);
301
302			if (pd->pipe_ctx.ctx_data != NULL) {
303				mdb_context_destroy(pd->pipe_ctx.ctx_data);
304				pd->pipe_ctx.ctx_data = NULL;
305			}
306
307		} else if (pd->pipe_rdiob == iob)
308			pd->pipe_rdiob = NULL; /* remove reader */
309	} else
310		IOP_UNLINK(io->io_next, iob);
311}
312
313static const mdb_io_ops_t pipeio_ops = {
314	pio_read,
315	pio_write,
316	no_io_seek,
317	pio_ctl,
318	pio_close,
319	pio_name,
320	pio_link,
321	pio_unlink,
322	no_io_setattr,
323	no_io_suspend,
324	no_io_resume
325};
326
327mdb_io_t *
328mdb_pipeio_create(mdb_iobsvc_f *rdsvc, mdb_iobsvc_f *wrsvc)
329{
330	mdb_io_t *io = mdb_alloc(sizeof (mdb_io_t), UM_SLEEP);
331	pipe_data_t *pd = mdb_zalloc(sizeof (pipe_data_t), UM_SLEEP);
332
333	ASSERT(rdsvc != NULL && wrsvc != NULL);
334	pd->pipe_rdsvc = rdsvc;
335	pd->pipe_wrsvc = wrsvc;
336	pd->pipe_free = BUFSIZ;
337
338	io->io_ops = &pipeio_ops;
339	io->io_data = pd;
340	io->io_next = NULL;
341	io->io_refcnt = 0;
342
343	return (io);
344}
345
346int
347mdb_iob_isapipe(mdb_iob_t *iob)
348{
349	mdb_io_t *io;
350
351	for (io = iob->iob_iop; io != NULL; io = io->io_next) {
352		if (io->io_ops == &pipeio_ops)
353			return (1);
354	}
355
356	return (0);
357}
358