[libc-commits] [libc] [libc] implement secure random buffer filling with vDSO (PR #109870)

[Michael Jones via libc-commits]

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@@ -0,0 +1,363 @@
+//===- Linux implementation of secure random buffer generation --*- 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
+//
+//===----------------------------------------------------------------------===//
+#include "src/__support/OSUtil/linux/cprng.h"
+#include "src/__support/CPP/atomic.h"
+#include "src/__support/CPP/mutex.h"
+#include "src/__support/CPP/new.h"
+#include "src/__support/OSUtil/linux/syscall.h"
+#include "src/__support/OSUtil/linux/vdso.h"
+#include "src/__support/block.h"
+#include "src/__support/libc_assert.h"
+#include "src/__support/threads/callonce.h"
+#include "src/__support/threads/linux/raw_mutex.h"
+#include "src/sched/sched_getaffinity.h"
+#include "src/sched/sched_getcpucount.h"
+#include "src/sys/mman/mmap.h"
+#include "src/sys/mman/munmap.h"
+#include "src/unistd/sysconf.h"
+
+extern "C" int __cxa_thread_atexit_impl(void (*)(void *), void *, void *);
+extern "C" int __cxa_atexit(void (*)(void *), void *, void *);
+extern "C" [[gnu::weak, gnu::visibility("hidden")]] void *__dso_handle =
+    nullptr;
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michaelrj-google wrote:

this is a dependency on the C++ runtime, which we can't have inside of the libc. If you need to register `atexit` callbacks it should go through the internal `atexit` mechanism. Calling external functions like this is very bad for the hermeticity of this library and should only be done in very specific scenarios.

https://github.com/llvm/llvm-project/pull/109870