diff options
Diffstat (limited to 'src/cmd/compile/internal/ssagen/abi.go')
| -rw-r--r-- | src/cmd/compile/internal/ssagen/abi.go | 367 |
1 files changed, 367 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssagen/abi.go b/src/cmd/compile/internal/ssagen/abi.go new file mode 100644 index 0000000000..af08fcb7c3 --- /dev/null +++ b/src/cmd/compile/internal/ssagen/abi.go @@ -0,0 +1,367 @@ +// 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. + +//go:generate go run mkbuiltin.go + +package ssagen + +import ( + "fmt" + "io/ioutil" + "log" + "os" + "strings" + + "cmd/compile/internal/base" + "cmd/compile/internal/escape" + "cmd/compile/internal/ir" + "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 + } + 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.Fatalf("Func.initLSym called twice") + } + + if nam := f.Nname; !ir.IsBlank(nam) { + + var wrapperABI obj.ABI + needABIWrapper := false + defABI, hasDefABI := symabiDefs[nam.Sym().LinksymName()] + if hasDefABI && defABI == obj.ABI0 { + // Symbol is defined as ABI0. Create an + // Internal -> ABI0 wrapper. + f.LSym = nam.Sym().LinksymABI0() + needABIWrapper, wrapperABI = true, obj.ABIInternal + } else { + f.LSym = nam.Sym().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. + var tail ir.Node + if tfn.Type().NumResults() == 0 && tfn.Type().NumParams() == 0 && tfn.Type().NumRecvs() == 0 { + tail = ir.NewBranchStmt(base.Pos, ir.ORETJMP, f.Nname.Sym()) + } else { + call := ir.NewCallExpr(base.Pos, ir.OCALL, f.Nname, nil) + call.Args.Set(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) +} |