// Copyright 2013 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.
// Identify mismatches between assembly files and Go func declarations.
package main
import (
"bytes"
"fmt"
"go/ast"
"go/token"
"regexp"
"strconv"
"strings"
)
// 'kind' is a kind of assembly variable.
// The kinds 1, 2, 4, 8 stand for values of that size.
type asmKind int
// These special kinds are not valid sizes.
const (
asmString asmKind = 100 + iota
asmSlice
asmInterface
asmEmptyInterface
)
// An asmArch describes assembly parameters for an architecture
type asmArch struct {
name string
ptrSize int
intSize int
maxAlign int
bigEndian bool
stack string
lr bool
}
// An asmFunc describes the expected variables for a function on a given architecture.
type asmFunc struct {
arch *asmArch
size int // size of all arguments
vars map[string]*asmVar
varByOffset map[int]*asmVar
}
// An asmVar describes a single assembly variable.
type asmVar struct {
name string
kind asmKind
typ string
off int
size int
inner []*asmVar
}
var (
asmArch386 = asmArch{"386", 4, 4, 4, false, "SP", false}
asmArchArm = asmArch{"arm", 4, 4, 4, false, "R13", true}
asmArchArm64 = asmArch{"arm64", 8, 8, 8, false, "RSP", true}
asmArchAmd64 = asmArch{"amd64", 8, 8, 8, false, "SP", false}
asmArchAmd64p32 = asmArch{"amd64p32", 4, 4, 8, false, "SP", false}
asmArchPpc64 = asmArch{"ppc64", 8, 8, 8, true, "R1", true}
asmArchPpc64LE = asmArch{"ppc64le", 8, 8, 8, false, "R1", true}
arches = []*asmArch{
&asmArch386,
&asmArchArm,
&asmArchArm64,
&asmArchAmd64,
&asmArchAmd64p32,
&asmArchPpc64,
&asmArchPpc64LE,
}
)
var (
re = regexp.MustCompile
asmPlusBuild = re(`//\s+\+build\s+([^\n]+)`)
asmTEXT = re(`\bTEXT\b.*·([^\(]+)\(SB\)(?:\s*,\s*([0-9A-Z|+]+))?(?:\s*,\s*\$(-?[0-9]+)(?:-([0-9]+))?)?`)
asmDATA = re(`\b(DATA|GLOBL)\b`)
asmNamedFP = re(`([a-zA-Z0-9_\xFF-\x{10FFFF}]+)(?:\+([0-9]+))\(FP\)`)
asmUnnamedFP = re(`[^+\-0-9](([0-9]+)\(FP\))`)
asmSP = re(`[^+\-0-9](([0-9]+)\(([A-Z0-9]+)\))`)
asmOpcode = re(`^\s*(?:[A-Z0-9a-z_]+:)?\s*([A-Z]+)\s*([^,]*)(?:,\s*(.*))?`)
ppc64Suff = re(`([BHWD])(ZU|Z|U|BR)?$`)
)
func asmCheck(pkg *Package) {
if !vet("asmdecl") {
return
}
// No work if no assembly files.
if !pkg.hasFileWithSuffix(".s") {
return
}
// Gather declarations. knownFunc[name][arch] is func description.
knownFunc := make(map[string]map[string]*asmFunc)
for _, f := range pkg.files {
if f.file != nil {
for _, decl := range f.file.Decls {
if decl, ok := decl.(*ast.FuncDecl); ok && decl.Body == nil {
knownFunc[decl.Name.Name] = f.asmParseDecl(decl)
}
}
}
}
Files:
for _, f := range pkg.files {
if !strings.HasSuffix(f.name, ".s") {
continue
}
Println("Checking file", f.name)
// Determine architecture from file name if possible.
var arch string
var archDef *asmArch
for _, a := range arches {
if strings.HasSuffix(f.name, "_"+a.name+".s") {
arch = a.name
archDef = a
break
}
}
lines := strings.SplitAfter(string(f.content), "\n")
var (
fn *asmFunc
fnName string
localSize, argSize int
wroteSP bool
haveRetArg bool
retLine []int
)
flushRet := func() {
if fn != nil && fn.vars["ret"] != nil && !haveRetArg && len(retLine) > 0 {
v := fn.vars["ret"]
for _, line := range retLine {
f.Badf(token.NoPos, "%s:%d: [%s] %s: RET without writing to %d-byte ret+%d(FP)", f.name, line, arch, fnName, v.size, v.off)
}
}
retLine = nil
}
for lineno, line := range lines {
lineno++
badf := func(format string, args ...interface{}) {
f.Badf(token.NoPos, "%s:%d: [%s] %s: %s", f.name, lineno, arch, fnName, fmt.Sprintf(format, args...))
}
if arch == "" {
// Determine architecture from +build line if possible.
if m := asmPlusBuild.FindStringSubmatch(line); m != nil {
Fields:
for _, fld := range strings.Fields(m[1]) {
for _, a := range arches {
if a.name == fld {
arch = a.name
archDef = a
break Fields
}
}
}
}
}
if m := asmTEXT.FindStringSubmatch(line); m != nil {
flushRet()
if arch == "" {
f.Warnf(token.NoPos, "%s: cannot determine architecture for assembly file", f.name)
continue Files
}
fnName = m[1]
fn = knownFunc[m[1]][arch]
if fn != nil {
size, _ := strconv.Atoi(m[4])
if size != fn.size && (m[2] != "7" && !strings.Contains(m[2], "NOSPLIT") || size != 0) {
badf("wrong argument size %d; expected $...-%d", size, fn.size)
}
}
localSize, _ = strconv.Atoi(m[3])
localSize += archDef.intSize
if archDef.lr {
// Account for caller's saved LR
localSize += archDef.intSize
}
argSize, _ = strconv.Atoi(m[4])
if fn == nil && !strings.Contains(fnName, "<>") {
badf("function %s missing Go declaration", fnName)
}
wroteSP = false
haveRetArg = false
continue
} else if strings.Contains(line, "TEXT") && strings.Contains(line, "SB") {
// function, but not visible from Go (didn't match asmTEXT), so stop checking
flushRet()
fn = nil
fnName = ""
continue
}
if strings.Contains(line, "RET") {
retLine = append(retLine, lineno)
}
if fnName == "" {
continue
}
if asmDATA.FindStringSubmatch(line) != nil {
fn = nil
}
if archDef == nil {
continue
}
if strings.Contains(line, ", "+archDef.stack) || strings.Contains(line, ",\t"+archDef.stack) {
wroteSP = true
continue
}
for _, m := range asmSP.FindAllStringSubmatch(line, -1) {
if m[3] != archDef.stack || wroteSP {
continue
}
off := 0
if m[1] != "" {
off, _ = strconv.Atoi(m[2])
}
if off >= localSize {
if fn != nil {
v := fn.varByOffset[off-localSize]
if v != nil {
badf("%s should be %s+%d(FP)", m[1], v.name, off-localSize)
continue
}
}
if off >= localSize+argSize {
badf("use of %s points beyond argument frame", m[1])
continue
}
badf("use of %s to access argument frame", m[1])
}
}
if fn == nil {
continue
}
for _, m := range asmUnnamedFP.FindAllStringSubmatch(line, -1) {
off, _ := strconv.Atoi(m[2])
v := fn.varByOffset[off]
if v != nil {
badf("use of unnamed argument %s; offset %d is %s+%d(FP)", m[1], off, v.name, v.off)
} else {
badf("use of unnamed argument %s", m[1])
}
}
for _, m := range asmNamedFP.FindAllStringSubmatch(line, -1) {
name := m[1]
off := 0
if m[2] != "" {
off, _ = strconv.Atoi(m[2])
}
if name == "ret" || strings.HasPrefix(name, "ret_") {
haveRetArg = true
}
v := fn.vars[name]
if v == nil {
// Allow argframe+0(FP).
if name == "argframe" && off == 0 {
continue
}
v = fn.varByOffset[off]
if v != nil {
badf("unknown variable %s; offset %d is %s+%d(FP)", name, off, v.name, v.off)
} else {
badf("unknown variable %s", name)
}
continue
}
asmCheckVar(badf, fn, line, m[0], off, v)
}
}
flushRet()
}
}
// asmParseDecl parses a function decl for expected assembly variables.
func (f *File) asmParseDecl(decl *ast.FuncDecl) map[string]*asmFunc {
var (
arch *asmArch
fn *asmFunc
offset int
failed bool
)
addVar := func(outer string, v asmVar) {
if vo := fn.vars[outer]; vo != nil {
vo.inner = append(vo.inner, &v)
}
fn.vars[v.name] = &v
for i := 0; i < v.size; i++ {
fn.varByOffset[v.off+i] = &v
}
}
addParams := func(list []*ast.Field) {
for i, fld := range list {
// Determine alignment, size, and kind of type in declaration.
var align, size int
var kind asmKind
names := fld.Names
typ := f.gofmt(fld.Type)
switch t := fld.Type.(type) {
default:
switch typ {
default:
f.Warnf(fld.Type.Pos(), "unknown assembly argument type %s", typ)
failed = true
return
case "int8", "uint8", "byte", "bool":
size = 1
case "int16", "uint16":
size = 2
case "int32", "uint32", "float32":
size = 4
case "int64", "uint64", "float64":
align = arch.maxAlign
size = 8
case "int", "uint":
size = arch.intSize
case "uintptr", "iword", "Word", "Errno", "unsafe.Pointer":
size = arch.ptrSize
case "string", "ErrorString":
size = arch.ptrSize * 2
align = arch.ptrSize
kind = asmString
}
case *ast.ChanType, *ast.FuncType, *ast.MapType, *ast.StarExpr:
size = arch.ptrSize
case *ast.InterfaceType:
align = arch.ptrSize
size = 2 * arch.ptrSize
if len(t.Methods.List) > 0 {
kind = asmInterface
} else {
kind = asmEmptyInterface
}
case *ast.ArrayType:
if t.Len == nil {
size = arch.ptrSize + 2*arch.intSize
align = arch.ptrSize
kind = asmSlice
break
}
f.Warnf(fld.Type.Pos(), "unsupported assembly argument type %s", typ)
failed = true
case *ast.StructType:
f.Warnf(fld.Type.Pos(), "unsupported assembly argument type %s", typ)
failed = true
}
if align == 0 {
align = size
}
if kind == 0 {
kind = asmKind(size)
}
offset += -offset & (align - 1)
// Create variable for each name being declared with this type.
if len(names) == 0 {
name := "unnamed"
if decl.Type.Results != nil && len(decl.Type.Results.List) > 0 && &list[0] == &decl.Type.Results.List[0] && i == 0 {
// Assume assembly will refer to single unnamed result as r.
name = "ret"
}
names = []*ast.Ident{{Name: name}}
}
for _, id := range names {
name := id.Name
addVar("", asmVar{
name: name,
kind: kind,
typ: typ,
off: offset,
size: size,
})
switch kind {
case 8:
if arch.ptrSize == 4 {
w1, w2 := "lo", "hi"
if arch.bigEndian {
w1, w2 = w2, w1
}
addVar(name, asmVar{
name: name + "_" + w1,
kind: 4,
typ: "half " + typ,
off: offset,
size: 4,
})
addVar(name, asmVar{
name: name + "_" + w2,
kind: 4,
typ: "half " + typ,
off: offset + 4,
size: 4,
})
}
case asmEmptyInterface:
addVar(name, asmVar{
name: name + "_type",
kind: asmKind(arch.ptrSize),
typ: "interface type",
off: offset,
size: arch.ptrSize,
})
addVar(name, asmVar{
name: name + "_data",
kind: asmKind(arch.ptrSize),
typ: "interface data",
off: offset + arch.ptrSize,
size: arch.ptrSize,
})
case asmInterface:
addVar(name, asmVar{
name: name + "_itable",
kind: asmKind(arch.ptrSize),
typ: "interface itable",
off: offset,
size: arch.ptrSize,
})
addVar(name, asmVar{
name: name + "_data",
kind: asmKind(arch.ptrSize),
typ: "interface data",
off: offset + arch.ptrSize,
size: arch.ptrSize,
})
case asmSlice:
addVar(name, asmVar{
name: name + "_base",
kind: asmKind(arch.ptrSize),
typ: "slice base",
off: offset,
size: arch.ptrSize,
})
addVar(name, asmVar{
name: name + "_len",
kind: asmKind(arch.intSize),
typ: "slice len",
off: offset + arch.ptrSize,
size: arch.intSize,
})
addVar(name, asmVar{
name: name + "_cap",
kind: asmKind(arch.intSize),
typ: "slice cap",
off: offset + arch.ptrSize + arch.intSize,
size: arch.intSize,
})
case asmString:
addVar(name, asmVar{
name: name + "_base",
kind: asmKind(arch.ptrSize),
typ: "string base",
off: offset,
size: arch.ptrSize,
})
addVar(name, asmVar{
name: name + "_len",
kind: asmKind(arch.intSize),
typ: "string len",
off: offset + arch.ptrSize,
size: arch.intSize,
})
}
offset += size
}
}
}
m := make(map[string]*asmFunc)
for _, arch = range arches {
fn = &asmFunc{
arch: arch,
vars: make(map[string]*asmVar),
varByOffset: make(map[int]*asmVar),
}
offset = 0
addParams(decl.Type.Params.List)
if decl.Type.Results != nil && len(decl.Type.Results.List) > 0 {
offset += -offset & (arch.maxAlign - 1)
addParams(decl.Type.Results.List)
}
fn.size = offset
m[arch.name] = fn
}
if failed {
return nil
}
return m
}
// asmCheckVar checks a single variable reference.
func asmCheckVar(badf func(string, ...interface{}), fn *asmFunc, line, expr string, off int, v *asmVar) {
m := asmOpcode.FindStringSubmatch(line)
if m == nil {
if !strings.HasPrefix(strings.TrimSpace(line), "//") {
badf("cannot find assembly opcode")
}
return
}
// Determine operand sizes from instruction.
// Typically the suffix suffices, but there are exceptions.
var src, dst, kind asmKind
op := m[1]
switch fn.arch.name + "." + op {
case "386.FMOVLP":
src, dst = 8, 4
case "arm.MOVD":
src = 8
case "arm.MOVW":
src = 4
case "arm.MOVH", "arm.MOVHU":
src = 2
case "arm.MOVB", "arm.MOVBU":
src = 1
// LEA* opcodes don't really read the second arg.
// They just take the address of it.
case "386.LEAL":
dst = 4
case "amd64.LEAQ":
dst = 8
case "amd64p32.LEAL":
dst = 4
default:
switch fn.arch.name {
case "386", "amd64":
if strings.HasPrefix(op, "F") && (strings.HasSuffix(op, "D") || strings.HasSuffix(op, "DP")) {
// FMOVDP, FXCHD, etc
src = 8
break
}
if strings.HasPrefix(op, "F") && (strings.HasSuffix(op, "F") || strings.HasSuffix(op, "FP")) {
// FMOVFP, FXCHF, etc
src = 4
break
}
if strings.HasSuffix(op, "SD") {
// MOVSD, SQRTSD, etc
src = 8
break
}
if strings.HasSuffix(op, "SS") {
// MOVSS, SQRTSS, etc
src = 4
break
}
if strings.HasPrefix(op, "SET") {
// SETEQ, etc
src = 1
break
}
switch op[len(op)-1] {
case 'B':
src = 1
case 'W':
src = 2
case 'L':
src = 4
case 'D', 'Q':
src = 8
}
case "ppc64", "ppc64le":
// Strip standard suffixes to reveal size letter.
m := ppc64Suff.FindStringSubmatch(op)
if m != nil {
switch m[1][0] {
case 'B':
src = 1
case 'H':
src = 2
case 'W':
src = 4
case 'D':
src = 8
}
}
}
}
if dst == 0 {
dst = src
}
// Determine whether the match we're holding
// is the first or second argument.
if strings.Index(line, expr) > strings.Index(line, ",") {
kind = dst
} else {
kind = src
}
vk := v.kind
vt := v.typ
switch vk {
case asmInterface, asmEmptyInterface, asmString, asmSlice:
// allow reference to first word (pointer)
vk = v.inner[0].kind
vt = v.inner[0].typ
}
if off != v.off {
var inner bytes.Buffer
for i, vi := range v.inner {
if len(v.inner) > 1 {
fmt.Fprintf(&inner, ",")
}
fmt.Fprintf(&inner, " ")
if i == len(v.inner)-1 {
fmt.Fprintf(&inner, "or ")
}
fmt.Fprintf(&inner, "%s+%d(FP)", vi.name, vi.off)
}
badf("invalid offset %s; expected %s+%d(FP)%s", expr, v.name, v.off, inner.String())
return
}
if kind != 0 && kind != vk {
var inner bytes.Buffer
if len(v.inner) > 0 {
fmt.Fprintf(&inner, " containing")
for i, vi := range v.inner {
if i > 0 && len(v.inner) > 2 {
fmt.Fprintf(&inner, ",")
}
fmt.Fprintf(&inner, " ")
if i > 0 && i == len(v.inner)-1 {
fmt.Fprintf(&inner, "and ")
}
fmt.Fprintf(&inner, "%s+%d(FP)", vi.name, vi.off)
}
}
badf("invalid %s of %s; %s is %d-byte value%s", op, expr, vt, vk, inner.String())
}
}