Re: [PATCH 2/2] target/arm: Fix big-endian handling of SVE gdb remote debugging

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 21/7/25 23:19, Vacha Bhavsar wrote:
> This patch adds big endian support for SVE GDB remote
> debugging. It replaces the use of pointer dereferencing with the use of
> ldq_p() as explained in the first part of this patch series. Additionally,
> the order in which the buffer content is loaded into the CPU struct is
> switched depending on target endianness to ensure the most significant bits
> are always in second element.
> 
> Signed-off-by: Vacha Bhavsar <vacha.bhavsar@oss.qualcomm.com>
> ---
>   target/arm/gdbstub64.c | 18 +++++++++++++-----
>   1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/target/arm/gdbstub64.c b/target/arm/gdbstub64.c
> index 8b7f15b920..cd61d946bb 100644
> --- a/target/arm/gdbstub64.c
> +++ b/target/arm/gdbstub64.c
> @@ -200,10 +200,18 @@ int aarch64_gdb_set_sve_reg(CPUState *cs, uint8_t *buf, int reg)

Alex,

Why is there a disconnection with gdb_register_coprocessor() and
"gdbstub/helpers.h" APIs? The former is older? Should we unify
using the latter API with GByteArray?

>       case 0 ... 31:
>       {
>           int vq, len = 0;
> -        uint64_t *p = (uint64_t *) buf;
>           for (vq = 0; vq < cpu->sve_max_vq; vq++) {
> -            env->vfp.zregs[reg].d[vq * 2 + 1] = *p++;
> -            env->vfp.zregs[reg].d[vq * 2] = *p++;
> +            if (target_big_endian()){
> +                env->vfp.zregs[reg].d[vq * 2 + 1] = ldq_p(buf);
> +                buf += 8;
> +                env->vfp.zregs[reg].d[vq * 2] = ldq_p(buf);
> +            }
> +            else{
> +                env->vfp.zregs[reg].d[vq * 2] = ldq_p(buf);
> +                buf += 8;
> +                env->vfp.zregs[reg].d[vq * 2 + 1] = ldq_p(buf);
> +            }
> +            buf += 8;
>               len += 16;
>           }
>           return len;
> @@ -218,9 +226,9 @@ int aarch64_gdb_set_sve_reg(CPUState *cs, uint8_t *buf, int reg)
>       {
>           int preg = reg - 34;
>           int vq, len = 0;
> -        uint64_t *p = (uint64_t *) buf;
>           for (vq = 0; vq < cpu->sve_max_vq; vq = vq + 4) {
> -            env->vfp.pregs[preg].p[vq / 4] = *p++;
> +            env->vfp.pregs[preg].p[vq/4] = ldq_p(buf);
> +            buf += 8;
>               len += 8;
>           }
>           return len;