On Tue, Feb 18, 2025 at 12:56 PM Deepak Gupta <de...@rivosinc.com> wrote:
>
> Commit:8205bc1 ("target/riscv: introduce ssp and enabling controls for
> zicfiss") introduced CSR_SSP but it mis-interpreted the spec on access
> to CSR_SSP in M-mode. Gated to CSR_SSP is not gated via `xSSE`. But
> rather rules clearly specified in section "2.2.4. Shadow Stack Pointer"
Do you mean "22.2.1. Shadow Stack Pointer (ssp) CSR access contr" in
the priv spec?
> of `zicfiss` specification. Thanks to Adam Zabrocki for bringing this
> to attention.
The thanks should probably be below the line
>
> Fixes: 8205bc127a83 ("target/riscv: introduce ssp and enabling controls
> for zicfiss"
>
> Reported-by: Adam Zabrocki <azabro...@nvidia.com>
> Signed-off-by: Deepak Gupta <de...@rivosinc.com>
The actual change looks good:
Reviewed-by: Alistair Francis <alistair.fran...@wdc.com>
Alistair
> ---
> target/riscv/csr.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index afb7544f07..75c661d2a1 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -191,6 +191,11 @@ static RISCVException cfi_ss(CPURISCVState *env, int
> csrno)
> return RISCV_EXCP_ILLEGAL_INST;
> }
>
> + /* If ext implemented, M-mode always have access to SSP CSR */
> + if (env->priv == PRV_M) {
> + return RISCV_EXCP_NONE;
> + }
> +
> /* if bcfi not active for current env, access to csr is illegal */
> if (!cpu_get_bcfien(env)) {
> #if !defined(CONFIG_USER_ONLY)
> --
> 2.34.1
>
>
