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Date: Tue, 18 Dec 2018 13:26:49 +0530
From: Amit Daniel Kachhap <amit.kachhap@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Christoffer Dall <christoffer.dall@....com>,
Marc Zyngier <marc.zyngier@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Andrew Jones <drjones@...hat.com>,
Dave Martin <Dave.Martin@....com>,
Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
kvmarm@...ts.cs.columbia.edu,
Kristina Martsenko <kristina.martsenko@....com>,
linux-kernel@...r.kernel.org,
Amit Daniel Kachhap <amit.kachhap@....com>,
Mark Rutland <mark.rutland@....com>
Subject: [PATCH v4 5/6] arm64/kvm: control accessibility of ptrauth key registers
According to userspace settings, ptrauth key registers are conditionally
present in guest system register list based on user specified flag
KVM_ARM_VCPU_PTRAUTH.
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Christoffer Dall <christoffer.dall@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: kvmarm@...ts.cs.columbia.edu
---
Documentation/arm64/pointer-authentication.txt | 3 +-
arch/arm64/kvm/sys_regs.c | 42 +++++++++++++++++++-------
2 files changed, 33 insertions(+), 12 deletions(-)
diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt
index a65dca2..729055a 100644
--- a/Documentation/arm64/pointer-authentication.txt
+++ b/Documentation/arm64/pointer-authentication.txt
@@ -94,4 +94,5 @@ in KVM guests and attempted use of the feature will result in an UNDEFINED
exception being injected into the guest.
Additionally, when KVM_ARM_VCPU_PTRAUTH is not set then KVM will mask the
-feature bits from ID_AA64ISAR1_EL1.
+feature bits from ID_AA64ISAR1_EL1 and pointer authentication key registers
+are hidden from userspace.
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index ce6144a..09302b2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1343,12 +1343,6 @@ static const struct sys_reg_desc sys_reg_descs[] = {
{ SYS_DESC(SYS_TTBR1_EL1), access_vm_reg, reset_unknown, TTBR1_EL1 },
{ SYS_DESC(SYS_TCR_EL1), access_vm_reg, reset_val, TCR_EL1, 0 },
- PTRAUTH_KEY(APIA),
- PTRAUTH_KEY(APIB),
- PTRAUTH_KEY(APDA),
- PTRAUTH_KEY(APDB),
- PTRAUTH_KEY(APGA),
-
{ SYS_DESC(SYS_AFSR0_EL1), access_vm_reg, reset_unknown, AFSR0_EL1 },
{ SYS_DESC(SYS_AFSR1_EL1), access_vm_reg, reset_unknown, AFSR1_EL1 },
{ SYS_DESC(SYS_ESR_EL1), access_vm_reg, reset_unknown, ESR_EL1 },
@@ -1500,6 +1494,14 @@ static const struct sys_reg_desc sys_reg_descs[] = {
{ SYS_DESC(SYS_FPEXC32_EL2), NULL, reset_val, FPEXC32_EL2, 0x70 },
};
+static const struct sys_reg_desc ptrauth_reg_descs[] = {
+ PTRAUTH_KEY(APIA),
+ PTRAUTH_KEY(APIB),
+ PTRAUTH_KEY(APDA),
+ PTRAUTH_KEY(APDB),
+ PTRAUTH_KEY(APGA),
+};
+
static bool trap_dbgidr(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
@@ -2100,6 +2102,8 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu,
r = find_reg(params, table, num);
if (!r)
r = find_reg(params, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+ if (!r && kvm_arm_vcpu_ptrauth_allowed(vcpu))
+ r = find_reg(params, ptrauth_reg_descs, ARRAY_SIZE(ptrauth_reg_descs));
if (likely(r)) {
perform_access(vcpu, params, r);
@@ -2213,6 +2217,8 @@ static const struct sys_reg_desc *index_to_sys_reg_desc(struct kvm_vcpu *vcpu,
r = find_reg_by_id(id, ¶ms, table, num);
if (!r)
r = find_reg(¶ms, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+ if (!r && kvm_arm_vcpu_ptrauth_allowed(vcpu))
+ r = find_reg(¶ms, ptrauth_reg_descs, ARRAY_SIZE(ptrauth_reg_descs));
/* Not saved in the sys_reg array and not otherwise accessible? */
if (r && !(r->reg || r->get_user))
@@ -2494,18 +2500,22 @@ static int walk_one_sys_reg(const struct sys_reg_desc *rd,
}
/* Assumed ordered tables, see kvm_sys_reg_table_init. */
-static int walk_sys_regs(struct kvm_vcpu *vcpu, u64 __user *uind)
+static int walk_sys_regs(struct kvm_vcpu *vcpu, u64 __user *uind,
+ const struct sys_reg_desc *desc, unsigned int len)
{
const struct sys_reg_desc *i1, *i2, *end1, *end2;
unsigned int total = 0;
size_t num;
int err;
+ if (desc == ptrauth_reg_descs && !kvm_arm_vcpu_ptrauth_allowed(vcpu))
+ return total;
+
/* We check for duplicates here, to allow arch-specific overrides. */
i1 = get_target_table(vcpu->arch.target, true, &num);
end1 = i1 + num;
- i2 = sys_reg_descs;
- end2 = sys_reg_descs + ARRAY_SIZE(sys_reg_descs);
+ i2 = desc;
+ end2 = desc + len;
BUG_ON(i1 == end1 || i2 == end2);
@@ -2533,7 +2543,10 @@ unsigned long kvm_arm_num_sys_reg_descs(struct kvm_vcpu *vcpu)
{
return ARRAY_SIZE(invariant_sys_regs)
+ num_demux_regs()
- + walk_sys_regs(vcpu, (u64 __user *)NULL);
+ + walk_sys_regs(vcpu, (u64 __user *)NULL, sys_reg_descs,
+ ARRAY_SIZE(sys_reg_descs))
+ + walk_sys_regs(vcpu, (u64 __user *)NULL, ptrauth_reg_descs,
+ ARRAY_SIZE(ptrauth_reg_descs));
}
int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
@@ -2548,7 +2561,12 @@ int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
uindices++;
}
- err = walk_sys_regs(vcpu, uindices);
+ err = walk_sys_regs(vcpu, uindices, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+ if (err < 0)
+ return err;
+ uindices += err;
+
+ err = walk_sys_regs(vcpu, uindices, ptrauth_reg_descs, ARRAY_SIZE(ptrauth_reg_descs));
if (err < 0)
return err;
uindices += err;
@@ -2582,6 +2600,7 @@ void kvm_sys_reg_table_init(void)
BUG_ON(check_sysreg_table(cp15_regs, ARRAY_SIZE(cp15_regs)));
BUG_ON(check_sysreg_table(cp15_64_regs, ARRAY_SIZE(cp15_64_regs)));
BUG_ON(check_sysreg_table(invariant_sys_regs, ARRAY_SIZE(invariant_sys_regs)));
+ BUG_ON(check_sysreg_table(ptrauth_reg_descs, ARRAY_SIZE(ptrauth_reg_descs)));
/* We abuse the reset function to overwrite the table itself. */
for (i = 0; i < ARRAY_SIZE(invariant_sys_regs); i++)
@@ -2623,6 +2642,7 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
/* Generic chip reset first (so target could override). */
reset_sys_reg_descs(vcpu, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+ reset_sys_reg_descs(vcpu, ptrauth_reg_descs, ARRAY_SIZE(ptrauth_reg_descs));
table = get_target_table(vcpu->arch.target, true, &num);
reset_sys_reg_descs(vcpu, table, num);
--
2.7.4
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