xref: /openbmc/qemu/util/iov.c (revision e2d05011)
1 /*
2  * Helpers for getting linearized buffers from iov / filling buffers into iovs
3  *
4  * Copyright IBM, Corp. 2007, 2008
5  * Copyright (C) 2010 Red Hat, Inc.
6  *
7  * Author(s):
8  *  Anthony Liguori <aliguori@us.ibm.com>
9  *  Amit Shah <amit.shah@redhat.com>
10  *  Michael Tokarev <mjt@tls.msk.ru>
11  *
12  * This work is licensed under the terms of the GNU GPL, version 2.  See
13  * the COPYING file in the top-level directory.
14  *
15  * Contributions after 2012-01-13 are licensed under the terms of the
16  * GNU GPL, version 2 or (at your option) any later version.
17  */
18 
19 #include "qemu/iov.h"
20 #include "qemu/sockets.h"
21 
22 size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
23                     size_t offset, const void *buf, size_t bytes)
24 {
25     size_t done;
26     unsigned int i;
27     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
28         if (offset < iov[i].iov_len) {
29             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
30             memcpy(iov[i].iov_base + offset, buf + done, len);
31             done += len;
32             offset = 0;
33         } else {
34             offset -= iov[i].iov_len;
35         }
36     }
37     assert(offset == 0);
38     return done;
39 }
40 
41 size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
42                   size_t offset, void *buf, size_t bytes)
43 {
44     size_t done;
45     unsigned int i;
46     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
47         if (offset < iov[i].iov_len) {
48             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
49             memcpy(buf + done, iov[i].iov_base + offset, len);
50             done += len;
51             offset = 0;
52         } else {
53             offset -= iov[i].iov_len;
54         }
55     }
56     assert(offset == 0);
57     return done;
58 }
59 
60 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
61                   size_t offset, int fillc, size_t bytes)
62 {
63     size_t done;
64     unsigned int i;
65     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
66         if (offset < iov[i].iov_len) {
67             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
68             memset(iov[i].iov_base + offset, fillc, len);
69             done += len;
70             offset = 0;
71         } else {
72             offset -= iov[i].iov_len;
73         }
74     }
75     assert(offset == 0);
76     return done;
77 }
78 
79 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
80 {
81     size_t len;
82     unsigned int i;
83 
84     len = 0;
85     for (i = 0; i < iov_cnt; i++) {
86         len += iov[i].iov_len;
87     }
88     return len;
89 }
90 
91 /* helper function for iov_send_recv() */
92 static ssize_t
93 do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
94 {
95 #ifdef CONFIG_POSIX
96     ssize_t ret;
97     struct msghdr msg;
98     memset(&msg, 0, sizeof(msg));
99     msg.msg_iov = iov;
100     msg.msg_iovlen = iov_cnt;
101     do {
102         ret = do_send
103             ? sendmsg(sockfd, &msg, 0)
104             : recvmsg(sockfd, &msg, 0);
105     } while (ret < 0 && errno == EINTR);
106     return ret;
107 #else
108     /* else send piece-by-piece */
109     /*XXX Note: windows has WSASend() and WSARecv() */
110     unsigned i = 0;
111     ssize_t ret = 0;
112     while (i < iov_cnt) {
113         ssize_t r = do_send
114             ? send(sockfd, iov[i].iov_base, iov[i].iov_len, 0)
115             : recv(sockfd, iov[i].iov_base, iov[i].iov_len, 0);
116         if (r > 0) {
117             ret += r;
118         } else if (!r) {
119             break;
120         } else if (errno == EINTR) {
121             continue;
122         } else {
123             /* else it is some "other" error,
124              * only return if there was no data processed. */
125             if (ret == 0) {
126                 ret = -1;
127             }
128             break;
129         }
130         i++;
131     }
132     return ret;
133 #endif
134 }
135 
136 ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
137                       size_t offset, size_t bytes,
138                       bool do_send)
139 {
140     ssize_t total = 0;
141     ssize_t ret;
142     size_t orig_len, tail;
143     unsigned niov;
144 
145     while (bytes > 0) {
146         /* Find the start position, skipping `offset' bytes:
147          * first, skip all full-sized vector elements, */
148         for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
149             offset -= iov[niov].iov_len;
150         }
151 
152         /* niov == iov_cnt would only be valid if bytes == 0, which
153          * we already ruled out in the loop condition.  */
154         assert(niov < iov_cnt);
155         iov += niov;
156         iov_cnt -= niov;
157 
158         if (offset) {
159             /* second, skip `offset' bytes from the (now) first element,
160              * undo it on exit */
161             iov[0].iov_base += offset;
162             iov[0].iov_len -= offset;
163         }
164         /* Find the end position skipping `bytes' bytes: */
165         /* first, skip all full-sized elements */
166         tail = bytes;
167         for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
168             tail -= iov[niov].iov_len;
169         }
170         if (tail) {
171             /* second, fixup the last element, and remember the original
172              * length */
173             assert(niov < iov_cnt);
174             assert(iov[niov].iov_len > tail);
175             orig_len = iov[niov].iov_len;
176             iov[niov++].iov_len = tail;
177             ret = do_send_recv(sockfd, iov, niov, do_send);
178             /* Undo the changes above before checking for errors */
179             iov[niov-1].iov_len = orig_len;
180         } else {
181             ret = do_send_recv(sockfd, iov, niov, do_send);
182         }
183         if (offset) {
184             iov[0].iov_base -= offset;
185             iov[0].iov_len += offset;
186         }
187 
188         if (ret < 0) {
189             assert(errno != EINTR);
190             if (errno == EAGAIN && total > 0) {
191                 return total;
192             }
193             return -1;
194         }
195 
196         if (ret == 0 && !do_send) {
197             /* recv returns 0 when the peer has performed an orderly
198              * shutdown. */
199             break;
200         }
201 
202         /* Prepare for the next iteration */
203         offset += ret;
204         total += ret;
205         bytes -= ret;
206     }
207 
208     return total;
209 }
210 
211 
212 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
213                  FILE *fp, const char *prefix, size_t limit)
214 {
215     int v;
216     size_t size = 0;
217     char *buf;
218 
219     for (v = 0; v < iov_cnt; v++) {
220         size += iov[v].iov_len;
221     }
222     size = size > limit ? limit : size;
223     buf = g_malloc(size);
224     iov_to_buf(iov, iov_cnt, 0, buf, size);
225     qemu_hexdump(buf, fp, prefix, size);
226     g_free(buf);
227 }
228 
229 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
230                  const struct iovec *iov, unsigned int iov_cnt,
231                  size_t offset, size_t bytes)
232 {
233     size_t len;
234     unsigned int i, j;
235     for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
236         if (offset >= iov[i].iov_len) {
237             offset -= iov[i].iov_len;
238             continue;
239         }
240         len = MIN(bytes, iov[i].iov_len - offset);
241 
242         dst_iov[j].iov_base = iov[i].iov_base + offset;
243         dst_iov[j].iov_len = len;
244         j++;
245         bytes -= len;
246         offset = 0;
247     }
248     assert(offset == 0);
249     return j;
250 }
251 
252 /* io vectors */
253 
254 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
255 {
256     qiov->iov = g_malloc(alloc_hint * sizeof(struct iovec));
257     qiov->niov = 0;
258     qiov->nalloc = alloc_hint;
259     qiov->size = 0;
260 }
261 
262 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
263 {
264     int i;
265 
266     qiov->iov = iov;
267     qiov->niov = niov;
268     qiov->nalloc = -1;
269     qiov->size = 0;
270     for (i = 0; i < niov; i++)
271         qiov->size += iov[i].iov_len;
272 }
273 
274 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
275 {
276     assert(qiov->nalloc != -1);
277 
278     if (qiov->niov == qiov->nalloc) {
279         qiov->nalloc = 2 * qiov->nalloc + 1;
280         qiov->iov = g_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
281     }
282     qiov->iov[qiov->niov].iov_base = base;
283     qiov->iov[qiov->niov].iov_len = len;
284     qiov->size += len;
285     ++qiov->niov;
286 }
287 
288 /*
289  * Concatenates (partial) iovecs from src_iov to the end of dst.
290  * It starts copying after skipping `soffset' bytes at the
291  * beginning of src and adds individual vectors from src to
292  * dst copies up to `sbytes' bytes total, or up to the end
293  * of src_iov if it comes first.  This way, it is okay to specify
294  * very large value for `sbytes' to indicate "up to the end
295  * of src".
296  * Only vector pointers are processed, not the actual data buffers.
297  */
298 size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
299                              struct iovec *src_iov, unsigned int src_cnt,
300                              size_t soffset, size_t sbytes)
301 {
302     int i;
303     size_t done;
304 
305     if (!sbytes) {
306         return 0;
307     }
308     assert(dst->nalloc != -1);
309     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
310         if (soffset < src_iov[i].iov_len) {
311             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
312             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
313             done += len;
314             soffset = 0;
315         } else {
316             soffset -= src_iov[i].iov_len;
317         }
318     }
319     assert(soffset == 0); /* offset beyond end of src */
320 
321     return done;
322 }
323 
324 /*
325  * Concatenates (partial) iovecs from src to the end of dst.
326  * It starts copying after skipping `soffset' bytes at the
327  * beginning of src and adds individual vectors from src to
328  * dst copies up to `sbytes' bytes total, or up to the end
329  * of src if it comes first.  This way, it is okay to specify
330  * very large value for `sbytes' to indicate "up to the end
331  * of src".
332  * Only vector pointers are processed, not the actual data buffers.
333  */
334 void qemu_iovec_concat(QEMUIOVector *dst,
335                        QEMUIOVector *src, size_t soffset, size_t sbytes)
336 {
337     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
338 }
339 
340 /*
341  * Check if the contents of the iovecs are all zero
342  */
343 bool qemu_iovec_is_zero(QEMUIOVector *qiov)
344 {
345     int i;
346     for (i = 0; i < qiov->niov; i++) {
347         size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
348         uint8_t *ptr = qiov->iov[i].iov_base;
349         if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
350             return false;
351         }
352         for (; offs < qiov->iov[i].iov_len; offs++) {
353             if (ptr[offs]) {
354                 return false;
355             }
356         }
357     }
358     return true;
359 }
360 
361 void qemu_iovec_destroy(QEMUIOVector *qiov)
362 {
363     assert(qiov->nalloc != -1);
364 
365     qemu_iovec_reset(qiov);
366     g_free(qiov->iov);
367     qiov->nalloc = 0;
368     qiov->iov = NULL;
369 }
370 
371 void qemu_iovec_reset(QEMUIOVector *qiov)
372 {
373     assert(qiov->nalloc != -1);
374 
375     qiov->niov = 0;
376     qiov->size = 0;
377 }
378 
379 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
380                          void *buf, size_t bytes)
381 {
382     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
383 }
384 
385 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
386                            const void *buf, size_t bytes)
387 {
388     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
389 }
390 
391 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
392                          int fillc, size_t bytes)
393 {
394     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
395 }
396 
397 /**
398  * Check that I/O vector contents are identical
399  *
400  * The IO vectors must have the same structure (same length of all parts).
401  * A typical usage is to compare vectors created with qemu_iovec_clone().
402  *
403  * @a:          I/O vector
404  * @b:          I/O vector
405  * @ret:        Offset to first mismatching byte or -1 if match
406  */
407 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
408 {
409     int i;
410     ssize_t offset = 0;
411 
412     assert(a->niov == b->niov);
413     for (i = 0; i < a->niov; i++) {
414         size_t len = 0;
415         uint8_t *p = (uint8_t *)a->iov[i].iov_base;
416         uint8_t *q = (uint8_t *)b->iov[i].iov_base;
417 
418         assert(a->iov[i].iov_len == b->iov[i].iov_len);
419         while (len < a->iov[i].iov_len && *p++ == *q++) {
420             len++;
421         }
422 
423         offset += len;
424 
425         if (len != a->iov[i].iov_len) {
426             return offset;
427         }
428     }
429     return -1;
430 }
431 
432 typedef struct {
433     int src_index;
434     struct iovec *src_iov;
435     void *dest_base;
436 } IOVectorSortElem;
437 
438 static int sortelem_cmp_src_base(const void *a, const void *b)
439 {
440     const IOVectorSortElem *elem_a = a;
441     const IOVectorSortElem *elem_b = b;
442 
443     /* Don't overflow */
444     if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
445         return -1;
446     } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
447         return 1;
448     } else {
449         return 0;
450     }
451 }
452 
453 static int sortelem_cmp_src_index(const void *a, const void *b)
454 {
455     const IOVectorSortElem *elem_a = a;
456     const IOVectorSortElem *elem_b = b;
457 
458     return elem_a->src_index - elem_b->src_index;
459 }
460 
461 /**
462  * Copy contents of I/O vector
463  *
464  * The relative relationships of overlapping iovecs are preserved.  This is
465  * necessary to ensure identical semantics in the cloned I/O vector.
466  */
467 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
468 {
469     IOVectorSortElem sortelems[src->niov];
470     void *last_end;
471     int i;
472 
473     /* Sort by source iovecs by base address */
474     for (i = 0; i < src->niov; i++) {
475         sortelems[i].src_index = i;
476         sortelems[i].src_iov = &src->iov[i];
477     }
478     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
479 
480     /* Allocate buffer space taking into account overlapping iovecs */
481     last_end = NULL;
482     for (i = 0; i < src->niov; i++) {
483         struct iovec *cur = sortelems[i].src_iov;
484         ptrdiff_t rewind = 0;
485 
486         /* Detect overlap */
487         if (last_end && last_end > cur->iov_base) {
488             rewind = last_end - cur->iov_base;
489         }
490 
491         sortelems[i].dest_base = buf - rewind;
492         buf += cur->iov_len - MIN(rewind, cur->iov_len);
493         last_end = MAX(cur->iov_base + cur->iov_len, last_end);
494     }
495 
496     /* Sort by source iovec index and build destination iovec */
497     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
498     for (i = 0; i < src->niov; i++) {
499         qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
500     }
501 }
502 
503 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
504                          size_t bytes)
505 {
506     size_t total = 0;
507     struct iovec *cur;
508 
509     for (cur = *iov; *iov_cnt > 0; cur++) {
510         if (cur->iov_len > bytes) {
511             cur->iov_base += bytes;
512             cur->iov_len -= bytes;
513             total += bytes;
514             break;
515         }
516 
517         bytes -= cur->iov_len;
518         total += cur->iov_len;
519         *iov_cnt -= 1;
520     }
521 
522     *iov = cur;
523     return total;
524 }
525 
526 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
527                         size_t bytes)
528 {
529     size_t total = 0;
530     struct iovec *cur;
531 
532     if (*iov_cnt == 0) {
533         return 0;
534     }
535 
536     cur = iov + (*iov_cnt - 1);
537 
538     while (*iov_cnt > 0) {
539         if (cur->iov_len > bytes) {
540             cur->iov_len -= bytes;
541             total += bytes;
542             break;
543         }
544 
545         bytes -= cur->iov_len;
546         total += cur->iov_len;
547         cur--;
548         *iov_cnt -= 1;
549     }
550 
551     return total;
552 }
553 
554 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
555 {
556     size_t total;
557     unsigned int niov = qiov->niov;
558 
559     assert(qiov->size >= bytes);
560     total = iov_discard_back(qiov->iov, &niov, bytes);
561     assert(total == bytes);
562 
563     qiov->niov = niov;
564     qiov->size -= bytes;
565 }
566