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From: Peter Maydell <peter.maydell@linaro.org>
Date: Wed, 11 Oct 2017 16:01:03 +0100
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Subject: Re: [Qemu-devel] [PATCH v2] tpm: Use EMSGSIZE instead of EBADMSG to
 compile on OpenBSD
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To: Stefan Berger <stefanb@linux.vnet.ibm.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>, amarnath.valluri@intel.com, =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= <marcandre.lureau@gmail.com>

On 11 October 2017 at 15:42, Stefan Berger <stefanb@linux.vnet.ibm.com> wrote:
> EBADMSG was only added to OpenBSD very recently. To make QEMU compilable
> on older OpenBSD versions use EMSGSIZE instead when a mismatch between
> number of received bytes and message size indicated in the header was
> found.
>
> Return -EMSGSIZE and convert all other errnos in the same functions to
> return the negative errno.
>
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> ---
>  hw/tpm/tpm_util.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/tpm/tpm_util.c b/hw/tpm/tpm_util.c
> index fb929f6..a83c6f4 100644
> --- a/hw/tpm/tpm_util.c
> +++ b/hw/tpm/tpm_util.c
> @@ -71,7 +71,7 @@ static int tpm_util_test(int fd,
>          return errno;
>      }
>      if (n != requestlen) {
> -        return EFAULT;
> +        return -EFAULT;
>      }
>
>      FD_ZERO(&readfds);
> @@ -85,13 +85,13 @@ static int tpm_util_test(int fd,
>
>      n = read(fd, &buf, sizeof(buf));
>      if (n < sizeof(struct tpm_resp_hdr)) {
> -        return EFAULT;
> +        return -EFAULT;
>      }
>
>      resp = (struct tpm_resp_hdr *)buf;
>      /* check the header */
>      if (be32_to_cpu(resp->len) != n) {
> -        return EBADMSG;
> +        return -EMSGSIZE;
>      }
>
>      *return_tag = be16_to_cpu(resp->tag);

You also need to change the "return errno;" lines. "errno"
contains positive errno values, so for a "return 0-or-negative-errno"
convention you want "return -errno;".

thanks
-- PMM