sys_windows.go

     1  // Copyright 2020 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 fuzz
     6  
     7  import (
     8  	"fmt"
     9  	"os"
    10  	"os/exec"
    11  	"syscall"
    12  	"unsafe"
    13  )
    14  
    15  type sharedMemSys struct {
    16  	mapObj syscall.Handle
    17  }
    18  
    19  func sharedMemMapFile(f *os.File, size int, removeOnClose bool) (mem *sharedMem, err error) {
    20  	defer func() {
    21  		if err != nil {
    22  			err = fmt.Errorf("mapping temporary file %s: %w", f.Name(), err)
    23  		}
    24  	}()
    25  
    26  	// Create a file mapping object. The object itself is not shared.
    27  	mapObj, err := syscall.CreateFileMapping(
    28  		syscall.Handle(f.Fd()), // fhandle
    29  		nil,                    // sa
    30  		syscall.PAGE_READWRITE, // prot
    31  		0,                      // maxSizeHigh
    32  		0,                      // maxSizeLow
    33  		nil,                    // name
    34  	)
    35  	if err != nil {
    36  		return nil, err
    37  	}
    38  
    39  	// Create a view from the file mapping object.
    40  	access := uint32(syscall.FILE_MAP_READ | syscall.FILE_MAP_WRITE)
    41  	addr, err := syscall.MapViewOfFile(
    42  		mapObj,        // handle
    43  		access,        // access
    44  		0,             // offsetHigh
    45  		0,             // offsetLow
    46  		uintptr(size), // length
    47  	)
    48  	if err != nil {
    49  		syscall.CloseHandle(mapObj)
    50  		return nil, err
    51  	}
    52  
    53  	region := unsafe.Slice((*byte)(unsafe.Pointer(addr)), size)
    54  	return &sharedMem{
    55  		f:             f,
    56  		region:        region,
    57  		removeOnClose: removeOnClose,
    58  		sys:           sharedMemSys{mapObj: mapObj},
    59  	}, nil
    60  }
    61  
    62  // Close unmaps the shared memory and closes the temporary file. If this
    63  // sharedMem was created with sharedMemTempFile, Close also removes the file.
    64  func (m *sharedMem) Close() error {
    65  	// Attempt all operations, even if we get an error for an earlier operation.
    66  	// os.File.Close may fail due to I/O errors, but we still want to delete
    67  	// the temporary file.
    68  	var errs []error
    69  	errs = append(errs,
    70  		syscall.UnmapViewOfFile(uintptr(unsafe.Pointer(&m.region[0]))),
    71  		syscall.CloseHandle(m.sys.mapObj),
    72  		m.f.Close())
    73  	if m.removeOnClose {
    74  		errs = append(errs, os.Remove(m.f.Name()))
    75  	}
    76  	for _, err := range errs {
    77  		if err != nil {
    78  			return err
    79  		}
    80  	}
    81  	return nil
    82  }
    83  
    84  // setWorkerComm configures communication channels on the cmd that will
    85  // run a worker process.
    86  func setWorkerComm(cmd *exec.Cmd, comm workerComm) {
    87  	mem := <-comm.memMu
    88  	memName := mem.f.Name()
    89  	comm.memMu <- mem
    90  	syscall.SetHandleInformation(syscall.Handle(comm.fuzzIn.Fd()), syscall.HANDLE_FLAG_INHERIT, 1)
    91  	syscall.SetHandleInformation(syscall.Handle(comm.fuzzOut.Fd()), syscall.HANDLE_FLAG_INHERIT, 1)
    92  	cmd.Env = append(cmd.Env, fmt.Sprintf("GO_TEST_FUZZ_WORKER_HANDLES=%x,%x,%q", comm.fuzzIn.Fd(), comm.fuzzOut.Fd(), memName))
    93  	cmd.SysProcAttr = &syscall.SysProcAttr{AdditionalInheritedHandles: []syscall.Handle{syscall.Handle(comm.fuzzIn.Fd()), syscall.Handle(comm.fuzzOut.Fd())}}
    94  }
    95  
    96  // getWorkerComm returns communication channels in the worker process.
    97  func getWorkerComm() (comm workerComm, err error) {
    98  	v := os.Getenv("GO_TEST_FUZZ_WORKER_HANDLES")
    99  	if v == "" {
   100  		return workerComm{}, fmt.Errorf("GO_TEST_FUZZ_WORKER_HANDLES not set")
   101  	}
   102  	var fuzzInFD, fuzzOutFD uintptr
   103  	var memName string
   104  	if _, err := fmt.Sscanf(v, "%x,%x,%q", &fuzzInFD, &fuzzOutFD, &memName); err != nil {
   105  		return workerComm{}, fmt.Errorf("parsing GO_TEST_FUZZ_WORKER_HANDLES=%s: %v", v, err)
   106  	}
   107  
   108  	fuzzIn := os.NewFile(fuzzInFD, "fuzz_in")
   109  	fuzzOut := os.NewFile(fuzzOutFD, "fuzz_out")
   110  	tmpFile, err := os.OpenFile(memName, os.O_RDWR, 0)
   111  	if err != nil {
   112  		return workerComm{}, fmt.Errorf("worker opening temp file: %w", err)
   113  	}
   114  	fi, err := tmpFile.Stat()
   115  	if err != nil {
   116  		return workerComm{}, fmt.Errorf("worker checking temp file size: %w", err)
   117  	}
   118  	size := int(fi.Size())
   119  	if int64(size) != fi.Size() {
   120  		return workerComm{}, fmt.Errorf("fuzz temp file exceeds maximum size")
   121  	}
   122  	removeOnClose := false
   123  	mem, err := sharedMemMapFile(tmpFile, size, removeOnClose)
   124  	if err != nil {
   125  		return workerComm{}, err
   126  	}
   127  	memMu := make(chan *sharedMem, 1)
   128  	memMu <- mem
   129  
   130  	return workerComm{fuzzIn: fuzzIn, fuzzOut: fuzzOut, memMu: memMu}, nil
   131  }
   132  
   133  func isInterruptError(err error) bool {
   134  	// On Windows, we can't tell whether the process was interrupted by the error
   135  	// returned by Wait. It looks like an ExitError with status 1.
   136  	return false
   137  }
   138  
   139  // terminationSignal returns -1 and false because Windows doesn't have signals.
   140  func terminationSignal(err error) (os.Signal, bool) {
   141  	return syscall.Signal(-1), false
   142  }
   143  
   144  // isCrashSignal is not implemented because Windows doesn't have signals.
   145  func isCrashSignal(signal os.Signal) bool {
   146  	panic("not implemented: no signals on windows")
   147  }
   148
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