drivers/xen/privcmd.o: warning: objtool: privcmd_ioctl()+0x1414: call to
hypercall_page() with UACCESS enabled
Xen needs to do HV calls with AC=1 for hysterical raisins. Make the
warning go away.
XXX: arguably we should rename ANNOTATE_NOSPEC_ALTERNATIVE to
ANNOTATE_IGNORE_ALTERNATIVE.
Cc: andrew.coop...@citrix.com
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
arch/x86/include/asm/xen/hypercall.h | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -214,6 +214,24 @@ xen_single_call(unsigned int call,
return (long)__res;
}
+static __always_inline void __xen_stac(void)
+{
+ /*
+ * This is just about as horrible as this interface; we abuse the
+ * nospec alternative annotation to supress objtool seeing the
+ * STAC/CLAC and getting confused about it calling random code with
+ * AC=1.
+ */
+ asm volatile(ANNOTATE_NOSPEC_ALTERNATIVE
+ ASM_STAC ::: "memory", "flags");
+}
+
+static __always_inline void __xen_clac(void)
+{
+ asm volatile(ANNOTATE_NOSPEC_ALTERNATIVE
+ ASM_CLAC ::: "memory", "flags");
+}
+
static inline long
privcmd_call(unsigned int call,
unsigned long a1, unsigned long a2,
@@ -222,9 +240,9 @@ privcmd_call(unsigned int call,
{
long res;
- stac();
+ __xen_stac();
res = xen_single_call(call, a1, a2, a3, a4, a5);
- clac();
+ __xen_clac();
return res;
}
@@ -430,9 +448,9 @@ HYPERVISOR_dm_op(
domid_t dom, unsigned int nr_bufs, struct xen_dm_op_buf *bufs)
{
int ret;
- stac();
+ __xen_stac();
ret = _hypercall3(int, dm_op, dom, nr_bufs, bufs);
- clac();
+ __xen_clac();
return ret;
}
