mmap panic

main.go

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"syscall"
	"unsafe"

	"golang.org/x/sys/unix"
)

type Foo struct {
	a int
}

func main() {
	f, err := ioutil.TempFile("", "test")
	if err != nil {
		panic(err)
	}
	defer os.Remove(f.Name())

	//m := []byte{0, 0} // it works

	m, err := unix.Mmap(int(f.Fd()), 0, 10, syscall.PROT_READ, syscall.MAP_SHARED) // error
	if err != nil {
		panic(err)
	}

	var data *[100]byte
	data = (*[100]byte)(unsafe.Pointer(&m[0]))

	foo := (*Foo)(unsafe.Pointer(&data[0]))
	if foo == nil {
		fmt.Println("foo is nil")
	}
	fmt.Println(foo.a)
}

$ go run main.go
unexpected fault address 0x11fe000
fatal error: fault
[signal SIGBUS: bus error code=0x2 addr=0x11fe000 pc=0x109feb5]

goroutine 1 [running]:
runtime.throw(0x10d018f, 0x5)
        /usr/local/Cellar/go/1.14.1/libexec/src/runtime/panic.go:1114 +0x72 fp=0xc00009aeb8 sp=0xc00009ae88 pc=0x102e802
runtime.sigpanic()
        /usr/local/Cellar/go/1.14.1/libexec/src/runtime/signal_unix.go:692 +0x443 fp=0xc00009aee8 sp=0xc00009aeb8 pc=0x1042863
main.main()
        /Users/teppei/src/github.com/knqyf263/playground/mmap/main.go:38 +0x145 fp=0xc00009af88 sp=0xc00009aee8 pc=0x109feb5
runtime.main()
        /usr/local/Cellar/go/1.14.1/libexec/src/runtime/proc.go:203 +0x212 fp=0xc00009afe0 sp=0xc00009af88 pc=0x1030e82
runtime.goexit()
        /usr/local/Cellar/go/1.14.1/libexec/src/runtime/asm_amd64.s:1373 +0x1 fp=0xc00009afe8 sp=0xc00009afe0 pc=0x105b1e1

Process finished with exit code 2