Re: [PATCH] target/riscv: Add User CSRs read-only check

[Bin Meng]

On Mon, Aug 9, 2021 at 6:37 PM LIU Zhiwei <zhiwei_liu@c-sky.com> wrote:
>
> For U-mode CSRs, read-only check is also needed.
>
> Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
> ---
>  target/riscv/csr.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 9a4ed18ac5..360e4bfa33 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -1422,11 +1422,11 @@ RISCVException riscv_csrrw(CPURISCVState *env, int 
> csrno,
>      RISCVException ret;
>      target_ulong old_value;
>      RISCVCPU *cpu = env_archcpu(env);
> +    int read_only = get_field(csrno, 0xC00) == 3;
>
>      /* check privileges and return -1 if check fails */
>  #if !defined(CONFIG_USER_ONLY)
>      int effective_priv = env->priv;
> -    int read_only = get_field(csrno, 0xC00) == 3;
>
>      if (riscv_has_ext(env, RVH) &&
>          env->priv == PRV_S &&
> @@ -1439,11 +1439,13 @@ RISCVException riscv_csrrw(CPURISCVState *env, int 
> csrno,
>          effective_priv++;
>      }
>
> -    if ((write_mask && read_only) ||
> -        (!env->debugger && (effective_priv < get_field(csrno, 0x300)))) {
> +    if (!env->debugger && (effective_priv < get_field(csrno, 0x300))) {
>          return RISCV_EXCP_ILLEGAL_INST;
>      }
>  #endif
> +    if (write_mask && read_only) {
> +        return -RISCV_EXCP_ILLEGAL_INST;

This should be RISCV_EXCP_ILLEGAL_INST

> +    }
>
>      /* ensure the CSR extension is enabled. */
>      if (!cpu->cfg.ext_icsr) {

Otherwise,
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>