From b6b7a8069d5f44bcc248f5d067cdb22debadfa56 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 27 Mar 2017 17:03:43 +0100 Subject: [PATCH] arm64: KVM: Do not corrupt registers on failed 64bit CP read If we fail to emulate a mrrc instruction, we: 1) deliver an exception, 2) spit a nastygram on the console, 3) write back some garbage to Rt/Rt2 While 1) and 2) are perfectly acceptable, 3) is out of the scope of the architecture... Let's mimick the code in kvm_handle_cp_32 and be more cautious. Reviewed-by: Christoffer Dall Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall --- arch/arm64/kvm/sys_regs.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 2f4418ed4a70..582d68ee4b01 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1678,20 +1678,25 @@ static int kvm_handle_cp_64(struct kvm_vcpu *vcpu, params.regval |= vcpu_get_reg(vcpu, Rt2) << 32; } - if (!emulate_cp(vcpu, ¶ms, target_specific, nr_specific)) - goto out; - if (!emulate_cp(vcpu, ¶ms, global, nr_global)) - goto out; - - unhandled_cp_access(vcpu, ¶ms); + /* + * Try to emulate the coprocessor access using the target + * specific table first, and using the global table afterwards. + * If either of the tables contains a handler, handle the + * potential register operation in the case of a read and return + * with success. + */ + if (!emulate_cp(vcpu, ¶ms, target_specific, nr_specific) || + !emulate_cp(vcpu, ¶ms, global, nr_global)) { + /* Split up the value between registers for the read side */ + if (!params.is_write) { + vcpu_set_reg(vcpu, Rt, lower_32_bits(params.regval)); + vcpu_set_reg(vcpu, Rt2, upper_32_bits(params.regval)); + } -out: - /* Split up the value between registers for the read side */ - if (!params.is_write) { - vcpu_set_reg(vcpu, Rt, lower_32_bits(params.regval)); - vcpu_set_reg(vcpu, Rt2, upper_32_bits(params.regval)); + return 1; } + unhandled_cp_access(vcpu, ¶ms); return 1; } -- 2.30.2