From f2d4f4ba80de8a03a1b0f300d271715a88a8433d Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 20 Jan 2017 14:37:33 +0100 Subject: [PATCH] x86emul: LOCK check adjustments BT, being encoded as DstBitBase just like BT{C,R,S}, nevertheless does not write its (register or memory) operand and hence also doesn't allow a LOCK prefix to be used. At the same time CLAC/STAC have no need to explicitly check lock_prefix - this is being taken care of by generic code. Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper --- xen/arch/x86/x86_emulate/x86_emulate.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index 520311f930..1c76379bb6 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -4668,8 +4668,7 @@ x86_emulate( case 0xca: /* clac */ case 0xcb: /* stac */ vcpu_must_have(smap); - generate_exception_if(lock_prefix || vex.pfx || !mode_ring0(), - EXC_UD); + generate_exception_if(vex.pfx || !mode_ring0(), EXC_UD); _regs._eflags &= ~EFLG_AC; if ( modrm == 0xcb ) @@ -5475,6 +5474,7 @@ x86_emulate( break; case X86EMUL_OPC(0x0f, 0xa3): bt: /* bt */ + generate_exception_if(lock_prefix, EXC_UD); emulate_2op_SrcV_nobyte("bt", src, dst, _regs._eflags); dst.type = OP_NONE; break; -- 2.30.2