diff mbox

[V3,13/13] linux-user: writev Partial Writes

Message ID 1407956688-16006-14-git-send-email-tommusta@gmail.com
State New
Headers show

Commit Message

Tom Musta Aug. 13, 2014, 7:04 p.m. UTC 
Although not technically not required by POSIX, the writev system call will
typically write out its buffers individually.  That is, if the first buffer
is written successfully, but the second buffer pointer is invalid, then
the first chuck will be written and its size is returned.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
---
V2: Use bool instead of int for "bad_address" per Peter Maydell's review.

 linux-user/syscall.c |   16 ++++++++++++++--
 1 files changed, 14 insertions(+), 2 deletions(-)
diff mbox

Patch

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index edc48e1..fb54f0e 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -1798,6 +1798,7 @@  static struct iovec *lock_iovec(int type, abi_ulong target_addr,
     abi_ulong total_len, max_len;
     int i;
     int err = 0;
+    bool bad_address = false;
 
     if (count == 0) {
         errno = 0;
@@ -1838,9 +1839,20 @@  static struct iovec *lock_iovec(int type, abi_ulong target_addr,
             vec[i].iov_base = 0;
         } else {
             vec[i].iov_base = lock_user(type, base, len, copy);
+            /* If the first buffer pointer is bad, this is a fault.  But
+             * subsequent bad buffers will result in a partial write; this
+             * is realized by filling the vector with null pointers and
+             * zero lengths. */
             if (!vec[i].iov_base) {
-                err = EFAULT;
-                goto fail;
+                if (i == 0) {
+                    err = EFAULT;
+                    goto fail;
+                } else {
+                    bad_address = true;
+                }
+            }
+            if (bad_address) {
+                len = 0;
             }
             if (len > max_len - total_len) {
                 len = max_len - total_len;