include/llvm/ExecutionEngine/SectionMemoryManager.h

   1 //===- SectionMemoryManager.h - Memory manager for MCJIT/RtDyld -*- 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 //
   9 // This file contains the declaration of a section-based memory manager used by
  10 // the MCJIT execution engine and RuntimeDyld.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H
  15 #define LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H
  16
  17 #include "llvm/ADT/SmallVector.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
  20 #include "llvm/Support/Memory.h"
  21 #include <cstdint>
  22 #include <string>
  23 #include <system_error>
  24
  25 namespace llvm {
  26
  27 /// This is a simple memory manager which implements the methods called by
  28 /// the RuntimeDyld class to allocate memory for section-based loading of
  29 /// objects, usually those generated by the MCJIT execution engine.
  30 ///
  31 /// This memory manager allocates all section memory as read-write.  The
  32 /// RuntimeDyld will copy JITed section memory into these allocated blocks
  33 /// and perform any necessary linking and relocations.
  34 ///
  35 /// Any client using this memory manager MUST ensure that section-specific
  36 /// page permissions have been applied before attempting to execute functions
  37 /// in the JITed object.  Permissions can be applied either by calling
  38 /// MCJIT::finalizeObject or by calling SectionMemoryManager::finalizeMemory
  39 /// directly.  Clients of MCJIT should call MCJIT::finalizeObject.
  40 class SectionMemoryManager : public RTDyldMemoryManager {
  41 public:
  42   /// This enum describes the various reasons to allocate pages from
  43   /// allocateMappedMemory.
  44   enum class AllocationPurpose {
  45     Code,
  46     ROData,
  47     RWData,
  48   };
  49
  50   /// Implementations of this interface are used by SectionMemoryManager to
  51   /// request pages from the operating system.
  52   class MemoryMapper {
  53   public:
  54     /// This method attempts to allocate \p NumBytes bytes of virtual memory for
  55     /// \p Purpose.  \p NearBlock may point to an existing allocation, in which
  56     /// case an attempt is made to allocate more memory near the existing block.
  57     /// The actual allocated address is not guaranteed to be near the requested
  58     /// address.  \p Flags is used to set the initial protection flags for the
  59     /// block of the memory.  \p EC [out] returns an object describing any error
  60     /// that occurs.
  61     ///
  62     /// This method may allocate more than the number of bytes requested.  The
  63     /// actual number of bytes allocated is indicated in the returned
  64     /// MemoryBlock.
  65     ///
  66     /// The start of the allocated block must be aligned with the system
  67     /// allocation granularity (64K on Windows, page size on Linux).  If the
  68     /// address following \p NearBlock is not so aligned, it will be rounded up
  69     /// to the next allocation granularity boundary.
  70     ///
  71     /// \r a non-null MemoryBlock if the function was successful, otherwise a
  72     /// null MemoryBlock with \p EC describing the error.
  73     virtual sys::MemoryBlock
  74     allocateMappedMemory(AllocationPurpose Purpose, size_t NumBytes,
  75                          const sys::MemoryBlock *const NearBlock,
  76                          unsigned Flags, std::error_code &EC) = 0;
  77
  78     /// This method sets the protection flags for a block of memory to the state
  79     /// specified by \p Flags.  The behavior is not specified if the memory was
  80     /// not allocated using the allocateMappedMemory method.
  81     /// \p Block describes the memory block to be protected.
  82     /// \p Flags specifies the new protection state to be assigned to the block.
  83     ///
  84     /// If \p Flags is MF_WRITE, the actual behavior varies with the operating
  85     /// system (i.e. MF_READ | MF_WRITE on Windows) and the target architecture
  86     /// (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386).
  87     ///
  88     /// \r error_success if the function was successful, or an error_code
  89     /// describing the failure if an error occurred.
  90     virtual std::error_code protectMappedMemory(const sys::MemoryBlock &Block,
  91                                                 unsigned Flags) = 0;
  92
  93     /// This method releases a block of memory that was allocated with the
  94     /// allocateMappedMemory method. It should not be used to release any memory
  95     /// block allocated any other way.
  96     /// \p Block describes the memory to be released.
  97     ///
  98     /// \r error_success if the function was successful, or an error_code
  99     /// describing the failure if an error occurred.
 100     virtual std::error_code releaseMappedMemory(sys::MemoryBlock &M) = 0;
 101
 102     virtual ~MemoryMapper();
 103   };
 104
 105   /// Creates a SectionMemoryManager instance with \p MM as the associated
 106   /// memory mapper.  If \p MM is nullptr then a default memory mapper is used
 107   /// that directly calls into the operating system.
 108   SectionMemoryManager(MemoryMapper *MM = nullptr);
 109   SectionMemoryManager(const SectionMemoryManager &) = delete;
 110   void operator=(const SectionMemoryManager &) = delete;
 111   ~SectionMemoryManager() override;
 112
 113   /// Allocates a memory block of (at least) the given size suitable for
 114   /// executable code.
 115   ///
 116   /// The value of \p Alignment must be a power of two.  If \p Alignment is zero
 117   /// a default alignment of 16 will be used.
 118   uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
 119                                unsigned SectionID,
 120                                StringRef SectionName) override;
 121
 122   /// Allocates a memory block of (at least) the given size suitable for
 123   /// executable code.
 124   ///
 125   /// The value of \p Alignment must be a power of two.  If \p Alignment is zero
 126   /// a default alignment of 16 will be used.
 127   uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
 128                                unsigned SectionID, StringRef SectionName,
 129                                bool isReadOnly) override;
 130
 131   /// Update section-specific memory permissions and other attributes.
 132   ///
 133   /// This method is called when object loading is complete and section page
 134   /// permissions can be applied.  It is up to the memory manager implementation
 135   /// to decide whether or not to act on this method.  The memory manager will
 136   /// typically allocate all sections as read-write and then apply specific
 137   /// permissions when this method is called.  Code sections cannot be executed
 138   /// until this function has been called.  In addition, any cache coherency
 139   /// operations needed to reliably use the memory are also performed.
 140   ///
 141   /// \returns true if an error occurred, false otherwise.
 142   bool finalizeMemory(std::string *ErrMsg = nullptr) override;
 143
 144   /// Invalidate instruction cache for code sections.
 145   ///
 146   /// Some platforms with separate data cache and instruction cache require
 147   /// explicit cache flush, otherwise JIT code manipulations (like resolved
 148   /// relocations) will get to the data cache but not to the instruction cache.
 149   ///
 150   /// This method is called from finalizeMemory.
 151   virtual void invalidateInstructionCache();
 152
 153 private:
 154   struct FreeMemBlock {
 155     // The actual block of free memory
 156     sys::MemoryBlock Free;
 157     // If there is a pending allocation from the same reservation right before
 158     // this block, store it's index in PendingMem, to be able to update the
 159     // pending region if part of this block is allocated, rather than having to
 160     // create a new one
 161     unsigned PendingPrefixIndex;
 162   };
 163
 164   struct MemoryGroup {
 165     // PendingMem contains all blocks of memory (subblocks of AllocatedMem)
 166     // which have not yet had their permissions applied, but have been given
 167     // out to the user. FreeMem contains all block of memory, which have
 168     // neither had their permissions applied, nor been given out to the user.
 169     SmallVector<sys::MemoryBlock, 16> PendingMem;
 170     SmallVector<FreeMemBlock, 16> FreeMem;
 171
 172     // All memory blocks that have been requested from the system
 173     SmallVector<sys::MemoryBlock, 16> AllocatedMem;
 174
 175     sys::MemoryBlock Near;
 176   };
 177
 178   uint8_t *allocateSection(AllocationPurpose Purpose, uintptr_t Size,
 179                            unsigned Alignment);
 180
 181   std::error_code applyMemoryGroupPermissions(MemoryGroup &MemGroup,
 182                                               unsigned Permissions);
 183
 184   void anchor() override;
 185
 186   MemoryGroup CodeMem;
 187   MemoryGroup RWDataMem;
 188   MemoryGroup RODataMem;
 189   MemoryMapper &MMapper;
 190 };
 191
 192 } // end namespace llvm
 193
 194 #endif // LLVM_EXECUTION_ENGINE_SECTION_MEMORY_MANAGER_H