asm-call-go-func.go

package main

import (
	"fmt"
	"syscall"
	"log"
	"unsafe"
)
const MMAP_FLAGS = syscall.MAP_ANONYMOUS

type sum2 func(a int, b int) (r int)


func sum2f (a int, b int) (r int) {
    fmt.Printf("a: %d \n", a)
    fmt.Printf("b: %d \n", b)
	r = a + b 
	return r
}

// function prototypes
type _call func(a int, b int, f sum2) (r int) 
// type sum2 func(a int, b int) (r int) 

func main() {

	var m = []uint8{
	0x64, 0x48, 0x8b, 0x0c, 0x25, 0x00, 0x00, 0x00, 0x00, 0x48, 0x3b, 0x61, 0x10, 0x76, 0x3c, 0x48, 
	0x83, 0xec, 0x28, 0x48, 0x89, 0x6c, 0x24, 0x20, 0x48, 0x8d, 0x6c, 0x24, 0x20, 0x48, 0x8b, 0x44, 
	0x24, 0x30, 0x48, 0x89, 0x04, 0x24, 0x48, 0x8b, 0x44, 0x24, 0x38, 0x48, 0x89, 0x44, 0x24, 0x08, 
	0x48, 0x8b, 0x44, 0x24, 0x40, 0x48, 0x89, 0x44, 0x24, 0x48, 0x48, 0x8b, 0x44, 0x24, 0x40, 0xff, 
	0xd0, 0x48, 0x8b, 0x6c, 0x24, 0x20, 0x48, 0x83, 0xc4, 0x28, 0xc3, 0xe8, 0x00, 0x00, 0x00, 0x00, 
	0xeb, 0xae, 


	}


	// jit part
	bin, err := syscall.Mmap(
        -1,
        0,
        len(m),
        syscall.PROT_READ | syscall.PROT_WRITE | syscall.PROT_EXEC, 
        syscall.MAP_PRIVATE | MMAP_FLAGS,
    )
    if err != nil {
        log.Fatalf("mmap failed: %v", err)
    }
    for i, b := range m {
        bin[i] = b
    }
    unsafeFunc := (uintptr)(unsafe.Pointer(&bin))
    callFunc := *(*_call)(unsafe.Pointer(&unsafeFunc))

    // run
	var a int
	var b int
	var r int

	a = 7 
	b = 9
	r = 3


    

    
    r = callFunc(a, b, sum2f)
    fmt.Printf("a: %d \n", a)
    fmt.Printf("b: %d \n", b)
    fmt.Printf("r: %d \n", r)
}