Re: [PATCH 2/3] target/arm/tcg: add PAC related instructions

["Alex Bennée" <alex.bennee@linaro.org>]

Torbjörn SVENSSON <torbjorn.svensson@foss.st.com> writes:

> This commit adds the pointer authentication instructions from the Arm
> v8.1-m PACBTI extension.
> While the instructions are properly recognized, they are all NOPs.
>
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
> ---
>  target/arm/tcg/t32.decode  | 21 +++++++++++++---
>  target/arm/tcg/translate.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 80 insertions(+), 3 deletions(-)
>
> diff --git a/target/arm/tcg/t32.decode b/target/arm/tcg/t32.decode
> index 49b8d0037e..a885eed101 100644
> --- a/target/arm/tcg/t32.decode
> +++ b/target/arm/tcg/t32.decode
> @@ -263,6 +263,7 @@ BFCI             1111 0011 011 0 .... 0 ... .... ..0.....     @bfi
>  @s0_rnadm        .... .... .... rn:4 ra:4 rd:4 .... rm:4      &s_rrrr s=0
>  @s0_rn0dm        .... .... .... rn:4 .... rd:4 .... rm:4      &s_rrrr ra=0 s=0
>  @rnadm           .... .... .... rn:4 ra:4 rd:4 .... rm:4      &rrrr
> +@rna0m           .... .... .... rn:4 ra:4 .... .... rm:4      &rrrr rd=0
>  @rn0dm           .... .... .... rn:4 .... rd:4 .... rm:4      &rrrr ra=0
>  @rndm            .... .... .... rn:4 .... rd:4 .... rm:4      &rrr
>  @rdm             .... .... .... .... .... rd:4 .... rm:4      &rr
> @@ -319,9 +320,18 @@ SMLALDX          1111 1011 1100 .... .... .... 1101 ....      @rnadm
>  SMLSLD           1111 1011 1101 .... .... .... 1100 ....      @rnadm
>  SMLSLDX          1111 1011 1101 .... .... .... 1101 ....      @rnadm
>  
> -SMMLA            1111 1011 0101 .... .... .... 0000 ....      @rnadm
> -SMMLAR           1111 1011 0101 .... .... .... 0001 ....      @rnadm
> -SMMLS            1111 1011 0110 .... .... .... 0000 ....      @rnadm
> +{
> +  AUTG           1111 1011 0101 .... .... 1111 0000 ....      @rna0m
> +  SMMLA          1111 1011 0101 .... .... .... 0000 ....      @rnadm
> +}
> +{
> +  BXAUT          1111 1011 0101 .... .... 1111 0001 ....      @rna0m
> +  SMMLAR         1111 1011 0101 .... .... .... 0001 ....      @rnadm
> +}
> +{
> +  PACG           1111 1011 0110 .... 1111 .... 0000 ....      @rndm
> +  SMMLS          1111 1011 0110 .... .... .... 0000 ....      @rnadm
> +}
>  SMMLSR           1111 1011 0110 .... .... .... 0001 ....      @rnadm
>  
>  SDIV             1111 1011 1001 .... 1111 .... 1111 ....      @rndm
> @@ -375,6 +385,11 @@ CLZ              1111 1010 1011 ---- 1111 .... 1000 ....      @rdm
>          # SEVL   1111 0011 1010 1111 1000 0000 0000 0101
>  
>          ESB      1111 0011 1010 1111 1000 0000 0001 0000
> +
> +        # v8.1-m PACBTI extention
> +        AUT      1111 0011 1010 1111 1000 0000 0010 1101
> +        PAC      1111 0011 1010 1111 1000 0000 0001 1101
> +        PACBTI   1111 0011 1010 1111 1000 0000 0000 1101
>        ]
>  
>        # The canonical nop ends in 0000 0000, but the whole rest
> diff --git a/target/arm/tcg/translate.c b/target/arm/tcg/translate.c
> index c744b16345..ae1351ef03 100644
> --- a/target/arm/tcg/translate.c
> +++ b/target/arm/tcg/translate.c
> @@ -5012,6 +5012,68 @@ static bool trans_SMMLSR(DisasContext *s, arg_rrrr *a)
>      return op_smmla(s, a, true, true);
>  }
>  
> +static bool trans_PAC(DisasContext *s, arg_empty *a)
> +{
> +    if (!arm_dc_feature(s, ARM_FEATURE_V8_1M)) {
> +        return false;
> +    }

These are the wrong feature tests. I would bring the
isar_feature_aa32_m_pacbti from 3/3 into this patch and invert the logic
in the same way the a64 does:

    if (dc_isar_feature(aa32_m_pacbti, s)) {
        /* treat as NOP for now */
        return true;
    }
    return false;

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro