Re: [Qemu-devel] [PATCH v5 3/5] target/arm: handle A-profile semihosting at translate time

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

On Wed, 11 Sep 2019 at 17:50, Alex Bennée <alex.bennee@linaro.org> wrote:
>
> As for the other semihosting calls we can resolve this at translate
> time.
>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>
> ---
> v2
>   - update for change to gen_exception_internal_insn API
> v3
>   - update for decode tree, merge T32 & A32 commits
>   - dropped r-b due to changes
> v4
>   - !IS_USER and !arm_dc_feature(s, ARM_FEATURE_M)
> v5
>   - only if !IS_USER for softmmu, linux-user is still allowed
> ---
>  target/arm/translate.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/target/arm/translate.c b/target/arm/translate.c
> index 6689acc911e..fac791c4b06 100644
> --- a/target/arm/translate.c
> +++ b/target/arm/translate.c
> @@ -10219,14 +10219,25 @@ static bool trans_CBZ(DisasContext *s, arg_CBZ *a)
>  }
>
>  /*
> - * Supervisor call
> + * Supervisor call - both T32 & A32 come here so we need to check
> + * which mode we are in when checking for semihosting.
>   */
>
>  static bool trans_SVC(DisasContext *s, arg_SVC *a)
>  {
> -    gen_set_pc_im(s, s->base.pc_next);
> -    s->svc_imm = a->imm;
> -    s->base.is_jmp = DISAS_SWI;
> +    const uint32_t semihost_imm = s->thumb ? 0xab : 0x123456;
> +
> +    if (!arm_dc_feature(s, ARM_FEATURE_M) && semihosting_enabled() &&
> +#ifndef CONFIG_USER_ONLY
> +        !IS_USER(s) &&
> +#endif
> +        (a->imm == semihost_imm)) {
> +        gen_exception_internal_insn(s, s->base.pc_next, EXCP_SEMIHOST);
> +    } else {
> +        gen_set_pc_im(s, s->base.pc_next);
> +        s->svc_imm = a->imm;
> +        s->base.is_jmp = DISAS_SWI;
> +    }
>      return true;
>  }

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM