From: Tim Deegan Subject: [PATCH] x86_emulate: split the {reg, mem} union in struct operand. Date: Thu, 26 Mar 2015 12:16:14 +0000 Message-ID: <1427372174-980-1-git-send-email-tim@xen.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: xen-devel@lists.xen.org Cc: Andrew Cooper , Keir Fraser , Jan Beulich List-Id: xen-devel@lists.xenproject.org In the hopes of making any future errors along the lines of XSA-123 into clean crashes instead of memory corruption bugs. Signed-off-by: Tim Deegan CC: Keir Fraser CC: Jan Beulich CC: Andrew Cooper --- xen/arch/x86/x86_emulate/x86_emulate.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index c082c9e..37d1fea 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -319,7 +319,7 @@ struct operand { /* Original operand value. */ unsigned long orig_val; - union { + struct { /* OP_REG: Pointer to register field. */ unsigned long *reg; /* OP_MEM: Segment and offset. */ @@ -329,6 +329,7 @@ struct operand { } mem; }; }; +#define REG_POISON ((unsigned long *) 0x8000000000008086UL) /* non-canonical */ typedef union { uint64_t mmx; @@ -1447,14 +1448,15 @@ x86_emulate( unsigned int op_bytes, def_op_bytes, ad_bytes, def_ad_bytes; bool_t lock_prefix = 0; int override_seg = -1, rc = X86EMUL_OKAY; - struct operand src, dst; + struct operand src = { .reg = REG_POISON }; + struct operand dst = { .reg = REG_POISON }; enum x86_swint_type swint_type; DECLARE_ALIGNED(mmval_t, mmval); /* * Data operand effective address (usually computed from ModRM). * Default is a memory operand relative to segment DS. */ - struct operand ea = { .type = OP_MEM }; + struct operand ea = { .type = OP_MEM, .reg = REG_POISON }; ea.mem.seg = x86_seg_ds; /* gcc may reject anon union initializer */ ctxt->retire.byte = 0; -- 2.1.4