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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 <cstdint>
- #include "base/allocator/partition_allocator/page_allocator.h"
- #include "base/allocator/partition_allocator/partition_alloc_base/fuchsia/fuchsia_logging.h"
- #include "base/allocator/partition_allocator/partition_alloc_check.h"
- #include "base/allocator/partition_allocator/partition_alloc_notreached.h"
- namespace partition_alloc::internal {
- 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:
- PA_DCHECK(false);
- return "";
- }
- }
- zx_vm_option_t PageAccessibilityToZxVmOptions(
- PageAccessibilityConfiguration accessibility) {
- switch (accessibility) {
- case PageAccessibilityConfiguration::kRead:
- return ZX_VM_PERM_READ;
- case PageAccessibilityConfiguration::kReadWrite:
- case PageAccessibilityConfiguration::kReadWriteTagged:
- return ZX_VM_PERM_READ | ZX_VM_PERM_WRITE;
- case PageAccessibilityConfiguration::kReadExecuteProtected:
- case PageAccessibilityConfiguration::kReadExecute:
- return ZX_VM_PERM_READ | ZX_VM_PERM_EXECUTE;
- case PageAccessibilityConfiguration::kReadWriteExecute:
- return ZX_VM_PERM_READ | ZX_VM_PERM_WRITE | ZX_VM_PERM_EXECUTE;
- default:
- PA_NOTREACHED();
- [[fallthrough]];
- case PageAccessibilityConfiguration::kInaccessible:
- 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};
- uintptr_t SystemAllocPagesInternal(uintptr_t hint,
- size_t length,
- PageAccessibilityConfiguration accessibility,
- PageTag page_tag) {
- zx::vmo vmo;
- zx_status_t status = zx::vmo::create(length, 0, &vmo);
- if (status != ZX_OK) {
- PA_ZX_DLOG(INFO, status) << "zx_vmo_create";
- return 0;
- }
- 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.
- PA_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) {
- PA_ZX_DLOG(INFO, status) << "zx_vmo_replace_as_executable";
- return 0;
- }
- }
- zx_vm_option_t options = PageAccessibilityToZxVmOptions(accessibility);
- uint64_t vmar_offset = 0;
- if (hint) {
- vmar_offset = hint;
- options |= ZX_VM_SPECIFIC;
- }
- uint64_t address;
- status =
- zx::vmar::root_self()->map(options, vmar_offset, vmo,
- /*vmo_offset=*/0, length, &address);
- if (status != ZX_OK) {
- // map() is expected to fail if |hint| is set to an already-in-use location.
- if (!hint) {
- PA_ZX_DLOG(ERROR, status) << "zx_vmar_map";
- }
- return 0;
- }
- return address;
- }
- uintptr_t TrimMappingInternal(uintptr_t base_address,
- size_t base_length,
- size_t trim_length,
- PageAccessibilityConfiguration accessibility,
- size_t pre_slack,
- size_t post_slack) {
- PA_DCHECK(base_length == trim_length + pre_slack + post_slack);
- // Unmap head if necessary.
- if (pre_slack) {
- zx_status_t status = zx::vmar::root_self()->unmap(base_address, pre_slack);
- PA_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);
- PA_ZX_CHECK(status == ZX_OK, status);
- }
- return base_address + pre_slack;
- }
- bool TrySetSystemPagesAccessInternal(
- uint64_t address,
- size_t length,
- PageAccessibilityConfiguration accessibility) {
- zx_status_t status = zx::vmar::root_self()->protect(
- PageAccessibilityToZxVmOptions(accessibility), address, length);
- return status == ZX_OK;
- }
- void SetSystemPagesAccessInternal(
- uint64_t address,
- size_t length,
- PageAccessibilityConfiguration accessibility) {
- zx_status_t status = zx::vmar::root_self()->protect(
- PageAccessibilityToZxVmOptions(accessibility), address, length);
- PA_ZX_CHECK(status == ZX_OK, status);
- }
- void FreePagesInternal(uint64_t address, size_t length) {
- zx_status_t status = zx::vmar::root_self()->unmap(address, length);
- PA_ZX_CHECK(status == ZX_OK, status);
- }
- void DiscardSystemPagesInternal(uint64_t address, size_t length) {
- // TODO(https://crbug.com/1022062): Mark pages as discardable, rather than
- // forcibly de-committing them immediately, when Fuchsia supports it.
- zx_status_t status = zx::vmar::root_self()->op_range(
- ZX_VMO_OP_DECOMMIT, address, length, nullptr, 0);
- PA_ZX_CHECK(status == ZX_OK, status);
- }
- void DecommitSystemPagesInternal(
- uint64_t address,
- size_t length,
- PageAccessibilityDisposition accessibility_disposition) {
- if (accessibility_disposition ==
- PageAccessibilityDisposition::kRequireUpdate) {
- SetSystemPagesAccess(address, length,
- PageAccessibilityConfiguration::kInaccessible);
- }
- // TODO(https://crbug.com/1022062): Review whether this implementation is
- // still appropriate once DiscardSystemPagesInternal() migrates to a "lazy"
- // discardable API.
- DiscardSystemPagesInternal(address, length);
- }
- void DecommitAndZeroSystemPagesInternal(uintptr_t address, size_t length) {
- SetSystemPagesAccess(address, length,
- PageAccessibilityConfiguration::kInaccessible);
- // TODO(https://crbug.com/1022062): this implementation will likely no longer
- // be appropriate once DiscardSystemPagesInternal() migrates to a "lazy"
- // discardable API.
- DiscardSystemPagesInternal(address, length);
- }
- void RecommitSystemPagesInternal(
- uintptr_t address,
- size_t length,
- PageAccessibilityConfiguration accessibility,
- PageAccessibilityDisposition accessibility_disposition) {
- // On Fuchsia systems, the caller needs to simply read the memory to recommit
- // it. However, if decommit changed the permissions, recommit has to change
- // them back.
- if (accessibility_disposition ==
- PageAccessibilityDisposition::kRequireUpdate) {
- SetSystemPagesAccess(address, length, accessibility);
- }
- }
- bool TryRecommitSystemPagesInternal(
- uintptr_t address,
- size_t length,
- PageAccessibilityConfiguration accessibility,
- PageAccessibilityDisposition accessibility_disposition) {
- // On Fuchsia systems, the caller needs to simply read the memory to recommit
- // it. However, if decommit changed the permissions, recommit has to change
- // them back.
- if (accessibility_disposition ==
- PageAccessibilityDisposition::kRequireUpdate) {
- return TrySetSystemPagesAccess(address, length, accessibility);
- }
- return true;
- }
- } // namespace partition_alloc::internal
- #endif // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_FUCHSIA_H_
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