dll_windows.go

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package windows
     6  
     7  import (
     8  	"sync"
     9  	"sync/atomic"
    10  	"syscall"
    11  	"unsafe"
    12  )
    13  
    14  // We need to use LoadLibrary and GetProcAddress from the Go runtime, because
    15  // the these symbols are loaded by the system linker and are required to
    16  // dynamically load additional symbols. Note that in the Go runtime, these
    17  // return syscall.Handle and syscall.Errno, but these are the same, in fact,
    18  // as windows.Handle and windows.Errno, and we intend to keep these the same.
    19  
    20  //go:linkname syscall_loadlibrary syscall.loadlibrary
    21  func syscall_loadlibrary(filename *uint16) (handle Handle, err Errno)
    22  
    23  //go:linkname syscall_getprocaddress syscall.getprocaddress
    24  func syscall_getprocaddress(handle Handle, procname *uint8) (proc uintptr, err Errno)
    25  
    26  // DLLError describes reasons for DLL load failures.
    27  type DLLError struct {
    28  	Err     error
    29  	ObjName string
    30  	Msg     string
    31  }
    32  
    33  func (e *DLLError) Error() string { return e.Msg }
    34  
    35  func (e *DLLError) Unwrap() error { return e.Err }
    36  
    37  // A DLL implements access to a single DLL.
    38  type DLL struct {
    39  	Name   string
    40  	Handle Handle
    41  }
    42  
    43  // LoadDLL loads DLL file into memory.
    44  //
    45  // Warning: using LoadDLL without an absolute path name is subject to
    46  // DLL preloading attacks. To safely load a system DLL, use LazyDLL
    47  // with System set to true, or use LoadLibraryEx directly.
    48  func LoadDLL(name string) (dll *DLL, err error) {
    49  	namep, err := UTF16PtrFromString(name)
    50  	if err != nil {
    51  		return nil, err
    52  	}
    53  	h, e := syscall_loadlibrary(namep)
    54  	if e != 0 {
    55  		return nil, &DLLError{
    56  			Err:     e,
    57  			ObjName: name,
    58  			Msg:     "Failed to load " + name + ": " + e.Error(),
    59  		}
    60  	}
    61  	d := &DLL{
    62  		Name:   name,
    63  		Handle: h,
    64  	}
    65  	return d, nil
    66  }
    67  
    68  // MustLoadDLL is like LoadDLL but panics if load operation failes.
    69  func MustLoadDLL(name string) *DLL {
    70  	d, e := LoadDLL(name)
    71  	if e != nil {
    72  		panic(e)
    73  	}
    74  	return d
    75  }
    76  
    77  // FindProc searches DLL d for procedure named name and returns *Proc
    78  // if found. It returns an error if search fails.
    79  func (d *DLL) FindProc(name string) (proc *Proc, err error) {
    80  	namep, err := BytePtrFromString(name)
    81  	if err != nil {
    82  		return nil, err
    83  	}
    84  	a, e := syscall_getprocaddress(d.Handle, namep)
    85  	if e != 0 {
    86  		return nil, &DLLError{
    87  			Err:     e,
    88  			ObjName: name,
    89  			Msg:     "Failed to find " + name + " procedure in " + d.Name + ": " + e.Error(),
    90  		}
    91  	}
    92  	p := &Proc{
    93  		Dll:  d,
    94  		Name: name,
    95  		addr: a,
    96  	}
    97  	return p, nil
    98  }
    99  
   100  // MustFindProc is like FindProc but panics if search fails.
   101  func (d *DLL) MustFindProc(name string) *Proc {
   102  	p, e := d.FindProc(name)
   103  	if e != nil {
   104  		panic(e)
   105  	}
   106  	return p
   107  }
   108  
   109  // FindProcByOrdinal searches DLL d for procedure by ordinal and returns *Proc
   110  // if found. It returns an error if search fails.
   111  func (d *DLL) FindProcByOrdinal(ordinal uintptr) (proc *Proc, err error) {
   112  	a, e := GetProcAddressByOrdinal(d.Handle, ordinal)
   113  	name := "#" + itoa(int(ordinal))
   114  	if e != nil {
   115  		return nil, &DLLError{
   116  			Err:     e,
   117  			ObjName: name,
   118  			Msg:     "Failed to find " + name + " procedure in " + d.Name + ": " + e.Error(),
   119  		}
   120  	}
   121  	p := &Proc{
   122  		Dll:  d,
   123  		Name: name,
   124  		addr: a,
   125  	}
   126  	return p, nil
   127  }
   128  
   129  // MustFindProcByOrdinal is like FindProcByOrdinal but panics if search fails.
   130  func (d *DLL) MustFindProcByOrdinal(ordinal uintptr) *Proc {
   131  	p, e := d.FindProcByOrdinal(ordinal)
   132  	if e != nil {
   133  		panic(e)
   134  	}
   135  	return p
   136  }
   137  
   138  // Release unloads DLL d from memory.
   139  func (d *DLL) Release() (err error) {
   140  	return FreeLibrary(d.Handle)
   141  }
   142  
   143  // A Proc implements access to a procedure inside a DLL.
   144  type Proc struct {
   145  	Dll  *DLL
   146  	Name string
   147  	addr uintptr
   148  }
   149  
   150  // Addr returns the address of the procedure represented by p.
   151  // The return value can be passed to Syscall to run the procedure.
   152  func (p *Proc) Addr() uintptr {
   153  	return p.addr
   154  }
   155  
   156  //go:uintptrescapes
   157  
   158  // Call executes procedure p with arguments a. It will panic, if more than 15 arguments
   159  // are supplied.
   160  //
   161  // The returned error is always non-nil, constructed from the result of GetLastError.
   162  // Callers must inspect the primary return value to decide whether an error occurred
   163  // (according to the semantics of the specific function being called) before consulting
   164  // the error. The error will be guaranteed to contain windows.Errno.
   165  func (p *Proc) Call(a ...uintptr) (r1, r2 uintptr, lastErr error) {
   166  	switch len(a) {
   167  	case 0:
   168  		return syscall.Syscall(p.Addr(), uintptr(len(a)), 0, 0, 0)
   169  	case 1:
   170  		return syscall.Syscall(p.Addr(), uintptr(len(a)), a[0], 0, 0)
   171  	case 2:
   172  		return syscall.Syscall(p.Addr(), uintptr(len(a)), a[0], a[1], 0)
   173  	case 3:
   174  		return syscall.Syscall(p.Addr(), uintptr(len(a)), a[0], a[1], a[2])
   175  	case 4:
   176  		return syscall.Syscall6(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], 0, 0)
   177  	case 5:
   178  		return syscall.Syscall6(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], 0)
   179  	case 6:
   180  		return syscall.Syscall6(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5])
   181  	case 7:
   182  		return syscall.Syscall9(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], 0, 0)
   183  	case 8:
   184  		return syscall.Syscall9(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], 0)
   185  	case 9:
   186  		return syscall.Syscall9(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8])
   187  	case 10:
   188  		return syscall.Syscall12(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], 0, 0)
   189  	case 11:
   190  		return syscall.Syscall12(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], 0)
   191  	case 12:
   192  		return syscall.Syscall12(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11])
   193  	case 13:
   194  		return syscall.Syscall15(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11], a[12], 0, 0)
   195  	case 14:
   196  		return syscall.Syscall15(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11], a[12], a[13], 0)
   197  	case 15:
   198  		return syscall.Syscall15(p.Addr(), uintptr(len(a)), a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11], a[12], a[13], a[14])
   199  	default:
   200  		panic("Call " + p.Name + " with too many arguments " + itoa(len(a)) + ".")
   201  	}
   202  }
   203  
   204  // A LazyDLL implements access to a single DLL.
   205  // It will delay the load of the DLL until the first
   206  // call to its Handle method or to one of its
   207  // LazyProc's Addr method.
   208  type LazyDLL struct {
   209  	Name string
   210  
   211  	// System determines whether the DLL must be loaded from the
   212  	// Windows System directory, bypassing the normal DLL search
   213  	// path.
   214  	System bool
   215  
   216  	mu  sync.Mutex
   217  	dll *DLL // non nil once DLL is loaded
   218  }
   219  
   220  // Load loads DLL file d.Name into memory. It returns an error if fails.
   221  // Load will not try to load DLL, if it is already loaded into memory.
   222  func (d *LazyDLL) Load() error {
   223  	// Non-racy version of:
   224  	// if d.dll != nil {
   225  	if atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&d.dll))) != nil {
   226  		return nil
   227  	}
   228  	d.mu.Lock()
   229  	defer d.mu.Unlock()
   230  	if d.dll != nil {
   231  		return nil
   232  	}
   233  
   234  	// kernel32.dll is special, since it's where LoadLibraryEx comes from.
   235  	// The kernel already special-cases its name, so it's always
   236  	// loaded from system32.
   237  	var dll *DLL
   238  	var err error
   239  	if d.Name == "kernel32.dll" {
   240  		dll, err = LoadDLL(d.Name)
   241  	} else {
   242  		dll, err = loadLibraryEx(d.Name, d.System)
   243  	}
   244  	if err != nil {
   245  		return err
   246  	}
   247  
   248  	// Non-racy version of:
   249  	// d.dll = dll
   250  	atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&d.dll)), unsafe.Pointer(dll))
   251  	return nil
   252  }
   253  
   254  // mustLoad is like Load but panics if search fails.
   255  func (d *LazyDLL) mustLoad() {
   256  	e := d.Load()
   257  	if e != nil {
   258  		panic(e)
   259  	}
   260  }
   261  
   262  // Handle returns d's module handle.
   263  func (d *LazyDLL) Handle() uintptr {
   264  	d.mustLoad()
   265  	return uintptr(d.dll.Handle)
   266  }
   267  
   268  // NewProc returns a LazyProc for accessing the named procedure in the DLL d.
   269  func (d *LazyDLL) NewProc(name string) *LazyProc {
   270  	return &LazyProc{l: d, Name: name}
   271  }
   272  
   273  // NewLazyDLL creates new LazyDLL associated with DLL file.
   274  func NewLazyDLL(name string) *LazyDLL {
   275  	return &LazyDLL{Name: name}
   276  }
   277  
   278  // NewLazySystemDLL is like NewLazyDLL, but will only
   279  // search Windows System directory for the DLL if name is
   280  // a base name (like "advapi32.dll").
   281  func NewLazySystemDLL(name string) *LazyDLL {
   282  	return &LazyDLL{Name: name, System: true}
   283  }
   284  
   285  // A LazyProc implements access to a procedure inside a LazyDLL.
   286  // It delays the lookup until the Addr method is called.
   287  type LazyProc struct {
   288  	Name string
   289  
   290  	mu   sync.Mutex
   291  	l    *LazyDLL
   292  	proc *Proc
   293  }
   294  
   295  // Find searches DLL for procedure named p.Name. It returns
   296  // an error if search fails. Find will not search procedure,
   297  // if it is already found and loaded into memory.
   298  func (p *LazyProc) Find() error {
   299  	// Non-racy version of:
   300  	// if p.proc == nil {
   301  	if atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&p.proc))) == nil {
   302  		p.mu.Lock()
   303  		defer p.mu.Unlock()
   304  		if p.proc == nil {
   305  			e := p.l.Load()
   306  			if e != nil {
   307  				return e
   308  			}
   309  			proc, e := p.l.dll.FindProc(p.Name)
   310  			if e != nil {
   311  				return e
   312  			}
   313  			// Non-racy version of:
   314  			// p.proc = proc
   315  			atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&p.proc)), unsafe.Pointer(proc))
   316  		}
   317  	}
   318  	return nil
   319  }
   320  
   321  // mustFind is like Find but panics if search fails.
   322  func (p *LazyProc) mustFind() {
   323  	e := p.Find()
   324  	if e != nil {
   325  		panic(e)
   326  	}
   327  }
   328  
   329  // Addr returns the address of the procedure represented by p.
   330  // The return value can be passed to Syscall to run the procedure.
   331  // It will panic if the procedure cannot be found.
   332  func (p *LazyProc) Addr() uintptr {
   333  	p.mustFind()
   334  	return p.proc.Addr()
   335  }
   336  
   337  //go:uintptrescapes
   338  
   339  // Call executes procedure p with arguments a. It will panic, if more than 15 arguments
   340  // are supplied. It will also panic if the procedure cannot be found.
   341  //
   342  // The returned error is always non-nil, constructed from the result of GetLastError.
   343  // Callers must inspect the primary return value to decide whether an error occurred
   344  // (according to the semantics of the specific function being called) before consulting
   345  // the error. The error will be guaranteed to contain windows.Errno.
   346  func (p *LazyProc) Call(a ...uintptr) (r1, r2 uintptr, lastErr error) {
   347  	p.mustFind()
   348  	return p.proc.Call(a...)
   349  }
   350  
   351  var canDoSearchSystem32Once struct {
   352  	sync.Once
   353  	v bool
   354  }
   355  
   356  func initCanDoSearchSystem32() {
   357  	// https://msdn.microsoft.com/en-us/library/ms684179(v=vs.85).aspx says:
   358  	// "Windows 7, Windows Server 2008 R2, Windows Vista, and Windows
   359  	// Server 2008: The LOAD_LIBRARY_SEARCH_* flags are available on
   360  	// systems that have KB2533623 installed. To determine whether the
   361  	// flags are available, use GetProcAddress to get the address of the
   362  	// AddDllDirectory, RemoveDllDirectory, or SetDefaultDllDirectories
   363  	// function. If GetProcAddress succeeds, the LOAD_LIBRARY_SEARCH_*
   364  	// flags can be used with LoadLibraryEx."
   365  	canDoSearchSystem32Once.v = (modkernel32.NewProc("AddDllDirectory").Find() == nil)
   366  }
   367  
   368  func canDoSearchSystem32() bool {
   369  	canDoSearchSystem32Once.Do(initCanDoSearchSystem32)
   370  	return canDoSearchSystem32Once.v
   371  }
   372  
   373  func isBaseName(name string) bool {
   374  	for _, c := range name {
   375  		if c == ':' || c == '/' || c == '\\' {
   376  			return false
   377  		}
   378  	}
   379  	return true
   380  }
   381  
   382  // loadLibraryEx wraps the Windows LoadLibraryEx function.
   383  //
   384  // See https://msdn.microsoft.com/en-us/library/windows/desktop/ms684179(v=vs.85).aspx
   385  //
   386  // If name is not an absolute path, LoadLibraryEx searches for the DLL
   387  // in a variety of automatic locations unless constrained by flags.
   388  // See: https://msdn.microsoft.com/en-us/library/ff919712%28VS.85%29.aspx
   389  func loadLibraryEx(name string, system bool) (*DLL, error) {
   390  	loadDLL := name
   391  	var flags uintptr
   392  	if system {
   393  		if canDoSearchSystem32() {
   394  			flags = LOAD_LIBRARY_SEARCH_SYSTEM32
   395  		} else if isBaseName(name) {
   396  			// WindowsXP or unpatched Windows machine
   397  			// trying to load "foo.dll" out of the system
   398  			// folder, but LoadLibraryEx doesn't support
   399  			// that yet on their system, so emulate it.
   400  			systemdir, err := GetSystemDirectory()
   401  			if err != nil {
   402  				return nil, err
   403  			}
   404  			loadDLL = systemdir + "\\" + name
   405  		}
   406  	}
   407  	h, err := LoadLibraryEx(loadDLL, 0, flags)
   408  	if err != nil {
   409  		return nil, err
   410  	}
   411  	return &DLL{Name: name, Handle: h}, nil
   412  }
   413  
   414  type errString string
   415  
   416  func (s errString) Error() string { return string(s) }
   417
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