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

[Schrodinger ZHU Yifan via libc-commits]

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@@ -0,0 +1,42 @@
+//===---------- x86/x86_64 vdso configuration ---------------------* 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 LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_X86_64_VDSO_H
+#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_X86_64_VDSO_H
+#include "src/__support/CPP/string_view.h"
+namespace LIBC_NAMESPACE {
+namespace vdso {
+// translate VDSOSym to symbol names
+// On x86, there are symbols defined without the __vdso_ prefix, however,
+// it is suggested that one should use the __vdso_ prefix.
+// Additionally, there is also an __vdso_sgx_enter_enclave, it is for the SGX
+// support, we do not include it here for now.
+// https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/entry/vdso/vdso.lds.S
+LIBC_INLINE constexpr cpp::string_view symbol_name(VDSOSym sym) {
+  switch (sym) {
+  case VDSOSym::ClockGetTime:
+    return "__vdso_clock_gettime";
+  case VDSOSym::GetTimeOfDay:
+    return "__vdso_gettimeofday";
+  case VDSOSym::GetCpu:
+    return "__vdso_getcpu";
+  case VDSOSym::Time:
+    return "__vdso_time";
+  case VDSOSym::ClockGetRes:
+    return "__vdso_clock_getres";
+  default:
+    return "";
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SchrodingerZhu wrote:

Theoretically, this can be done by checking unknown names.
However, a symbol in VSDO can have multiple names (see the x86 examples).

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