Module Name: src
Committed By: cherry
Date: Wed Feb 13 05:36:59 UTC 2019
Modified Files:
src/sys/arch/amd64/amd64: locore.S
src/sys/arch/i386/i386: locore.S
Log Message:
Rig the hypercall callback page such that when the kernel happens to
run without a XEN domain loader having previously overwritten the
hypercall page with its hypercall trampoline machine code, we still
get to detect its presence by calling the xen_version hypercall stub.
We use this hack to detect the presence or absence of the hypervisor,
without relying on the MSR support on HVM domains.
This works as an added sanity check that the hypercall page
registration has indeed succeeded in HVM mode.
To generate a diff of this commit:
cvs rdiff -u -r1.176 -r1.177 src/sys/arch/amd64/amd64/locore.S
cvs rdiff -u -r1.163 -r1.164 src/sys/arch/i386/i386/locore.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/amd64/amd64/locore.S
diff -u src/sys/arch/amd64/amd64/locore.S:1.176 src/sys/arch/amd64/amd64/locore.S:1.177
--- src/sys/arch/amd64/amd64/locore.S:1.176 Mon Feb 11 14:59:32 2019
+++ src/sys/arch/amd64/amd64/locore.S Wed Feb 13 05:36:59 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: locore.S,v 1.176 2019/02/11 14:59:32 cherry Exp $ */
+/* $NetBSD: locore.S,v 1.177 2019/02/13 05:36:59 cherry Exp $ */
/*
* Copyright-o-rama!
@@ -278,6 +278,8 @@
#define __ASSEMBLY__
#include <xen/include/public/elfnote.h>
#include <xen/include/public/xen.h>
+#endif /* XEN */
+
#ifdef XENPV
#define ELFNOTE(name, type, desctype, descdata...) \
.pushsection .note.name ; \
@@ -312,7 +314,6 @@
ELFNOTE(Xen, XEN_ELFNOTE_BSD_SYMTAB, .asciz, "yes")
#endif
#endif /* XENPV */
-#endif /* XEN */
/*
* Initialization
@@ -979,9 +980,12 @@ END(start)
#if defined(XEN)
/* space for the hypercall call page */
#define HYPERCALL_PAGE_OFFSET 0x1000
-.org HYPERCALL_PAGE_OFFSET
-ENTRY(hypercall_page)
-.skip 0x1000
+.align HYPERCALL_PAGE_OFFSET
+ENTRY(hypercall_page) /* Returns -1, on HYPERVISOR_xen_version() */
+.skip (__HYPERVISOR_xen_version*32), 0x90
+ movq $-1, %rax
+ retq
+.align HYPERCALL_PAGE_OFFSET, 0x90
END(hypercall_page)
#endif /* XEN */
Index: src/sys/arch/i386/i386/locore.S
diff -u src/sys/arch/i386/i386/locore.S:1.163 src/sys/arch/i386/i386/locore.S:1.164
--- src/sys/arch/i386/i386/locore.S:1.163 Mon Feb 11 14:59:32 2019
+++ src/sys/arch/i386/i386/locore.S Wed Feb 13 05:36:59 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: locore.S,v 1.163 2019/02/11 14:59:32 cherry Exp $ */
+/* $NetBSD: locore.S,v 1.164 2019/02/13 05:36:59 cherry Exp $ */
/*
* Copyright-o-rama!
@@ -128,7 +128,7 @@
*/
#include <machine/asm.h>
-__KERNEL_RCSID(0, "$NetBSD: locore.S,v 1.163 2019/02/11 14:59:32 cherry Exp $");
+__KERNEL_RCSID(0, "$NetBSD: locore.S,v 1.164 2019/02/13 05:36:59 cherry Exp $");
#include "opt_copy_symtab.h"
#include "opt_ddb.h"
@@ -242,6 +242,20 @@ __KERNEL_RCSID(0, "$NetBSD: locore.S,v 1
loop 1b ;
+#ifdef XEN
+/*
+ * Unfortunately, the Xen codebase uses nonstandard preprocessing tools.
+ * See: https://xenbits.xen.org/gitweb/?p=xen.git&a=search&h=HEAD&st=grep&s=__UnDeF__
+ * for a fine selection of examples.
+ *
+ * What this means for us here is that we can't include the standard
+ * xen.h header in assembler code.
+ *
+ * So we have to manually define, and keep track of the values we need, ourselves.
+ */
+#define __HYPERVISOR_xen_version 17
+#endif /* XEN */
+
#ifdef XENPV
/*
* Xen guest identifier and loader selection
@@ -916,9 +930,12 @@ END(start)
#if defined(XEN)
/* space for the hypercall call page */
#define HYPERCALL_PAGE_OFFSET 0x1000
-.org HYPERCALL_PAGE_OFFSET
-ENTRY(hypercall_page)
-.skip 0x1000
+.align HYPERCALL_PAGE_OFFSET
+ENTRY(hypercall_page) /* Returns -1, on HYPERVISOR_xen_version() */
+.skip (__HYPERVISOR_xen_version*32), 0x90
+ movl $-1, %eax
+ retl
+.align HYPERCALL_PAGE_OFFSET, 0x90
END(hypercall_page)
#ifdef XENPV
