On 26/03/15 12:16, Tim Deegan wrote:
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 <t...@xen.org>
CC: Keir Fraser <k...@xen.org>
CC: Jan Beulich <jbeul...@suse.com>
CC: Andrew Cooper <andrew.coop...@citrix.com>
I am very much in favour of this change.
Does REG_POISON work with a 32bit compile of the test harness?
Independent of this, it might be easier to spot in crashes if the upper
word of the address was also 8086
~Andrew
---
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;
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