Re: [RFC v3 13/27] lib: rspdm: Support SPDM get_capabilities

[Wilfred Mallawa]

[snip]
> +
> +    /// Obtain the supported capabilities from an SPDM session and
> store the
> +    /// information in the `SpdmState`.
> +    pub(crate) fn get_capabilities(&mut self) -> Result<(), Error> {
> +        let mut request = GetCapabilitiesReq::default();
> +        request.version = self.version;
> +
> +        let (req_sz, rsp_sz) = match self.version {
> +            SPDM_VER_10 => (4, 8),
> +            SPDM_VER_11 => (8, 8),
> +            _ => {
> +                request.data_transfer_size =
> self.transport_sz.to_le();
> +                request.max_spdm_msg_size =
> request.data_transfer_size;
> +
> +                (
> +                    core::mem::size_of::<GetCapabilitiesReq>(),
> +                    core::mem::size_of::<GetCapabilitiesRsp>(),
> +                )
> +            }
> +        };
> +
> +        // SAFETY: `request` is repr(C) and packed, so we can
> convert it to a slice
> +        let request_buf = unsafe { from_raw_parts_mut(&mut request
> as *mut _ as *mut u8, req_sz) };
> +
> +        let mut response_vec: KVec<u8> = KVec::with_capacity(rsp_sz,
> GFP_KERNEL)?;
> +        // SAFETY: `request` is repr(C) and packed, so we can
> convert it to a slice

Same here about the SAFETY comment.

> +        let response_buf = unsafe {
> from_raw_parts_mut(response_vec.as_mut_ptr(), rsp_sz) };
> +
> +        let rc = self.spdm_exchange(request_buf, response_buf)?;
> +
> +        if rc < (rsp_sz as i32) {
> +            pr_err!("Truncated capabilities response\n");
> +            to_result(-(bindings::EIO as i32))?;
> +        }
> +
> +        // SAFETY: `rc` is the length of data read, which will be
> smaller
> +        // then the capacity of the vector
> +        unsafe { response_vec.inc_len(rc as usize) };
> +
> +        let response: &mut GetCapabilitiesRsp =
> +            Untrusted::new_mut(&mut response_vec).validate_mut()?;
> +
> +        self.rsp_caps = u32::from_le(response.flags);
> +        if (self.rsp_caps & SPDM_RSP_MIN_CAPS) != SPDM_RSP_MIN_CAPS
> {

Might be useful for debugging to have a pr_err() here.  

Wilfred