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Re: [PATCH v8] xen/domain: rewrite emulation_flags_ok()
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
- Date: Tue, 17 Jun 2025 08:53:51 +0200
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- Delivery-date: Tue, 17 Jun 2025 06:54:08 +0000
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On 2025-06-17 08:19, Jan Beulich wrote:
On 17.06.2025 03:15, dmkhn@xxxxxxxxx wrote:
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -743,32 +743,75 @@ int arch_sanitise_domain_config(struct
xen_domctl_createdomain *config)
return 0;
}
+/*
+ * Verify that the domain's emulation flags resolve to a supported
configuration.
+ *
+ * This ensures we only allow a known, safe subset of emulation
combinations
+ * (for both functionality and security). Arbitrary mixes are likely
to cause
+ * errors (e.g. null pointer dereferences).
+ *
+ * NB: use the internal X86_EMU_XXX symbols, not the public
XEN_X86_EMU_XXX
+ * symbols, to take build-time config options (e.g. CONFIG_HVM) into
account
+ * for short-circuited emulations.
+ */
static bool emulation_flags_ok(const struct domain *d, uint32_t
emflags)
{
+ enum domain_capability {
+ CAP_PV = BIT(0, U),
+ CAP_HVM = BIT(1, U),
+ CAP_HWDOM = BIT(2, U),
+ CAP_DOMU = BIT(3, U),
+ };
+ static const struct {
+ enum domain_capability caps;
+ uint32_t min;
+ uint32_t opt;
+ } configs[] = {
+#ifdef CONFIG_PV
+ /* PV dom0 and domU */
+ {
+ .caps = CAP_PV | CAP_HWDOM | CAP_DOMU,
Just to double check - are we sure Misra / Eclair will like this
(ab)use
of an enum?
Jan
Likely not, but x86_64 is build with CONFIG_PV=n
--
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253
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