Il 27/03/2014 13:25, Feng Wu ha scritto:
+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, smep;
+ bool fault, x, w, u, wf, uf, ff, smep, smap;
smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
+ smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP);
for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) {
pfec = byte << 1;
map = 0;
@@ -3617,11 +3618,26 @@ static void update_permission_bitmask(struct kvm_vcpu
*vcpu,
w |= !is_write_protection(vcpu) && !uf;
/* Disallow supervisor fetches of user code if
cr4.smep */
x &= !(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
+ * - An user page is accessed
+ * - !(CPL<3 && X86_EFLAGS_AC is set)
+ * - Page fault in kernel mode
+ */
+ smap = smap && u && !uf &&
+ !((kvm_x86_ops->get_cpl(vcpu) < 3) &&
+ ((kvm_x86_ops->get_rflags(vcpu) &
+ X86_EFLAGS_AC) == 1));
Unfortunately this doesn't work.
The reason is that changing X86_EFLAGS_AC doesn't trigger
update_permission_bitmask. So the value of CPL < 3 && AC = 1 must not
be checked in update_permission_bitmask; instead, it must be included in
the index into the permissions array. You can reuse the PFERR_RSVD_MASK
bit, like
smapf = pfec & PFERR_RSVD_MASK;
...
smap = smap && smapf u && !uf;
The VCPU can then be passed to permission_fault in order to get the
value of the CPL and the AC bit.
Please test nested virtualization too. I think PFERR_RSVD_MASK should
be removed in translate_nested_gpa.
Paolo
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