Re: [PATCH v7 06/11] firmware: qcom: scm: add support for object invocation

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 8/13/25 2:35 AM, Amirreza Zarrabi wrote:
> Qualcomm TEE (QTEE) hosts Trusted Applications (TAs) and services in
> the secure world, accessed via objects. A QTEE client can invoke these
> objects to request services. Similarly, QTEE can request services from
> the nonsecure world using objects exported to the secure world.
> 
> Add low-level primitives to facilitate the invocation of objects hosted
> in QTEE, as well as those hosted in the nonsecure world.
> 
> If support for object invocation is available, the qcom_scm allocates
> a dedicated child platform device. The driver for this device communicates
> with QTEE using low-level primitives.
> 
> Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
> Tested-by: Harshal Dev <quic_hdev@quicinc.com>
> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@oss.qualcomm.com>
> ---

[...]

> +int qcom_scm_qtee_invoke_smc(phys_addr_t inbuf, size_t inbuf_size,
> +			     phys_addr_t outbuf, size_t outbuf_size,
> +			     u64 *result, u64 *response_type)
> +{
> +	struct qcom_scm_desc desc = {
> +		.svc = QCOM_SCM_SVC_SMCINVOKE,
> +		.cmd = QCOM_SCM_SMCINVOKE_INVOKE,
> +		.owner = ARM_SMCCC_OWNER_TRUSTED_OS,
> +		.args[0] = inbuf,
> +		.args[1] = inbuf_size,
> +		.args[2] = outbuf,
> +		.args[3] = outbuf_size,
> +		.arginfo = QCOM_SCM_ARGS(4, QCOM_SCM_RW, QCOM_SCM_VAL,
> +					 QCOM_SCM_RW, QCOM_SCM_VAL),
> +	};
> +	struct qcom_scm_res res;
> +	int ret;
> +
> +	ret = qcom_scm_call(__scm->dev, &desc, &res);
> +	if (ret)
> +		return ret;
> +
> +	*response_type = res.result[0];
> +	*result = res.result[1];

These are dereferenced without checking, which will surely upset static
checkers (and users)

I see that res.result[2] should also return some (aptly named) "data"
which you handled in v1, but dropped in v2 (without a comment AFAICT)

Looking at it, we could probably wrap it in qcom_scm_qseecom_call()
which this seems to be fit for

> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(qcom_scm_qtee_invoke_smc);
> +
> +/**
> + * qcom_scm_qtee_callback_response() - Submit response for callback request.
> + * @buf: start address of memory area used for outbound buffer.
> + * @buf_size: size of the memory area used for outbound buffer.
> + * @result: Result of QTEE object invocation.
> + * @response_type: Response type returned by QTEE.
> + *
> + * @response_type determines how the contents of @buf should be processed.
> + *
> + * Return: On success, return 0 or <0 on failure.
> + */
> +int qcom_scm_qtee_callback_response(phys_addr_t buf, size_t buf_size,
> +				    u64 *result, u64 *response_type)

These should be aligned

> +{
> +	struct qcom_scm_desc desc = {
> +		.svc = QCOM_SCM_SVC_SMCINVOKE,
> +		.cmd = QCOM_SCM_SMCINVOKE_CB_RSP,
> +		.owner = ARM_SMCCC_OWNER_TRUSTED_OS,
> +		.args[0] = buf,
> +		.args[1] = buf_size,
> +		.arginfo = QCOM_SCM_ARGS(2, QCOM_SCM_RW, QCOM_SCM_VAL),
> +	};
> +	struct qcom_scm_res res;
> +	int ret;
> +
> +	ret = qcom_scm_call(__scm->dev, &desc, &res);
> +	if (ret)
> +		return ret;
> +
> +	*response_type = res.result[0];
> +	*result = res.result[1];

this also seems like a good candidate for qcom_scm_qseecom_call()

[...]

>  /**
>   * qcom_scm_is_available() - Checks if SCM is available
>   */
> @@ -2326,6 +2444,16 @@ static int qcom_scm_probe(struct platform_device *pdev)
>  	ret = qcom_scm_qseecom_init(scm);
>  	WARN(ret < 0, "failed to initialize qseecom: %d\n", ret);
>  
> +	/*
> +	 * Initialize the QTEE object interface.
> +	 *
> +	 * This only represents the availability for QTEE object invocation
> +	 * and callback support. On failure, ignore the result. Any subsystem
> +	 * depending on it may fail if it tries to access this interface.
> +	 */
> +	ret = qcom_scm_qtee_init(scm);
> +	WARN(ret < 0, "failed to initialize qcomtee: %d\n", ret);

This will throw a WARN on *a lot* of platforms, ranging from
Chromebooks running TF-A (with a reduced SMC handler), through
platforms requiring QCOM_SCM_SMCINVOKE_INVOKE_LEGACY (0x00) cmd

Konrad