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Date:	Mon, 20 Oct 2014 14:54:59 +0400
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michal Marek <mmarek@...e.cz>,
	Sasha Levin <sasha.levin@...cle.com>, x86@...nel.org,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Andrey Ryabinin <a.ryabinin@...sung.com>,
	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Konstantin Khlebnikov <koct9i@...il.com>
Subject: [RFC PATCH] UBSan: run-time undefined behavior sanity checker


UBSan uses compile-time instrumentation to catch undefined behavior (UB).
Compiler inserts code that perform certain kinds of
checks before operations that could cause UB.
If check fails (i.e. UB detected) __ubsan_handle_* function called.
to print error message.

So the most of the work is done by compiler.
This patch just implements ubsan handlers printing errors.

GCC supports this since 4.9, however upcoming GCC 5.0 has
more checkers implemented.

Different kinds of checks could be enabled via boot parameter:
ubsan_handle=OEAINVBSLF.
If ubsan_handle not present in cmdline default options are used: ELNVBSLF

	O - different kinds of overflows
	E - negation overflow, division overflow, division by zero.
	A - misaligned memory access.
	I - load from/store to an object with insufficient space.
	N - null argument declared with nonnull attribute,
	  returned null from function which never returns null, null ptr dereference.
	V - variable size array with non-positive length
	B - out-of-bounds accesses.
	S - shifting out-of-bounds.
	L - load of invalid value (value out of range for the enum type, loading other then 0/1 to bool type)
	F - call to function through pointer with incorrect function type
	    (AFAIK this is not implemented in gcc yet, probably works with clang, though
	    	   I didn't check ubsan with clang at all).

Instrumentation in kernel/printk/printk.c is disabled because struct printk_log is not properly aligned,
therefore we are recursively taking logbuf_lock while trying to print error in __ubsan_handle*().

Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
---
 Makefile                              |  12 +-
 arch/x86/Kconfig                      |   1 +
 arch/x86/boot/Makefile                |   1 +
 arch/x86/boot/compressed/Makefile     |   1 +
 arch/x86/realmode/rm/Makefile         |   1 +
 arch/x86/vdso/Makefile                |   2 +
 drivers/firmware/efi/libstub/Makefile |   1 +
 include/linux/sched.h                 |   4 +
 kernel/printk/Makefile                |   1 +
 lib/Kconfig.debug                     |  23 ++
 lib/Makefile                          |   3 +
 lib/ubsan.c                           | 559 ++++++++++++++++++++++++++++++++++
 lib/ubsan.h                           |  84 +++++
 scripts/Makefile.lib                  |   6 +
 14 files changed, 698 insertions(+), 1 deletion(-)
 create mode 100644 lib/ubsan.c
 create mode 100644 lib/ubsan.h

diff --git a/Makefile b/Makefile
index 05d67af..d3e23f9 100644
--- a/Makefile
+++ b/Makefile
@@ -377,6 +377,9 @@ LDFLAGS_MODULE  =
 CFLAGS_KERNEL	=
 AFLAGS_KERNEL	=
 CFLAGS_GCOV	= -fprofile-arcs -ftest-coverage
+CFLAGS_UBSAN	= $(call cc-option, -fsanitize=undefined) \
+			$(call cc-option, -fno-sanitize=unreachable) \
+			$(call cc-option, -fno-sanitize=float-cast-overflow)
 
 
 # Use USERINCLUDE when you must reference the UAPI directories only.
@@ -421,7 +424,7 @@ export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE
 export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS
-export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV
+export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV CFLAGS_UBSAN
 export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
 export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
 export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
@@ -670,6 +673,13 @@ endif
 endif
 KBUILD_CFLAGS += $(stackp-flag)
 
+ifdef CONFIG_UBSAN
+  ifeq ($(strip $(CFLAGS_UBSAN)),)
+    $(warning Cannot use CONFIG_UBSAN: \
+             -fsanitize=undefined not supported by compiler)
+  endif
+endif
+
 ifeq ($(COMPILER),clang)
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
 KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f2327e8..b318fe8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -55,6 +55,7 @@ config X86
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_FP_TEST
+	select HAVE_ARCH_UBSAN_SANTIZE_ALL
 	select HAVE_SYSCALL_TRACEPOINTS
 	select SYSCTL_EXCEPTION_TRACE
 	select HAVE_KVM
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index 5b016e2..95bf522 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -57,6 +57,7 @@ endif
 KBUILD_CFLAGS	:= $(USERINCLUDE) $(REALMODE_CFLAGS) -D_SETUP
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
+UBSAN_SANITIZE := n
 
 $(obj)/bzImage: asflags-y  := $(SVGA_MODE)
 
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 704f58a..16940f8 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -19,6 +19,7 @@ KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
 
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
+UBSAN_SANITIZE :=n
 
 LDFLAGS := -m elf_$(UTS_MACHINE)
 LDFLAGS_vmlinux := -T
diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
index 7c0d7be..5c48444 100644
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -69,3 +69,4 @@ KBUILD_CFLAGS	:= $(LINUXINCLUDE) $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
 		   -I$(srctree)/arch/x86/boot
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
+UBSAN_SANITIZE := n
diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
index 5a4affe..3054473 100644
--- a/arch/x86/vdso/Makefile
+++ b/arch/x86/vdso/Makefile
@@ -4,6 +4,8 @@
 
 KBUILD_CFLAGS += $(DISABLE_LTO)
 
+UBSAN_SANITIZE := n
+
 VDSO64-$(CONFIG_X86_64)		:= y
 VDSOX32-$(CONFIG_X86_X32_ABI)	:= y
 VDSO32-$(CONFIG_X86_32)		:= y
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index b14bc2b..7b07624 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -19,6 +19,7 @@ KBUILD_CFLAGS			:= $(cflags-y) \
 				   $(call cc-option,-fno-stack-protector)
 
 GCOV_PROFILE			:= n
+UBSAN_SANITIZE			:= n
 
 lib-y				:= efi-stub-helper.o
 lib-$(CONFIG_EFI_ARMSTUB)	+= arm-stub.o fdt.o
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5e344bb..cfba635 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1661,6 +1661,10 @@ struct task_struct {
 	unsigned int	sequential_io;
 	unsigned int	sequential_io_avg;
 #endif
+
+#ifdef CONFIG_UBSAN
+	unsigned int in_ubsan;
+#endif
 };
 
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
index 85405bd..36461b5 100644
--- a/kernel/printk/Makefile
+++ b/kernel/printk/Makefile
@@ -1,2 +1,3 @@
 obj-y	= printk.o
 obj-$(CONFIG_A11Y_BRAILLE_CONSOLE)	+= braille.o
+UBSAN_SANITIZE := n
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 4e35a5d..7dc9b89 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -646,6 +646,29 @@ config DEBUG_SHIRQ
 	  Drivers ought to be able to handle interrupts coming in at those
 	  points; some don't and need to be caught.
 
+config HAVE_ARCH_UBSAN_SANTIZE_ALL
+	bool
+
+config UBSAN
+	bool "Undefined behaviour sanity checker"
+	help
+	  This option enables undefined behaviour sanity checker
+	  Compile-time instrumentataion used to detect various undefined
+	  behaviours in runtime. Different kinds of checks could be enabled
+	  via boot parameter ubsan_handle (see: Documentation/ubsan.txt).
+	  (TODO: write docs).
+
+config UBSAN_SANITIZE_ALL
+	bool "Enable instrumentation for the entire kernel"
+	depends on UBSAN
+	depends on HAVE_ARCH_UBSAN_SANTIZE_ALL
+	default y
+	help
+	  This option acitivates instrumentation for the entire kernel.
+	  If you don't enable this option, you have to explicitly specify
+	  UBSAN_SANITIZE := y for the files/directories you want to check for UB.
+
+
 menu "Debug Lockups and Hangs"
 
 config LOCKUP_DETECTOR
diff --git a/lib/Makefile b/lib/Makefile
index 7512dc9..d8c05c68 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -196,3 +196,6 @@ quiet_cmd_build_OID_registry = GEN     $@
 clean-files	+= oid_registry_data.c
 
 obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
+obj-$(CONFIG_UBSAN) += ubsan.o
+
+UBSAN_SANITIZE_ubsan.o := n
diff --git a/lib/ubsan.c b/lib/ubsan.c
new file mode 100644
index 0000000..7788f47
--- /dev/null
+++ b/lib/ubsan.c
@@ -0,0 +1,559 @@
+#include <linux/bug.h>
+#include <linux/ctype.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+
+#include "ubsan.h"
+
+const char *type_check_kinds[] = {
+	"load of",
+	"store to",
+	"reference binding to",
+	"member access within",
+	"member call on",
+	"constructor call on",
+	"downcast of",
+	"downcast of"
+};
+
+enum {
+	SUM_OVERFLOW,
+	SUB_OVERFLOW,
+	MUL_OVERFLOW,
+	NEG_OVERFLOW,
+	DIVREM_OVERFLOW,
+	ALIGNMENT,
+	OBJECT_SIZE,
+	NONNULL_ARG,
+	NONNULL_RET,
+	NULL_PTR,
+	VLA_BOUND,
+	OUT_OF_BOUNDS,
+	SHIFT_OUT_OF_BOUNDS,
+	INVALID_LOAD,
+	FUNC_TYPE_MISMATCH,
+	HANDLERS_END,
+};
+
+/* By default enable everything except signed overflows and
+ * misaligned accesses
+ */
+static unsigned long ubsan_handle = GENMASK(HANDLERS_END, 0) &
+	~(BIT_MASK(SUM_OVERFLOW) | BIT_MASK(SUB_OVERFLOW) |
+		BIT_MASK(NEG_OVERFLOW) | BIT_MASK(ALIGNMENT));
+
+static void enable_handler(unsigned int handler)
+{
+	set_bit(handler, &ubsan_handle);
+}
+
+static bool handler_enabled(unsigned int handler)
+{
+	return test_bit(handler, &ubsan_handle);
+}
+
+#define REPORTED_BIT 31
+#define COLUMN_MASK (~(1U << REPORTED_BIT))
+
+static bool is_disabled(struct source_location *location)
+{
+	return test_and_set_bit(REPORTED_BIT,
+				(unsigned long *)&location->column);
+}
+
+static void print_source_location(const char *prefix, struct source_location *loc)
+{
+	pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
+		loc->line, loc->column & COLUMN_MASK);
+}
+
+static bool type_is_int(struct type_descriptor *type)
+{
+	return type->type_kind == type_kind_int;
+}
+
+static bool type_is_signed(struct type_descriptor *type)
+{
+	return type_is_int(type) && (type->type_info & 1);
+}
+
+static unsigned type_bit_width(struct type_descriptor *type)
+{
+	return 1 << (type->type_info >> 1);
+}
+
+static bool is_inline_int(struct type_descriptor *type)
+{
+	unsigned inline_bits = sizeof(unsigned long)*8;
+	unsigned bits = type_bit_width(type);
+
+	return bits <= inline_bits;
+}
+
+static s_max get_signed_val(struct type_descriptor *type, unsigned long val)
+{
+	if (is_inline_int(type)) {
+		unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
+		return ((s_max)val) << extra_bits >> extra_bits;
+	}
+
+	if (type_bit_width(type) == 64)
+		return *(s64 *)val;
+
+	return *(s_max *)val;
+}
+
+static bool val_is_negative(struct type_descriptor *type, unsigned long val)
+{
+	return type_is_signed(type) && get_signed_val(type, val) < 0;
+}
+
+static u_max get_unsigned_val(struct type_descriptor *type, unsigned long val)
+{
+	if (is_inline_int(type))
+		return val;
+
+	if (type_bit_width(type) == 64)
+		return *(u64 *)val;
+
+	return *(u_max *)val;
+}
+
+static void val_to_string(char *str, size_t size, struct type_descriptor *type,
+	unsigned long value)
+{
+	u_max val = get_unsigned_val(type, value);
+
+	if (type_is_int(type)) {
+		if (type_bit_width(type) == 128)
+			scnprintf(str, size, "0x%08x%08x%08x%08x",
+				(u32)(val >> 96),
+				(u32)(val >> 64),
+				(u32)(val >> 32),
+				(u32)(val));
+		else if (type_is_signed(type))
+			scnprintf(str, size, "%lld",
+				(s64)get_signed_val(type, value));
+		else
+			scnprintf(str, size, "%llu",
+				(u64)get_unsigned_val(type, value));
+	}
+}
+
+static bool location_is_valid(struct source_location *loc)
+{
+	return loc->file_name != NULL;
+}
+
+static void ubsan_prologue(struct source_location *location)
+{
+	current->in_ubsan++;
+	pr_err("========================================"
+		"========================================\n");
+	print_source_location("UBSan: Undefined behaviour in", location);
+}
+
+static void ubsan_epilogue(void)
+{
+	dump_stack();
+	pr_err("========================================"
+		"========================================\n");
+	current->in_ubsan--;
+}
+
+static void handle_overflow(struct overflow_data *data, unsigned long lhs,
+			unsigned long rhs, char op)
+{
+
+	struct type_descriptor *type = data->type;
+	char lhs_val_str[60];
+	char rhs_val_str[60];
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
+	val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
+	pr_err("%s integer overflow:\n",
+		type_is_signed(type) ? "signed" : "unsigned");
+	pr_err("%s %c %s cannot be represented in type %s\n",
+		lhs_val_str,
+		op,
+		rhs_val_str,
+		type->type_name);
+
+	ubsan_epilogue();
+}
+
+void __ubsan_handle_add_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+
+	if (handler_enabled(SUM_OVERFLOW))
+		handle_overflow(data, lhs, rhs, '+');
+}
+EXPORT_SYMBOL(__ubsan_handle_add_overflow);
+
+void __ubsan_handle_sub_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+	if (handler_enabled(SUB_OVERFLOW))
+		handle_overflow(data, lhs, rhs, '-');
+}
+EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
+
+void __ubsan_handle_mul_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+	if (handler_enabled(MUL_OVERFLOW))
+		handle_overflow(data, lhs, rhs, '*');
+}
+EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
+
+void __ubsan_handle_negate_overflow(struct overflow_data *data,
+				unsigned long old_val)
+{
+
+	char old_val_str[60];
+
+	if (!handler_enabled(NEG_OVERFLOW))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
+
+	pr_err("negation of %s cannot be represented in type %s:\n",
+		old_val_str, data->type->type_name);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
+
+
+void __ubsan_handle_divrem_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+	char rhs_val_str[60];
+
+	if (!handler_enabled(DIVREM_OVERFLOW))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
+
+	if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
+		pr_err("division of %s by -1 cannot be represented in type %s\n",
+			rhs_val_str, data->type->type_name);
+	else
+		pr_err("division by zero\n");
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
+
+void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
+				unsigned long ptr)
+{
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	if (!ptr) {
+		if (!handler_enabled(NULL_PTR))
+			return;
+
+		ubsan_prologue(&data->location);
+
+		pr_err("%s null pointer of type %s\n",
+			type_check_kinds[data->type_check_kind],
+			data->type->type_name);
+	} else if (data->alignment && (ptr & (data->alignment - 1))) {
+		if (!handler_enabled(ALIGNMENT))
+			return;
+
+		ubsan_prologue(&data->location);
+		pr_err("%s misaligned address %p for type %s "
+			"which requires %ld byte alignment\n",
+			type_check_kinds[data->type_check_kind],
+			(void *)ptr, data->type->type_name, data->alignment);
+	} else {
+		if (!handler_enabled(OBJECT_SIZE))
+			return;
+
+		ubsan_prologue(&data->location);
+		pr_err("%s address %pk with insufficient space\n",
+			type_check_kinds[data->type_check_kind],
+			(void *) ptr);
+		pr_err("for an object of type %s\n", data->type->type_name);
+	}
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
+
+void __ubsan_handle_nonnull_arg(struct nonnull_arg_data *data)
+{
+
+	if (!handler_enabled(NONNULL_ARG))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	pr_err("null pointer passed as argument %d, declared with nonnull attribute\n",
+		data->arg_index);
+
+	if (location_is_valid(&data->attr_location))
+		print_source_location("nonnull attribute declared in ",
+				&data->attr_location);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_nonnull_arg);
+
+void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
+{
+	if (!handler_enabled(NONNULL_RET))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	pr_err("null pointer returned from function declared to never return null\n");
+
+	if (location_is_valid(&data->attr_location))
+		print_source_location("returns_nonnull attribute specified in",
+				&data->attr_location);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_nonnull_return);
+
+void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
+					unsigned long bound)
+{
+	char bound_str[60];
+
+	if (!handler_enabled(VLA_BOUND))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	val_to_string(bound_str, sizeof(bound_str), data->type, bound);
+	pr_err("variable length array bound value %s <= 0\n", bound_str);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_vla_bound_not_positive);
+
+void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data,
+				unsigned long index)
+{
+	char index_str[60];
+
+	if (!handler_enabled(OUT_OF_BOUNDS))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	val_to_string(index_str, sizeof(index_str), data->index_type, index);
+	pr_err("index %s out of bounds for type %s\n", index_str,
+		data->array_type->type_name);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
+
+void __ubsan_handle_shift_out_of_bounds(
+	struct shift_out_of_bounds_data *data,
+	unsigned long lhs,
+	unsigned long rhs)
+{
+	struct type_descriptor *rhs_type = data->rhs_type;
+	struct type_descriptor *lhs_type = data->lhs_type;
+	char rhs_str[60];
+	char lhs_str[60];
+
+	if (!handler_enabled(SHIFT_OUT_OF_BOUNDS))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
+	val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
+
+	if (val_is_negative(rhs_type, rhs))
+		pr_err("shift exponent %s is negative\n", rhs_str);
+
+	else if (get_unsigned_val(rhs_type, rhs) >=
+		type_bit_width(lhs_type))
+		pr_err("shift exponent %s is to large for %u-bit type %s\n",
+			rhs_str,
+			type_bit_width(lhs_type),
+			lhs_type->type_name);
+	else if (val_is_negative(lhs_type, lhs))
+		pr_err("left shift of negative value %s\n",
+			lhs_str);
+	else
+		pr_err("left shift of %s by %s places cannot be"
+			"represented in type %s\n",
+			lhs_str, rhs_str,
+			lhs_type->type_name);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
+
+void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
+				unsigned long val)
+{
+	char val_str[60];
+
+	if (!handler_enabled(INVALID_LOAD))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	val_to_string(val_str, sizeof(val_str), data->type, val);
+
+	pr_err("load of value %s is not a valid value for type %s\n",
+		val_str, data->type->type_name);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
+
+
+void __ubsan_handle_function_type_mismatch(struct func_type_mismatch_data *data,
+					unsigned long function)
+{
+
+	if (!handler_enabled(FUNC_TYPE_MISMATCH))
+		return;
+
+	if (current->in_ubsan)
+		return;
+
+	if (is_disabled(&data->location))
+		return;
+
+	ubsan_prologue(&data->location);
+
+	pr_err("call to function %pF through pointer to incorrect function type %s\n",
+		(void *)function, data->type->type_name);
+
+	ubsan_epilogue();
+}
+EXPORT_SYMBOL(__ubsan_handle_function_type_mismatch);
+
+static int __init setup_ubsan_handlers(char *str)
+{
+	ubsan_handle = 0;
+
+	for (; *str; str++) {
+		switch (tolower(*str)) {
+		case 'o':
+			enable_handler(SUM_OVERFLOW);
+			enable_handler(SUB_OVERFLOW);
+			enable_handler(MUL_OVERFLOW);
+			break;
+		case 'e':
+			enable_handler(NEG_OVERFLOW);
+			enable_handler(DIVREM_OVERFLOW);
+			break;
+		case 'a':
+			enable_handler(ALIGNMENT);
+			break;
+		case 'i':
+			enable_handler(OBJECT_SIZE);
+			break;
+		case 'n':
+			enable_handler(NONNULL_ARG);
+			enable_handler(NONNULL_RET);
+			enable_handler(NULL_PTR);
+			break;
+		case 'v':
+			enable_handler(VLA_BOUND);
+			break;
+		case 'b':
+			enable_handler(OUT_OF_BOUNDS);
+			break;
+		case 's':
+			enable_handler(SHIFT_OUT_OF_BOUNDS);
+			break;
+		case 'l':
+			enable_handler(INVALID_LOAD);
+			break;
+		case 'f':
+			enable_handler(FUNC_TYPE_MISMATCH);
+			break;
+		default:
+			pr_err("skipping unknown option '%c'\n", *str);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+early_param("ubsan_handle", setup_ubsan_handlers);
diff --git a/lib/ubsan.h b/lib/ubsan.h
new file mode 100644
index 0000000..e2d8634
--- /dev/null
+++ b/lib/ubsan.h
@@ -0,0 +1,84 @@
+#ifndef _LIB_UBSAN_H
+#define _LIB_UBSAN_H
+
+enum {
+	type_kind_int = 0,
+	type_kind_float = 1,
+	type_unknown = 0xffff
+};
+
+struct type_descriptor {
+	u16 type_kind;
+	u16 type_info;
+	char type_name[1];
+};
+
+struct source_location {
+	const char *file_name;
+	u32 line;
+	u32 column;
+};
+
+struct overflow_data {
+	struct source_location location;
+	struct type_descriptor *type;
+};
+
+struct type_mismatch_data {
+	struct source_location location;
+	struct type_descriptor *type;
+	unsigned long alignment;
+	unsigned char type_check_kind;
+};
+
+struct nonnull_arg_data {
+	struct source_location location;
+	struct source_location attr_location;
+	int arg_index;
+};
+
+struct nonnull_return_data {
+	struct source_location location;
+	struct source_location attr_location;
+};
+
+struct vla_bound_data {
+	struct source_location location;
+	struct type_descriptor *type;
+};
+
+struct out_of_bounds_data {
+	struct source_location location;
+	struct type_descriptor *array_type;
+	struct type_descriptor *index_type;
+};
+
+struct shift_out_of_bounds_data {
+	struct source_location location;
+	struct type_descriptor *lhs_type;
+	struct type_descriptor *rhs_type;
+};
+
+struct unreachable_data {
+	struct source_location location;
+};
+
+struct invalid_value_data {
+	struct source_location location;
+	struct type_descriptor *type;
+};
+
+struct func_type_mismatch_data {
+	struct source_location location;
+	struct type_descriptor *type;
+};
+
+#ifdef CONFIG_ARCH_SUPPORTS_INT128
+typedef __int128 s_max;
+typedef unsigned __int128 u_max;
+#else
+typedef s64 s_max;
+typedef u64 u_max;
+#endif
+
+#endif
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 54be19a..3f631b9 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -119,6 +119,12 @@ _c_flags += $(if $(patsubst n%,, \
 		$(CFLAGS_GCOV))
 endif
 
+ifeq ($(CONFIG_UBSAN),y)
+_c_flags += $(if $(patsubst n%,, \
+		$(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANITIZE_ALL)), \
+		$(CFLAGS_UBSAN))
+endif
+
 # If building the kernel in a separate objtree expand all occurrences
 # of -Idir to -I$(srctree)/dir except for absolute paths (starting with '/').
 
-- 
2.1.2

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