unix/mkasm_darwin.go

// Copyright 2018 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 ignore
// +build ignore

// mkasm_darwin.go generates assembly trampolines to call libSystem routines from Go.
//This program must be run after mksyscall.go.
package main

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strings"
)

const ptrsize = 8 // Pointer size. All supported platforms are 64-bit.

func writeASMFile(in string, fileName string, buildTags string) {
	trampolines := map[string]bool{}

	var out bytes.Buffer

	fmt.Fprintf(&out, "// go run mkasm_darwin.go %s\n", strings.Join(os.Args[1:], " "))
	fmt.Fprintf(&out, "// Code generated by the command above; DO NOT EDIT.\n")
	fmt.Fprintf(&out, "\n")
	fmt.Fprintf(&out, "//go:build %s\n", buildTags)
	fmt.Fprintf(&out, "// +build %s\n", buildTags)
	fmt.Fprintf(&out, "\n")
	fmt.Fprintf(&out, "#include \"textflag.h\"\n")
	for _, line := range strings.Split(in, "\n") {
		const prefix = "var "
		const suffix = "_trampoline_addr uintptr"
		if !strings.HasPrefix(line, prefix) || !strings.HasSuffix(line, suffix) {
			continue
		}
		fn := strings.TrimSuffix(strings.TrimPrefix(line, prefix), suffix)
		if !trampolines[fn] {
			trampolines[fn] = true
			fmt.Fprintf(&out, "\nTEXT %s_trampoline<>(SB),NOSPLIT,$0-0\n", fn)
			fmt.Fprintf(&out, "\tJMP\t%s(SB)\n\n", fn)
			fmt.Fprintf(&out, "GLOBL\t·%s_trampoline_addr(SB), RODATA, $%d\n", fn, ptrsize)
			fmt.Fprintf(&out, "DATA\t·%s_trampoline_addr(SB)/%d, $%s_trampoline<>(SB)\n", fn, ptrsize, fn)
		}
	}
	err := ioutil.WriteFile(fileName, out.Bytes(), 0644)
	if err != nil {
		log.Fatalf("can't write %s: %s", fileName, err)
	}
}

func main() {
	in1, err := ioutil.ReadFile("syscall_darwin.go")
	if err != nil {
		log.Fatalf("can't open syscall_darwin.go: %s", err)
	}
	arch := os.Args[1]
	in2, err := ioutil.ReadFile(fmt.Sprintf("syscall_darwin_%s.go", arch))
	if err != nil {
		log.Fatalf("can't open syscall_darwin_%s.go: %s", arch, err)
	}
	in3, err := ioutil.ReadFile(fmt.Sprintf("zsyscall_darwin_%s.go", arch))
	if err != nil {
		log.Fatalf("can't open zsyscall_darwin_%s.go: %s", arch, err)
	}
	in := string(in1) + string(in2) + string(in3)

	writeASMFile(in, fmt.Sprintf("zsyscall_darwin_%s.s", arch), "go1.12")

	in1, err = ioutil.ReadFile("syscall_darwin.1_13.go")
	if err != nil {
		log.Fatalf("can't open syscall_darwin.1_13.go: %s", err)
	}
	in2, err = ioutil.ReadFile(fmt.Sprintf("zsyscall_darwin_%s.1_13.go", arch))
	if err != nil {
		log.Fatalf("can't open zsyscall_darwin_%s.1_13.go: %s", arch, err)
	}

	in = string(in1) + string(in2)

	writeASMFile(in, fmt.Sprintf("zsyscall_darwin_%s.1_13.s", arch), "go1.13")
}