wireguard-go/tun/wintun/memmod/memmod_windows.go
Jason A. Donenfeld 3957e9b9dd memmod: register exception handler tables
Otherwise recent WDK binaries fail on ARM64, where an exception handler
is used for trapping an illegal instruction when ARMv8.1 atomics are
being tested for functionality.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2021-08-05 14:56:48 +02:00

636 lines
22 KiB
Go

/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
package memmod
import (
"errors"
"fmt"
"syscall"
"unsafe"
"golang.org/x/sys/windows"
)
type addressList struct {
next *addressList
address uintptr
}
func (head *addressList) free() {
for node := head; node != nil; node = node.next {
windows.VirtualFree(node.address, 0, windows.MEM_RELEASE)
}
}
type Module struct {
headers *IMAGE_NT_HEADERS
codeBase uintptr
modules []windows.Handle
initialized bool
isDLL bool
isRelocated bool
nameExports map[string]uint16
entry uintptr
blockedMemory *addressList
}
func (module *Module) headerDirectory(idx int) *IMAGE_DATA_DIRECTORY {
return &module.headers.OptionalHeader.DataDirectory[idx]
}
func (module *Module) copySections(address uintptr, size uintptr, oldHeaders *IMAGE_NT_HEADERS) error {
sections := module.headers.Sections()
for i := range sections {
if sections[i].SizeOfRawData == 0 {
// Section doesn't contain data in the dll itself, but may define uninitialized data.
sectionSize := oldHeaders.OptionalHeader.SectionAlignment
if sectionSize == 0 {
continue
}
dest, err := windows.VirtualAlloc(module.codeBase+uintptr(sections[i].VirtualAddress),
uintptr(sectionSize),
windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
return fmt.Errorf("Error allocating section: %w", err)
}
// Always use position from file to support alignments smaller than page size (allocation above will align to page size).
dest = module.codeBase + uintptr(sections[i].VirtualAddress)
// NOTE: On 64bit systems we truncate to 32bit here but expand again later when "PhysicalAddress" is used.
sections[i].SetPhysicalAddress((uint32)(dest & 0xffffffff))
var dst []byte
unsafeSlice(unsafe.Pointer(&dst), a2p(dest), int(sectionSize))
for j := range dst {
dst[j] = 0
}
continue
}
if size < uintptr(sections[i].PointerToRawData+sections[i].SizeOfRawData) {
return errors.New("Incomplete section")
}
// Commit memory block and copy data from dll.
dest, err := windows.VirtualAlloc(module.codeBase+uintptr(sections[i].VirtualAddress),
uintptr(sections[i].SizeOfRawData),
windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
return fmt.Errorf("Error allocating memory block: %w", err)
}
// Always use position from file to support alignments smaller than page size (allocation above will align to page size).
memcpy(
module.codeBase+uintptr(sections[i].VirtualAddress),
address+uintptr(sections[i].PointerToRawData),
uintptr(sections[i].SizeOfRawData))
// NOTE: On 64bit systems we truncate to 32bit here but expand again later when "PhysicalAddress" is used.
sections[i].SetPhysicalAddress((uint32)(dest & 0xffffffff))
}
return nil
}
func (module *Module) realSectionSize(section *IMAGE_SECTION_HEADER) uintptr {
size := section.SizeOfRawData
if size != 0 {
return uintptr(size)
}
if (section.Characteristics & IMAGE_SCN_CNT_INITIALIZED_DATA) != 0 {
return uintptr(module.headers.OptionalHeader.SizeOfInitializedData)
}
if (section.Characteristics & IMAGE_SCN_CNT_UNINITIALIZED_DATA) != 0 {
return uintptr(module.headers.OptionalHeader.SizeOfUninitializedData)
}
return 0
}
type sectionFinalizeData struct {
address uintptr
alignedAddress uintptr
size uintptr
characteristics uint32
last bool
}
func (module *Module) finalizeSection(sectionData *sectionFinalizeData) error {
if sectionData.size == 0 {
return nil
}
if (sectionData.characteristics & IMAGE_SCN_MEM_DISCARDABLE) != 0 {
// Section is not needed any more and can safely be freed.
if sectionData.address == sectionData.alignedAddress &&
(sectionData.last ||
(sectionData.size%uintptr(module.headers.OptionalHeader.SectionAlignment)) == 0) {
// Only allowed to decommit whole pages.
windows.VirtualFree(sectionData.address, sectionData.size, windows.MEM_DECOMMIT)
}
return nil
}
// determine protection flags based on characteristics
var ProtectionFlags = [8]uint32{
windows.PAGE_NOACCESS, // not writeable, not readable, not executable
windows.PAGE_EXECUTE, // not writeable, not readable, executable
windows.PAGE_READONLY, // not writeable, readable, not executable
windows.PAGE_EXECUTE_READ, // not writeable, readable, executable
windows.PAGE_WRITECOPY, // writeable, not readable, not executable
windows.PAGE_EXECUTE_WRITECOPY, // writeable, not readable, executable
windows.PAGE_READWRITE, // writeable, readable, not executable
windows.PAGE_EXECUTE_READWRITE, // writeable, readable, executable
}
protect := ProtectionFlags[sectionData.characteristics>>29]
if (sectionData.characteristics & IMAGE_SCN_MEM_NOT_CACHED) != 0 {
protect |= windows.PAGE_NOCACHE
}
// Change memory access flags.
var oldProtect uint32
err := windows.VirtualProtect(sectionData.address, sectionData.size, protect, &oldProtect)
if err != nil {
return fmt.Errorf("Error protecting memory page: %w", err)
}
return nil
}
var rtlAddFunctionTable = windows.NewLazySystemDLL("ntdll.dll").NewProc("RtlAddFunctionTable")
func (module *Module) registerExceptionHandlers() {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXCEPTION)
if directory.Size == 0 || directory.VirtualAddress == 0 {
return
}
rtlAddFunctionTable.Call(module.codeBase+uintptr(directory.VirtualAddress), uintptr(directory.Size)/unsafe.Sizeof(IMAGE_RUNTIME_FUNCTION_ENTRY{}), module.codeBase)
}
func (module *Module) finalizeSections() error {
sections := module.headers.Sections()
imageOffset := module.headers.OptionalHeader.imageOffset()
sectionData := sectionFinalizeData{}
sectionData.address = uintptr(sections[0].PhysicalAddress()) | imageOffset
sectionData.alignedAddress = alignDown(sectionData.address, uintptr(module.headers.OptionalHeader.SectionAlignment))
sectionData.size = module.realSectionSize(&sections[0])
sections[0].SetVirtualSize(uint32(sectionData.size))
sectionData.characteristics = sections[0].Characteristics
// Loop through all sections and change access flags.
for i := uint16(1); i < module.headers.FileHeader.NumberOfSections; i++ {
sectionAddress := uintptr(sections[i].PhysicalAddress()) | imageOffset
alignedAddress := alignDown(sectionAddress, uintptr(module.headers.OptionalHeader.SectionAlignment))
sectionSize := module.realSectionSize(&sections[i])
sections[i].SetVirtualSize(uint32(sectionSize))
// Combine access flags of all sections that share a page.
// TODO: We currently share flags of a trailing large section with the page of a first small section. This should be optimized.
if sectionData.alignedAddress == alignedAddress || sectionData.address+sectionData.size > alignedAddress {
// Section shares page with previous.
if (sections[i].Characteristics&IMAGE_SCN_MEM_DISCARDABLE) == 0 || (sectionData.characteristics&IMAGE_SCN_MEM_DISCARDABLE) == 0 {
sectionData.characteristics = (sectionData.characteristics | sections[i].Characteristics) &^ IMAGE_SCN_MEM_DISCARDABLE
} else {
sectionData.characteristics |= sections[i].Characteristics
}
sectionData.size = sectionAddress + sectionSize - sectionData.address
continue
}
err := module.finalizeSection(&sectionData)
if err != nil {
return fmt.Errorf("Error finalizing section: %w", err)
}
sectionData.address = sectionAddress
sectionData.alignedAddress = alignedAddress
sectionData.size = sectionSize
sectionData.characteristics = sections[i].Characteristics
}
sectionData.last = true
err := module.finalizeSection(&sectionData)
if err != nil {
return fmt.Errorf("Error finalizing section: %w", err)
}
return nil
}
func (module *Module) executeTLS() {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_TLS)
if directory.VirtualAddress == 0 {
return
}
tls := (*IMAGE_TLS_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
callback := tls.AddressOfCallbacks
if callback != 0 {
for {
f := *(*uintptr)(a2p(callback))
if f == 0 {
break
}
syscall.Syscall(f, 3, module.codeBase, uintptr(DLL_PROCESS_ATTACH), uintptr(0))
callback += unsafe.Sizeof(f)
}
}
}
func (module *Module) performBaseRelocation(delta uintptr) (relocated bool, err error) {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_BASERELOC)
if directory.Size == 0 {
return delta == 0, nil
}
relocationHdr := (*IMAGE_BASE_RELOCATION)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
for relocationHdr.VirtualAddress > 0 {
dest := module.codeBase + uintptr(relocationHdr.VirtualAddress)
var relInfos []uint16
unsafeSlice(
unsafe.Pointer(&relInfos),
a2p(uintptr(unsafe.Pointer(relocationHdr))+unsafe.Sizeof(*relocationHdr)),
int((uintptr(relocationHdr.SizeOfBlock)-unsafe.Sizeof(*relocationHdr))/unsafe.Sizeof(relInfos[0])))
for _, relInfo := range relInfos {
// The upper 4 bits define the type of relocation.
relType := relInfo >> 12
// The lower 12 bits define the offset.
relOffset := uintptr(relInfo & 0xfff)
switch relType {
case IMAGE_REL_BASED_ABSOLUTE:
// Skip relocation.
case IMAGE_REL_BASED_LOW:
*(*uint16)(a2p(dest + relOffset)) += uint16(delta & 0xffff)
break
case IMAGE_REL_BASED_HIGH:
*(*uint16)(a2p(dest + relOffset)) += uint16(uint32(delta) >> 16)
break
case IMAGE_REL_BASED_HIGHLOW:
*(*uint32)(a2p(dest + relOffset)) += uint32(delta)
case IMAGE_REL_BASED_DIR64:
*(*uint64)(a2p(dest + relOffset)) += uint64(delta)
case IMAGE_REL_BASED_THUMB_MOV32:
inst := *(*uint32)(a2p(dest + relOffset))
imm16 := ((inst << 1) & 0x0800) + ((inst << 12) & 0xf000) +
((inst >> 20) & 0x0700) + ((inst >> 16) & 0x00ff)
if (inst & 0x8000fbf0) != 0x0000f240 {
return false, fmt.Errorf("Wrong Thumb2 instruction %08x, expected MOVW", inst)
}
imm16 += uint32(delta) & 0xffff
hiDelta := (uint32(delta&0xffff0000) >> 16) + ((imm16 & 0xffff0000) >> 16)
*(*uint32)(a2p(dest + relOffset)) = (inst & 0x8f00fbf0) + ((imm16 >> 1) & 0x0400) +
((imm16 >> 12) & 0x000f) +
((imm16 << 20) & 0x70000000) +
((imm16 << 16) & 0xff0000)
if hiDelta != 0 {
inst = *(*uint32)(a2p(dest + relOffset + 4))
imm16 = ((inst << 1) & 0x0800) + ((inst << 12) & 0xf000) +
((inst >> 20) & 0x0700) + ((inst >> 16) & 0x00ff)
if (inst & 0x8000fbf0) != 0x0000f2c0 {
return false, fmt.Errorf("Wrong Thumb2 instruction %08x, expected MOVT", inst)
}
imm16 += hiDelta
if imm16 > 0xffff {
return false, fmt.Errorf("Resulting immediate value won't fit: %08x", imm16)
}
*(*uint32)(a2p(dest + relOffset + 4)) = (inst & 0x8f00fbf0) +
((imm16 >> 1) & 0x0400) +
((imm16 >> 12) & 0x000f) +
((imm16 << 20) & 0x70000000) +
((imm16 << 16) & 0xff0000)
}
default:
return false, fmt.Errorf("Unsupported relocation: %v", relType)
}
}
// Advance to next relocation block.
relocationHdr = (*IMAGE_BASE_RELOCATION)(a2p(uintptr(unsafe.Pointer(relocationHdr)) + uintptr(relocationHdr.SizeOfBlock)))
}
return true, nil
}
func (module *Module) buildImportTable() error {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_IMPORT)
if directory.Size == 0 {
return nil
}
module.modules = make([]windows.Handle, 0, 16)
importDesc := (*IMAGE_IMPORT_DESCRIPTOR)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
for importDesc.Name != 0 {
handle, err := windows.LoadLibraryEx(windows.BytePtrToString((*byte)(a2p(module.codeBase+uintptr(importDesc.Name)))), 0, windows.LOAD_LIBRARY_SEARCH_SYSTEM32)
if err != nil {
return fmt.Errorf("Error loading module: %w", err)
}
var thunkRef, funcRef *uintptr
if importDesc.OriginalFirstThunk() != 0 {
thunkRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.OriginalFirstThunk())))
funcRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.FirstThunk)))
} else {
// No hint table.
thunkRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.FirstThunk)))
funcRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.FirstThunk)))
}
for *thunkRef != 0 {
if IMAGE_SNAP_BY_ORDINAL(*thunkRef) {
*funcRef, err = windows.GetProcAddressByOrdinal(handle, IMAGE_ORDINAL(*thunkRef))
} else {
thunkData := (*IMAGE_IMPORT_BY_NAME)(a2p(module.codeBase + *thunkRef))
*funcRef, err = windows.GetProcAddress(handle, windows.BytePtrToString(&thunkData.Name[0]))
}
if err != nil {
windows.FreeLibrary(handle)
return fmt.Errorf("Error getting function address: %w", err)
}
thunkRef = (*uintptr)(a2p(uintptr(unsafe.Pointer(thunkRef)) + unsafe.Sizeof(*thunkRef)))
funcRef = (*uintptr)(a2p(uintptr(unsafe.Pointer(funcRef)) + unsafe.Sizeof(*funcRef)))
}
module.modules = append(module.modules, handle)
importDesc = (*IMAGE_IMPORT_DESCRIPTOR)(a2p(uintptr(unsafe.Pointer(importDesc)) + unsafe.Sizeof(*importDesc)))
}
return nil
}
func (module *Module) buildNameExports() error {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXPORT)
if directory.Size == 0 {
return errors.New("No export table found")
}
exports := (*IMAGE_EXPORT_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
if exports.NumberOfNames == 0 || exports.NumberOfFunctions == 0 {
return errors.New("No functions exported")
}
if exports.NumberOfNames == 0 {
return errors.New("No functions exported by name")
}
var nameRefs []uint32
unsafeSlice(unsafe.Pointer(&nameRefs), a2p(module.codeBase+uintptr(exports.AddressOfNames)), int(exports.NumberOfNames))
var ordinals []uint16
unsafeSlice(unsafe.Pointer(&ordinals), a2p(module.codeBase+uintptr(exports.AddressOfNameOrdinals)), int(exports.NumberOfNames))
module.nameExports = make(map[string]uint16)
for i := range nameRefs {
nameArray := windows.BytePtrToString((*byte)(a2p(module.codeBase + uintptr(nameRefs[i]))))
module.nameExports[nameArray] = ordinals[i]
}
return nil
}
// LoadLibrary loads module image to memory.
func LoadLibrary(data []byte) (module *Module, err error) {
addr := uintptr(unsafe.Pointer(&data[0]))
size := uintptr(len(data))
if size < unsafe.Sizeof(IMAGE_DOS_HEADER{}) {
return nil, errors.New("Incomplete IMAGE_DOS_HEADER")
}
dosHeader := (*IMAGE_DOS_HEADER)(a2p(addr))
if dosHeader.E_magic != IMAGE_DOS_SIGNATURE {
return nil, fmt.Errorf("Not an MS-DOS binary (provided: %x, expected: %x)", dosHeader.E_magic, IMAGE_DOS_SIGNATURE)
}
if (size < uintptr(dosHeader.E_lfanew)+unsafe.Sizeof(IMAGE_NT_HEADERS{})) {
return nil, errors.New("Incomplete IMAGE_NT_HEADERS")
}
oldHeader := (*IMAGE_NT_HEADERS)(a2p(addr + uintptr(dosHeader.E_lfanew)))
if oldHeader.Signature != IMAGE_NT_SIGNATURE {
return nil, fmt.Errorf("Not an NT binary (provided: %x, expected: %x)", oldHeader.Signature, IMAGE_NT_SIGNATURE)
}
if oldHeader.FileHeader.Machine != imageFileProcess {
return nil, fmt.Errorf("Foreign platform (provided: %x, expected: %x)", oldHeader.FileHeader.Machine, imageFileProcess)
}
if (oldHeader.OptionalHeader.SectionAlignment & 1) != 0 {
return nil, errors.New("Unaligned section")
}
lastSectionEnd := uintptr(0)
sections := oldHeader.Sections()
optionalSectionSize := oldHeader.OptionalHeader.SectionAlignment
for i := range sections {
var endOfSection uintptr
if sections[i].SizeOfRawData == 0 {
// Section without data in the DLL
endOfSection = uintptr(sections[i].VirtualAddress) + uintptr(optionalSectionSize)
} else {
endOfSection = uintptr(sections[i].VirtualAddress) + uintptr(sections[i].SizeOfRawData)
}
if endOfSection > lastSectionEnd {
lastSectionEnd = endOfSection
}
}
alignedImageSize := alignUp(uintptr(oldHeader.OptionalHeader.SizeOfImage), uintptr(oldHeader.OptionalHeader.SectionAlignment))
if alignedImageSize != alignUp(lastSectionEnd, uintptr(oldHeader.OptionalHeader.SectionAlignment)) {
return nil, errors.New("Section is not page-aligned")
}
module = &Module{isDLL: (oldHeader.FileHeader.Characteristics & IMAGE_FILE_DLL) != 0}
defer func() {
if err != nil {
module.Free()
module = nil
}
}()
// Reserve memory for image of library.
// TODO: Is it correct to commit the complete memory region at once? Calling DllEntry raises an exception if we don't.
module.codeBase, err = windows.VirtualAlloc(oldHeader.OptionalHeader.ImageBase,
alignedImageSize,
windows.MEM_RESERVE|windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
// Try to allocate memory at arbitrary position.
module.codeBase, err = windows.VirtualAlloc(0,
alignedImageSize,
windows.MEM_RESERVE|windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
err = fmt.Errorf("Error allocating code: %w", err)
return
}
}
err = module.check4GBBoundaries(alignedImageSize)
if err != nil {
err = fmt.Errorf("Error reallocating code: %w", err)
return
}
if size < uintptr(oldHeader.OptionalHeader.SizeOfHeaders) {
err = errors.New("Incomplete headers")
return
}
// Commit memory for headers.
headers, err := windows.VirtualAlloc(module.codeBase,
uintptr(oldHeader.OptionalHeader.SizeOfHeaders),
windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
err = fmt.Errorf("Error allocating headers: %w", err)
return
}
// Copy PE header to code.
memcpy(headers, addr, uintptr(oldHeader.OptionalHeader.SizeOfHeaders))
module.headers = (*IMAGE_NT_HEADERS)(a2p(headers + uintptr(dosHeader.E_lfanew)))
// Update position.
module.headers.OptionalHeader.ImageBase = module.codeBase
// Copy sections from DLL file block to new memory location.
err = module.copySections(addr, size, oldHeader)
if err != nil {
err = fmt.Errorf("Error copying sections: %w", err)
return
}
// Adjust base address of imported data.
locationDelta := module.headers.OptionalHeader.ImageBase - oldHeader.OptionalHeader.ImageBase
if locationDelta != 0 {
module.isRelocated, err = module.performBaseRelocation(locationDelta)
if err != nil {
err = fmt.Errorf("Error relocating module: %w", err)
return
}
} else {
module.isRelocated = true
}
// Load required dlls and adjust function table of imports.
err = module.buildImportTable()
if err != nil {
err = fmt.Errorf("Error building import table: %w", err)
return
}
// Mark memory pages depending on section headers and release sections that are marked as "discardable".
err = module.finalizeSections()
if err != nil {
err = fmt.Errorf("Error finalizing sections: %w", err)
return
}
// Register exception tables, if they exist.
module.registerExceptionHandlers()
// TLS callbacks are executed BEFORE the main loading.
module.executeTLS()
// Get entry point of loaded module.
if module.headers.OptionalHeader.AddressOfEntryPoint != 0 {
module.entry = module.codeBase + uintptr(module.headers.OptionalHeader.AddressOfEntryPoint)
if module.isDLL {
// Notify library about attaching to process.
r0, _, _ := syscall.Syscall(module.entry, 3, module.codeBase, uintptr(DLL_PROCESS_ATTACH), 0)
successful := r0 != 0
if !successful {
err = windows.ERROR_DLL_INIT_FAILED
return
}
module.initialized = true
}
}
module.buildNameExports()
return
}
// Free releases module resources and unloads it.
func (module *Module) Free() {
if module.initialized {
// Notify library about detaching from process.
syscall.Syscall(module.entry, 3, module.codeBase, uintptr(DLL_PROCESS_DETACH), 0)
module.initialized = false
}
if module.modules != nil {
// Free previously opened libraries.
for _, handle := range module.modules {
windows.FreeLibrary(handle)
}
module.modules = nil
}
if module.codeBase != 0 {
windows.VirtualFree(module.codeBase, 0, windows.MEM_RELEASE)
module.codeBase = 0
}
if module.blockedMemory != nil {
module.blockedMemory.free()
module.blockedMemory = nil
}
}
// ProcAddressByName returns function address by exported name.
func (module *Module) ProcAddressByName(name string) (uintptr, error) {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXPORT)
if directory.Size == 0 {
return 0, errors.New("No export table found")
}
exports := (*IMAGE_EXPORT_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
if module.nameExports == nil {
return 0, errors.New("No functions exported by name")
}
if idx, ok := module.nameExports[name]; ok {
if uint32(idx) > exports.NumberOfFunctions {
return 0, errors.New("Ordinal number too high")
}
// AddressOfFunctions contains the RVAs to the "real" functions.
return module.codeBase + uintptr(*(*uint32)(a2p(module.codeBase + uintptr(exports.AddressOfFunctions) + uintptr(idx)*4))), nil
}
return 0, errors.New("Function not found by name")
}
// ProcAddressByOrdinal returns function address by exported ordinal.
func (module *Module) ProcAddressByOrdinal(ordinal uint16) (uintptr, error) {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXPORT)
if directory.Size == 0 {
return 0, errors.New("No export table found")
}
exports := (*IMAGE_EXPORT_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
if uint32(ordinal) < exports.Base {
return 0, errors.New("Ordinal number too low")
}
idx := ordinal - uint16(exports.Base)
if uint32(idx) > exports.NumberOfFunctions {
return 0, errors.New("Ordinal number too high")
}
// AddressOfFunctions contains the RVAs to the "real" functions.
return module.codeBase + uintptr(*(*uint32)(a2p(module.codeBase + uintptr(exports.AddressOfFunctions) + uintptr(idx)*4))), nil
}
func alignDown(value, alignment uintptr) uintptr {
return value & ^(alignment - 1)
}
func alignUp(value, alignment uintptr) uintptr {
return (value + alignment - 1) & ^(alignment - 1)
}
func a2p(addr uintptr) unsafe.Pointer {
return unsafe.Pointer(addr)
}
func memcpy(dst, src, size uintptr) {
var d, s []byte
unsafeSlice(unsafe.Pointer(&d), a2p(dst), int(size))
unsafeSlice(unsafe.Pointer(&s), a2p(src), int(size))
copy(d, s)
}
// unsafeSlice updates the slice slicePtr to be a slice
// referencing the provided data with its length & capacity set to
// lenCap.
//
// TODO: when Go 1.16 or Go 1.17 is the minimum supported version,
// update callers to use unsafe.Slice instead of this.
func unsafeSlice(slicePtr, data unsafe.Pointer, lenCap int) {
type sliceHeader struct {
Data unsafe.Pointer
Len int
Cap int
}
h := (*sliceHeader)(slicePtr)
h.Data = data
h.Len = lenCap
h.Cap = lenCap
}