qemu

iov.c (20660B)

---

 /*
  * Helpers for getting linearized buffers from iov / filling buffers into iovs
  *
  * Copyright IBM, Corp. 2007, 2008
  * Copyright (C) 2010 Red Hat, Inc.
  *
  * Author(s):
  *  Anthony Liguori <aliguori@us.ibm.com>
  *  Amit Shah <amit.shah@redhat.com>
  *  Michael Tokarev <mjt@tls.msk.ru>
  *
  * This work is licensed under the terms of the GNU GPL, version 2.  See
  * the COPYING file in the top-level directory.
  *
  * Contributions after 2012-01-13 are licensed under the terms of the
  * GNU GPL, version 2 or (at your option) any later version.
  */
 
 #include "qemu/osdep.h"
 #include "qemu/iov.h"
 #include "qemu/sockets.h"
 #include "qemu/cutils.h"
 
 size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
                          size_t offset, const void *buf, size_t bytes)
 {
     size_t done;
     unsigned int i;
     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
         if (offset < iov[i].iov_len) {
             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
             memcpy(iov[i].iov_base + offset, buf + done, len);
             done += len;
             offset = 0;
         } else {
             offset -= iov[i].iov_len;
         }
     }
     assert(offset == 0);
     return done;
 }
 
 size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
                        size_t offset, void *buf, size_t bytes)
 {
     size_t done;
     unsigned int i;
     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
         if (offset < iov[i].iov_len) {
             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
             memcpy(buf + done, iov[i].iov_base + offset, len);
             done += len;
             offset = 0;
         } else {
             offset -= iov[i].iov_len;
         }
     }
     assert(offset == 0);
     return done;
 }
 
 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
                   size_t offset, int fillc, size_t bytes)
 {
     size_t done;
     unsigned int i;
     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
         if (offset < iov[i].iov_len) {
             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
             memset(iov[i].iov_base + offset, fillc, len);
             done += len;
             offset = 0;
         } else {
             offset -= iov[i].iov_len;
         }
     }
     assert(offset == 0);
     return done;
 }
 
 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
 {
     size_t len;
     unsigned int i;
 
     len = 0;
     for (i = 0; i < iov_cnt; i++) {
         len += iov[i].iov_len;
     }
     return len;
 }
 
 /* helper function for iov_send_recv() */
 static ssize_t
 do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
 {
 #ifdef CONFIG_POSIX
     ssize_t ret;
     struct msghdr msg;
     memset(&msg, 0, sizeof(msg));
     msg.msg_iov = iov;
     msg.msg_iovlen = iov_cnt;
     do {
         ret = do_send
             ? sendmsg(sockfd, &msg, 0)
             : recvmsg(sockfd, &msg, 0);
     } while (ret < 0 && errno == EINTR);
     return ret;
 #else
     /* else send piece-by-piece */
     /*XXX Note: windows has WSASend() and WSARecv() */
     unsigned i = 0;
     ssize_t ret = 0;
     ssize_t off = 0;
     while (i < iov_cnt) {
         ssize_t r = do_send
             ? send(sockfd, iov[i].iov_base + off, iov[i].iov_len - off, 0)
             : recv(sockfd, iov[i].iov_base + off, iov[i].iov_len - off, 0);
         if (r > 0) {
             ret += r;
             off += r;
             if (off < iov[i].iov_len) {
                 continue;
             }
         } else if (!r) {
             break;
         } else if (errno == EINTR) {
             continue;
         } else {
             /* else it is some "other" error,
              * only return if there was no data processed. */
             if (ret == 0) {
                 ret = -1;
             }
             break;
         }
         off = 0;
         i++;
     }
     return ret;
 #endif
 }
 
 ssize_t iov_send_recv(int sockfd, const struct iovec *_iov, unsigned iov_cnt,
                       size_t offset, size_t bytes,
                       bool do_send)
 {
     ssize_t total = 0;
     ssize_t ret;
     size_t orig_len, tail;
     unsigned niov;
     struct iovec *local_iov, *iov;
 
     if (bytes <= 0) {
         return 0;
     }
 
     local_iov = g_new0(struct iovec, iov_cnt);
     iov_copy(local_iov, iov_cnt, _iov, iov_cnt, offset, bytes);
     offset = 0;
     iov = local_iov;
 
     while (bytes > 0) {
         /* Find the start position, skipping `offset' bytes:
          * first, skip all full-sized vector elements, */
         for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
             offset -= iov[niov].iov_len;
         }
 
         /* niov == iov_cnt would only be valid if bytes == 0, which
          * we already ruled out in the loop condition.  */
         assert(niov < iov_cnt);
         iov += niov;
         iov_cnt -= niov;
 
         if (offset) {
             /* second, skip `offset' bytes from the (now) first element,
              * undo it on exit */
             iov[0].iov_base += offset;
             iov[0].iov_len -= offset;
         }
         /* Find the end position skipping `bytes' bytes: */
         /* first, skip all full-sized elements */
         tail = bytes;
         for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
             tail -= iov[niov].iov_len;
         }
         if (tail) {
             /* second, fixup the last element, and remember the original
              * length */
             assert(niov < iov_cnt);
             assert(iov[niov].iov_len > tail);
             orig_len = iov[niov].iov_len;
             iov[niov++].iov_len = tail;
             ret = do_send_recv(sockfd, iov, niov, do_send);
             /* Undo the changes above before checking for errors */
             iov[niov-1].iov_len = orig_len;
         } else {
             ret = do_send_recv(sockfd, iov, niov, do_send);
         }
         if (offset) {
             iov[0].iov_base -= offset;
             iov[0].iov_len += offset;
         }
 
         if (ret < 0) {
             assert(errno != EINTR);
             g_free(local_iov);
             if (errno == EAGAIN && total > 0) {
                 return total;
             }
             return -1;
         }
 
         if (ret == 0 && !do_send) {
             /* recv returns 0 when the peer has performed an orderly
              * shutdown. */
             break;
         }
 
         /* Prepare for the next iteration */
         offset += ret;
         total += ret;
         bytes -= ret;
     }
 
     g_free(local_iov);
     return total;
 }
 
 
 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
                  FILE *fp, const char *prefix, size_t limit)
 {
     int v;
     size_t size = 0;
     char *buf;
 
     for (v = 0; v < iov_cnt; v++) {
         size += iov[v].iov_len;
     }
     size = size > limit ? limit : size;
     buf = g_malloc(size);
     iov_to_buf(iov, iov_cnt, 0, buf, size);
     qemu_hexdump(fp, prefix, buf, size);
     g_free(buf);
 }
 
 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
                  const struct iovec *iov, unsigned int iov_cnt,
                  size_t offset, size_t bytes)
 {
     size_t len;
     unsigned int i, j;
     for (i = 0, j = 0;
          i < iov_cnt && j < dst_iov_cnt && (offset || bytes); i++) {
         if (offset >= iov[i].iov_len) {
             offset -= iov[i].iov_len;
             continue;
         }
         len = MIN(bytes, iov[i].iov_len - offset);
 
         dst_iov[j].iov_base = iov[i].iov_base + offset;
         dst_iov[j].iov_len = len;
         j++;
         bytes -= len;
         offset = 0;
     }
     assert(offset == 0);
     return j;
 }
 
 /* io vectors */
 
 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
 {
     qiov->iov = g_new(struct iovec, alloc_hint);
     qiov->niov = 0;
     qiov->nalloc = alloc_hint;
     qiov->size = 0;
 }
 
 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
 {
     int i;
 
     qiov->iov = iov;
     qiov->niov = niov;
     qiov->nalloc = -1;
     qiov->size = 0;
     for (i = 0; i < niov; i++)
         qiov->size += iov[i].iov_len;
 }
 
 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 {
     assert(qiov->nalloc != -1);
 
     if (qiov->niov == qiov->nalloc) {
         qiov->nalloc = 2 * qiov->nalloc + 1;
         qiov->iov = g_renew(struct iovec, qiov->iov, qiov->nalloc);
     }
     qiov->iov[qiov->niov].iov_base = base;
     qiov->iov[qiov->niov].iov_len = len;
     qiov->size += len;
     ++qiov->niov;
 }
 
 /*
  * Concatenates (partial) iovecs from src_iov to the end of dst.
  * It starts copying after skipping `soffset' bytes at the
  * beginning of src and adds individual vectors from src to
  * dst copies up to `sbytes' bytes total, or up to the end
  * of src_iov if it comes first.  This way, it is okay to specify
  * very large value for `sbytes' to indicate "up to the end
  * of src".
  * Only vector pointers are processed, not the actual data buffers.
  */
 size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
                              struct iovec *src_iov, unsigned int src_cnt,
                              size_t soffset, size_t sbytes)
 {
     int i;
     size_t done;
 
     if (!sbytes) {
         return 0;
     }
     assert(dst->nalloc != -1);
     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
         if (soffset < src_iov[i].iov_len) {
             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
             done += len;
             soffset = 0;
         } else {
             soffset -= src_iov[i].iov_len;
         }
     }
     assert(soffset == 0); /* offset beyond end of src */
 
     return done;
 }
 
 /*
  * Concatenates (partial) iovecs from src to the end of dst.
  * It starts copying after skipping `soffset' bytes at the
  * beginning of src and adds individual vectors from src to
  * dst copies up to `sbytes' bytes total, or up to the end
  * of src if it comes first.  This way, it is okay to specify
  * very large value for `sbytes' to indicate "up to the end
  * of src".
  * Only vector pointers are processed, not the actual data buffers.
  */
 void qemu_iovec_concat(QEMUIOVector *dst,
                        QEMUIOVector *src, size_t soffset, size_t sbytes)
 {
     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 }
 
 /*
  * qiov_find_iov
  *
  * Return pointer to iovec structure, where byte at @offset in original vector
  * @iov exactly is.
  * Set @remaining_offset to be offset inside that iovec to the same byte.
  */
 static struct iovec *iov_skip_offset(struct iovec *iov, size_t offset,
                                      size_t *remaining_offset)
 {
     while (offset > 0 && offset >= iov->iov_len) {
         offset -= iov->iov_len;
         iov++;
     }
     *remaining_offset = offset;
 
     return iov;
 }
 
 /*
  * qiov_slice
  *
  * Find subarray of iovec's, containing requested range. @head would
  * be offset in first iov (returned by the function), @tail would be
  * count of extra bytes in last iovec (returned iov + @niov - 1).
  */
 static struct iovec *qiov_slice(QEMUIOVector *qiov,
                                 size_t offset, size_t len,
                                 size_t *head, size_t *tail, int *niov)
 {
     struct iovec *iov, *end_iov;
 
     assert(offset + len <= qiov->size);
 
     iov = iov_skip_offset(qiov->iov, offset, head);
     end_iov = iov_skip_offset(iov, *head + len, tail);
 
     if (*tail > 0) {
         assert(*tail < end_iov->iov_len);
         *tail = end_iov->iov_len - *tail;
         end_iov++;
     }
 
     *niov = end_iov - iov;
 
     return iov;
 }
 
 int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len)
 {
     size_t head, tail;
     int niov;
 
     qiov_slice(qiov, offset, len, &head, &tail, &niov);
 
     return niov;
 }
 
 /*
  * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,
  * and @tail_buf buffer into new qiov.
  */
 int qemu_iovec_init_extended(
         QEMUIOVector *qiov,
         void *head_buf, size_t head_len,
         QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
         void *tail_buf, size_t tail_len)
 {
     size_t mid_head, mid_tail;
     int total_niov, mid_niov = 0;
     struct iovec *p, *mid_iov = NULL;
 
     assert(mid_qiov->niov <= IOV_MAX);
 
     if (SIZE_MAX - head_len < mid_len ||
         SIZE_MAX - head_len - mid_len < tail_len)
     {
         return -EINVAL;
     }
 
     if (mid_len) {
         mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len,
                              &mid_head, &mid_tail, &mid_niov);
     }
 
     total_niov = !!head_len + mid_niov + !!tail_len;
     if (total_niov > IOV_MAX) {
         return -EINVAL;
     }
 
     if (total_niov == 1) {
         qemu_iovec_init_buf(qiov, NULL, 0);
         p = &qiov->local_iov;
     } else {
         qiov->niov = qiov->nalloc = total_niov;
         qiov->size = head_len + mid_len + tail_len;
         p = qiov->iov = g_new(struct iovec, qiov->niov);
     }
 
     if (head_len) {
         p->iov_base = head_buf;
         p->iov_len = head_len;
         p++;
     }
 
     assert(!mid_niov == !mid_len);
     if (mid_niov) {
         memcpy(p, mid_iov, mid_niov * sizeof(*p));
         p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head;
         p[0].iov_len -= mid_head;
         p[mid_niov - 1].iov_len -= mid_tail;
         p += mid_niov;
     }
 
     if (tail_len) {
         p->iov_base = tail_buf;
         p->iov_len = tail_len;
     }
 
     return 0;
 }
 
 /*
  * Check if the contents of subrange of qiov data is all zeroes.
  */
 bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes)
 {
     struct iovec *iov;
     size_t current_offset;
 
     assert(offset + bytes <= qiov->size);
 
     iov = iov_skip_offset(qiov->iov, offset, &current_offset);
 
     while (bytes) {
         uint8_t *base = (uint8_t *)iov->iov_base + current_offset;
         size_t len = MIN(iov->iov_len - current_offset, bytes);
 
         if (!buffer_is_zero(base, len)) {
             return false;
         }
 
         current_offset = 0;
         bytes -= len;
         iov++;
     }
 
     return true;
 }
 
 void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
                            size_t offset, size_t len)
 {
     int ret;
 
     assert(source->size >= len);
     assert(source->size - len >= offset);
 
     /* We shrink the request, so we can't overflow neither size_t nor MAX_IOV */
     ret = qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
     assert(ret == 0);
 }
 
 void qemu_iovec_destroy(QEMUIOVector *qiov)
 {
     if (qiov->nalloc != -1) {
         g_free(qiov->iov);
     }
 
     memset(qiov, 0, sizeof(*qiov));
 }
 
 void qemu_iovec_reset(QEMUIOVector *qiov)
 {
     assert(qiov->nalloc != -1);
 
     qiov->niov = 0;
     qiov->size = 0;
 }
 
 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
                          void *buf, size_t bytes)
 {
     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 }
 
 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
                            const void *buf, size_t bytes)
 {
     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 }
 
 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
                          int fillc, size_t bytes)
 {
     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 }
 
 /**
  * Check that I/O vector contents are identical
  *
  * The IO vectors must have the same structure (same length of all parts).
  * A typical usage is to compare vectors created with qemu_iovec_clone().
  *
  * @a:          I/O vector
  * @b:          I/O vector
  * @ret:        Offset to first mismatching byte or -1 if match
  */
 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
 {
     int i;
     ssize_t offset = 0;
 
     assert(a->niov == b->niov);
     for (i = 0; i < a->niov; i++) {
         size_t len = 0;
         uint8_t *p = (uint8_t *)a->iov[i].iov_base;
         uint8_t *q = (uint8_t *)b->iov[i].iov_base;
 
         assert(a->iov[i].iov_len == b->iov[i].iov_len);
         while (len < a->iov[i].iov_len && *p++ == *q++) {
             len++;
         }
 
         offset += len;
 
         if (len != a->iov[i].iov_len) {
             return offset;
         }
     }
     return -1;
 }
 
 typedef struct {
     int src_index;
     struct iovec *src_iov;
     void *dest_base;
 } IOVectorSortElem;
 
 static int sortelem_cmp_src_base(const void *a, const void *b)
 {
     const IOVectorSortElem *elem_a = a;
     const IOVectorSortElem *elem_b = b;
 
     /* Don't overflow */
     if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
         return -1;
     } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
         return 1;
     } else {
         return 0;
     }
 }
 
 static int sortelem_cmp_src_index(const void *a, const void *b)
 {
     const IOVectorSortElem *elem_a = a;
     const IOVectorSortElem *elem_b = b;
 
     return elem_a->src_index - elem_b->src_index;
 }
 
 /**
  * Copy contents of I/O vector
  *
  * The relative relationships of overlapping iovecs are preserved.  This is
  * necessary to ensure identical semantics in the cloned I/O vector.
  */
 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
 {
     IOVectorSortElem sortelems[src->niov];
     void *last_end;
     int i;
 
     /* Sort by source iovecs by base address */
     for (i = 0; i < src->niov; i++) {
         sortelems[i].src_index = i;
         sortelems[i].src_iov = &src->iov[i];
     }
     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
 
     /* Allocate buffer space taking into account overlapping iovecs */
     last_end = NULL;
     for (i = 0; i < src->niov; i++) {
         struct iovec *cur = sortelems[i].src_iov;
         ptrdiff_t rewind = 0;
 
         /* Detect overlap */
         if (last_end && last_end > cur->iov_base) {
             rewind = last_end - cur->iov_base;
         }
 
         sortelems[i].dest_base = buf - rewind;
         buf += cur->iov_len - MIN(rewind, cur->iov_len);
         last_end = MAX(cur->iov_base + cur->iov_len, last_end);
     }
 
     /* Sort by source iovec index and build destination iovec */
     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
     for (i = 0; i < src->niov; i++) {
         qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
     }
 }
 
 void iov_discard_undo(IOVDiscardUndo *undo)
 {
     /* Restore original iovec if it was modified */
     if (undo->modified_iov) {
         *undo->modified_iov = undo->orig;
     }
 }
 
 size_t iov_discard_front_undoable(struct iovec **iov,
                                   unsigned int *iov_cnt,
                                   size_t bytes,
                                   IOVDiscardUndo *undo)
 {
     size_t total = 0;
     struct iovec *cur;
 
     if (undo) {
         undo->modified_iov = NULL;
     }
 
     for (cur = *iov; *iov_cnt > 0; cur++) {
         if (cur->iov_len > bytes) {
             if (undo) {
                 undo->modified_iov = cur;
                 undo->orig = *cur;
             }
 
             cur->iov_base += bytes;
             cur->iov_len -= bytes;
             total += bytes;
             break;
         }
 
         bytes -= cur->iov_len;
         total += cur->iov_len;
         *iov_cnt -= 1;
     }
 
     *iov = cur;
     return total;
 }
 
 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
                          size_t bytes)
 {
     return iov_discard_front_undoable(iov, iov_cnt, bytes, NULL);
 }
 
 size_t iov_discard_back_undoable(struct iovec *iov,
                                  unsigned int *iov_cnt,
                                  size_t bytes,
                                  IOVDiscardUndo *undo)
 {
     size_t total = 0;
     struct iovec *cur;
 
     if (undo) {
         undo->modified_iov = NULL;
     }
 
     if (*iov_cnt == 0) {
         return 0;
     }
 
     cur = iov + (*iov_cnt - 1);
 
     while (*iov_cnt > 0) {
         if (cur->iov_len > bytes) {
             if (undo) {
                 undo->modified_iov = cur;
                 undo->orig = *cur;
             }
 
             cur->iov_len -= bytes;
             total += bytes;
             break;
         }
 
         bytes -= cur->iov_len;
         total += cur->iov_len;
         cur--;
         *iov_cnt -= 1;
     }
 
     return total;
 }
 
 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
                         size_t bytes)
 {
     return iov_discard_back_undoable(iov, iov_cnt, bytes, NULL);
 }
 
 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
 {
     size_t total;
     unsigned int niov = qiov->niov;
 
     assert(qiov->size >= bytes);
     total = iov_discard_back(qiov->iov, &niov, bytes);
     assert(total == bytes);
 
     qiov->niov = niov;
     qiov->size -= bytes;
 }