diff options
| author | James Hogan <james.hogan@imgtec.com> | 2016-06-15 19:29:57 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-06-15 23:58:36 +0200 |
| commit | 42aa12e74e91f790d239bfb852260d07573ce83f (patch) | |
| tree | cf476b04bf159f8959fcce5340130bb823fbe1b2 /arch/mips/kvm/dyntrans.c | |
| parent | 05108709526716e1d40210fe3b9d7acd1cb694ea (diff) | |
MIPS: KVM: Move commpage so 0x0 is unmapped
The comm page which is mapped into the guest kernel address space at
0x0 has the unfortunate side effect of allowing guest kernel NULL
pointer dereferences to succeed. The only constraint on this address is
that it must be within 32KiB of 0x0, so that single lw/sw instructions
(which have 16-bit signed offset fields) can be used to access it, using
the zero register as a base.
So lets move the comm page as high as possible within that constraint so
that 0x0 can be left unmapped, at least for page sizes < 32KiB.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/mips/kvm/dyntrans.c')
| -rw-r--r-- | arch/mips/kvm/dyntrans.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/mips/kvm/dyntrans.c b/arch/mips/kvm/dyntrans.c index a3031dae8d1b..8a1833b9eb38 100644 --- a/arch/mips/kvm/dyntrans.c +++ b/arch/mips/kvm/dyntrans.c @@ -93,7 +93,7 @@ int kvm_mips_trans_mfc0(union mips_instruction inst, u32 *opc, } else { mfc0_inst.i_format.opcode = lw_op; mfc0_inst.i_format.rt = inst.c0r_format.rt; - mfc0_inst.i_format.simmediate = + mfc0_inst.i_format.simmediate = KVM_GUEST_COMMPAGE_ADDR | offsetof(struct kvm_mips_commpage, cop0.reg[rd][sel]); } @@ -111,7 +111,7 @@ int kvm_mips_trans_mtc0(union mips_instruction inst, u32 *opc, mtc0_inst.i_format.opcode = sw_op; mtc0_inst.i_format.rt = inst.c0r_format.rt; - mtc0_inst.i_format.simmediate = + mtc0_inst.i_format.simmediate = KVM_GUEST_COMMPAGE_ADDR | offsetof(struct kvm_mips_commpage, cop0.reg[rd][sel]); return kvm_mips_trans_replace(vcpu, opc, mtc0_inst); |