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authorFeng Wu <feng.wu@intel.com>2014-04-01 11:46:34 +0200
committerMarcelo Tosatti <mtosatti@redhat.com>2014-04-14 22:50:34 +0200
commit97ec8c067d322d32effdc1701760d3babbc5595f (patch)
tree16892fd16ce9e3d60c68b01f7bf11a8821eb3295 /arch/x86/kvm/mmu.c
parentKVM: Remove SMAP bit from CR4_RESERVED_BITS (diff)
downloadlinux-97ec8c067d322d32effdc1701760d3babbc5595f.tar.xz
linux-97ec8c067d322d32effdc1701760d3babbc5595f.zip
KVM: Add SMAP support when setting CR4
This patch adds SMAP handling logic when setting CR4 for guests Thanks a lot to Paolo Bonzini for his suggestion to use the branchless way to detect SMAP violation. Signed-off-by: Feng Wu <feng.wu@intel.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch/x86/kvm/mmu.c')
-rw-r--r--arch/x86/kvm/mmu.c34
1 files changed, 31 insertions, 3 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f5704d9e5ddc..084caf3efaf5 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3601,20 +3601,27 @@ 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, cr4_smap, smep, smap = 0;
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;
+ /*
+ * 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.
+ */
+ smapf = !(pfec & PFERR_RSVD_MASK);
for (bit = 0; bit < 8; ++bit) {
x = bit & ACC_EXEC_MASK;
w = bit & ACC_WRITE_MASK;
@@ -3627,11 +3634,32 @@ 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
+ * - 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;
} 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) ||
+ (smapf && smap);
map |= fault << bit;
}
mmu->permissions[byte] = map;