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s390: fix save and restore of the floating-point-control register

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The FPC_VALID_MASK has been used to check the validity of the value
to be loaded into the floating-point-control register. With the
introduction of the floating-point extension facility and the
decimal-floating-point additional bits have been defined which need
to be checked in a non straight forward way. So far these bits have
been ignored which can cause an incorrect results for decimal-
floating-point operations, e.g. an incorrect rounding mode to be
set after signal return.

The static check with the FPC_VALID_MASK is replaced with a trial
load of the floating-point-control value, see test_fp_ctl.

In addition an information leak with the padding word between the
floating-point-control word and the floating-point registers in
the s390_fp_regs is fixed.

Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2013-10-15 16:08:34 +02:00
parent 01a7cfa24a
commit 4725c86055
10 changed files with 177 additions and 113 deletions
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23
arch/s390/kvm/kvm-s390.c
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@@ -343,10 +343,11 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
save_fp_regs(&vcpu->arch.host_fpregs);
save_fp_ctl(&vcpu->arch.host_fpregs.fpc);
save_fp_regs(vcpu->arch.host_fpregs.fprs);
save_access_regs(vcpu->arch.host_acrs);
vcpu->arch.guest_fpregs.fpc &= FPC_VALID_MASK;
restore_fp_regs(&vcpu->arch.guest_fpregs);
restore_fp_ctl(&vcpu->arch.guest_fpregs.fpc);
restore_fp_regs(vcpu->arch.guest_fpregs.fprs);
restore_access_regs(vcpu->run->s.regs.acrs);
gmap_enable(vcpu->arch.gmap);
atomic_set_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);
@@ -356,9 +357,11 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
atomic_clear_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);
gmap_disable(vcpu->arch.gmap);
save_fp_regs(&vcpu->arch.guest_fpregs);
save_fp_ctl(&vcpu->arch.guest_fpregs.fpc);
save_fp_regs(vcpu->arch.guest_fpregs.fprs);
save_access_regs(vcpu->run->s.regs.acrs);
restore_fp_regs(&vcpu->arch.host_fpregs);
restore_fp_ctl(&vcpu->arch.host_fpregs.fpc);
restore_fp_regs(vcpu->arch.host_fpregs.fprs);
restore_access_regs(vcpu->arch.host_acrs);
}
@@ -618,9 +621,12 @@ int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu,
int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
{
if (test_fp_ctl(fpu->fpc))
return -EINVAL;
memcpy(&vcpu->arch.guest_fpregs.fprs, &fpu->fprs, sizeof(fpu->fprs));
vcpu->arch.guest_fpregs.fpc = fpu->fpc & FPC_VALID_MASK;
restore_fp_regs(&vcpu->arch.guest_fpregs);
vcpu->arch.guest_fpregs.fpc = fpu->fpc;
restore_fp_ctl(&vcpu->arch.guest_fpregs.fpc);
restore_fp_regs(vcpu->arch.guest_fpregs.fprs);
return 0;
}
@@ -876,7 +882,8 @@ int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu, unsigned long addr)
* copying in vcpu load/put. Lets update our copies before we save
* it into the save area
*/
save_fp_regs(&vcpu->arch.guest_fpregs);
save_fp_ctl(&vcpu->arch.guest_fpregs.fpc);
save_fp_regs(vcpu->arch.guest_fpregs.fprs);
save_access_regs(vcpu->run->s.regs.acrs);
if (__guestcopy(vcpu, addr + offsetof(struct save_area, fp_regs),