arm64: Support Clang UBSAN trap codes for better reporting

When building with CONFIG_UBSAN_TRAP=y on arm64, Clang encodes the UBSAN
check (handler) type in the esr. Extract this and actually report these
traps as coming from the specific UBSAN check that tripped.

Before:

  Internal error: BRK handler: 00000000f20003e8 [#1] PREEMPT SMP

After:

  Internal error: UBSAN: shift out of bounds: 00000000f2005514 [#1] PREEMPT SMP

Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Mukesh Ojha <quic_mojha@quicinc.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: John Stultz <jstultz@google.com>
Cc: Yongqin Liu <yongqin.liu@linaro.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Yury Norov <yury.norov@gmail.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: llvm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 68 insertions, 0 deletions

diff --git a/lib/ubsan.c b/lib/ubsan.c
index 60c7099857a0..6620e0719c9d 100644
--- a/lib/ubsan.c
+++ b/lib/ubsan.c
@@ -14,10 +14,76 @@
 #include <linux/types.h>
 #include <linux/sched.h>
 #include <linux/uaccess.h>
+#include <linux/ubsan.h>
 #include <kunit/test-bug.h>
 
 #include "ubsan.h"
 
+#ifdef CONFIG_UBSAN_TRAP
+/*
+ * Only include matches for UBSAN checks that are actually compiled in.
+ * The mappings of struct SanitizerKind (the -fsanitize=xxx args) to
+ * enum SanitizerHandler (the traps) in Clang is in clang/lib/CodeGen/.
+ */
+const char *report_ubsan_failure(struct pt_regs *regs, u32 check_type)
+{
+	switch (check_type) {
+#ifdef CONFIG_UBSAN_BOUNDS
+	/*
+	 * SanitizerKind::ArrayBounds and SanitizerKind::LocalBounds
+	 * emit SanitizerHandler::OutOfBounds.
+	 */
+	case ubsan_out_of_bounds:
+		return "UBSAN: array index out of bounds";
+#endif
+#ifdef CONFIG_UBSAN_SHIFT
+	/*
+	 * SanitizerKind::ShiftBase and SanitizerKind::ShiftExponent
+	 * emit SanitizerHandler::ShiftOutOfBounds.
+	 */
+	case ubsan_shift_out_of_bounds:
+		return "UBSAN: shift out of bounds";
+#endif
+#ifdef CONFIG_UBSAN_DIV_ZERO
+	/*
+	 * SanitizerKind::IntegerDivideByZero emits
+	 * SanitizerHandler::DivremOverflow.
+	 */
+	case ubsan_divrem_overflow:
+		return "UBSAN: divide/remainder overflow";
+#endif
+#ifdef CONFIG_UBSAN_UNREACHABLE
+	/*
+	 * SanitizerKind::Unreachable emits
+	 * SanitizerHandler::BuiltinUnreachable.
+	 */
+	case ubsan_builtin_unreachable:
+		return "UBSAN: unreachable code";
+#endif
+#if defined(CONFIG_UBSAN_BOOL) || defined(CONFIG_UBSAN_ENUM)
+	/*
+	 * SanitizerKind::Bool and SanitizerKind::Enum emit
+	 * SanitizerHandler::LoadInvalidValue.
+	 */
+	case ubsan_load_invalid_value:
+		return "UBSAN: loading invalid value";
+#endif
+#ifdef CONFIG_UBSAN_ALIGNMENT
+	/*
+	 * SanitizerKind::Alignment emits SanitizerHandler::TypeMismatch
+	 * or SanitizerHandler::AlignmentAssumption.
+	 */
+	case ubsan_alignment_assumption:
+		return "UBSAN: alignment assumption";
+	case ubsan_type_mismatch:
+		return "UBSAN: type mismatch";
+#endif
+	default:
+		return "UBSAN: unrecognized failure code";
+	}
+}
+
+#else
 static const char * const type_check_kinds[] = {
 	"load of",
 	"store to",
@@ -384,3 +450,5 @@ void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
 	ubsan_epilogue();
 }
 EXPORT_SYMBOL(__ubsan_handle_alignment_assumption);
+
+#endif /* !CONFIG_UBSAN_TRAP */