plist.go

Documentation: cmd/internal/obj

     1  // Copyright 2013 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  package obj
     6  
     7  import (
     8  	"cmd/internal/objabi"
     9  	"fmt"
    10  	"strings"
    11  )
    12  
    13  type Plist struct {
    14  	Firstpc *Prog
    15  	Curfn   interface{} // holds a *gc.Node, if non-nil
    16  }
    17  
    18  // ProgAlloc is a function that allocates Progs.
    19  // It is used to provide access to cached/bulk-allocated Progs to the assemblers.
    20  type ProgAlloc func() *Prog
    21  
    22  func Flushplist(ctxt *Link, plist *Plist, newprog ProgAlloc, myimportpath string) {
    23  	// Build list of symbols, and assign instructions to lists.
    24  	var curtext *LSym
    25  	var etext *Prog
    26  	var text []*LSym
    27  
    28  	var plink *Prog
    29  	for p := plist.Firstpc; p != nil; p = plink {
    30  		if ctxt.Debugasm > 0 && ctxt.Debugvlog {
    31  			fmt.Printf("obj: %v\n", p)
    32  		}
    33  		plink = p.Link
    34  		p.Link = nil
    35  
    36  		switch p.As {
    37  		case AEND:
    38  			continue
    39  
    40  		case ATEXT:
    41  			s := p.From.Sym
    42  			if s == nil {
    43  				// func _() { }
    44  				curtext = nil
    45  				continue
    46  			}
    47  			text = append(text, s)
    48  			etext = p
    49  			curtext = s
    50  			continue
    51  
    52  		case AFUNCDATA:
    53  			// Rewrite reference to go_args_stackmap(SB) to the Go-provided declaration information.
    54  			if curtext == nil { // func _() {}
    55  				continue
    56  			}
    57  			if p.To.Sym.Name == "go_args_stackmap" {
    58  				if p.From.Type != TYPE_CONST || p.From.Offset != objabi.FUNCDATA_ArgsPointerMaps {
    59  					ctxt.Diag("FUNCDATA use of go_args_stackmap(SB) without FUNCDATA_ArgsPointerMaps")
    60  				}
    61  				p.To.Sym = ctxt.LookupDerived(curtext, curtext.Name+".args_stackmap")
    62  			}
    63  
    64  		}
    65  
    66  		if curtext == nil {
    67  			etext = nil
    68  			continue
    69  		}
    70  		etext.Link = p
    71  		etext = p
    72  	}
    73  
    74  	if newprog == nil {
    75  		newprog = ctxt.NewProg
    76  	}
    77  
    78  	// Add reference to Go arguments for assembly functions without them.
    79  	if ctxt.IsAsm {
    80  		for _, s := range text {
    81  			if !strings.HasPrefix(s.Name, "\"\".") {
    82  				continue
    83  			}
    84  			// The current args_stackmap generation in the compiler assumes
    85  			// that the function in question is ABI0, so avoid introducing
    86  			// an args_stackmap reference if the func is not ABI0 (better to
    87  			// have no stackmap than an incorrect/lying stackmap).
    88  			if s.ABI() != ABI0 {
    89  				continue
    90  			}
    91  			foundArgMap, foundArgInfo := false, false
    92  			for p := s.Func().Text; p != nil; p = p.Link {
    93  				if p.As == AFUNCDATA && p.From.Type == TYPE_CONST {
    94  					if p.From.Offset == objabi.FUNCDATA_ArgsPointerMaps {
    95  						foundArgMap = true
    96  					}
    97  					if p.From.Offset == objabi.FUNCDATA_ArgInfo {
    98  						foundArgInfo = true
    99  					}
   100  					if foundArgMap && foundArgInfo {
   101  						break
   102  					}
   103  				}
   104  			}
   105  			if !foundArgMap {
   106  				p := Appendp(s.Func().Text, newprog)
   107  				p.As = AFUNCDATA
   108  				p.From.Type = TYPE_CONST
   109  				p.From.Offset = objabi.FUNCDATA_ArgsPointerMaps
   110  				p.To.Type = TYPE_MEM
   111  				p.To.Name = NAME_EXTERN
   112  				p.To.Sym = ctxt.LookupDerived(s, s.Name+".args_stackmap")
   113  			}
   114  			if !foundArgInfo {
   115  				p := Appendp(s.Func().Text, newprog)
   116  				p.As = AFUNCDATA
   117  				p.From.Type = TYPE_CONST
   118  				p.From.Offset = objabi.FUNCDATA_ArgInfo
   119  				p.To.Type = TYPE_MEM
   120  				p.To.Name = NAME_EXTERN
   121  				p.To.Sym = ctxt.LookupDerived(s, fmt.Sprintf("%s.arginfo%d", s.Name, s.ABI()))
   122  			}
   123  		}
   124  	}
   125  
   126  	// Turn functions into machine code images.
   127  	for _, s := range text {
   128  		mkfwd(s)
   129  		if ctxt.Arch.ErrorCheck != nil {
   130  			ctxt.Arch.ErrorCheck(ctxt, s)
   131  		}
   132  		linkpatch(ctxt, s, newprog)
   133  		ctxt.Arch.Preprocess(ctxt, s, newprog)
   134  		ctxt.Arch.Assemble(ctxt, s, newprog)
   135  		if ctxt.Errors > 0 {
   136  			continue
   137  		}
   138  		linkpcln(ctxt, s)
   139  		if myimportpath != "" {
   140  			ctxt.populateDWARF(plist.Curfn, s, myimportpath)
   141  		}
   142  	}
   143  }
   144  
   145  func (ctxt *Link) InitTextSym(s *LSym, flag int) {
   146  	if s == nil {
   147  		// func _() { }
   148  		return
   149  	}
   150  	if s.Func() != nil {
   151  		ctxt.Diag("InitTextSym double init for %s", s.Name)
   152  	}
   153  	s.NewFuncInfo()
   154  	if s.OnList() {
   155  		ctxt.Diag("symbol %s listed multiple times", s.Name)
   156  	}
   157  	name := strings.Replace(s.Name, "\"\"", ctxt.Pkgpath, -1)
   158  	s.Func().FuncID = objabi.GetFuncID(name, flag&WRAPPER != 0 || flag&ABIWRAPPER != 0)
   159  	s.Func().FuncFlag = toFuncFlag(flag)
   160  	s.Set(AttrOnList, true)
   161  	s.Set(AttrDuplicateOK, flag&DUPOK != 0)
   162  	s.Set(AttrNoSplit, flag&NOSPLIT != 0)
   163  	s.Set(AttrReflectMethod, flag&REFLECTMETHOD != 0)
   164  	s.Set(AttrWrapper, flag&WRAPPER != 0)
   165  	s.Set(AttrABIWrapper, flag&ABIWRAPPER != 0)
   166  	s.Set(AttrNeedCtxt, flag&NEEDCTXT != 0)
   167  	s.Set(AttrNoFrame, flag&NOFRAME != 0)
   168  	s.Type = objabi.STEXT
   169  	ctxt.Text = append(ctxt.Text, s)
   170  
   171  	// Set up DWARF entries for s
   172  	ctxt.dwarfSym(s)
   173  }
   174  
   175  func toFuncFlag(flag int) objabi.FuncFlag {
   176  	var out objabi.FuncFlag
   177  	if flag&TOPFRAME != 0 {
   178  		out |= objabi.FuncFlag_TOPFRAME
   179  	}
   180  	return out
   181  }
   182  
   183  func (ctxt *Link) Globl(s *LSym, size int64, flag int) {
   184  	if s.OnList() {
   185  		ctxt.Diag("symbol %s listed multiple times", s.Name)
   186  	}
   187  	s.Set(AttrOnList, true)
   188  	ctxt.Data = append(ctxt.Data, s)
   189  	s.Size = size
   190  	if s.Type == 0 {
   191  		s.Type = objabi.SBSS
   192  	}
   193  	if flag&DUPOK != 0 {
   194  		s.Set(AttrDuplicateOK, true)
   195  	}
   196  	if flag&RODATA != 0 {
   197  		s.Type = objabi.SRODATA
   198  	} else if flag&NOPTR != 0 {
   199  		if s.Type == objabi.SDATA {
   200  			s.Type = objabi.SNOPTRDATA
   201  		} else {
   202  			s.Type = objabi.SNOPTRBSS
   203  		}
   204  	} else if flag&TLSBSS != 0 {
   205  		s.Type = objabi.STLSBSS
   206  	}
   207  	if strings.HasPrefix(s.Name, "\"\"."+StaticNamePref) {
   208  		s.Set(AttrStatic, true)
   209  	}
   210  }
   211  
   212  // EmitEntryLiveness generates PCDATA Progs after p to switch to the
   213  // liveness map active at the entry of function s. It returns the last
   214  // Prog generated.
   215  func (ctxt *Link) EmitEntryLiveness(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   216  	pcdata := ctxt.EmitEntryStackMap(s, p, newprog)
   217  	pcdata = ctxt.EmitEntryUnsafePoint(s, pcdata, newprog)
   218  	return pcdata
   219  }
   220  
   221  // Similar to EmitEntryLiveness, but just emit stack map.
   222  func (ctxt *Link) EmitEntryStackMap(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   223  	pcdata := Appendp(p, newprog)
   224  	pcdata.Pos = s.Func().Text.Pos
   225  	pcdata.As = APCDATA
   226  	pcdata.From.Type = TYPE_CONST
   227  	pcdata.From.Offset = objabi.PCDATA_StackMapIndex
   228  	pcdata.To.Type = TYPE_CONST
   229  	pcdata.To.Offset = -1 // pcdata starts at -1 at function entry
   230  
   231  	return pcdata
   232  }
   233  
   234  // Similar to EmitEntryLiveness, but just emit unsafe point map.
   235  func (ctxt *Link) EmitEntryUnsafePoint(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   236  	pcdata := Appendp(p, newprog)
   237  	pcdata.Pos = s.Func().Text.Pos
   238  	pcdata.As = APCDATA
   239  	pcdata.From.Type = TYPE_CONST
   240  	pcdata.From.Offset = objabi.PCDATA_UnsafePoint
   241  	pcdata.To.Type = TYPE_CONST
   242  	pcdata.To.Offset = -1
   243  
   244  	return pcdata
   245  }
   246  
   247  // StartUnsafePoint generates PCDATA Progs after p to mark the
   248  // beginning of an unsafe point. The unsafe point starts immediately
   249  // after p.
   250  // It returns the last Prog generated.
   251  func (ctxt *Link) StartUnsafePoint(p *Prog, newprog ProgAlloc) *Prog {
   252  	pcdata := Appendp(p, newprog)
   253  	pcdata.As = APCDATA
   254  	pcdata.From.Type = TYPE_CONST
   255  	pcdata.From.Offset = objabi.PCDATA_UnsafePoint
   256  	pcdata.To.Type = TYPE_CONST
   257  	pcdata.To.Offset = objabi.PCDATA_UnsafePointUnsafe
   258  
   259  	return pcdata
   260  }
   261  
   262  // EndUnsafePoint generates PCDATA Progs after p to mark the end of an
   263  // unsafe point, restoring the register map index to oldval.
   264  // The unsafe point ends right after p.
   265  // It returns the last Prog generated.
   266  func (ctxt *Link) EndUnsafePoint(p *Prog, newprog ProgAlloc, oldval int64) *Prog {
   267  	pcdata := Appendp(p, newprog)
   268  	pcdata.As = APCDATA
   269  	pcdata.From.Type = TYPE_CONST
   270  	pcdata.From.Offset = objabi.PCDATA_UnsafePoint
   271  	pcdata.To.Type = TYPE_CONST
   272  	pcdata.To.Offset = oldval
   273  
   274  	return pcdata
   275  }
   276  
   277  // MarkUnsafePoints inserts PCDATAs to mark nonpreemptible and restartable
   278  // instruction sequences, based on isUnsafePoint and isRestartable predicate.
   279  // p0 is the start of the instruction stream.
   280  // isUnsafePoint(p) returns true if p is not safe for async preemption.
   281  // isRestartable(p) returns true if we can restart at the start of p (this Prog)
   282  // upon async preemption. (Currently multi-Prog restartable sequence is not
   283  // supported.)
   284  // isRestartable can be nil. In this case it is treated as always returning false.
   285  // If isUnsafePoint(p) and isRestartable(p) are both true, it is treated as
   286  // an unsafe point.
   287  func MarkUnsafePoints(ctxt *Link, p0 *Prog, newprog ProgAlloc, isUnsafePoint, isRestartable func(*Prog) bool) {
   288  	if isRestartable == nil {
   289  		// Default implementation: nothing is restartable.
   290  		isRestartable = func(*Prog) bool { return false }
   291  	}
   292  	prev := p0
   293  	prevPcdata := int64(-1) // entry PC data value
   294  	prevRestart := int64(0)
   295  	for p := prev.Link; p != nil; p, prev = p.Link, p {
   296  		if p.As == APCDATA && p.From.Offset == objabi.PCDATA_UnsafePoint {
   297  			prevPcdata = p.To.Offset
   298  			continue
   299  		}
   300  		if prevPcdata == objabi.PCDATA_UnsafePointUnsafe {
   301  			continue // already unsafe
   302  		}
   303  		if isUnsafePoint(p) {
   304  			q := ctxt.StartUnsafePoint(prev, newprog)
   305  			q.Pc = p.Pc
   306  			q.Link = p
   307  			// Advance to the end of unsafe point.
   308  			for p.Link != nil && isUnsafePoint(p.Link) {
   309  				p = p.Link
   310  			}
   311  			if p.Link == nil {
   312  				break // Reached the end, don't bother marking the end
   313  			}
   314  			p = ctxt.EndUnsafePoint(p, newprog, prevPcdata)
   315  			p.Pc = p.Link.Pc
   316  			continue
   317  		}
   318  		if isRestartable(p) {
   319  			val := int64(objabi.PCDATA_Restart1)
   320  			if val == prevRestart {
   321  				val = objabi.PCDATA_Restart2
   322  			}
   323  			prevRestart = val
   324  			q := Appendp(prev, newprog)
   325  			q.As = APCDATA
   326  			q.From.Type = TYPE_CONST
   327  			q.From.Offset = objabi.PCDATA_UnsafePoint
   328  			q.To.Type = TYPE_CONST
   329  			q.To.Offset = val
   330  			q.Pc = p.Pc
   331  			q.Link = p
   332  
   333  			if p.Link == nil {
   334  				break // Reached the end, don't bother marking the end
   335  			}
   336  			if isRestartable(p.Link) {
   337  				// Next Prog is also restartable. No need to mark the end
   338  				// of this sequence. We'll just go ahead mark the next one.
   339  				continue
   340  			}
   341  			p = Appendp(p, newprog)
   342  			p.As = APCDATA
   343  			p.From.Type = TYPE_CONST
   344  			p.From.Offset = objabi.PCDATA_UnsafePoint
   345  			p.To.Type = TYPE_CONST
   346  			p.To.Offset = prevPcdata
   347  			p.Pc = p.Link.Pc
   348  		}
   349  	}
   350  }
   351
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