[PATCH 3/4] xenguest: Allows writev_exact to change iov array

[Frediano Ziglio <freddy77@xxxxxxxxx>]

From: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>

Avoid having to allocate and copy the array if a partial write
happens.
The implementation in tools/libs/store/xs.c already use this
signature and method.

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
---
 tools/libs/ctrl/xc_private.c | 26 +++++---------------------
 tools/libs/ctrl/xc_private.h |  2 +-
 2 files changed, 6 insertions(+), 22 deletions(-)

diff --git a/tools/libs/ctrl/xc_private.c b/tools/libs/ctrl/xc_private.c
index bb0f81d6f3..946fc307aa 100644
--- a/tools/libs/ctrl/xc_private.c
+++ b/tools/libs/ctrl/xc_private.c
@@ -635,7 +635,7 @@ int write_exact(int fd, const void *data, size_t size)
 /*
  * MiniOS's libc doesn't know about writev(). Implement it as multiple 
write()s.
  */
-int writev_exact(int fd, const struct iovec *iov, int iovcnt)
+int writev_exact(int fd, struct iovec *iov, int iovcnt)
 {
     int rc, i;
 
@@ -649,9 +649,8 @@ int writev_exact(int fd, const struct iovec *iov, int 
iovcnt)
     return 0;
 }
 #else
-int writev_exact(int fd, const struct iovec *iov, int iovcnt)
+int writev_exact(int fd, struct iovec *iov, int iovcnt)
 {
-    struct iovec *local_iov = NULL;
     int rc = 0, iov_idx = 0, saved_errno = 0;
     ssize_t len;
 
@@ -686,23 +685,9 @@ int writev_exact(int fd, const struct iovec *iov, int 
iovcnt)
                 len -= iov[iov_idx++].iov_len;
             else
             {
-                /* Partial write of iov[iov_idx]. Copy iov so we can adjust
-                 * element iov_idx and resubmit the rest. */
-                if ( !local_iov )
-                {
-                    local_iov = malloc(iovcnt * sizeof(*iov));
-                    if ( !local_iov )
-                    {
-                        saved_errno = ENOMEM;
-                        rc = -1;
-                        goto out;
-                    }
-
-                    iov = memcpy(local_iov, iov, iovcnt * sizeof(*iov));
-                }
-
-                local_iov[iov_idx].iov_base += len;
-                local_iov[iov_idx].iov_len  -= len;
+                /* Partial write of iov[iov_idx]. */
+                iov[iov_idx].iov_base += len;
+                iov[iov_idx].iov_len  -= len;
                 break;
             }
         }
@@ -711,7 +696,6 @@ int writev_exact(int fd, const struct iovec *iov, int 
iovcnt)
     saved_errno = 0;
 
  out:
-    free(local_iov);
     errno = saved_errno;
     return rc;
 }
diff --git a/tools/libs/ctrl/xc_private.h b/tools/libs/ctrl/xc_private.h
index b5892ae8dc..3af996e900 100644
--- a/tools/libs/ctrl/xc_private.h
+++ b/tools/libs/ctrl/xc_private.h
@@ -383,7 +383,7 @@ int xc_flush_mmu_updates(xc_interface *xch, struct xc_mmu 
*mmu);
 /* Return 0 on success; -1 on error setting errno. */
 int read_exact(int fd, void *data, size_t size); /* EOF => -1, errno=0 */
 int write_exact(int fd, const void *data, size_t size);
-int writev_exact(int fd, const struct iovec *iov, int iovcnt);
+int writev_exact(int fd, struct iovec *iov, int iovcnt);
 
 int xc_ffs8(uint8_t x);
 int xc_ffs16(uint16_t x);
-- 
2.43.0