blob: 7180b3816ceea1daa0f6171ac02b8ad970a1f0f2 [file] [log] [blame]
// Copyright 2009 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.
package ssagen
import (
"fmt"
"io/ioutil"
"log"
"os"
"strings"
"cmd/compile/internal/base"
"cmd/compile/internal/escape"
"cmd/compile/internal/ir"
"cmd/compile/internal/staticdata"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/obj"
"cmd/internal/objabi"
)
// useNewABIWrapGen returns TRUE if the compiler should generate an
// ABI wrapper for the function 'f'.
func useABIWrapGen(f *ir.Func) bool {
if !base.Flag.ABIWrap {
return false
}
// Support limit option for bisecting.
if base.Flag.ABIWrapLimit == 1 {
return false
}
if base.Flag.ABIWrapLimit < 1 {
return true
}
base.Flag.ABIWrapLimit--
if base.Debug.ABIWrap != 0 && base.Flag.ABIWrapLimit == 1 {
fmt.Fprintf(os.Stderr, "=-= limit reached after new wrapper for %s\n",
f.LSym.Name)
}
return true
}
// symabiDefs and symabiRefs record the defined and referenced ABIs of
// symbols required by non-Go code. These are keyed by link symbol
// name, where the local package prefix is always `"".`
var symabiDefs, symabiRefs map[string]obj.ABI
func CgoSymABIs() {
// The linker expects an ABI0 wrapper for all cgo-exported
// functions.
for _, prag := range typecheck.Target.CgoPragmas {
switch prag[0] {
case "cgo_export_static", "cgo_export_dynamic":
if symabiRefs == nil {
symabiRefs = make(map[string]obj.ABI)
}
symabiRefs[prag[1]] = obj.ABI0
}
}
}
// ReadSymABIs reads a symabis file that specifies definitions and
// references of text symbols by ABI.
//
// The symabis format is a set of lines, where each line is a sequence
// of whitespace-separated fields. The first field is a verb and is
// either "def" for defining a symbol ABI or "ref" for referencing a
// symbol using an ABI. For both "def" and "ref", the second field is
// the symbol name and the third field is the ABI name, as one of the
// named cmd/internal/obj.ABI constants.
func ReadSymABIs(file, myimportpath string) {
data, err := ioutil.ReadFile(file)
if err != nil {
log.Fatalf("-symabis: %v", err)
}
symabiDefs = make(map[string]obj.ABI)
symabiRefs = make(map[string]obj.ABI)
localPrefix := ""
if myimportpath != "" {
// Symbols in this package may be written either as
// "".X or with the package's import path already in
// the symbol.
localPrefix = objabi.PathToPrefix(myimportpath) + "."
}
for lineNum, line := range strings.Split(string(data), "\n") {
lineNum++ // 1-based
line = strings.TrimSpace(line)
if line == "" || strings.HasPrefix(line, "#") {
continue
}
parts := strings.Fields(line)
switch parts[0] {
case "def", "ref":
// Parse line.
if len(parts) != 3 {
log.Fatalf(`%s:%d: invalid symabi: syntax is "%s sym abi"`, file, lineNum, parts[0])
}
sym, abistr := parts[1], parts[2]
abi, valid := obj.ParseABI(abistr)
if !valid {
log.Fatalf(`%s:%d: invalid symabi: unknown abi "%s"`, file, lineNum, abistr)
}
// If the symbol is already prefixed with
// myimportpath, rewrite it to start with ""
// so it matches the compiler's internal
// symbol names.
if localPrefix != "" && strings.HasPrefix(sym, localPrefix) {
sym = `"".` + sym[len(localPrefix):]
}
// Record for later.
if parts[0] == "def" {
symabiDefs[sym] = abi
} else {
symabiRefs[sym] = abi
}
default:
log.Fatalf(`%s:%d: invalid symabi type "%s"`, file, lineNum, parts[0])
}
}
}
// InitLSym defines f's obj.LSym and initializes it based on the
// properties of f. This includes setting the symbol flags and ABI and
// creating and initializing related DWARF symbols.
//
// InitLSym must be called exactly once per function and must be
// called for both functions with bodies and functions without bodies.
// For body-less functions, we only create the LSym; for functions
// with bodies call a helper to setup up / populate the LSym.
func InitLSym(f *ir.Func, hasBody bool) {
// FIXME: for new-style ABI wrappers, we set up the lsym at the
// point the wrapper is created.
if f.LSym != nil && base.Flag.ABIWrap {
return
}
staticdata.NeedFuncSym(f.Sym())
selectLSym(f, hasBody)
if hasBody {
setupTextLSym(f, 0)
}
}
// selectLSym sets up the LSym for a given function, and
// makes calls to helpers to create ABI wrappers if needed.
func selectLSym(f *ir.Func, hasBody bool) {
if f.LSym != nil {
base.FatalfAt(f.Pos(), "InitLSym called twice on %v", f)
}
if nam := f.Nname; !ir.IsBlank(nam) {
var wrapperABI obj.ABI
needABIWrapper := false
defABI, hasDefABI := symabiDefs[nam.Linksym().Name]
if hasDefABI && defABI == obj.ABI0 {
// Symbol is defined as ABI0. Create an
// Internal -> ABI0 wrapper.
f.LSym = nam.LinksymABI(obj.ABI0)
needABIWrapper, wrapperABI = true, obj.ABIInternal
} else {
f.LSym = nam.Linksym()
// No ABI override. Check that the symbol is
// using the expected ABI.
want := obj.ABIInternal
if f.LSym.ABI() != want {
base.Fatalf("function symbol %s has the wrong ABI %v, expected %v", f.LSym.Name, f.LSym.ABI(), want)
}
}
if f.Pragma&ir.Systemstack != 0 {
f.LSym.Set(obj.AttrCFunc, true)
}
isLinknameExported := nam.Sym().Linkname != "" && (hasBody || hasDefABI)
if abi, ok := symabiRefs[f.LSym.Name]; (ok && abi == obj.ABI0) || isLinknameExported {
// Either 1) this symbol is definitely
// referenced as ABI0 from this package; or 2)
// this symbol is defined in this package but
// given a linkname, indicating that it may be
// referenced from another package. Create an
// ABI0 -> Internal wrapper so it can be
// called as ABI0. In case 2, it's important
// that we know it's defined in this package
// since other packages may "pull" symbols
// using linkname and we don't want to create
// duplicate ABI wrappers.
if f.LSym.ABI() != obj.ABI0 {
needABIWrapper, wrapperABI = true, obj.ABI0
}
}
if needABIWrapper {
if !useABIWrapGen(f) {
// Fallback: use alias instead. FIXME.
// These LSyms have the same name as the
// native function, so we create them directly
// rather than looking them up. The uniqueness
// of f.lsym ensures uniqueness of asym.
asym := &obj.LSym{
Name: f.LSym.Name,
Type: objabi.SABIALIAS,
R: []obj.Reloc{{Sym: f.LSym}}, // 0 size, so "informational"
}
asym.SetABI(wrapperABI)
asym.Set(obj.AttrDuplicateOK, true)
base.Ctxt.ABIAliases = append(base.Ctxt.ABIAliases, asym)
} else {
if base.Debug.ABIWrap != 0 {
fmt.Fprintf(os.Stderr, "=-= %v to %v wrapper for %s.%s\n",
wrapperABI, 1-wrapperABI, types.LocalPkg.Path, f.LSym.Name)
}
makeABIWrapper(f, wrapperABI)
}
}
}
}
// makeABIWrapper creates a new function that wraps a cross-ABI call
// to "f". The wrapper is marked as an ABIWRAPPER.
func makeABIWrapper(f *ir.Func, wrapperABI obj.ABI) {
// Q: is this needed?
savepos := base.Pos
savedclcontext := typecheck.DeclContext
savedcurfn := ir.CurFunc
base.Pos = base.AutogeneratedPos
typecheck.DeclContext = ir.PEXTERN
// At the moment we don't support wrapping a method, we'd need machinery
// below to handle the receiver. Panic if we see this scenario.
ft := f.Nname.Ntype.Type()
if ft.NumRecvs() != 0 {
panic("makeABIWrapper support for wrapping methods not implemented")
}
// Manufacture a new func type to use for the wrapper.
var noReceiver *ir.Field
tfn := ir.NewFuncType(base.Pos,
noReceiver,
typecheck.NewFuncParams(ft.Params(), true),
typecheck.NewFuncParams(ft.Results(), false))
// Reuse f's types.Sym to create a new ODCLFUNC/function.
fn := typecheck.DeclFunc(f.Nname.Sym(), tfn)
fn.SetDupok(true)
fn.SetWrapper(true) // ignore frame for panic+recover matching
// Select LSYM now.
asym := base.Ctxt.LookupABI(f.LSym.Name, wrapperABI)
asym.Type = objabi.STEXT
if fn.LSym != nil {
panic("unexpected")
}
fn.LSym = asym
// ABI0-to-ABIInternal wrappers will be mainly loading params from
// stack into registers (and/or storing stack locations back to
// registers after the wrapped call); in most cases they won't
// need to allocate stack space, so it should be OK to mark them
// as NOSPLIT in these cases. In addition, my assumption is that
// functions written in assembly are NOSPLIT in most (but not all)
// cases. In the case of an ABIInternal target that has too many
// parameters to fit into registers, the wrapper would need to
// allocate stack space, but this seems like an unlikely scenario.
// Hence: mark these wrappers NOSPLIT.
//
// ABIInternal-to-ABI0 wrappers on the other hand will be taking
// things in registers and pushing them onto the stack prior to
// the ABI0 call, meaning that they will always need to allocate
// stack space. If the compiler marks them as NOSPLIT this seems
// as though it could lead to situations where the the linker's
// nosplit-overflow analysis would trigger a link failure. On the
// other hand if they not tagged NOSPLIT then this could cause
// problems when building the runtime (since there may be calls to
// asm routine in cases where it's not safe to grow the stack). In
// most cases the wrapper would be (in effect) inlined, but are
// there (perhaps) indirect calls from the runtime that could run
// into trouble here.
// FIXME: at the moment all.bash does not pass when I leave out
// NOSPLIT for these wrappers, so all are currently tagged with NOSPLIT.
setupTextLSym(fn, obj.NOSPLIT|obj.ABIWRAPPER)
// Generate call. Use tail call if no params and no returns,
// but a regular call otherwise.
//
// Note: ideally we would be using a tail call in cases where
// there are params but no returns for ABI0->ABIInternal wrappers,
// provided that all params fit into registers (e.g. we don't have
// to allocate any stack space). Doing this will require some
// extra work in typecheck/walk/ssa, might want to add a new node
// OTAILCALL or something to this effect.
tailcall := tfn.Type().NumResults() == 0 && tfn.Type().NumParams() == 0 && tfn.Type().NumRecvs() == 0
if base.Ctxt.Arch.Name == "ppc64le" && base.Ctxt.Flag_dynlink {
// cannot tailcall on PPC64 with dynamic linking, as we need
// to restore R2 after call.
tailcall = false
}
if base.Ctxt.Arch.Name == "amd64" && wrapperABI == obj.ABIInternal {
// cannot tailcall from ABIInternal to ABI0 on AMD64, as we need
// to special registers (X15) when returning to ABIInternal.
tailcall = false
}
var tail ir.Node
if tailcall {
tail = ir.NewTailCallStmt(base.Pos, f.Nname)
} else {
call := ir.NewCallExpr(base.Pos, ir.OCALL, f.Nname, nil)
call.Args = ir.ParamNames(tfn.Type())
call.IsDDD = tfn.Type().IsVariadic()
tail = call
if tfn.Type().NumResults() > 0 {
n := ir.NewReturnStmt(base.Pos, nil)
n.Results = []ir.Node{call}
tail = n
}
}
fn.Body.Append(tail)
typecheck.FinishFuncBody()
if base.Debug.DclStack != 0 {
types.CheckDclstack()
}
typecheck.Func(fn)
ir.CurFunc = fn
typecheck.Stmts(fn.Body)
escape.Batch([]*ir.Func{fn}, false)
typecheck.Target.Decls = append(typecheck.Target.Decls, fn)
// Restore previous context.
base.Pos = savepos
typecheck.DeclContext = savedclcontext
ir.CurFunc = savedcurfn
}
// setupTextLsym initializes the LSym for a with-body text symbol.
func setupTextLSym(f *ir.Func, flag int) {
if f.Dupok() {
flag |= obj.DUPOK
}
if f.Wrapper() {
flag |= obj.WRAPPER
}
if f.Needctxt() {
flag |= obj.NEEDCTXT
}
if f.Pragma&ir.Nosplit != 0 {
flag |= obj.NOSPLIT
}
if f.ReflectMethod() {
flag |= obj.REFLECTMETHOD
}
// Clumsy but important.
// See test/recover.go for test cases and src/reflect/value.go
// for the actual functions being considered.
if base.Ctxt.Pkgpath == "reflect" {
switch f.Sym().Name {
case "callReflect", "callMethod":
flag |= obj.WRAPPER
}
}
base.Ctxt.InitTextSym(f.LSym, flag)
}