[libcxx-commits] [libcxx] [libc++][hardening] Introduce a dylib function to log hardening errors. (PR #148266)
Konstantin Varlamov via libcxx-commits
libcxx-commits at lists.llvm.org
Fri Jul 11 10:51:08 PDT 2025
https://github.com/var-const created https://github.com/llvm/llvm-project/pull/148266
Unlike `verbose_abort`, this function merely logs the error but does not
terminate execution. It is intended to make it possible to implement the
`observe` semantic for Hardening.
>From 1fcfec368e34964811270b9a10ad969814e3a691 Mon Sep 17 00:00:00 2001
From: Konstantin Varlamov <varconst at apple.com>
Date: Fri, 11 Jul 2025 10:29:10 -0700
Subject: [PATCH] [libc++][hardening] Introduce a dylib function to log
hardening errors.
Unlike `verbose_abort`, this function merely logs the error but does not
terminate execution. It is intended to make it possible to implement the
`observe` semantic for Hardening.
---
libcxx/include/CMakeLists.txt | 1 +
libcxx/include/__configuration/availability.h | 5 ++
libcxx/include/__log_hardening_failure | 45 +++++++++++++++++
libcxx/src/CMakeLists.txt | 1 +
libcxx/src/log_hardening_failure.cpp | 49 +++++++++++++++++++
5 files changed, 101 insertions(+)
create mode 100644 libcxx/include/__log_hardening_failure
create mode 100644 libcxx/src/log_hardening_failure.cpp
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index c8e6d28584623..2f8be540e73e2 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -535,6 +535,7 @@ set(files
__locale_dir/time.h
__locale_dir/wbuffer_convert.h
__locale_dir/wstring_convert.h
+ __log_hardening_failure
__math/abs.h
__math/copysign.h
__math/error_functions.h
diff --git a/libcxx/include/__configuration/availability.h b/libcxx/include/__configuration/availability.h
index ae58e36b508b4..cb72e927caa9c 100644
--- a/libcxx/include/__configuration/availability.h
+++ b/libcxx/include/__configuration/availability.h
@@ -304,6 +304,11 @@
#define _LIBCPP_AVAILABILITY_HAS_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15
#define _LIBCPP_AVAILABILITY_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15_ATTRIBUTE
+// This controls whether the library provides a function to log hardening failures without terminating the program (for
+// the `observe` assertion semantic).
+#define _LIBCPP_AVAILABILITY_HAS_LOG_HARDENING_FAILURE _LIBCPP_INTRODUCED_IN_LLVM_21
+#define _LIBCPP_AVAILABILITY_LOG_HARDENING_FAILURE _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE
+
// This controls the availability of the C++17 std::pmr library,
// which is implemented in large part in the built library.
//
diff --git a/libcxx/include/__log_hardening_failure b/libcxx/include/__log_hardening_failure
new file mode 100644
index 0000000000000..73cff0ac64155
--- /dev/null
+++ b/libcxx/include/__log_hardening_failure
@@ -0,0 +1,45 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___LOG_HARDENING_FAILURE
+#define _LIBCPP___LOG_HARDENING_FAILURE
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// This function should never be called directly from the code -- it should only be called through the
+// `_LIBCPP_LOG_HARDENING_FAILURE` macro.
+_LIBCPP_AVAILABILITY_LOG_HARDENING_FAILURE _LIBCPP_OVERRIDABLE_FUNC_VIS void
+__libcpp_log_hardening_failure(const char* message) _NOEXCEPT;
+
+// _LIBCPP_LOG_HARDENING_FAILURE(message)
+//
+// This macro is used to log a hardening failure without terminating the program (as is the case if the `observe`
+// assertion semantic is used). Where possible, it logs in a way that indicates a fatal error (which might include
+// capturing the stack trace).
+#if !defined(_LIBCPP_LOG_HARDENING_FAILURE)
+
+# if !_LIBCPP_AVAILABILITY_HAS_LOG_HARDENING_FAILURE
+// The decltype is there to suppress -Wunused warnings in this configuration.
+void __use(const char*);
+# define _LIBCPP_LOG_HARDENING_FAILURE(message) (decltype(::std::__use(message))())
+# else
+# define _LIBCPP_LOG_HARDENING_FAILURE(message) ::std::__libcpp_log_hardening_failure(message)
+# endif
+
+#endif // !defined(_LIBCPP_LOG_HARDENING_FAILURE)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___LOG_HARDENING_FAILURE
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 97fe57a5f24f8..926deb3a1c732 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -30,6 +30,7 @@ set(LIBCXX_SOURCES
include/ryu/ryu.h
include/to_chars_floating_point.h
include/from_chars_floating_point.h
+ log_hardening_failure.cpp
memory.cpp
memory_resource.cpp
new_handler.cpp
diff --git a/libcxx/src/log_hardening_failure.cpp b/libcxx/src/log_hardening_failure.cpp
new file mode 100644
index 0000000000000..7e408a6f010b4
--- /dev/null
+++ b/libcxx/src/log_hardening_failure.cpp
@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__log_hardening_failure>
+#include <cstdio>
+
+#ifdef __BIONIC__
+# include <syslog.h>
+extern "C" void android_set_abort_message(const char* msg);
+#endif // __BIONIC__
+
+#if defined(__APPLE__) && __has_include(<os/reason_private.h>)
+# include <os/reason_private.h>
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_WEAK void __libcpp_log_hardening_failure(const char* message) noexcept {
+ // On Apple platforms, use the `os_fault_with_payload` OS function that simulates a crash.
+#if defined(__APPLE__) && __has_include(<os/reason_private.h>)
+ os_fault_with_payload(
+ /*reason_namespace=*/OS_REASON_SECURITY,
+ /*reason_code=*/0,
+ /*payload=*/nullptr,
+ /*payload_size=*/0,
+ /*reason_string=*/message,
+ /*reason_flags=*/0);
+
+#elif defined(__BIONIC__)
+ // Show error in tombstone.
+ android_set_abort_message(message);
+
+ // Show error in logcat.
+ openlog("libc++", 0, 0);
+ syslog(LOG_CRIT, "%s", message);
+ closelog();
+
+#else
+ fprintf(stderr, "%s", message);
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_STD
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