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//===- llvm/Support/Memory.h - Memory Support --------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the llvm::sys::Memory class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_MEMORY_H
#define LLVM_SUPPORT_MEMORY_H
#include "llvm/Support/DataTypes.h"
#include <string>
#include <system_error>
namespace llvm {
namespace sys {
/// This class encapsulates the notion of a memory block which has an address
/// and a size. It is used by the Memory class (a friend) as the result of
/// various memory allocation operations.
/// @see Memory
/// @brief Memory block abstraction.
class MemoryBlock {
public:
MemoryBlock() : Address(nullptr), Size(0) { }
MemoryBlock(void *addr, size_t size) : Address(addr), Size(size) { }
void *base() const { return Address; }
size_t size() const { return Size; }
private:
void *Address; ///< Address of first byte of memory area
size_t Size; ///< Size, in bytes of the memory area
friend class Memory;
};
/// This class provides various memory handling functions that manipulate
/// MemoryBlock instances.
/// @since 1.4
/// @brief An abstraction for memory operations.
class Memory {
public:
enum ProtectionFlags {
MF_READ = 0x1000000,
MF_WRITE = 0x2000000,
MF_EXEC = 0x4000000
};
/// This method allocates a block of memory that is suitable for loading
/// dynamically generated code (e.g. JIT). An attempt to allocate
/// \p NumBytes bytes of virtual memory is made.
/// \p NearBlock may point to an existing allocation in which case
/// an attempt is made to allocate more memory near the existing block.
/// The actual allocated address is not guaranteed to be near the requested
/// address.
/// \p Flags is used to set the initial protection flags for the block
/// of the memory.
/// \p EC [out] returns an object describing any error that occurs.
///
/// This method may allocate more than the number of bytes requested. The
/// actual number of bytes allocated is indicated in the returned
/// MemoryBlock.
///
/// The start of the allocated block must be aligned with the
/// system allocation granularity (64K on Windows, page size on Linux).
/// If the address following \p NearBlock is not so aligned, it will be
/// rounded up to the next allocation granularity boundary.
///
/// \r a non-null MemoryBlock if the function was successful,
/// otherwise a null MemoryBlock is with \p EC describing the error.
///
/// @brief Allocate mapped memory.
static MemoryBlock allocateMappedMemory(size_t NumBytes,
const MemoryBlock *const NearBlock,
unsigned Flags,
std::error_code &EC);
/// This method releases a block of memory that was allocated with the
/// allocateMappedMemory method. It should not be used to release any
/// memory block allocated any other way.
/// \p Block describes the memory to be released.
///
/// \r error_success if the function was successful, or an error_code
/// describing the failure if an error occurred.
///
/// @brief Release mapped memory.
static std::error_code releaseMappedMemory(MemoryBlock &Block);
/// This method sets the protection flags for a block of memory to the
/// state specified by /p Flags. The behavior is not specified if the
/// memory was not allocated using the allocateMappedMemory method.
/// \p Block describes the memory block to be protected.
/// \p Flags specifies the new protection state to be assigned to the block.
/// \p ErrMsg [out] returns a string describing any error that occurred.
///
/// If \p Flags is MF_WRITE, the actual behavior varies
/// with the operating system (i.e. MF_READ | MF_WRITE on Windows) and the
/// target architecture (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386).
///
/// \r error_success if the function was successful, or an error_code
/// describing the failure if an error occurred.
///
/// @brief Set memory protection state.
static std::error_code protectMappedMemory(const MemoryBlock &Block,
unsigned Flags);
/// This method allocates a block of Read/Write/Execute memory that is
/// suitable for executing dynamically generated code (e.g. JIT). An
/// attempt to allocate \p NumBytes bytes of virtual memory is made.
/// \p NearBlock may point to an existing allocation in which case
/// an attempt is made to allocate more memory near the existing block.
///
/// On success, this returns a non-null memory block, otherwise it returns
/// a null memory block and fills in *ErrMsg.
///
/// @brief Allocate Read/Write/Execute memory.
static MemoryBlock AllocateRWX(size_t NumBytes,
const MemoryBlock *NearBlock,
std::string *ErrMsg = nullptr);
/// This method releases a block of Read/Write/Execute memory that was
/// allocated with the AllocateRWX method. It should not be used to
/// release any memory block allocated any other way.
///
/// On success, this returns false, otherwise it returns true and fills
/// in *ErrMsg.
/// @brief Release Read/Write/Execute memory.
static bool ReleaseRWX(MemoryBlock &block, std::string *ErrMsg = nullptr);
/// InvalidateInstructionCache - Before the JIT can run a block of code
/// that has been emitted it must invalidate the instruction cache on some
/// platforms.
static void InvalidateInstructionCache(const void *Addr, size_t Len);
/// setExecutable - Before the JIT can run a block of code, it has to be
/// given read and executable privilege. Return true if it is already r-x
/// or the system is able to change its previlege.
static bool setExecutable(MemoryBlock &M, std::string *ErrMsg = nullptr);
/// setWritable - When adding to a block of code, the JIT may need
/// to mark a block of code as RW since the protections are on page
/// boundaries, and the JIT internal allocations are not page aligned.
static bool setWritable(MemoryBlock &M, std::string *ErrMsg = nullptr);
/// setRangeExecutable - Mark the page containing a range of addresses
/// as executable.
static bool setRangeExecutable(const void *Addr, size_t Size);
/// setRangeWritable - Mark the page containing a range of addresses
/// as writable.
static bool setRangeWritable(const void *Addr, size_t Size);
};
}
}
#endif
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