Re: [PATCH 3/4] firmware: Add support for Qualcomm UEFI Secure Application

[Maximilian Luz]

On 1/17/23 12:05, Johan Hovold wrote:
> On Sun, Jul 24, 2022 at 12:49:48AM +0200, Maximilian Luz wrote:
> > On platforms using the Qualcomm UEFI Secure Application (uefisecapp),
> > EFI variables cannot be accessed via the standard interface in EFI
> > runtime mode. The respective functions return EFI_UNSUPPORTED. On these
> > platforms, we instead need to talk to uefisecapp. This commit provides
> > support for this and registers the respective efivars operations to
> > access EFI variables from the kernel.
> >
> > Communication with uefisecapp follows the standard Qualcomm Trusted
> > Environment (TEE or TrEE) / Secure OS conventions via the respective SCM
> > call interface. This is also the reason why variable access works
> > normally while boot services are active. During this time, said SCM
> > interface is managed by the boot services. When calling
> > ExitBootServices(), the ownership is transferred to the kernel.
> > Therefore, UEFI must not use that interface itself (as multiple parties
> > accessing this interface at the same time may lead to complications) and
> > cannot access variables for us.
> >
> > Signed-off-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
> > ---
>
> > +static int qcom_uefisecapp_probe(struct platform_device *pdev)
> > +{
> > +	struct qcuefi_client *qcuefi;
> > +	int status;
>
> [...]
>
> > +	/* Set up kobject for efivars interface. */
> > +	qcuefi->kobj = kobject_create_and_add("qcom_tee_uefisecapp", firmware_kobj);
> > +	if (!qcuefi->kobj) {
> > +		status = -ENOMEM;
> > +		goto err_kobj;
>
> When preparing some related EFI patches, I noticed that the error labels
> here are named after where you jump from rather than after what they do
> (as is suggested by the coding standard).
>
> Would you mind changing that (throughout) for your v2?

Not at all. Will change that for v2.

Regards,
Max

> > +	}
> > +
> > +	/* Register global reference. */
> > +	platform_set_drvdata(pdev, qcuefi);
> > +	status = qcuefi_set_reference(qcuefi);
> > +	if (status)
> > +		goto err_ref;
> > +
> > +	/* Register efivar ops. */
> > +	status = efivars_register(&qcuefi->efivars, &qcom_efivar_ops, qcuefi->kobj);
> > +	if (status)
> > +		goto err_register;
> > +
> > +	return 0;
> > +
> > +err_register:
> > +	qcuefi_set_reference(NULL);
> > +err_ref:
> > +	kobject_put(qcuefi->kobj);
> > +err_kobj:
> > +	qctee_dma_free(qcuefi->dev, &qcuefi->dma);
> > +	return status;
> > +}
>
> Johan