libc/src/__support/OSUtil/linux/vdso.h

   1 //===------------- Linux VDSO Header ----------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 #ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_VDSO_H
   9 #define LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_VDSO_H
  10 #include "src/__support/CPP/array.h"
  11 #include "src/__support/common.h"
  12 #include "src/__support/macros/attributes.h"
  13 #include "src/__support/macros/properties/architectures.h"
  14 #include "src/__support/threads/callonce.h"
  15
  16 #if defined(LIBC_TARGET_ARCH_IS_X86)
  17 #include "x86_64/vdso.h"
  18 #elif defined(LIBC_TARGET_ARCH_IS_AARCH64)
  19 #include "aarch64/vdso.h"
  20 #elif defined(LIBC_TARGET_ARCH_IS_ARM)
  21 #include "arm/vdso.h"
  22 #elif defined(LIBC_TARGET_ARCH_IS_ANY_RISCV)
  23 #include "riscv/vdso.h"
  24 #else
  25 #error "unknown arch"
  26 #endif
  27
  28 namespace LIBC_NAMESPACE_DECL {
  29 namespace vdso {
  30
  31 class Symbol {
  32   VDSOSym sym;
  33
  34 public:
  35   LIBC_INLINE_VAR static constexpr size_t COUNT =
  36       static_cast<size_t>(VDSOSym::VDSOSymCount);
  37   LIBC_INLINE constexpr explicit Symbol(VDSOSym sym) : sym(sym) {}
  38   LIBC_INLINE constexpr Symbol(size_t idx) : sym(static_cast<VDSOSym>(idx)) {}
  39   LIBC_INLINE constexpr cpp::string_view name() const {
  40     return symbol_name(sym);
  41   }
  42   LIBC_INLINE constexpr cpp::string_view version() const {
  43     return symbol_version(sym);
  44   }
  45   LIBC_INLINE constexpr operator size_t() const {
  46     return static_cast<size_t>(sym);
  47   }
  48   LIBC_INLINE constexpr bool is_valid() const {
  49     return *this < Symbol::global_cache.size();
  50   }
  51   using VDSOArray = cpp::array<void *, Symbol::COUNT>;
  52
  53 private:
  54   static CallOnceFlag once_flag;
  55   static VDSOArray global_cache;
  56   static void initialize_vdso_global_cache();
  57
  58   LIBC_INLINE void *get() const {
  59     if (name().empty() || !is_valid())
  60       return nullptr;
  61
  62     callonce(&once_flag, Symbol::initialize_vdso_global_cache);
  63     return (global_cache[*this]);
  64   }
  65   template <VDSOSym sym> friend struct TypedSymbol;
  66 };
  67
  68 template <VDSOSym sym> struct TypedSymbol {
  69   LIBC_INLINE constexpr operator VDSOSymType<sym>() const {
  70     return cpp::bit_cast<VDSOSymType<sym>>(Symbol{sym}.get());
  71   }
  72   template <typename... Args>
  73   LIBC_INLINE auto operator()(Args &&...args) const {
  74     return this->operator VDSOSymType<sym>()(cpp::forward<Args>(args)...);
  75   }
  76 };
  77
  78 } // namespace vdso
  79
  80 } // namespace LIBC_NAMESPACE_DECL
  81 #endif // LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_VDSO_H