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