Re: [PATCH V3 11/30] x86/sgx: Keep record of SGX page type

Jarkko Sakkinen
2022-04-05T06:59:52Z

On Mon, Apr 04, 2022 at 09:49:19AM -0700, Reinette Chatre wrote:
> SGX2 functions are not allowed on all page types. For example,
> ENCLS[EMODPR] is only allowed on regular SGX enclave pages and
> ENCLS[EMODPT] is only allowed on TCS and regular pages. If these
> functions are attempted on another type of page the hardware would
> trigger a fault.
>
> Keep a record of the SGX page type so that there is more
> certainty whether an SGX2 instruction can succeed and faults
> can be treated as real failures.
>
> The page type is a property of struct sgx_encl_page
> and thus does not cover the VA page type. VA pages are maintained
> in separate structures and their type can be determined in
> a different way. The SGX2 instructions needing the page type do not
> operate on VA pages and this is thus not a scenario needing to
> be covered at this time.
>
> struct sgx_encl_page hosting this information is maintained for each
> enclave page so the space consumed by the struct is important.
> The existing sgx_encl_page->vm_max_prot_bits is already unsigned long
> while only using three bits. Transition to a bitfield for the two
> members to support the additional information without increasing
> the space consumed by the struct.
>
> Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
> Changes since V2:
> - Update changelog to motivate transition to bitfield that
> was previously done when (now removed) vm_run_prot_bits was
> added.
>
> Changes since V1:
> - Add Acked-by from Jarkko.
>
> arch/x86/include/asm/sgx.h | 3 +++
> arch/x86/kernel/cpu/sgx/encl.h | 3 ++-
> arch/x86/kernel/cpu/sgx/ioctl.c | 2 ++
> 3 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
> index d67810b50a81..eae20fa52b93 100644
> --- a/arch/x86/include/asm/sgx.h
> +++ b/arch/x86/include/asm/sgx.h
> @@ -239,6 +239,9 @@ struct sgx_pageinfo {
> * %SGX_PAGE_TYPE_REG: a regular page
> * %SGX_PAGE_TYPE_VA: a VA page
> * %SGX_PAGE_TYPE_TRIM: a page in trimmed state
> + *
> + * Make sure when making changes to this enum that its values can still fit
> + * in the bitfield within &struct sgx_encl_page
> */
> enum sgx_page_type {
> SGX_PAGE_TYPE_SECS,
> diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
> index 1b15d22f6757..07abfc70c8e3 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.h
> +++ b/arch/x86/kernel/cpu/sgx/encl.h
> @@ -27,7 +27,8 @@
>
> struct sgx_encl_page {
> unsigned long desc;
> - unsigned long vm_max_prot_bits;
> + unsigned long vm_max_prot_bits:8;
> + enum sgx_page_type type:16;
> struct sgx_epc_page *epc_page;
> struct sgx_encl *encl;
> struct sgx_va_page *va_page;
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index f487549bccba..0c211af8e948 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -107,6 +107,7 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
> set_bit(SGX_ENCL_DEBUG, &encl->flags);
>
> encl->secs.encl = encl;
> + encl->secs.type = SGX_PAGE_TYPE_SECS;
> encl->base = secs->base;
> encl->size = secs->size;
> encl->attributes = secs->attributes;
> @@ -344,6 +345,7 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long src,
> */
> encl_page->encl = encl;
> encl_page->epc_page = epc_page;
> + encl_page->type = (secinfo->flags & SGX_SECINFO_PAGE_TYPE_MASK) >> 8;
> encl->secs_child_cnt++;
>
> if (flags & SGX_PAGE_MEASURE) {
> --
> 2.25.1
>

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko