Re: [PATCH v2] efi_loader: Don't limit the StMM buffer size explicitly

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

> > 
[...]
> >   	rc = tee_invoke_func(conn.tee, &arg, 2, param);
> >   	tee_shm_free(shm);
> > +	/*
> > +	 * Although the max payload is configurable on StMM, we only share
> > +	 * four pages from OP-TEE for the non-secure buffer used to communicate
> > +	 * with StMM. OP-TEE will reject anything bigger than that and will
> > +	 * return.  So le'ts at least warn users
> > +	 */
> >   	tee_close_session(conn.tee, conn.session);
> > -	if (rc || arg.ret != TEE_SUCCESS)
> > +	if (rc || arg.ret != TEE_SUCCESS) {
> 
> tee_close_session(): Will arg.ret be valid if rc != 0?

Depends when tee_invoke_func() failed.  But why do we care?
The connection needs to close regardless and we then have to reason with
the error.

Regards
/Ilias
> 
> Best regards
> 
> Heinrich
> 
> > +		if (arg.ret == TEE_ERROR_EXCESS_DATA)
> > +			log_err("Variable payload too large\n");
> >   		return EFI_DEVICE_ERROR;
> > +	}
> > 
> >   	switch (param[1].u.value.a) {
> >   	case ARM_SVC_SPM_RET_SUCCESS:
> > @@ -255,15 +263,6 @@ efi_status_t EFIAPI get_max_payload(efi_uintn_t *size)
> >   		goto out;
> >   	}
> >   	*size = var_payload->size;
> > -	/*
> > -	 * Although the max payload is configurable on StMM, we only share a
> > -	 * single page from OP-TEE for the non-secure buffer used to communicate
> > -	 * with StMM. Since OP-TEE will reject to map anything bigger than that,
> > -	 * make sure we are in bounds.
> > -	 */
> > -	if (*size > OPTEE_PAGE_SIZE)
> > -		*size = OPTEE_PAGE_SIZE - MM_COMMUNICATE_HEADER_SIZE  -
> > -			MM_VARIABLE_COMMUNICATE_SIZE;
> >   	/*
> >   	 * There seems to be a bug in EDK2 miscalculating the boundaries and
> >   	 * size checks, so deduct 2 more bytes to fulfill this requirement. Fix
>