[libc-commits] [libc] [libc] implement vdso (PR #91572)

[Nick Desaulniers via libc-commits]

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@@ -0,0 +1,258 @@
+//===------------- Linux VDSO Implementation --------------------*- 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/vdso.h"
+#include "src/__support/CPP/array.h"
+#include "src/__support/CPP/optional.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/threads/callonce.h"
+#include "src/__support/threads/linux/futex_word.h"
+#include "src/errno/libc_errno.h"
+#include "x86_64/vdso.h"
+#include <cstddef>
+#include <linux/auxvec.h>
+#include <linux/elf.h>
+
+#ifndef ElfW
+#if __POINTER_WIDTH__ == 32
+#define ElfW(type) Elf32_##type
+#else
+#define ElfW(type) Elf64_##type
+#endif
+#endif
+
+namespace LIBC_NAMESPACE {
+
+// we don't include getauxval.h as it may forcibly pull in elf.h (via
+// sys/auxv.h) in overlay mode instead, we provide a separate declaration for
+// getauxval
+unsigned long getauxval(unsigned long id);
+
+namespace vdso {
+
+namespace {
+
+// Helper functions to convert between VDSOSym and its index
+constexpr VDSOSym symbolize(size_t index) {
+  return static_cast<VDSOSym>(index);
+}
+constexpr size_t numeralize(VDSOSym sym) { return static_cast<size_t>(sym); }
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nickdesaulniers wrote:

These are explicit conversation functions.  I meant implicit casts (constructors).

https://github.com/llvm/llvm-project/pull/91572