1 files changed, 70 insertions, 51 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f47cccace1a1..2a8a6e3e2a31 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4204,66 +4204,85 @@ reset_ept_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
 				    boot_cpu_data.x86_phys_bits, execonly);
 }
 
+#define BYTE_MASK(access) \
+	((1 & (access) ? 2 : 0) | \
+	 (2 & (access) ? 4 : 0) | \
+	 (3 & (access) ? 8 : 0) | \
+	 (4 & (access) ? 16 : 0) | \
+	 (5 & (access) ? 32 : 0) | \
+	 (6 & (access) ? 64 : 0) | \
+	 (7 & (access) ? 128 : 0))
+
+
 static void update_permission_bitmask(struct kvm_vcpu *vcpu,
 				      struct kvm_mmu *mmu, bool ept)
 {
-	unsigned bit, byte, pfec;
-	u8 map;
-	bool fault, x, w, u, wf, uf, ff, smapf, cr4_smap, cr4_smep, smap = 0;
+	unsigned byte;
+
+	const u8 x = BYTE_MASK(ACC_EXEC_MASK);
+	const u8 w = BYTE_MASK(ACC_WRITE_MASK);
+	const u8 u = BYTE_MASK(ACC_USER_MASK);
+
+	bool cr4_smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP) != 0;
+	bool cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP) != 0;
+	bool cr0_wp = is_write_protection(vcpu);
 
-	cr4_smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
-	cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP);
 	for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) {
-		pfec = byte << 1;
-		map = 0;
-		wf = pfec & PFERR_WRITE_MASK;
-		uf = pfec & PFERR_USER_MASK;
-		ff = pfec & PFERR_FETCH_MASK;
+		unsigned pfec = byte << 1;
+
 		/*
-		 * PFERR_RSVD_MASK bit is set in PFEC if the access is not
-		 * subject to SMAP restrictions, and cleared otherwise. The
-		 * bit is only meaningful if the SMAP bit is set in CR4.
+		 * Each "*f" variable has a 1 bit for each UWX value
+		 * that causes a fault with the given PFEC.
 		 */
-		smapf = !(pfec & PFERR_RSVD_MASK);
-		for (bit = 0; bit < 8; ++bit) {
-			x = bit & ACC_EXEC_MASK;
-			w = bit & ACC_WRITE_MASK;
-			u = bit & ACC_USER_MASK;
-
-			if (!ept) {
-				/* Not really needed: !nx will cause pte.nx to fault */
-				x |= !mmu->nx;
-				/* Allow supervisor writes if !cr0.wp */
-				w |= !is_write_protection(vcpu) && !uf;
-				/* Disallow supervisor fetches of user code if cr4.smep */
-				x &= !(cr4_smep && u && !uf);
-
-				/*
-				 * SMAP:kernel-mode data accesses from user-mode
-				 * mappings should fault. A fault is considered
-				 * as a SMAP violation if all of the following
-				 * conditions are ture:
-				 *   - X86_CR4_SMAP is set in CR4
-				 *   - A user page is accessed
-				 *   - Page fault in kernel mode
-				 *   - if CPL = 3 or X86_EFLAGS_AC is clear
-				 *
-				 *   Here, we cover the first three conditions.
-				 *   The fourth is computed dynamically in
-				 *   permission_fault() and is in smapf.
-				 *
-				 *   Also, SMAP does not affect instruction
-				 *   fetches, add the !ff check here to make it
-				 *   clearer.
-				 */
-				smap = cr4_smap && u && !uf && !ff;
-			}
 
-			fault = (ff && !x) || (uf && !u) || (wf && !w) ||
-				(smapf && smap);
-			map |= fault << bit;
+		/* Faults from writes to non-writable pages */
+		u8 wf = (pfec & PFERR_WRITE_MASK) ? ~w : 0;
+		/* Faults from user mode accesses to supervisor pages */
+		u8 uf = (pfec & PFERR_USER_MASK) ? ~u : 0;
+		/* Faults from fetches of non-executable pages*/
+		u8 ff = (pfec & PFERR_FETCH_MASK) ? ~x : 0;
+		/* Faults from kernel mode fetches of user pages */
+		u8 smepf = 0;
+		/* Faults from kernel mode accesses of user pages */
+		u8 smapf = 0;
+
+		if (!ept) {
+			/* Faults from kernel mode accesses to user pages */
+			u8 kf = (pfec & PFERR_USER_MASK) ? 0 : u;
+
+			/* Not really needed: !nx will cause pte.nx to fault */
+			if (!mmu->nx)
+				ff = 0;
+
+			/* Allow supervisor writes if !cr0.wp */
+			if (!cr0_wp)
+				wf = (pfec & PFERR_USER_MASK) ? wf : 0;
+
+			/* Disallow supervisor fetches of user code if cr4.smep */
+			if (cr4_smep)
+				smepf = (pfec & PFERR_FETCH_MASK) ? kf : 0;
+
+			/*
+			 * SMAP:kernel-mode data accesses from user-mode
+			 * mappings should fault. A fault is considered
+			 * as a SMAP violation if all of the following
+			 * conditions are ture:
+			 *   - X86_CR4_SMAP is set in CR4
+			 *   - A user page is accessed
+			 *   - The access is not a fetch
+			 *   - Page fault in kernel mode
+			 *   - if CPL = 3 or X86_EFLAGS_AC is clear
+			 *
+			 * Here, we cover the first three conditions.
+			 * The fourth is computed dynamically in permission_fault();
+			 * PFERR_RSVD_MASK bit will be set in PFEC if the access is
+			 * *not* subject to SMAP restrictions.
+			 */
+			if (cr4_smap)
+				smapf = (pfec & (PFERR_RSVD_MASK|PFERR_FETCH_MASK)) ? 0 : kf;
 		}
-		mmu->permissions[byte] = map;
+
+		mmu->permissions[byte] = ff | uf | wf | smepf | smapf;
 	}
 }