1 files changed, 131 insertions, 0 deletions
diff --git a/src/internal/fuzz/sys_posix.go b/src/internal/fuzz/sys_posix.go
new file mode 100644
index 00000000000..2473274ecf2
--- /dev/null
+++ b/src/internal/fuzz/sys_posix.go
@@ -0,0 +1,131 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin || linux
+// +build darwin linux
+
+package fuzz
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"syscall"
+)
+
+type sharedMemSys struct{}
+
+func sharedMemMapFile(f *os.File, size int, removeOnClose bool) (*sharedMem, error) {
+	prot := syscall.PROT_READ | syscall.PROT_WRITE
+	flags := syscall.MAP_FILE | syscall.MAP_SHARED
+	region, err := syscall.Mmap(int(f.Fd()), 0, size, prot, flags)
+	if err != nil {
+		return nil, err
+	}
+
+	return &sharedMem{f: f, region: region, removeOnClose: removeOnClose}, nil
+}
+
+// Close unmaps the shared memory and closes the temporary file. If this
+// sharedMem was created with sharedMemTempFile, Close also removes the file.
+func (m *sharedMem) Close() error {
+	// Attempt all operations, even if we get an error for an earlier operation.
+	// os.File.Close may fail due to I/O errors, but we still want to delete
+	// the temporary file.
+	var errs []error
+	errs = append(errs,
+		syscall.Munmap(m.region),
+		m.f.Close())
+	if m.removeOnClose {
+		errs = append(errs, os.Remove(m.f.Name()))
+	}
+	for _, err := range errs {
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// setWorkerComm configures communciation channels on the cmd that will
+// run a worker process.
+func setWorkerComm(cmd *exec.Cmd, comm workerComm) {
+	mem := <-comm.memMu
+	memFile := mem.f
+	comm.memMu <- mem
+	cmd.ExtraFiles = []*os.File{comm.fuzzIn, comm.fuzzOut, memFile}
+}
+
+// getWorkerComm returns communication channels in the worker process.
+func getWorkerComm() (comm workerComm, err error) {
+	fuzzIn := os.NewFile(3, "fuzz_in")
+	fuzzOut := os.NewFile(4, "fuzz_out")
+	memFile := os.NewFile(5, "fuzz_mem")
+	fi, err := memFile.Stat()
+	if err != nil {
+		return workerComm{}, err
+	}
+	size := int(fi.Size())
+	if int64(size) != fi.Size() {
+		return workerComm{}, fmt.Errorf("fuzz temp file exceeds maximum size")
+	}
+	removeOnClose := false
+	mem, err := sharedMemMapFile(memFile, size, removeOnClose)
+	if err != nil {
+		return workerComm{}, err
+	}
+	memMu := make(chan *sharedMem, 1)
+	memMu <- mem
+	return workerComm{fuzzIn: fuzzIn, fuzzOut: fuzzOut, memMu: memMu}, nil
+}
+
+// isInterruptError returns whether an error was returned by a process that
+// was terminated by an interrupt signal (SIGINT).
+func isInterruptError(err error) bool {
+	exitErr, ok := err.(*exec.ExitError)
+	if !ok || exitErr.ExitCode() >= 0 {
+		return false
+	}
+	status := exitErr.Sys().(syscall.WaitStatus)
+	return status.Signal() == syscall.SIGINT
+}
+
+// terminationSignal checks if err is an exec.ExitError with a signal status.
+// If it is, terminationSignal returns the signal and true.
+// If not, -1 and false.
+func terminationSignal(err error) (os.Signal, bool) {
+	exitErr, ok := err.(*exec.ExitError)
+	if !ok || exitErr.ExitCode() >= 0 {
+		return syscall.Signal(-1), false
+	}
+	status := exitErr.Sys().(syscall.WaitStatus)
+	return status.Signal(), status.Signaled()
+}
+
+// isCrashSignal returns whether a signal was likely to have been caused by an
+// error in the program that received it, triggered by a fuzz input. For
+// example, SIGSEGV would be received after a nil pointer dereference.
+// Other signals like SIGKILL or SIGHUP are more likely to have been sent by
+// another process, and we shouldn't record a crasher if the worker process
+// receives one of these.
+//
+// Note that Go installs its own signal handlers on startup, so some of these
+// signals may only be received if signal handlers are changed. For example,
+// SIGSEGV is normally transformed into a panic that causes the process to exit
+// with status 2 if not recovered, which we handle as a crash.
+func isCrashSignal(signal os.Signal) bool {
+	switch signal {
+	case
+		syscall.SIGILL,  // illegal instruction
+		syscall.SIGTRAP, // breakpoint
+		syscall.SIGABRT, // abort() called
+		syscall.SIGBUS,  // invalid memory access (e.g., misaligned address)
+		syscall.SIGFPE,  // math error, e.g., integer divide by zero
+		syscall.SIGSEGV, // invalid memory access (e.g., write to read-only)
+		syscall.SIGPIPE: // sent data to closed pipe or socket
+		return true
+	default:
+		return false
+	}
+}