On Fri, 04 Mar 2022 06:28:52 -0600, Jarkko Sakkinen <jarkko@xxxxxxxxxx>
wrote:
> With SGX1 an enclave needs to be created with its maximum memory
demands
> allocated. Pages cannot be added to an enclave after it is
initialized.
> SGX2 introduces a new function, ENCLS[EAUG], that can be used to add
> pages
> to an initialized enclave. With SGX2 the enclave still needs to set
aside
> address space for its maximum memory demands during enclave creation,
but
> all pages need not be added before enclave initialization. Pages can
be
> added during enclave runtime.
>
> Add support for dynamically adding pages to an initialized enclave
with
> SGX_IOC_ENCLAVE_AUGMENT_PAGES, which performs EAUG's to a given range
of
> pages. Do not enforce any particular permissions from kernel, like is
> done
> for the pages added during the pre-initialization phase, as enclave
> controls the final permissions and content for these pages by issuing
> either ENCLU[EACCEPT] (empty RW) or ENCLU[EACCEPTCOPY] (arbitrary data
> and
> permissions).
>
> Explicit EAUG ioctl is a better choice than an implicit EAUG from a
page
> fault handler because it allows to have O(1) number of kernel-enclave
> round
> trips for EAUG-EACCEPT{COPY} process, instead of O(n), as it is in the
> case
> when a page fault handler EAUG single page at a time.
>
> Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> Cc: Nathaniel McCallum <nathaniel@xxxxxxxxxxx>
> Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> ---
> Is contained in sgx2-v2.1 branch of
> git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-sgx.git
> ---
> arch/x86/include/uapi/asm/sgx.h | 14 +++
> arch/x86/kernel/cpu/sgx/ioctl.c | 159
++++++++++++++++++++++++++++++++
> 2 files changed, 173 insertions(+)
>
> diff --git a/arch/x86/include/uapi/asm/sgx.h
> b/arch/x86/include/uapi/asm/sgx.h
> index c4e0326d281d..2b3a606e78fe 100644
> --- a/arch/x86/include/uapi/asm/sgx.h
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -35,6 +35,8 @@ enum sgx_page_flags {
> _IOWR(SGX_MAGIC, 0x06, struct sgx_enclave_modt)
> #define SGX_IOC_ENCLAVE_REMOVE_PAGES \
> _IOWR(SGX_MAGIC, 0x08, struct sgx_enclave_remove_pages)
> +#define SGX_IOC_ENCLAVE_AUGMENT_PAGES \
> + _IOWR(SGX_MAGIC, 0x09, struct sgx_enclave_augment_pages)
> /**
> * struct sgx_enclave_create - parameter structure for the
> @@ -138,6 +140,18 @@ struct sgx_enclave_remove_pages {
> __u64 count;
> };
> +/**
> + * struct sgx_enclave_augment_pages - parameter structure for the
> %SGX_IOC_ENCLAVE_ADD_PAGE ioctl
> + * @offset: starting page offset
> + * @length: length of the data (multiple of the page size)
> + * @count: number of bytes added (multiple of the page size)
> + */
> +struct sgx_enclave_augment_pages {
> + __u64 offset;
> + __u64 length;
> + __u64 count;
> +};
> +
As I stated in another thread, we need a mechanism to allow EAUG page
lazily, e.g., on #PF. Can we add a field here to indicate that?
