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

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Date:   Mon,  4 Apr 2022 09:49:19 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     dave.hansen@...ux.intel.com, jarkko@...nel.org, tglx@...utronix.de,
        bp@...en8.de, luto@...nel.org, mingo@...hat.com,
        linux-sgx@...r.kernel.org, x86@...nel.org
Cc:     seanjc@...gle.com, kai.huang@...el.com, cathy.zhang@...el.com,
        cedric.xing@...el.com, haitao.huang@...el.com,
        mark.shanahan@...el.com, hpa@...or.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH V3 11/30] x86/sgx: Keep record of SGX page type

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@...nel.org>
Signed-off-by: Reinette Chatre <reinette.chatre@...el.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