Re: [Qemu-devel] [RFC PATCH 08/11] target/arm: correct return values for WRITE/READ in arm-semi

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 5/14/19 5:52 PM, Alex Bennée wrote:
> The documentation says the write should return the number of bytes not
> written on an error (0 means everything was written). Read provides a
> buffer length and the return value should be the buffer length - bytes
> actually read. Remove the incorrect FIXME's and return the correct
> values.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>  target/arm/arm-semi.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c
> index a3bbef18ef7..3ae8f05d51b 100644
> --- a/target/arm/arm-semi.c
> +++ b/target/arm/arm-semi.c
> @@ -334,13 +334,15 @@ target_ulong do_arm_semihosting(CPUARMState *env)
>          } else {
>              s = lock_user(VERIFY_READ, arg1, len, 1);
>              if (!s) {
> -                /* FIXME - should this error code be -TARGET_EFAULT ? */
> -                return (uint32_t)-1;
> +                /* Return bytes not written on error */
> +                return len;
>              }
>              ret = set_swi_errno(ts, write(arg0, s, len));
>              unlock_user(s, arg1, 0);
> -            if (ret == (uint32_t)-1)
> -                return -1;
> +            if (ret == (uint32_t)-1) {
> +                ret = 0;
> +            }
> +            /* Return bytes not written */
>              return len - ret;
>          }
>      case TARGET_SYS_READ:
> @@ -355,15 +357,17 @@ target_ulong do_arm_semihosting(CPUARMState *env)
>          } else {
>              s = lock_user(VERIFY_WRITE, arg1, len, 0);
>              if (!s) {
> -                /* FIXME - should this error code be -TARGET_EFAULT ? */
> -                return (uint32_t)-1;
> +                /* return bytes not read */
> +                return len;
>              }
>              do {
>                  ret = set_swi_errno(ts, read(arg0, s, len));
>              } while (ret == -1 && errno == EINTR);
>              unlock_user(s, arg1, len);
> -            if (ret == (uint32_t)-1)
> -                return -1;
> +            if (ret == (uint32_t)-1) {
> +                ret = 0;
> +            }
> +            /* Return bytes not read */
>              return len - ret;
>          }
>      case TARGET_SYS_READC:
>