[PATCH v2 3/3] xen: hook up UBSAN with CONFIG_UBSAN

[Wei Liu <wei.liu2@citrix.com>]

Make the following changes:

1. Introduce CONFIG_UBSAN and other auxiliary options.
2. Introduce Build system rune to filter objects.
3. Make ubsan.c build.

Currently only x86 is supported. All init.o's are filtered out because
of limitation in the build system. There is no user of noubsan-y yet
but it is worth keeping to ease future development.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
---
 xen/Kconfig              |  6 ++++++
 xen/Kconfig.debug        | 10 ++++++++++
 xen/Rules.mk             |  4 ++++
 xen/arch/x86/Kconfig     |  2 ++
 xen/common/Kconfig       |  3 +++
 xen/common/Makefile      |  1 +
 xen/common/ubsan/ubsan.c | 19 ++++++++++++-------
 7 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/xen/Kconfig b/xen/Kconfig
index 65d491d776..ea7229ad1f 100644
--- a/xen/Kconfig
+++ b/xen/Kconfig
@@ -38,4 +38,10 @@ config LTO
 
 	  If unsure, say N.
 
+#
+# For architectures that know their compiler __int128 support is sound
+#
+config ARCH_SUPPORTS_INT128
+	bool
+
 source "Kconfig.debug"
diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
index 195d504147..3329c75bfd 100644
--- a/xen/Kconfig.debug
+++ b/xen/Kconfig.debug
@@ -121,6 +121,16 @@ config SCRUB_DEBUG
 	  Verify that pages that need to be scrubbed before being allocated to
 	  a guest are indeed scrubbed.
 
+config UBSAN
+	bool "Undefined behaviour sanitizer"
+	depends on HAS_UBSAN
+	---help---
+	  Enable undefined behaviour sanitizer. It uses compiler to insert code
+	  snippets so that undefined behaviours in C are detected during runtime.
+	  This requires a UBSAN capable compiler and it is a debug only feature.
+
+	  If unsure, say N here.
+
 endif # DEBUG || EXPERT
 
 endmenu
diff --git a/xen/Rules.mk b/xen/Rules.mk
index cafc67b86e..2659f8a4d1 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -119,6 +119,10 @@ ifeq ($(CONFIG_GCOV),y)
 $(filter-out %.init.o $(nogcov-y),$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS += -fprofile-arcs -ftest-coverage
 endif
 
+ifeq ($(CONFIG_UBSAN),y)
+$(filter-out %.init.o $(noubsan-y),$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS += -fsanitize=undefined
+endif
+
 ifeq ($(CONFIG_LTO),y)
 CFLAGS += -flto
 LDFLAGS-$(clang) += -plugin LLVMgold.so
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 30c2769684..64955dc017 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -5,6 +5,7 @@ config X86
 	def_bool y
 	select ACPI
 	select ACPI_LEGACY_TABLES_LOOKUP
+	select ARCH_SUPPORTS_INT128
 	select COMPAT
 	select CORE_PARKING
 	select HAS_ALTERNATIVE
@@ -21,6 +22,7 @@ config X86
 	select HAS_PASSTHROUGH
 	select HAS_PCI
 	select HAS_PDX
+	select HAS_UBSAN
 	select NUMA
 	select VGA
 
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index e9bb849298..103ef44cb5 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -32,6 +32,9 @@ config HAS_MEM_SHARING
 config HAS_PDX
 	bool
 
+config HAS_UBSAN
+	bool
+
 config HAS_KEXEC
 	bool
 
diff --git a/xen/common/Makefile b/xen/common/Makefile
index 39e2614546..66cc2c8995 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -75,6 +75,7 @@ tmem-$(CONFIG_COMPAT) += compat/tmem_xen.o
 obj-$(CONFIG_TMEM) += $(tmem-y)
 
 subdir-$(CONFIG_GCOV) += gcov
+subdir-$(CONFIG_UBSAN) += ubsan
 
 subdir-y += libelf
 subdir-$(CONFIG_HAS_DEVICE_TREE) += libfdt
diff --git a/xen/common/ubsan/ubsan.c b/xen/common/ubsan/ubsan.c
index 685b4de0d6..fbe568562a 100644
--- a/xen/common/ubsan/ubsan.c
+++ b/xen/common/ubsan/ubsan.c
@@ -10,13 +10,18 @@
  *
  */
 
-#include <linux/bitops.h>
-#include <linux/bug.h>
-#include <linux/ctype.h>
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/types.h>
-#include <linux/sched.h>
+#include <xen/spinlock.h>
+#include <xen/percpu.h>
+
+#define __noreturn    noreturn
+#define pr_err(...) printk(XENLOG_ERR __VA_ARGS__)
+struct xen_ubsan { int in_ubsan; };
+static DEFINE_PER_CPU(struct xen_ubsan[1], in_ubsan);
+#undef current
+#define current this_cpu(in_ubsan)
+#define dump_stack dump_execution_state
+#define u64 long long unsigned int
+#define s64 long long int
 
 #include "ubsan.h"
 
-- 
2.11.0


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