dll_unix.go

//go:build unix

package goinvoke

import (
	"github.com/ebitengine/purego"
	"github.com/jamesits/goinvoke/utils"
	"golang.org/x/sys/unix"
	"reflect"
	"runtime"
	"sync"
	"sync/atomic"
	"unsafe"
)

var typeOfLazyProc = reflect.TypeOf((*LazyProc)(nil))
var typeOfProc = reflect.TypeOf((*Proc)(nil))

// convert a LazyDLL to DLL, assume it has been loaded.
func unLazy(lazyDLL *LazyDLL) *DLL {
	return &DLL{
		Name:   lazyDLL.Name,
		Handle: lazyDLL.Handle(),
	}
}

func newLazyDLL(path string) *LazyDLL {
	if utils.IsImplicitRelativePath(path) {
		return NewLazySystemDLL(path)
	} else {
		return NewLazyDLL(path)
	}
}

// A DLL implements access to a single DLL.
type DLL struct {
	Name   string
	Handle uintptr
}

// LoadDLL loads the named DLL file into memory.
//
// If name is not an absolute path and is not a known system DLL used by
// Go, Windows will search for the named DLL in many locations, causing
// potential DLL preloading attacks.
//
// Use LazyDLL in golang.org/x/sys/windows for a secure way to
// load system DLLs.
func LoadDLL(name string) (*DLL, error) {
	h, err := purego.Dlopen(name, purego.RTLD_NOW|purego.RTLD_LOCAL)
	if err != nil {
		return nil, err
	}
	return &DLL{
		Name:   name,
		Handle: h,
	}, nil
}

// MustLoadDLL is like LoadDLL but panics if load operation fails.
func MustLoadDLL(name string) *DLL {
	d, e := LoadDLL(name)
	if e != nil {
		panic(e)
	}
	return d
}

// FindProc searches DLL d for procedure named name and returns *Proc
// if found. It returns an error if search fails.
func (d *DLL) FindProc(name string) (proc *Proc, err error) {
	proc = &Proc{
		Name: name,
		Dll:  d,
	}
	proc.addr, err = purego.Dlsym(d.Handle, name)
	if err != nil {
		return nil, err
	}
	return
}

// MustFindProc is like FindProc but panics if search fails.
func (d *DLL) MustFindProc(name string) *Proc {
	p, e := d.FindProc(name)
	if e != nil {
		panic(e)
	}
	return p
}

// Release unloads DLL d from memory.
func (d *DLL) Release() error {
	return purego.Dlclose(d.Handle)
}

// A Proc implements access to a procedure inside a DLL.
type Proc struct {
	Dll  *DLL
	Name string
	addr uintptr
}

// Addr returns the address of the procedure represented by p.
// The return value can be passed to Syscall to run the procedure.
func (p *Proc) Addr() uintptr {
	return p.addr
}

// Call executes procedure p with arguments a.
//
// The returned error is always non-nil, constructed from the result of GetLastError.
// Callers must inspect the primary return value to decide whether an error occurred
// (according to the semantics of the specific function being called) before consulting
// the error. The error always has type syscall.Errno.
//
// On amd64, Call can pass and return floating-point values. To pass
// an argument x with C type "float", use
// uintptr(math.Float32bits(x)). To pass an argument with C type
// "double", use uintptr(math.Float64bits(x)). Floating-point return
// values are returned in r2. The return value for C type "float" is
// math.Float32frombits(uint32(r2)). For C type "double", it is
// math.Float64frombits(uint64(r2)).
//
//go:uintptrescapes
func (p *Proc) Call(a ...uintptr) (uintptr, uintptr, error) {
	x, y, z := purego.SyscallN(p.addr, a...)
	if z == 0 {
		return x, y, nil
	}
	return x, y, unix.Errno(z)
}

// A LazyDLL implements access to a single DLL.
// It will delay the load of the DLL until the first
// call to its Handle method or to one of its
// LazyProc's Addr method.
//
// LazyDLL is subject to the same DLL preloading attacks as documented
// on LoadDLL.
//
// Use LazyDLL in golang.org/x/sys/windows for a secure way to
// load system DLLs.
type LazyDLL struct {
	mu     sync.Mutex
	dll    *DLL // non nil once DLL is loaded
	Name   string
	System bool // unused
}

// Load loads DLL file d.Name into memory. It returns an error if fails.
// Load will not try to load DLL, if it is already loaded into memory.
func (d *LazyDLL) Load() error {
	dllPath := ""

	// We do not really need a "System" load option here since dlopen() does this automatically.
	if runtime.GOOS == "darwin" && d.Name == "libSystem.B.dylib" {
		dllPath = "/usr/lib/libSystem.B.dylib" // macOS hardcoded value
	} else {
		dllPath = d.Name
	}
	if dllPath == "" {
		return ErrorNotFound
	}

	// Non-racy version of:
	// if d.dll == nil {
	if atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&d.dll))) == nil {
		d.mu.Lock()
		defer d.mu.Unlock()
		if d.dll == nil {
			dll, e := LoadDLL(dllPath)
			if e != nil {
				return e
			}
			// Non-racy version of:
			// d.dll = dll
			atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&d.dll)), unsafe.Pointer(dll))
		}
	}
	return nil
}

// mustLoad is like Load but panics if search fails.
func (d *LazyDLL) mustLoad() {
	e := d.Load()
	if e != nil {
		panic(e)
	}
}

// Handle returns d's module handle.
func (d *LazyDLL) Handle() uintptr {
	d.mustLoad()
	return uintptr(d.dll.Handle)
}

// NewProc returns a LazyProc for accessing the named procedure in the DLL d.
func (d *LazyDLL) NewProc(name string) *LazyProc {
	return &LazyProc{l: d, Name: name}
}

// NewLazyDLL creates new LazyDLL associated with DLL file.
func NewLazyDLL(name string) *LazyDLL {
	return &LazyDLL{Name: name}
}

// NewLazySystemDLL is like NewLazyDLL, but will only
// search Windows System directory for the DLL if name is
// a base name (like "advapi32.dll").
func NewLazySystemDLL(name string) *LazyDLL {
	return &LazyDLL{Name: name, System: true}
}

// A LazyProc implements access to a procedure inside a LazyDLL.
// It delays the lookup until the Addr, Call, or Find method is called.
type LazyProc struct {
	mu   sync.Mutex
	Name string
	l    *LazyDLL
	proc *Proc
}

// Find searches DLL for procedure named p.Name. It returns
// an error if search fails. Find will not search procedure,
// if it is already found and loaded into memory.
func (p *LazyProc) Find() error {
	// Non-racy version of:
	// if p.proc == nil {
	if atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&p.proc))) == nil {
		p.mu.Lock()
		defer p.mu.Unlock()
		if p.proc == nil {
			e := p.l.Load()
			if e != nil {
				return e
			}
			proc, e := p.l.dll.FindProc(p.Name)
			if e != nil {
				return e
			}
			// Non-racy version of:
			// p.proc = proc
			atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&p.proc)), unsafe.Pointer(proc))
		}
	}
	return nil
}

// mustFind is like Find but panics if search fails.
func (p *LazyProc) mustFind() {
	e := p.Find()
	if e != nil {
		panic(e)
	}
}

// Addr returns the address of the procedure represented by p.
// The return value can be passed to Syscall to run the procedure.
func (p *LazyProc) Addr() uintptr {
	p.mustFind()
	return p.proc.Addr()
}

// Call executes procedure p with arguments a. See the documentation of
// Proc.Call for more information.
//
//go:uintptrescapes
func (p *LazyProc) Call(a ...uintptr) (r1, r2 uintptr, lastErr error) {
	p.mustFind()
	return p.proc.Call(a...)
}