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package platform
import (
"fmt"
"syscall"
"unsafe"
)
var (
kernel32 = syscall.NewLazyDLL("kernel32.dll")
procVirtualAlloc = kernel32.NewProc("VirtualAlloc")
procVirtualProtect = kernel32.NewProc("VirtualProtect")
procVirtualFree = kernel32.NewProc("VirtualFree")
)
const (
windows_MEM_COMMIT uintptr = 0x00001000
windows_MEM_RELEASE uintptr = 0x00008000
windows_PAGE_READWRITE uintptr = 0x00000004
windows_PAGE_EXECUTE_READ uintptr = 0x00000020
windows_PAGE_EXECUTE_READWRITE uintptr = 0x00000040
)
const MmapSupported = true
func munmapCodeSegment(code []byte) error {
return freeMemory(code)
}
// allocateMemory commits the memory region via the "VirtualAlloc" function.
// See https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-virtualalloc
func allocateMemory(size uintptr, protect uintptr) (uintptr, error) {
address := uintptr(0) // system determines where to allocate the region.
alloctype := windows_MEM_COMMIT
if r, _, err := procVirtualAlloc.Call(address, size, alloctype, protect); r == 0 {
return 0, fmt.Errorf("compiler: VirtualAlloc error: %w", ensureErr(err))
} else {
return r, nil
}
}
// freeMemory releases the memory region via the "VirtualFree" function.
// See https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-virtualfree
func freeMemory(code []byte) error {
address := unsafe.Pointer(&code[0])
size := uintptr(0) // size must be 0 because we're using MEM_RELEASE.
freetype := windows_MEM_RELEASE
if r, _, err := procVirtualFree.Call(uintptr(address), size, freetype); r == 0 {
return fmt.Errorf("compiler: VirtualFree error: %w", ensureErr(err))
}
return nil
}
func virtualProtect(address, size, newprotect uintptr, oldprotect *uint32) error {
if r, _, err := procVirtualProtect.Call(address, size, newprotect, uintptr(unsafe.Pointer(oldprotect))); r == 0 {
return fmt.Errorf("compiler: VirtualProtect error: %w", ensureErr(err))
}
return nil
}
func mmapCodeSegmentAMD64(size int) ([]byte, error) {
p, err := allocateMemory(uintptr(size), windows_PAGE_EXECUTE_READWRITE)
if err != nil {
return nil, err
}
return unsafe.Slice((*byte)(unsafe.Pointer(p)), size), nil
}
func mmapCodeSegmentARM64(size int) ([]byte, error) {
p, err := allocateMemory(uintptr(size), windows_PAGE_READWRITE)
if err != nil {
return nil, err
}
return unsafe.Slice((*byte)(unsafe.Pointer(p)), size), nil
}
var old = uint32(windows_PAGE_READWRITE)
func MprotectRX(b []byte) (err error) {
err = virtualProtect(uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)), windows_PAGE_EXECUTE_READ, &old)
return
}
// ensureErr returns syscall.EINVAL when the input error is nil.
//
// We are supposed to use "GetLastError" which is more precise, but it is not safe to execute in goroutines. While
// "GetLastError" is thread-local, goroutines are not pinned to threads.
//
// See https://docs.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-getlasterror
func ensureErr(err error) error {
if err != nil {
return err
}
return syscall.EINVAL
}
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