From 6e616a3cef4d782253787904bf3d641112eafa14 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 15 Dec 2016 11:13:32 +0100 Subject: [PATCH] x86emul: ignore most segment bases for 64-bit mode in is_aligned() ops->read_segment() will report whatever is actually there in the register, so we need to actively distinguish ES/CS/SS/DS from FS/GS. Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper --- xen/arch/x86/x86_emulate/x86_emulate.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index 05fa342a94..dfdcd6ce7b 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -1642,12 +1642,17 @@ static bool is_aligned(enum x86_segment seg, unsigned long offs, /* Expecting powers of two only. */ ASSERT(!(size & (size - 1))); - /* No alignment checking when we have no way to read segment data. */ - if ( !ops->read_segment ) - return true; + if ( mode_64bit() && seg < x86_seg_fs ) + memset(®, 0, sizeof(reg)); + else + { + /* No alignment checking when we have no way to read segment data. */ + if ( !ops->read_segment ) + return true; - if ( ops->read_segment(seg, ®, ctxt) != X86EMUL_OKAY ) - return false; + if ( ops->read_segment(seg, ®, ctxt) != X86EMUL_OKAY ) + return false; + } return !((reg.base + offs) & (size - 1)); } -- 2.30.2