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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/* This source code was derived from Chromium code, and as such is also subject
* to the [Chromium license](ipc/chromium/src/LICENSE). */
#include "mozilla/ipc/SharedMemory.h"
#include <windows.h>
#include "base/logging.h"
#include "base/win_util.h"
#include "base/string_util.h"
#include "mozilla/ipc/ProtocolUtils.h"
#include "mozilla/RandomNum.h"
#include "nsDebug.h"
#include "nsString.h"
#ifdef MOZ_MEMORY
# include "mozmemory_utils.h"
#endif
namespace {
// NtQuerySection is an internal (but believed to be stable) API and the
// structures it uses are defined in nt_internals.h.
// So we have to define them ourselves.
typedef enum _SECTION_INFORMATION_CLASS {
SectionBasicInformation,
} SECTION_INFORMATION_CLASS;
typedef struct _SECTION_BASIC_INFORMATION {
PVOID BaseAddress;
ULONG Attributes;
LARGE_INTEGER Size;
} SECTION_BASIC_INFORMATION, *PSECTION_BASIC_INFORMATION;
typedef ULONG(__stdcall* NtQuerySectionType)(
HANDLE SectionHandle, SECTION_INFORMATION_CLASS SectionInformationClass,
PVOID SectionInformation, ULONG SectionInformationLength,
PULONG ResultLength);
// Checks if the section object is safe to map. At the moment this just means
// it's not an image section.
bool IsSectionSafeToMap(HANDLE handle) {
static NtQuerySectionType nt_query_section_func =
reinterpret_cast<NtQuerySectionType>(
::GetProcAddress(::GetModuleHandle(L"ntdll.dll"), "NtQuerySection"));
DCHECK(nt_query_section_func);
// The handle must have SECTION_QUERY access for this to succeed.
SECTION_BASIC_INFORMATION basic_information = {};
ULONG status =
nt_query_section_func(handle, SectionBasicInformation, &basic_information,
sizeof(basic_information), nullptr);
if (status) {
return false;
}
return (basic_information.Attributes & SEC_IMAGE) != SEC_IMAGE;
}
} // namespace
namespace mozilla::ipc {
void SharedMemory::ResetImpl() {};
SharedMemory::Handle SharedMemory::CloneHandle(const Handle& aHandle) {
HANDLE handle = INVALID_HANDLE_VALUE;
if (DuplicateHandle(GetCurrentProcess(), aHandle.get(), GetCurrentProcess(),
&handle, 0, false, DUPLICATE_SAME_ACCESS)) {
return SharedMemoryHandle(handle);
}
NS_WARNING("DuplicateHandle Failed!");
return nullptr;
}
void* SharedMemory::FindFreeAddressSpace(size_t size) {
void* memory = VirtualAlloc(NULL, size, MEM_RESERVE, PAGE_NOACCESS);
if (memory) {
VirtualFree(memory, 0, MEM_RELEASE);
}
return memory;
}
Maybe<void*> SharedMemory::MapImpl(size_t nBytes, void* fixedAddress) {
if (mExternalHandle && !IsSectionSafeToMap(mHandle.get())) {
return Nothing();
}
void* mem = MapViewOfFileEx(
mHandle.get(), mReadOnly ? FILE_MAP_READ : FILE_MAP_READ | FILE_MAP_WRITE,
0, 0, nBytes, fixedAddress);
if (mem) {
MOZ_ASSERT(!fixedAddress || mem == fixedAddress,
"MapViewOfFileEx returned an expected address");
return Some(mem);
}
return Nothing();
}
void SharedMemory::UnmapImpl(size_t nBytes, void* address) {
UnmapViewOfFile(address);
}
// Wrapper around CreateFileMappingW for pagefile-backed regions. When out of
// memory, may attempt to stall and retry rather than returning immediately, in
//
// This method is largely a copy of the MozVirtualAlloc method from
// mozjemalloc.cpp, which implements this strategy for VirtualAlloc calls,
// except re-purposed to handle CreateFileMapping.
static HANDLE MozCreateFileMappingW(
LPSECURITY_ATTRIBUTES lpFileMappingAttributes, DWORD flProtect,
DWORD dwMaximumSizeHigh, DWORD dwMaximumSizeLow, LPCWSTR lpName) {
#ifdef MOZ_MEMORY
constexpr auto IsOOMError = [] {
return ::GetLastError() == ERROR_COMMITMENT_LIMIT;
};
{
HANDLE handle = ::CreateFileMappingW(
INVALID_HANDLE_VALUE, lpFileMappingAttributes, flProtect,
dwMaximumSizeHigh, dwMaximumSizeLow, lpName);
if (MOZ_LIKELY(handle)) {
MOZ_DIAGNOSTIC_ASSERT(handle != INVALID_HANDLE_VALUE,
"::CreateFileMapping should return NULL, not "
"INVALID_HANDLE_VALUE, on failure");
return handle;
}
// We can't do anything for errors other than OOM.
if (!IsOOMError()) {
return nullptr;
}
}
// Retry as many times as desired (possibly zero).
const mozilla::StallSpecs stallSpecs = mozilla::GetAllocatorStallSpecs();
const auto ret =
stallSpecs.StallAndRetry(&::Sleep, [&]() -> std::optional<HANDLE> {
HANDLE handle = ::CreateFileMappingW(
INVALID_HANDLE_VALUE, lpFileMappingAttributes, flProtect,
dwMaximumSizeHigh, dwMaximumSizeLow, lpName);
if (handle) {
MOZ_DIAGNOSTIC_ASSERT(handle != INVALID_HANDLE_VALUE,
"::CreateFileMapping should return NULL, not "
"INVALID_HANDLE_VALUE, on failure");
return handle;
}
// Failure for some reason other than OOM.
if (!IsOOMError()) {
return nullptr;
}
return std::nullopt;
});
return ret.value_or(nullptr);
#else
return ::CreateFileMappingW(INVALID_HANDLE_VALUE, lpFileMappingAttributes,
flProtect, dwMaximumSizeHigh, dwMaximumSizeLow,
lpName);
#endif
}
bool SharedMemory::CreateImpl(size_t size, bool freezable) {
// If the shared memory object has no DACL, any process can
// duplicate its handles with any access rights; e.g., re-add write
// access to a read-only handle. To prevent that, we give it an
// empty DACL, so that no process can do that.
SECURITY_ATTRIBUTES sa, *psa = nullptr;
SECURITY_DESCRIPTOR sd;
ACL dacl;
if (freezable) {
psa = &sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = &sd;
sa.bInheritHandle = FALSE;
if (NS_WARN_IF(!InitializeAcl(&dacl, sizeof(dacl), ACL_REVISION)) ||
NS_WARN_IF(
!InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION)) ||
NS_WARN_IF(!SetSecurityDescriptorDacl(&sd, TRUE, &dacl, FALSE))) {
return false;
}
}
mHandle.reset(MozCreateFileMappingW(psa, PAGE_READWRITE, 0,
static_cast<DWORD>(size), nullptr));
return (bool)mHandle;
}
Maybe<SharedMemory::Handle> SharedMemory::ReadOnlyCopyImpl() {
HANDLE ro_handle;
if (!::DuplicateHandle(GetCurrentProcess(), mHandle.get(),
GetCurrentProcess(), &ro_handle,
GENERIC_READ | FILE_MAP_READ, false, 0)) {
return Nothing();
}
return Some(ro_handle);
}
void SharedMemory::SystemProtect(char* aAddr, size_t aSize, int aRights) {
if (!SystemProtectFallible(aAddr, aSize, aRights)) {
MOZ_CRASH("can't VirtualProtect()");
}
}
bool SharedMemory::SystemProtectFallible(char* aAddr, size_t aSize,
int aRights) {
DWORD flags;
if ((aRights & RightsRead) && (aRights & RightsWrite))
flags = PAGE_READWRITE;
else if (aRights & RightsRead)
flags = PAGE_READONLY;
else
flags = PAGE_NOACCESS;
DWORD oldflags;
return VirtualProtect(aAddr, aSize, flags, &oldflags);
}
size_t SharedMemory::SystemPageSize() {
SYSTEM_INFO si;
GetSystemInfo(&si);
return si.dwPageSize;
}
} // namespace mozilla::ipc