linux-user: Translate flags argument to dup3 syscall

The third argument to dup3() is a flags word which may be
O_CLOEXEC. We weren't translating this flag from target to
host value, which meant that if the target used a different
value from the host (eg sparc guest and x86 host) the dup3()
call would fail EINVAL. Do the correct translation.

Fixes: https://bugs.launchpad.net/qemu/+bug/1704658Reported-by: NBruno Haible  <bruno@clisp.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NLaurent Vivier <laurent@vivier.eu>
Message-Id: <1513351080-25917-1-git-send-email-peter.maydell@linaro.org>
Signed-off-by: NLaurent Vivier <laurent@vivier.eu>

linux-user/syscall.c

@@ -8490,11 +8490,19 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
 #endif
 #if defined(CONFIG_DUP3) && defined(TARGET_NR_dup3)
     case TARGET_NR_dup3:
-        ret = get_errno(dup3(arg1, arg2, arg3));
+    {
+        int host_flags;
+
+        if ((arg3 & ~TARGET_O_CLOEXEC) != 0) {
+            return -EINVAL;
+        }
+        host_flags = target_to_host_bitmask(arg3, fcntl_flags_tbl);
+        ret = get_errno(dup3(arg1, arg2, host_flags));
         if (ret >= 0) {
             fd_trans_dup(arg1, arg2);
         }
         break;
+    }
 #endif
 #ifdef TARGET_NR_getppid /* not on alpha */
     case TARGET_NR_getppid: