Fuchsia: Memory reservation and partial unmapping

runtime/vm/virtual_memory_fuchsia.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_OS_FUCHSIA)
 
 #include "vm/virtual_memory.h"
 
+#include <magenta/status.h>
 #include <magenta/syscalls.h>
-#include <unistd.h>  // NOLINT
+#include <sys/mman.h>
+#include <unistd.h>
 
 #include "platform/assert.h"
+#include "vm/isolate.h"
 #include "vm/memory_region.h"
 #include "vm/os.h"
 
+// #define VIRTUAL_MEMORY_LOGGING 1
+#if defined(VIRTUAL_MEMORY_LOGGING)
+#define LOG_ERR(msg, ...)                                                      \
+  OS::PrintErr("VMVM: %s:%d: " msg, __FILE__, __LINE__, ##__VA_ARGS__)
+#define LOG_INFO(msg, ...)                                                     \
+  OS::Print("VMVM: %s:%d: " msg, __FILE__, __LINE__, ##__VA_ARGS__)
+#else
+#define LOG_ERR(msg, ...)
+#define LOG_INFO(msg, ...)
+#endif  // defined(VIRTUAL_MEMORY_LOGGING)
+
 namespace dart {
 
 uword VirtualMemory::page_size_ = 0;
 
 
 void VirtualMemory::InitOnce() {
   page_size_ = getpagesize();
 }
 
 
 VirtualMemory* VirtualMemory::ReserveInternal(intptr_t size) {
-  mx_handle_t vmo = MX_HANDLE_INVALID;
-  mx_status_t status = mx_vmo_create(size, 0u, &vmo);
+  mx_handle_t vmar = MX_HANDLE_INVALID;
+  uword addr = 0;
+  const uint32_t flags = MX_VM_FLAG_COMPACT | MX_VM_FLAG_CAN_MAP_SPECIFIC |
+                         MX_VM_FLAG_CAN_MAP_READ | MX_VM_FLAG_CAN_MAP_WRITE |
+                         MX_VM_FLAG_CAN_MAP_EXECUTE;
+  mx_status_t status =
+      mx_vmar_allocate(mx_vmar_root_self(), 0, size, flags, &vmar, &addr);
   if (status != NO_ERROR) {
-    return NULL;
-  }
-
-  // TODO(zra): map with PERM_NONE, when that works, and relax with
-  // Commit and Protect when they are implemented.
-  // Issue MG-161.
-  const int prot =
-      MX_VM_FLAG_PERM_READ | MX_VM_FLAG_PERM_WRITE | MX_VM_FLAG_PERM_EXECUTE;
-  uintptr_t addr;
-  status = mx_vmar_map(mx_vmar_root_self(), 0, vmo, 0, size, prot, &addr);
-  if (status != NO_ERROR) {
-    mx_handle_close(vmo);
-    FATAL("VirtualMemory::ReserveInternal FAILED");
+    LOG_ERR("mx_vmar_allocate(size = %ld) failed: %s\n", size,
+            mx_status_get_string(status));
     return NULL;
   }
 
   MemoryRegion region(reinterpret_cast<void*>(addr), size);
-  return new VirtualMemory(region, vmo);
+  return new VirtualMemory(region, vmar);
 }
 
 
 VirtualMemory::~VirtualMemory() {
   if (!embedder_allocated()) {
-    // TODO(zra): Use reserved_size_.
-    // Issue MG-162.
-    uintptr_t addr = reinterpret_cast<uintptr_t>(address());
-    mx_status_t status =
-        mx_vmar_unmap(mx_vmar_root_self(), addr, 0 /*reserved_size_*/);
+    mx_handle_t vmar = static_cast<mx_handle_t>(handle());
+    mx_status_t status = mx_vmar_destroy(vmar);
     if (status != NO_ERROR) {
-      FATAL("VirtualMemory::~VirtualMemory: unamp FAILED");
+      LOG_ERR("mx_vmar_destroy failed: %s\n", mx_status_get_string(status));
     }
-
-    status = mx_handle_close(handle());
+    status = mx_handle_close(vmar);
     if (status != NO_ERROR) {
-      FATAL("VirtualMemory::~VirtualMemory: handle_close FAILED");
+      LOG_ERR("mx_handle_close failed: %s\n", mx_status_get_string(status));
     }
   }
 }
 
 
-bool VirtualMemory::FreeSubSegment(void* address, intptr_t size) {
-  // TODO(zra): It should be possible to free a subsegment after
-  // Issue MG-162 is addressed.
-  return false;
+bool VirtualMemory::FreeSubSegment(int32_t handle,
+                                   void* address,
+                                   intptr_t size) {
+  mx_handle_t vmar = static_cast<mx_handle_t>(handle);
+  mx_status_t status =
+      mx_vmar_unmap(vmar, reinterpret_cast<uintptr_t>(address), size);
+  if (status != NO_ERROR) {
+    LOG_ERR("mx_vmar_unmap failed: %s\n", mx_status_get_string(status));
+    return false;
+  }
+  return true;
 }
 
 
 bool VirtualMemory::Commit(uword addr, intptr_t size, bool executable) {
-  // TODO(zra): Implement when the protections for a mapping can be changed.
-  // Issue MG-133.
+  ASSERT(Contains(addr));
+  ASSERT(Contains(addr + size) || (addr + size == end()));
+  mx_handle_t vmo = MX_HANDLE_INVALID;
+  mx_status_t status = mx_vmo_create(size, 0u, &vmo);
+  if (status != NO_ERROR) {
+    LOG_ERR("mx_vmo_create(%ld) failed: %s\n", size,
+            mx_status_get_string(status));
+    return false;
+  }
+
+  mx_handle_t vmar = static_cast<mx_handle_t>(handle());
+  const size_t offset = addr - start();
+  const uint32_t flags = MX_VM_FLAG_SPECIFIC | MX_VM_FLAG_PERM_READ |
+                         MX_VM_FLAG_PERM_WRITE | MX_VM_FLAG_PERM_EXECUTE;
+  uintptr_t mapped_addr;
+  status = mx_vmar_map(vmar, offset, vmo, 0, size, flags, &mapped_addr);
+  if (status != NO_ERROR) {
+    mx_handle_close(vmo);
+    LOG_ERR("mx_vmar_map(%ld, %ld, %u) failed: %s\n", offset, size, flags,
+            mx_status_get_string(status));
+    return false;
+  }
+  if (addr != mapped_addr) {
+    LOG_ERR("mx_vmar_map: addr != mapped_addr: %lx != %lx\n", addr,
+            mapped_addr);
+    return false;
+  }
   return true;
 }
 
 
 bool VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
-  // TODO(zra): Implement when Fuchsia has an mprotect-like call.
   return true;
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_FUCHSIA)