Current File : //usr/local/go119/src/cmd/internal/obj/plist.go
// 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.
package obj
import (
"cmd/internal/objabi"
"fmt"
"strings"
)
type Plist struct {
Firstpc *Prog
Curfn interface{} // holds a *gc.Node, if non-nil
}
// ProgAlloc is a function that allocates Progs.
// It is used to provide access to cached/bulk-allocated Progs to the assemblers.
type ProgAlloc func() *Prog
func Flushplist(ctxt *Link, plist *Plist, newprog ProgAlloc, myimportpath string) {
// Build list of symbols, and assign instructions to lists.
var curtext *LSym
var etext *Prog
var text []*LSym
var plink *Prog
for p := plist.Firstpc; p != nil; p = plink {
if ctxt.Debugasm > 0 && ctxt.Debugvlog {
fmt.Printf("obj: %v\n", p)
}
plink = p.Link
p.Link = nil
switch p.As {
case AEND:
continue
case ATEXT:
s := p.From.Sym
if s == nil {
// func _() { }
curtext = nil
continue
}
text = append(text, s)
etext = p
curtext = s
continue
case AFUNCDATA:
// Rewrite reference to go_args_stackmap(SB) to the Go-provided declaration information.
if curtext == nil { // func _() {}
continue
}
switch p.To.Sym.Name {
case "go_args_stackmap":
if p.From.Type != TYPE_CONST || p.From.Offset != objabi.FUNCDATA_ArgsPointerMaps {
ctxt.Diag("FUNCDATA use of go_args_stackmap(SB) without FUNCDATA_ArgsPointerMaps")
}
p.To.Sym = ctxt.LookupDerived(curtext, curtext.Name+".args_stackmap")
case "no_pointers_stackmap":
if p.From.Type != TYPE_CONST || p.From.Offset != objabi.FUNCDATA_LocalsPointerMaps {
ctxt.Diag("FUNCDATA use of no_pointers_stackmap(SB) without FUNCDATA_LocalsPointerMaps")
}
// funcdata for functions with no local variables in frame.
// Define two zero-length bitmaps, because the same index is used
// for the local variables as for the argument frame, and assembly
// frames have two argument bitmaps, one without results and one with results.
// Write []uint32{2, 0}.
b := make([]byte, 8)
ctxt.Arch.ByteOrder.PutUint32(b, 2)
s := ctxt.GCLocalsSym(b)
if !s.OnList() {
ctxt.Globl(s, int64(len(s.P)), int(RODATA|DUPOK))
}
p.To.Sym = s
}
}
if curtext == nil {
etext = nil
continue
}
etext.Link = p
etext = p
}
if newprog == nil {
newprog = ctxt.NewProg
}
// Add reference to Go arguments for assembly functions without them.
if ctxt.IsAsm {
for _, s := range text {
if !strings.HasPrefix(s.Name, "\"\".") {
continue
}
// The current args_stackmap generation in the compiler assumes
// that the function in question is ABI0, so avoid introducing
// an args_stackmap reference if the func is not ABI0 (better to
// have no stackmap than an incorrect/lying stackmap).
if s.ABI() != ABI0 {
continue
}
foundArgMap, foundArgInfo := false, false
for p := s.Func().Text; p != nil; p = p.Link {
if p.As == AFUNCDATA && p.From.Type == TYPE_CONST {
if p.From.Offset == objabi.FUNCDATA_ArgsPointerMaps {
foundArgMap = true
}
if p.From.Offset == objabi.FUNCDATA_ArgInfo {
foundArgInfo = true
}
if foundArgMap && foundArgInfo {
break
}
}
}
if !foundArgMap {
p := Appendp(s.Func().Text, newprog)
p.As = AFUNCDATA
p.From.Type = TYPE_CONST
p.From.Offset = objabi.FUNCDATA_ArgsPointerMaps
p.To.Type = TYPE_MEM
p.To.Name = NAME_EXTERN
p.To.Sym = ctxt.LookupDerived(s, s.Name+".args_stackmap")
}
if !foundArgInfo {
p := Appendp(s.Func().Text, newprog)
p.As = AFUNCDATA
p.From.Type = TYPE_CONST
p.From.Offset = objabi.FUNCDATA_ArgInfo
p.To.Type = TYPE_MEM
p.To.Name = NAME_EXTERN
p.To.Sym = ctxt.LookupDerived(s, fmt.Sprintf("%s.arginfo%d", s.Name, s.ABI()))
}
}
}
// Turn functions into machine code images.
for _, s := range text {
mkfwd(s)
if ctxt.Arch.ErrorCheck != nil {
ctxt.Arch.ErrorCheck(ctxt, s)
}
linkpatch(ctxt, s, newprog)
ctxt.Arch.Preprocess(ctxt, s, newprog)
ctxt.Arch.Assemble(ctxt, s, newprog)
if ctxt.Errors > 0 {
continue
}
linkpcln(ctxt, s)
if myimportpath != "" {
ctxt.populateDWARF(plist.Curfn, s, myimportpath)
}
}
}
func (ctxt *Link) InitTextSym(s *LSym, flag int) {
if s == nil {
// func _() { }
return
}
if s.Func() != nil {
ctxt.Diag("InitTextSym double init for %s", s.Name)
}
s.NewFuncInfo()
if s.OnList() {
ctxt.Diag("symbol %s listed multiple times", s.Name)
}
// TODO(mdempsky): Remove once cmd/asm stops writing "" symbols.
name := strings.Replace(s.Name, "\"\"", ctxt.Pkgpath, -1)
s.Func().FuncID = objabi.GetFuncID(name, flag&WRAPPER != 0 || flag&ABIWRAPPER != 0)
s.Func().FuncFlag = ctxt.toFuncFlag(flag)
s.Set(AttrOnList, true)
s.Set(AttrDuplicateOK, flag&DUPOK != 0)
s.Set(AttrNoSplit, flag&NOSPLIT != 0)
s.Set(AttrReflectMethod, flag&REFLECTMETHOD != 0)
s.Set(AttrWrapper, flag&WRAPPER != 0)
s.Set(AttrABIWrapper, flag&ABIWRAPPER != 0)
s.Set(AttrNeedCtxt, flag&NEEDCTXT != 0)
s.Set(AttrNoFrame, flag&NOFRAME != 0)
s.Type = objabi.STEXT
ctxt.Text = append(ctxt.Text, s)
// Set up DWARF entries for s
ctxt.dwarfSym(s)
}
func (ctxt *Link) toFuncFlag(flag int) objabi.FuncFlag {
var out objabi.FuncFlag
if flag&TOPFRAME != 0 {
out |= objabi.FuncFlag_TOPFRAME
}
if ctxt.IsAsm {
out |= objabi.FuncFlag_ASM
}
return out
}
func (ctxt *Link) Globl(s *LSym, size int64, flag int) {
if s.OnList() {
ctxt.Diag("symbol %s listed multiple times", s.Name)
}
s.Set(AttrOnList, true)
ctxt.Data = append(ctxt.Data, s)
s.Size = size
if s.Type == 0 {
s.Type = objabi.SBSS
}
if flag&DUPOK != 0 {
s.Set(AttrDuplicateOK, true)
}
if flag&RODATA != 0 {
s.Type = objabi.SRODATA
} else if flag&NOPTR != 0 {
if s.Type == objabi.SDATA {
s.Type = objabi.SNOPTRDATA
} else {
s.Type = objabi.SNOPTRBSS
}
} else if flag&TLSBSS != 0 {
s.Type = objabi.STLSBSS
}
}
// EmitEntryLiveness generates PCDATA Progs after p to switch to the
// liveness map active at the entry of function s. It returns the last
// Prog generated.
func (ctxt *Link) EmitEntryLiveness(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
pcdata := ctxt.EmitEntryStackMap(s, p, newprog)
pcdata = ctxt.EmitEntryUnsafePoint(s, pcdata, newprog)
return pcdata
}
// Similar to EmitEntryLiveness, but just emit stack map.
func (ctxt *Link) EmitEntryStackMap(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
pcdata := Appendp(p, newprog)
pcdata.Pos = s.Func().Text.Pos
pcdata.As = APCDATA
pcdata.From.Type = TYPE_CONST
pcdata.From.Offset = objabi.PCDATA_StackMapIndex
pcdata.To.Type = TYPE_CONST
pcdata.To.Offset = -1 // pcdata starts at -1 at function entry
return pcdata
}
// Similar to EmitEntryLiveness, but just emit unsafe point map.
func (ctxt *Link) EmitEntryUnsafePoint(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
pcdata := Appendp(p, newprog)
pcdata.Pos = s.Func().Text.Pos
pcdata.As = APCDATA
pcdata.From.Type = TYPE_CONST
pcdata.From.Offset = objabi.PCDATA_UnsafePoint
pcdata.To.Type = TYPE_CONST
pcdata.To.Offset = -1
return pcdata
}
// StartUnsafePoint generates PCDATA Progs after p to mark the
// beginning of an unsafe point. The unsafe point starts immediately
// after p.
// It returns the last Prog generated.
func (ctxt *Link) StartUnsafePoint(p *Prog, newprog ProgAlloc) *Prog {
pcdata := Appendp(p, newprog)
pcdata.As = APCDATA
pcdata.From.Type = TYPE_CONST
pcdata.From.Offset = objabi.PCDATA_UnsafePoint
pcdata.To.Type = TYPE_CONST
pcdata.To.Offset = objabi.PCDATA_UnsafePointUnsafe
return pcdata
}
// EndUnsafePoint generates PCDATA Progs after p to mark the end of an
// unsafe point, restoring the register map index to oldval.
// The unsafe point ends right after p.
// It returns the last Prog generated.
func (ctxt *Link) EndUnsafePoint(p *Prog, newprog ProgAlloc, oldval int64) *Prog {
pcdata := Appendp(p, newprog)
pcdata.As = APCDATA
pcdata.From.Type = TYPE_CONST
pcdata.From.Offset = objabi.PCDATA_UnsafePoint
pcdata.To.Type = TYPE_CONST
pcdata.To.Offset = oldval
return pcdata
}
// MarkUnsafePoints inserts PCDATAs to mark nonpreemptible and restartable
// instruction sequences, based on isUnsafePoint and isRestartable predicate.
// p0 is the start of the instruction stream.
// isUnsafePoint(p) returns true if p is not safe for async preemption.
// isRestartable(p) returns true if we can restart at the start of p (this Prog)
// upon async preemption. (Currently multi-Prog restartable sequence is not
// supported.)
// isRestartable can be nil. In this case it is treated as always returning false.
// If isUnsafePoint(p) and isRestartable(p) are both true, it is treated as
// an unsafe point.
func MarkUnsafePoints(ctxt *Link, p0 *Prog, newprog ProgAlloc, isUnsafePoint, isRestartable func(*Prog) bool) {
if isRestartable == nil {
// Default implementation: nothing is restartable.
isRestartable = func(*Prog) bool { return false }
}
prev := p0
prevPcdata := int64(-1) // entry PC data value
prevRestart := int64(0)
for p := prev.Link; p != nil; p, prev = p.Link, p {
if p.As == APCDATA && p.From.Offset == objabi.PCDATA_UnsafePoint {
prevPcdata = p.To.Offset
continue
}
if prevPcdata == objabi.PCDATA_UnsafePointUnsafe {
continue // already unsafe
}
if isUnsafePoint(p) {
q := ctxt.StartUnsafePoint(prev, newprog)
q.Pc = p.Pc
q.Link = p
// Advance to the end of unsafe point.
for p.Link != nil && isUnsafePoint(p.Link) {
p = p.Link
}
if p.Link == nil {
break // Reached the end, don't bother marking the end
}
p = ctxt.EndUnsafePoint(p, newprog, prevPcdata)
p.Pc = p.Link.Pc
continue
}
if isRestartable(p) {
val := int64(objabi.PCDATA_Restart1)
if val == prevRestart {
val = objabi.PCDATA_Restart2
}
prevRestart = val
q := Appendp(prev, newprog)
q.As = APCDATA
q.From.Type = TYPE_CONST
q.From.Offset = objabi.PCDATA_UnsafePoint
q.To.Type = TYPE_CONST
q.To.Offset = val
q.Pc = p.Pc
q.Link = p
if p.Link == nil {
break // Reached the end, don't bother marking the end
}
if isRestartable(p.Link) {
// Next Prog is also restartable. No need to mark the end
// of this sequence. We'll just go ahead mark the next one.
continue
}
p = Appendp(p, newprog)
p.As = APCDATA
p.From.Type = TYPE_CONST
p.From.Offset = objabi.PCDATA_UnsafePoint
p.To.Type = TYPE_CONST
p.To.Offset = prevPcdata
p.Pc = p.Link.Pc
}
}
}
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