如何在Golang中使用在汇编代码中定义的函数？

Question

In golangs AES crypto package cipher_amd64.go makes use of functions that are defined in assembler code (asm_amd64.s). In the mentioned go file only the function headers are defined:

// defined in asm_amd64.s
func encryptBlockAsm(nr int, xk *uint32, dst, src *byte)
func decryptBlockAsm(nr int, xk *uint32, dst, src *byte)
func expandKeyAsm(nr int, key *byte, enc *uint32, dec *uint32)

How can I use these functions in my own code? Just declaring the headers and importing "crypto/aes" as in the mentioned .go file does not work (undefined: expandKeyAsm).

Thank you very much!

Answer 1

1. Copy the asm_amd64.s contents over to your package
2. Define the functions somewehere in that package
3. Use those functions in the package

Example (with the asm_amd64.s in the same package):

package main

import "fmt"

func encryptBlockAsm(nr int, xk *uint32, dst, src *byte)
func decryptBlockAsm(nr int, xk *uint32, dst, src *byte)
func expandKeyAsm(nr int, key *byte, enc *uint32, dec *uint32)

func main() {
    var nr int
    var xk uint32
    var dst byte
    var src byte

    fmt.Printf("Before:\t%v, %v, %v, %v
", nr, xk, dst, src)

    encryptBlockAsm(nr, &xk, &dst, &src)

    fmt.Printf("After:\t%v, %v, %v, %v
", nr, xk, dst, src)
}

Yields:

Before: 0, 0, 0, 0
After:  0, 0, 231, 173

I have no idea what the inputs should be but at least it demonstrates this does something :)