src/base/platform/platform-macos.cc

// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Platform-specific code for MacOS goes here. Code shared between iOS and
// macOS is in platform-darwin.cc, while the POSIX-compatible are in in
// platform-posix.cc.

#include <mach/mach.h>
#include <mach/mach_vm.h>
#include <mach/vm_map.h>

#include "src/base/platform/platform.h"

namespace v8 {
namespace base {

namespace {

vm_prot_t GetVMProtFromMemoryPermission(OS::MemoryPermission access) {
  switch (access) {
    case OS::MemoryPermission::kNoAccess:
    case OS::MemoryPermission::kNoAccessWillJitLater:
      return VM_PROT_NONE;
    case OS::MemoryPermission::kRead:
      return VM_PROT_READ;
    case OS::MemoryPermission::kReadWrite:
      return VM_PROT_READ | VM_PROT_WRITE;
    case OS::MemoryPermission::kReadWriteExecute:
      return VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE;
    case OS::MemoryPermission::kReadExecute:
      return VM_PROT_READ | VM_PROT_EXECUTE;
  }
  UNREACHABLE();
}

kern_return_t mach_vm_map_wrapper(mach_vm_address_t* address,
                                  mach_vm_size_t size, int flags,
                                  mach_port_t port,
                                  memory_object_offset_t offset,
                                  vm_prot_t prot) {
  vm_prot_t current_prot = prot;
  vm_prot_t maximum_prot = current_prot;
  return mach_vm_map(mach_task_self(), address, size, 0, flags, port, offset,
                     FALSE, current_prot, maximum_prot, VM_INHERIT_NONE);
}

}  // namespace

// static
PlatformSharedMemoryHandle OS::CreateSharedMemoryHandleForTesting(size_t size) {
  mach_vm_size_t vm_size = size;
  mach_port_t port;
  kern_return_t kr = mach_make_memory_entry_64(
      mach_task_self(), &vm_size, 0,
      MAP_MEM_NAMED_CREATE | VM_PROT_READ | VM_PROT_WRITE, &port,
      MACH_PORT_NULL);
  if (kr != KERN_SUCCESS) return kInvalidSharedMemoryHandle;
  return SharedMemoryHandleFromMachMemoryEntry(port);
}

// static
void OS::DestroySharedMemoryHandle(PlatformSharedMemoryHandle handle) {
  DCHECK_NE(kInvalidSharedMemoryHandle, handle);
  mach_port_t port = MachMemoryEntryFromSharedMemoryHandle(handle);
  CHECK_EQ(KERN_SUCCESS, mach_port_deallocate(mach_task_self(), port));
}

// static
void* OS::AllocateShared(void* hint, size_t size, MemoryPermission access,
                         PlatformSharedMemoryHandle handle, uint64_t offset) {
  DCHECK_EQ(0, size % AllocatePageSize());

  mach_vm_address_t addr = reinterpret_cast<mach_vm_address_t>(hint);
  vm_prot_t prot = GetVMProtFromMemoryPermission(access);
  mach_port_t shared_mem_port = MachMemoryEntryFromSharedMemoryHandle(handle);
  kern_return_t kr = mach_vm_map_wrapper(&addr, size, VM_FLAGS_FIXED,
                                         shared_mem_port, offset, prot);

  if (kr != KERN_SUCCESS) {
    // Retry without hint.
    kr = mach_vm_map_wrapper(&addr, size, VM_FLAGS_ANYWHERE, shared_mem_port,
                             offset, prot);
  }

  if (kr != KERN_SUCCESS) return nullptr;
  return reinterpret_cast<void*>(addr);
}

// static
bool OS::RemapPages(const void* address, size_t size, void* new_address,
                    MemoryPermission access) {
  DCHECK(IsAligned(reinterpret_cast<uintptr_t>(address), AllocatePageSize()));
  DCHECK(
      IsAligned(reinterpret_cast<uintptr_t>(new_address), AllocatePageSize()));
  DCHECK(IsAligned(size, AllocatePageSize()));

  vm_prot_t cur_protection = GetVMProtFromMemoryPermission(access);
  vm_prot_t max_protection;
  // Asks the kernel to remap *on top* of an existing mapping, rather than
  // copying the data.
  int flags = VM_FLAGS_FIXED | VM_FLAGS_OVERWRITE;
  mach_vm_address_t target = reinterpret_cast<mach_vm_address_t>(new_address);
  kern_return_t ret =
      mach_vm_remap(mach_task_self(), &target, size, 0, flags, mach_task_self(),
                    reinterpret_cast<mach_vm_address_t>(address), FALSE,
                    &cur_protection, &max_protection, VM_INHERIT_NONE);

  if (ret != KERN_SUCCESS) return false;

  // Did we get the address we wanted?
  CHECK_EQ(new_address, reinterpret_cast<void*>(target));

  return true;
}

bool AddressSpaceReservation::AllocateShared(void* address, size_t size,
                                             OS::MemoryPermission access,
                                             PlatformSharedMemoryHandle handle,
                                             uint64_t offset) {
  DCHECK(Contains(address, size));

  vm_prot_t prot = GetVMProtFromMemoryPermission(access);
  mach_vm_address_t addr = reinterpret_cast<mach_vm_address_t>(address);
  mach_port_t shared_mem_port = MachMemoryEntryFromSharedMemoryHandle(handle);
  kern_return_t kr =
      mach_vm_map_wrapper(&addr, size, VM_FLAGS_FIXED | VM_FLAGS_OVERWRITE,
                          shared_mem_port, offset, prot);
  return kr == KERN_SUCCESS;
}

}  // namespace base
}  // namespace v8