golang.org/x/sys@v0.20.1-0.20240517151509-673e0f94c16d/unix/mkasm.go (about)

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build ignore
     6  
     7  // mkasm.go generates assembly trampolines to call library routines from Go.
     8  // This program must be run after mksyscall.go.
     9  package main
    10  
    11  import (
    12  	"bytes"
    13  	"fmt"
    14  	"log"
    15  	"os"
    16  	"sort"
    17  	"strings"
    18  )
    19  
    20  func archPtrSize(arch string) int {
    21  	switch arch {
    22  	case "386", "arm":
    23  		return 4
    24  	case "amd64", "arm64", "mips64", "ppc64", "riscv64":
    25  		return 8
    26  	default:
    27  		log.Fatalf("Unknown arch %q", arch)
    28  		return 0
    29  	}
    30  }
    31  
    32  func generateASMFile(goos, arch string, inFileNames []string, outFileName string) map[string]bool {
    33  	trampolines := map[string]bool{}
    34  	var orderedTrampolines []string
    35  	for _, inFileName := range inFileNames {
    36  		in, err := os.ReadFile(inFileName)
    37  		if err != nil {
    38  			log.Fatalf("Failed to read file: %v", err)
    39  		}
    40  		for _, line := range strings.Split(string(in), "\n") {
    41  			const prefix = "var "
    42  			const suffix = "_trampoline_addr uintptr"
    43  			if !strings.HasPrefix(line, prefix) || !strings.HasSuffix(line, suffix) {
    44  				continue
    45  			}
    46  			fn := strings.TrimSuffix(strings.TrimPrefix(line, prefix), suffix)
    47  			if !trampolines[fn] {
    48  				orderedTrampolines = append(orderedTrampolines, fn)
    49  				trampolines[fn] = true
    50  			}
    51  		}
    52  	}
    53  
    54  	ptrSize := archPtrSize(arch)
    55  
    56  	var out bytes.Buffer
    57  	fmt.Fprintf(&out, "// go run mkasm.go %s\n", strings.Join(os.Args[1:], " "))
    58  	fmt.Fprintf(&out, "// Code generated by the command above; DO NOT EDIT.\n")
    59  	fmt.Fprintf(&out, "\n")
    60  	fmt.Fprintf(&out, "#include \"textflag.h\"\n")
    61  	for _, fn := range orderedTrampolines {
    62  		fmt.Fprintf(&out, "\nTEXT %s_trampoline<>(SB),NOSPLIT,$0-0\n", fn)
    63  		if goos == "openbsd" && arch == "ppc64" {
    64  			fmt.Fprintf(&out, "\tCALL\t%s(SB)\n", fn)
    65  			fmt.Fprintf(&out, "\tRET\n")
    66  		} else {
    67  			fmt.Fprintf(&out, "\tJMP\t%s(SB)\n", fn)
    68  		}
    69  		fmt.Fprintf(&out, "GLOBL\t·%s_trampoline_addr(SB), RODATA, $%d\n", fn, ptrSize)
    70  		fmt.Fprintf(&out, "DATA\t·%s_trampoline_addr(SB)/%d, $%s_trampoline<>(SB)\n", fn, ptrSize, fn)
    71  	}
    72  
    73  	if err := os.WriteFile(outFileName, out.Bytes(), 0644); err != nil {
    74  		log.Fatalf("Failed to write assembly file %q: %v", outFileName, err)
    75  	}
    76  
    77  	return trampolines
    78  }
    79  
    80  const darwinTestTemplate = `// go run mkasm.go %s
    81  // Code generated by the command above; DO NOT EDIT.
    82  
    83  //go:build darwin
    84  
    85  package unix
    86  
    87  // All the _trampoline functions in zsyscall_darwin_%s.s.
    88  var darwinTests = [...]darwinTest{
    89  %s}
    90  `
    91  
    92  func writeDarwinTest(trampolines map[string]bool, fileName, arch string) {
    93  	var sortedTrampolines []string
    94  	for fn := range trampolines {
    95  		sortedTrampolines = append(sortedTrampolines, fn)
    96  	}
    97  	sort.Strings(sortedTrampolines)
    98  
    99  	var out bytes.Buffer
   100  
   101  	const prefix = "libc_"
   102  	for _, fn := range sortedTrampolines {
   103  		fmt.Fprintf(&out, fmt.Sprintf("\t{%q, %s_trampoline_addr},\n", strings.TrimPrefix(fn, prefix), fn))
   104  	}
   105  	lines := out.String()
   106  
   107  	out.Reset()
   108  	fmt.Fprintf(&out, darwinTestTemplate, strings.Join(os.Args[1:], " "), arch, lines)
   109  
   110  	if err := os.WriteFile(fileName, out.Bytes(), 0644); err != nil {
   111  		log.Fatalf("Failed to write test file %q: %v", fileName, err)
   112  	}
   113  }
   114  
   115  func main() {
   116  	if len(os.Args) != 3 {
   117  		log.Fatalf("Usage: %s <goos> <arch>", os.Args[0])
   118  	}
   119  	goos, arch := os.Args[1], os.Args[2]
   120  
   121  	syscallFilename := fmt.Sprintf("syscall_%s.go", goos)
   122  	syscallArchFilename := fmt.Sprintf("syscall_%s_%s.go", goos, arch)
   123  	zsyscallArchFilename := fmt.Sprintf("zsyscall_%s_%s.go", goos, arch)
   124  	zsyscallASMFileName := fmt.Sprintf("zsyscall_%s_%s.s", goos, arch)
   125  
   126  	inFileNames := []string{
   127  		syscallFilename,
   128  		syscallArchFilename,
   129  		zsyscallArchFilename,
   130  	}
   131  
   132  	trampolines := generateASMFile(goos, arch, inFileNames, zsyscallASMFileName)
   133  
   134  	if goos == "darwin" {
   135  		writeDarwinTest(trampolines, fmt.Sprintf("darwin_%s_test.go", arch), arch)
   136  	}
   137  }