Re: [Qemu-devel] [PATCH v2 1/3] linux-user: pass sockaddr from host to target

[Peter Maydell <peter.maydell@linaro.org>]

On 16 July 2012 11:13, Jing Huang <jing.huang.pku@gmail.com> wrote:
> This patch pass sockaddr from host to target.
>
> Signed-off-by: Jing Huang <jing.huang.pku@gmail.com>
> ---
>  linux-user/syscall.c |   10 +++++++++-
>  1 files changed, 9 insertions(+), 1 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 539af3f..28c8ba5 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -1873,8 +1873,16 @@ static abi_long do_sendrecvmsg(int fd, abi_ulong target_msg,
>          if (!is_error(ret)) {
>              len = ret;
>              ret = host_to_target_cmsg(msgp, &msg);
> -            if (!is_error(ret))
> +            if (!is_error(ret)) {
> +                msgp->msg_namelen = msg.msg_namelen;

You need to swap msg_namelen using tswap32().

> +                ret = host_to_target_sockaddr(tswapal(msgp->msg_name),
> +                                    msg.msg_name, msg.msg_namelen);

host_to_target_sockaddr assumes msg.msg_name isn't NULL, so you need
to enclose this in an if() to avoid that.

> +                if (ret) {
> +                    qemu_log("Failed to pass sockaddr to target guest");

Don't print any logging here -- we should only be logging
anything for (a) unimplemented features or (b) debug tracing
which is guarded by #ifdef DEBUG.

> +                    return ret;

Returning here bypasses the unlocking of the iovec and user struct.

> +                }
>                  ret = len;


...the above two points mean you wanted
  if (!is_error(ret)) {
      ret = len;
  }

here.

> +            }

-- PMM