---
 arch/arm64/include/asm/brk-imm.h |  2 ++
 arch/arm64/kernel/traps.c        | 21 +++++++++++++
 include/linux/ubsan.h            |  9 ++++++
 lib/Makefile                     |  2 --
 lib/ubsan.c                      | 54 ++++++++++++++++++++++++++++++++
 lib/ubsan.h                      | 28 +++++++++++++++++
 6 files changed, 114 insertions(+), 2 deletions(-)
 create mode 100644 include/linux/ubsan.h

diff --git a/arch/arm64/include/asm/brk-imm.h b/arch/arm64/include/asm/brk-imm.h
index 6e000113e508..3f0f0d03268b 100644
--- a/arch/arm64/include/asm/brk-imm.h
+++ b/arch/arm64/include/asm/brk-imm.h

@@ -28,6 +28,8 @@
 #define BUG_BRK_IMM                    0x800
 #define KASAN_BRK_IMM                  0x900
 #define KASAN_BRK_MASK                 0x0ff
+#define UBSAN_BRK_IMM                  0x5500
+#define UBSAN_BRK_MASK                 0x00ff

 #define CFI_BRK_IMM_TARGET             GENMASK(4, 0)
 #define CFI_BRK_IMM_TYPE               GENMASK(9, 5)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 4c0caa589e12..87f42eb1c950 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c

@@ -26,6 +26,7 @@
 #include <linux/syscalls.h>
 #include <linux/mm_types.h>
 #include <linux/kasan.h>
+#include <linux/ubsan.h>
 #include <linux/cfi.h>

 #include <asm/atomic.h>

@@ -1074,6 +1075,19 @@ static struct break_hook kasan_break_hook = {
 };
 #endif

+#ifdef CONFIG_UBSAN_TRAP
+static int ubsan_handler(struct pt_regs *regs, unsigned long esr)
+{
+       die(report_ubsan_failure(regs, esr & UBSAN_BRK_MASK), regs, esr);
+       return DBG_HOOK_HANDLED;
+}
+
+static struct break_hook ubsan_break_hook = {
+       .fn     = ubsan_handler,
+       .imm    = UBSAN_BRK_IMM,
+       .mask   = UBSAN_BRK_MASK,
+};
+#endif

 #define esr_comment(esr) ((esr) & ESR_ELx_BRK64_ISS_COMMENT_MASK)

@@ -1091,6 +1105,10 @@ int __init early_brk64(unsigned long addr, unsigned long esr,
 #ifdef CONFIG_KASAN_SW_TAGS
        if ((esr_comment(esr) & ~KASAN_BRK_MASK) == KASAN_BRK_IMM)
                return kasan_handler(regs, esr) != DBG_HOOK_HANDLED;
+#endif
+#ifdef CONFIG_UBSAN_TRAP
+       if ((esr_comment(esr) & ~UBSAN_BRK_MASK) == UBSAN_BRK_IMM)
+               return ubsan_handler(regs, esr) != DBG_HOOK_HANDLED;
 #endif
        return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
 }

@@ -1104,6 +1122,9 @@ void __init trap_init(void)
        register_kernel_break_hook(&fault_break_hook);
 #ifdef CONFIG_KASAN_SW_TAGS
        register_kernel_break_hook(&kasan_break_hook);
+#endif
+#ifdef CONFIG_UBSAN_TRAP
+       register_kernel_break_hook(&ubsan_break_hook);
 #endif
        debug_traps_init();
 }

diff --git a/include/linux/ubsan.h b/include/linux/ubsan.h
new file mode 100644
index 000000000000..bff7445498de
--- /dev/null
+++ b/include/linux/ubsan.h

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_UBSAN_H
+#define _LINUX_UBSAN_H
+
+#ifdef CONFIG_UBSAN_TRAP
+const char *report_ubsan_failure(struct pt_regs *regs, u32 check_type);
+#endif
+
+#endif

diff --git a/lib/Makefile b/lib/Makefile
index 4d9461bfea42..81b988bf9448 100644
--- a/lib/Makefile
+++ b/lib/Makefile

@@ -340,9 +340,7 @@ quiet_cmd_build_OID_registry = GEN     $@
 clean-files    += oid_registry_data.c

 obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
-ifneq ($(CONFIG_UBSAN_TRAP),y)
 obj-$(CONFIG_UBSAN) += ubsan.o
-endif

 UBSAN_SANITIZE_ubsan.o := n
 KASAN_SANITIZE_ubsan.o := n

diff --git a/lib/ubsan.c b/lib/ubsan.c
index 60c7099857a0..98a671ec56e9 100644
--- a/lib/ubsan.c
+++ b/lib/ubsan.c

@@ -18,6 +18,58 @@

 #include "ubsan.h"

+#ifdef CONFIG_UBSAN_TRAP
+const char *report_ubsan_failure(struct pt_regs *regs, u32 check_type)
+{
+       switch (check_type) {
+       case ubsan_add_overflow:
+               return "UBSAN: addition overflow";

+       case ubsan_builtin_unreachable:
+               return "UBSAN: unreachable code";
+       case ubsan_cfi_check_fail:
+               return "UBSAN: CFI failure";
+       case ubsan_divrem_overflow:
+               return "UBSAN: divide/remainder overflow";
+       case ubsan_function_type_mismatch:
+               return "UBSAN: function type mismatch";
+       case ubsan_implicit_conversion:
+               return "UBSAN: implicit conversion";
+       case ubsan_invalid_builtin:
+               return "UBSAN: invalid builtin";
+       case ubsan_invalid_objc_cast:
+               return "UBSAN: invalid object cast";
+       case ubsan_load_invalid_value:
+               return "UBSAN: loading invalid value";
+       case ubsan_missing_return:
+               return "UBSAN: missing return";
+       case ubsan_mul_overflow:
+               return "UBSAN: multiplication overflow";
+       case ubsan_negate_overflow:
+               return "UBSAN: negation overflow";
+       case ubsan_nonnull_arg:
+               return "UBSAN: non-NULL argument";
+       case ubsan_nonnull_return:
+               return "UBSAN: non-NULL return";
+       case ubsan_out_of_bounds:
+               return "UBSAN: array index out of bounds";
+       case ubsan_pointer_overflow:
+               return "UBSAN: pointer overflow";
+       case ubsan_shift_out_of_bounds:
+               return "UBSAN: shift out of bounds";
+       case ubsan_sub_overflow:
+               return "UBSAN: subtraction overflow";
+       case ubsan_type_mismatch:
+               return "UBSAN: type mismatch";
+       case ubsan_alignment_assumption:
+               return "UBSAN: alignment assumption";
+       case ubsan_vla_bound_not_positive:
+               return "UBSAN: VLA bounds not positive";
+       default:
+               return "UBSAN: unknown failure";
+       }
+}
+
+#else
 static const char * const type_check_kinds[] = {
        "load of",
        "store to",

@@ -384,3 +436,5 @@ void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
        ubsan_epilogue();
 }
 EXPORT_SYMBOL(__ubsan_handle_alignment_assumption);
+
+#endif /* !CONFIG_UBSAN_TRAP */

diff --git a/lib/ubsan.h b/lib/ubsan.h
index 9a0b71c5ff9f..9c7f00f550f5 100644
--- a/lib/ubsan.h
+++ b/lib/ubsan.h

@@ -2,6 +2,34 @@
 #ifndef _LIB_UBSAN_H
 #define _LIB_UBSAN_H

+enum ubsan_checks {
+       ubsan_add_overflow,
+       ubsan_builtin_unreachable,
+       ubsan_cfi_check_fail,
+       ubsan_divrem_overflow,
+       ubsan_dynamic_type_cache_miss,
+       ubsan_float_cast_overflow,
+       ubsan_function_type_mismatch,
+       ubsan_implicit_conversion,
+       ubsan_invalid_builtin,
+       ubsan_invalid_objc_cast,
+       ubsan_load_invalid_value,
+       ubsan_missing_return,
+       ubsan_mul_overflow,
+       ubsan_negate_overflow,
+       ubsan_nullability_arg,
+       ubsan_nullability_return,
+       ubsan_nonnull_arg,
+       ubsan_nonnull_return,
+       ubsan_out_of_bounds,
+       ubsan_pointer_overflow,
+       ubsan_shift_out_of_bounds,
+       ubsan_sub_overflow,
+       ubsan_type_mismatch,
+       ubsan_alignment_assumption,
+       ubsan_vla_bound_not_positive,
+};
+
 enum {
        type_kind_int = 0,
        type_kind_float = 1,
--

2.34.1