[libcxx-commits] [libcxx] [libc++][hardening] Introduce a dylib function to log hardening errors. (PR #148266)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_error>
+#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 <TargetConditionals.h>
+#  include <os/reason_private.h>
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace {
+
+void log_security_failure(const char* message) noexcept {
+  // Always log the message to `stderr` in case the platform-specific system calls fail.
+  fputs(message, stderr);
+
+  // On Apple platforms, use the `os_fault_with_payload` OS function that simulates a crash.
+#if defined(__APPLE__) && __has_include(<os/reason_private.h>) && !TARGET_OS_SIMULATOR
+  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();
+#endif
+}
+
+} // namespace
+
+void __log_error(__log_error_reason reason, const char* message) noexcept {
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ldionne wrote:

Can we add a simple test inside `libcxx/test/libcxx` to exercise this function? Otherwise this is entirely dead code.

We won't be able to test much, but we can at least ensure that the function can be called at runtime and that it's `noexcept`. That's better than nothing!

https://github.com/llvm/llvm-project/pull/148266