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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// This file implements memory allocation primitives for PageAllocator using
// Fuchsia's VMOs (Virtual Memory Objects). VMO API is documented in
// https://fuchsia.dev/fuchsia-src/zircon/objects/vm_object . A VMO is a kernel
// object that corresponds to a set of memory pages. VMO pages may be mapped
// to an address space. The code below creates VMOs for each memory allocations
// and maps them to the default address space of the current process.
#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_FUCHSIA_H_
#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_FUCHSIA_H_
#include <lib/zx/vmar.h>
#include <lib/zx/vmo.h>
#include "base/allocator/partition_allocator/page_allocator.h"
#include "base/fuchsia/fuchsia_logging.h"
#include "base/logging.h"
namespace base {
namespace {
// Returns VMO name for a PageTag.
const char* PageTagToName(PageTag tag) {
switch (tag) {
case PageTag::kBlinkGC:
return "cr_blink_gc";
case PageTag::kPartitionAlloc:
return "cr_partition_alloc";
case PageTag::kChromium:
return "cr_chromium";
case PageTag::kV8:
return "cr_v8";
default:
DCHECK(false);
return "";
}
}
zx_vm_option_t PageAccessibilityToZxVmOptions(
PageAccessibilityConfiguration accessibility) {
switch (accessibility) {
case PageRead:
return ZX_VM_PERM_READ;
case PageReadWrite:
return ZX_VM_PERM_READ | ZX_VM_PERM_WRITE;
case PageReadExecute:
return ZX_VM_PERM_READ | ZX_VM_PERM_EXECUTE;
case PageReadWriteExecute:
return ZX_VM_PERM_READ | ZX_VM_PERM_WRITE | ZX_VM_PERM_EXECUTE;
default:
NOTREACHED();
FALLTHROUGH;
case PageInaccessible:
return 0;
}
}
} // namespace
// zx_vmar_map() will fail if the VMO cannot be mapped at |vmar_offset|, i.e.
// |hint| is not advisory.
constexpr bool kHintIsAdvisory = false;
std::atomic<int32_t> s_allocPageErrorCode{0};
void* SystemAllocPagesInternal(void* hint,
size_t length,
PageAccessibilityConfiguration accessibility,
PageTag page_tag,
bool commit) {
zx::vmo vmo;
zx_status_t status = zx::vmo::create(length, 0, &vmo);
if (status != ZX_OK) {
ZX_DLOG(INFO, status) << "zx_vmo_create";
return nullptr;
}
const char* vmo_name = PageTagToName(page_tag);
status = vmo.set_property(ZX_PROP_NAME, vmo_name, strlen(vmo_name));
// VMO names are used only for debugging, so failure to set a name is not
// fatal.
ZX_DCHECK(status == ZX_OK, status);
if (page_tag == PageTag::kV8) {
// V8 uses JIT. Call zx_vmo_replace_as_executable() to allow code execution
// in the new VMO.
status = vmo.replace_as_executable(zx::resource(), &vmo);
if (status != ZX_OK) {
ZX_DLOG(INFO, status) << "zx_vmo_replace_as_executable";
return nullptr;
}
}
zx_vm_option_t options = PageAccessibilityToZxVmOptions(accessibility);
uint64_t vmar_offset = 0;
if (hint) {
vmar_offset = reinterpret_cast<uint64_t>(hint);
options |= ZX_VM_SPECIFIC;
}
uint64_t address;
status =
zx::vmar::root_self()->map(vmar_offset, vmo,
/*vmo_offset=*/0, length, options, &address);
if (status != ZX_OK) {
// map() is expected to fail if |hint| is set to an already-in-use location.
if (!hint) {
ZX_DLOG(ERROR, status) << "zx_vmar_map";
}
return nullptr;
}
return reinterpret_cast<void*>(address);
}
void* TrimMappingInternal(void* base,
size_t base_length,
size_t trim_length,
PageAccessibilityConfiguration accessibility,
bool commit,
size_t pre_slack,
size_t post_slack) {
DCHECK_EQ(base_length, trim_length + pre_slack + post_slack);
uint64_t base_address = reinterpret_cast<uint64_t>(base);
// Unmap head if necessary.
if (pre_slack) {
zx_status_t status = zx::vmar::root_self()->unmap(base_address, pre_slack);
ZX_CHECK(status == ZX_OK, status);
}
// Unmap tail if necessary.
if (post_slack) {
zx_status_t status = zx::vmar::root_self()->unmap(
base_address + pre_slack + trim_length, post_slack);
ZX_CHECK(status == ZX_OK, status);
}
return reinterpret_cast<void*>(base_address + pre_slack);
}
bool TrySetSystemPagesAccessInternal(
void* address,
size_t length,
PageAccessibilityConfiguration accessibility) {
zx_status_t status = zx::vmar::root_self()->protect(
reinterpret_cast<uint64_t>(address), length,
PageAccessibilityToZxVmOptions(accessibility));
return status == ZX_OK;
}
void SetSystemPagesAccessInternal(
void* address,
size_t length,
PageAccessibilityConfiguration accessibility) {
zx_status_t status = zx::vmar::root_self()->protect(
reinterpret_cast<uint64_t>(address), length,
PageAccessibilityToZxVmOptions(accessibility));
ZX_CHECK(status == ZX_OK, status);
}
void FreePagesInternal(void* address, size_t length) {
uint64_t address_int = reinterpret_cast<uint64_t>(address);
zx_status_t status = zx::vmar::root_self()->unmap(address_int, length);
ZX_CHECK(status == ZX_OK, status);
}
void DiscardSystemPagesInternal(void* address, size_t length) {
// TODO(https://crbug.com/1022062): Mark pages as discardable, rather than
// forcibly de-committing them immediately, when Fuchsia supports it.
uint64_t address_int = reinterpret_cast<uint64_t>(address);
zx_status_t status = zx::vmar::root_self()->op_range(
ZX_VMO_OP_DECOMMIT, address_int, length, nullptr, 0);
ZX_CHECK(status == ZX_OK, status);
}
void DecommitSystemPagesInternal(void* address, size_t length) {
// TODO(https://crbug.com/1022062): Review whether this implementation is
// still appropriate once DiscardSystemPagesInternal() migrates to a "lazy"
// discardable API.
DiscardSystemPagesInternal(address, length);
SetSystemPagesAccessInternal(address, length, PageInaccessible);
}
bool RecommitSystemPagesInternal(void* address,
size_t length,
PageAccessibilityConfiguration accessibility) {
SetSystemPagesAccessInternal(address, length, accessibility);
return true;
}
} // namespace base
#endif // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_FUCHSIA_H_
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