RE: [RFC PATCH 3/9] x86/sgx: Allow userspace to add multiple pages in single ioctl()

[Xing, Cedric]

> From: Christopherson, Sean J
> Sent: Friday, May 31, 2019 4:32 PM
> 
> +/**
> + * sgx_ioc_enclave_add_pages - handler for %SGX_IOC_ENCLAVE_ADD_PAGES
> + *
> + * @filep:	open file to /dev/sgx
> + * @cmd:	the command value
> + * @arg:	pointer to an &sgx_enclave_add_page instance
> + *
> + * Add a range of pages to an uninitialized enclave (EADD), and
> +optionally
> + * extend the enclave's measurement with the contents of the page (EEXTEND).
> + * The range of pages must be virtually contiguous.  The SECINFO and
> + * measurement maskare applied to all pages, i.e. pages with different
> + * properties must be added in separate calls.
> + *
> + * EADD and EEXTEND are done asynchronously via worker threads.  A
> +successful
> + * sgx_ioc_enclave_add_page() only indicates the pages have been added
> +to the
> + * work queue, it does not guarantee adding the pages to the enclave
> +will
> + * succeed.
> + *
> + * Return:
> + *   0 on success,
> + *   -errno otherwise
> + */
> +static long sgx_ioc_enclave_add_pages(struct file *filep, unsigned int cmd,
> +				      unsigned long arg)
> +{
> +	struct sgx_enclave_add_pages *addp = (void *)arg;
> +	struct sgx_encl *encl = filep->private_data;
> +	struct sgx_secinfo secinfo;
> +	unsigned int i;
> +	int ret;
> +
> +	if (copy_from_user(&secinfo, (void __user *)addp->secinfo,
> +			   sizeof(secinfo)))
> +		return -EFAULT;
> +
> +	for (i = 0, ret = 0; i < addp->nr_pages && !ret; i++) {
> +		if (signal_pending(current))
> +			return -ERESTARTSYS;

If interrupted, how would user mode code know how many pages have been EADD'ed?

> +
> +		if (need_resched())
> +			cond_resched();
> +
> +		ret = sgx_encl_add_page(encl, addp->addr + i*PAGE_SIZE,
> +					addp->src + i*PAGE_SIZE,
> +					&secinfo, addp->mrmask);
> +	}
>  	return ret;
>  }
> 
> @@ -823,8 +845,8 @@ long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  	case SGX_IOC_ENCLAVE_CREATE:
>  		handler = sgx_ioc_enclave_create;
>  		break;
> -	case SGX_IOC_ENCLAVE_ADD_PAGE:
> -		handler = sgx_ioc_enclave_add_page;
> +	case SGX_IOC_ENCLAVE_ADD_PAGES:
> +		handler = sgx_ioc_enclave_add_pages;
>  		break;
>  	case SGX_IOC_ENCLAVE_INIT:
>  		handler = sgx_ioc_enclave_init;
> --
> 2.21.0