This patch adds SMAP handling logic when setting CR4 for guests
Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
arch/x86/kvm/cpuid.h | 8 ++++++++
arch/x86/kvm/mmu.c | 24 +++++++++++++++++++++---
arch/x86/kvm/mmu.h | 26 +++++++++++++++++++++++---
arch/x86/kvm/paging_tmpl.h | 2 +-
arch/x86/kvm/x86.c | 9 ++++++++-
5 files changed, 61 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index a2a1bb7..eeecbed 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -48,6 +48,14 @@ static inline bool guest_cpuid_has_smep(struct kvm_vcpu *vcpu)
return best && (best->ebx & bit(X86_FEATURE_SMEP));
}
+static inline bool guest_cpuid_has_smap(struct kvm_vcpu *vcpu)
+{
+ struct kvm_cpuid_entry2 *best;
+
+ best = kvm_find_cpuid_entry(vcpu, 7, 0);
+ return best && (best->ebx & bit(X86_FEATURE_SMAP));
+}
+
static inline bool guest_cpuid_has_fsgsbase(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9b53135..83b7f8d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3601,20 +3601,22 @@ static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu,
}
}
-static void update_permission_bitmask(struct kvm_vcpu *vcpu,
+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, smapf, 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;
wf = pfec & PFERR_WRITE_MASK;
uf = pfec & PFERR_USER_MASK;
ff = pfec & PFERR_FETCH_MASK;
+ smapf = pfec & PFERR_RSVD_MASK;
for (bit = 0; bit < 8; ++bit) {
x = bit & ACC_EXEC_MASK;
w = bit & ACC_WRITE_MASK;
@@ -3627,11 +3629,27 @@ 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
+ * - Page fault in kernel mode
+ * - !(CPL<3 && X86_EFLAGS_AC is set)
+ *
+ * Here, we cover the first three conditions,
+ * we need to check CPL and X86_EFLAGS_AC in
+ * permission_fault() dynamiccally
+ */
+ smap = smap && smapf && u && !uf;
} else
/* Not really needed: no U/S accesses on ept */
u = 1;
- fault = (ff && !x) || (uf && !u) || (wf && !w);
+ fault = (ff && !x) || (uf && !u) || (wf && !w) || smap;
map |= fault << bit;
}
mmu->permissions[byte] = map;
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 2926152..9d7a0b3 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -73,6 +73,8 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct);
void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context,
bool execonly);
+void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
+ bool ept);
static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm)
{
@@ -110,10 +112,28 @@ static inline bool is_write_protection(struct kvm_vcpu *vcpu)
* Will a fault with a given page-fault error code (pfec) cause a permission
* fault with the given access (in ACC_* format)?
*/
-static inline bool permission_fault(struct kvm_mmu *mmu, unsigned pte_access,
- unsigned pfec)
+static inline bool permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
+ unsigned pte_access, unsigned pfec)
{
- return (mmu->permissions[pfec >> 1] >> pte_access) & 1;
+ bool smapf;
+ int cpl = kvm_x86_ops->get_cpl(vcpu);
+ unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
+
+ /*
+ * If CPL < 3, SMAP protections are disabled if EFLAGS.AC = 1.
+ *
+ * If CPL = 3, SMAP applies to all supervisor-mode data accesses
+ * (these are implicit supervisor accesses) regardless of the value
+ * of EFLAGS.AC.
+ *
+ * So we need to check CPL and EFLAGS.AC to detect whether there is
+ * a SMAP violation.
+ */
+
+ smapf = ((mmu->permissions[(pfec|PFERR_RSVD_MASK) >> 1] >> pte_access) &
+ 1) && !((cpl < 3) && ((rflags & X86_EFLAGS_AC) == 1));
+
+ return ((mmu->permissions[pfec >> 1] >> pte_access) & 1) || smapf;
}
void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm);
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index cba218a..4107765 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -353,7 +353,7 @@ retry_walk:
walker->ptes[walker->level - 1] = pte;
} while (!is_last_gpte(mmu, walker->level, pte));
- if (unlikely(permission_fault(mmu, pte_access, access))) {
+ if (unlikely(permission_fault(vcpu, mmu, pte_access, access))) {
errcode |= PFERR_PRESENT_MASK;
goto error;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2b85784..5869c6d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -646,6 +646,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
if (!guest_cpuid_has_smep(vcpu) && (cr4 & X86_CR4_SMEP))
return 1;
+ if (!guest_cpuid_has_smap(vcpu) && (cr4 & X86_CR4_SMAP))
+ return 1;
+
if (!guest_cpuid_has_fsgsbase(vcpu) && (cr4 & X86_CR4_FSGSBASE))
return 1;
@@ -674,6 +677,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
(!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE)))
kvm_mmu_reset_context(vcpu);
+ if ((cr4 ^ old_cr4) & X86_CR4_SMAP)
+ update_permission_bitmask(vcpu, vcpu->arch.walk_mmu, false);
+
if ((cr4 ^ old_cr4) & X86_CR4_OSXSAVE)
kvm_update_cpuid(vcpu);
@@ -4108,7 +4114,8 @@ static int vcpu_mmio_gva_to_gpa(struct kvm_vcpu *vcpu, unsigned long gva,
| (write ? PFERR_WRITE_MASK : 0);
if (vcpu_match_mmio_gva(vcpu, gva)
- && !permission_fault(vcpu->arch.walk_mmu, vcpu->arch.access, access)) {
+ && !permission_fault(vcpu, vcpu->arch.walk_mmu,
+ vcpu->arch.access, access)) {
*gpa = vcpu->arch.mmio_gfn << PAGE_SHIFT |
(gva & (PAGE_SIZE - 1));
trace_vcpu_match_mmio(gva, *gpa, write, false);
--
1.8.3.1
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