Reapply "[UBSan] [compiler-rt] add preservecc variants of handlers" (#168973)

compiler-rt/lib/ubsan_minimal/ubsan_minimal_handlers.cpp

@@ -12,6 +12,22 @@ static void message(const char *msg) { ubsan_message(msg); }
 static void message(const char *msg) { (void)write(2, msg, strlen(msg)); }
 #endif
 
+// If for some reason we cannot build the runtime with preserve_all, don't
+// emit any symbol. Programs that need them will fail to link, but that is
+// better than randomly corrupted registers.
+// Some architectures don't support preserve_all (but clang still has the)
+// attribute. For now, only support x86-64 and aarch64.
+#if defined(__clang__) && defined(__has_cpp_attribute) &&                      \
+    (defined(__x86_64__) || defined(__aarch64__))
+#if __has_cpp_attribute(clang::preserve_all)
+#define PRESERVE_HANDLERS true
+#else
+#define PRESERVE_HANDLERS false
+#endif
+#else
+#define PRESERVE_HANDLERS false
+#endif
+
 static const int kMaxCallerPcs = 20;
 static __sanitizer::atomic_uintptr_t caller_pcs[kMaxCallerPcs];
 // Number of elements in caller_pcs. A special value of kMaxCallerPcs + 1 means
@@ -85,6 +101,18 @@ SANITIZER_INTERFACE_WEAK_DEF(void, __ubsan_report_error, const char *kind,
   }
 }
 
+#if PRESERVE_HANDLERS
+SANITIZER_INTERFACE_WEAK_DEF(void, __ubsan_report_error_preserve,
+                             const char *kind, uintptr_t caller)
+[[clang::preserve_all]] {
+  // Additional indirecton so the user can override this with their own
+  // preserve_all function. This would allow, e.g., a function that reports the
+  // first error only, so for all subsequent calls we can skip the register save
+  // / restore.
+  __ubsan_report_error(kind, caller);
+}
+#endif
+
 SANITIZER_INTERFACE_WEAK_DEF(void, __ubsan_report_error_fatal, const char *kind,
                              uintptr_t caller) {
   // Use another handlers, in case it's already overriden.
@@ -119,6 +147,16 @@ void NORETURN CheckFailed(const char *file, int, const char *cond, u64, u64) {
 
 #define INTERFACE extern "C" __attribute__((visibility("default")))
 
+#if PRESERVE_HANDLERS
+#define HANDLER_PRESERVE(name, kind)                                           \
+  INTERFACE void __ubsan_handle_##name##_minimal_preserve()                    \
+      [[clang::preserve_all]] {                                                \
+    __ubsan_report_error_preserve(kind, GET_CALLER_PC());                      \
+  }
+#else
+#define HANDLER_PRESERVE(name, kind)
+#endif
+
 #define HANDLER_RECOVER(name, kind)                                            \
   INTERFACE void __ubsan_handle_##name##_minimal() {                           \
     __ubsan_report_error(kind, GET_CALLER_PC());                               \
@@ -133,7 +171,8 @@ void NORETURN CheckFailed(const char *file, int, const char *cond, u64, u64) {
 
 #define HANDLER(name, kind)                                                    \
   HANDLER_RECOVER(name, kind)                                                  \
-  HANDLER_NORECOVER(name, kind)
+  HANDLER_NORECOVER(name, kind)                                                \
+  HANDLER_PRESERVE(name, kind)
 
 HANDLER(type_mismatch, "type-mismatch")
 HANDLER(alignment_assumption, "alignment-assumption")

compiler-rt/test/ubsan_minimal/TestCases/test-darwin-interface.c

@@ -4,6 +4,7 @@
 // REQUIRES: x86_64-darwin
 
 // RUN: nm -jgU `%clangxx_min_runtime -fsanitize-minimal-runtime -fsanitize=undefined %s -o %t '-###' 2>&1 | grep "libclang_rt.ubsan_minimal_osx_dynamic.dylib" | sed -e 's/.*"\(.*libclang_rt.ubsan_minimal_osx_dynamic.dylib\)".*/\1/'` | grep "^___ubsan_handle" \
+// RUN:  | grep -vE "_minimal_preserve" \
 // RUN:  | sed 's/_minimal//g' \
 // RUN:  > %t.minimal.symlist
 //