On 07/08/2010 12:23 AM, Mohammed Gamal wrote:
This patch adds segment limit checks to the x86 emulator, in addition to some
helper functions and changes to the return values of emulate_push to accomodate
the new checks.
+static u32 seg_limit(struct x86_emulate_ctxt *ctxt,
+ struct x86_emulate_ops *ops, int seg)
+{
+ if (ctxt->mode == X86EMUL_MODE_PROT64&& seg< VCPU_SREG_FS)
Why the check on VCPU_SREG_FS? There are no limits in long mode (well
there's some AMD thing that does allow them).
+ return 0;
better to return -1ULL, that indicates no practical limit.
+
+ return ops->get_cached_segment_limit(seg, ctxt->vcpu);
+}
+
static void emulate_exception(struct x86_emulate_ctxt *ctxt, int vec,
u32 error, bool valid)
{
@@ -718,6 +745,11 @@ static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
{
int rc;
+ if (eip + size> cs_base(ctxt, ops) + cs_limit(ctxt, ops)) {
This can wrap around, for example if cs.base=0xf0000000, cs.limit=0x2000000.
Comparing eip - cs_base + size < cs_limit works around that.
@@ -1202,6 +1234,10 @@ done_prefixes:
c->src.ptr = (unsigned long *)
register_address(c, seg_override_base(ctxt, ops, c),
c->regs[VCPU_REGS_RSI]);
+ if (c->src.ptr> (unsigned long *) (es_base(ctxt, ops) +
es_limit(ctxt, ops))) {
+ emulate_gp(ctxt, 0);
+ return X86EMUL_PROPAGATE_FAULT;
Need to take into account the size fetched from src.ptr. For data
segments, there are expand-down segments which modify the check. See
SDM 5.3, "Limit Checking".
--
error compiling committee.c: too many arguments to function
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