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Source file src/cmd/internal/obj/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 C or assembly functions without them.
    79  	for _, s := range text {
    80  		if !strings.HasPrefix(s.Name, "\"\".") {
    81  			continue
    82  		}
    83  		found := false
    84  		for p := s.Func().Text; p != nil; p = p.Link {
    85  			if p.As == AFUNCDATA && p.From.Type == TYPE_CONST && p.From.Offset == objabi.FUNCDATA_ArgsPointerMaps {
    86  				found = true
    87  				break
    88  			}
    89  		}
    90  
    91  		if !found {
    92  			p := Appendp(s.Func().Text, newprog)
    93  			p.As = AFUNCDATA
    94  			p.From.Type = TYPE_CONST
    95  			p.From.Offset = objabi.FUNCDATA_ArgsPointerMaps
    96  			p.To.Type = TYPE_MEM
    97  			p.To.Name = NAME_EXTERN
    98  			p.To.Sym = ctxt.LookupDerived(s, s.Name+".args_stackmap")
    99  		}
   100  	}
   101  
   102  	// Turn functions into machine code images.
   103  	for _, s := range text {
   104  		mkfwd(s)
   105  		linkpatch(ctxt, s, newprog)
   106  		ctxt.Arch.Preprocess(ctxt, s, newprog)
   107  		ctxt.Arch.Assemble(ctxt, s, newprog)
   108  		if ctxt.Errors > 0 {
   109  			continue
   110  		}
   111  		linkpcln(ctxt, s)
   112  		if myimportpath != "" {
   113  			ctxt.populateDWARF(plist.Curfn, s, myimportpath)
   114  		}
   115  	}
   116  }
   117  
   118  func (ctxt *Link) InitTextSym(s *LSym, flag int) {
   119  	if s == nil {
   120  		// func _() { }
   121  		return
   122  	}
   123  	if s.Func() != nil {
   124  		ctxt.Diag("InitTextSym double init for %s", s.Name)
   125  	}
   126  	s.NewFuncInfo()
   127  	if s.OnList() {
   128  		ctxt.Diag("symbol %s listed multiple times", s.Name)
   129  	}
   130  	name := strings.Replace(s.Name, "\"\"", ctxt.Pkgpath, -1)
   131  	s.Func().FuncID = objabi.GetFuncID(name, flag&WRAPPER != 0)
   132  	s.Set(AttrOnList, true)
   133  	s.Set(AttrDuplicateOK, flag&DUPOK != 0)
   134  	s.Set(AttrNoSplit, flag&NOSPLIT != 0)
   135  	s.Set(AttrReflectMethod, flag&REFLECTMETHOD != 0)
   136  	s.Set(AttrWrapper, flag&WRAPPER != 0)
   137  	s.Set(AttrNeedCtxt, flag&NEEDCTXT != 0)
   138  	s.Set(AttrNoFrame, flag&NOFRAME != 0)
   139  	s.Set(AttrTopFrame, flag&TOPFRAME != 0)
   140  	s.Type = objabi.STEXT
   141  	ctxt.Text = append(ctxt.Text, s)
   142  
   143  	// Set up DWARF entries for s
   144  	ctxt.dwarfSym(s)
   145  }
   146  
   147  func (ctxt *Link) Globl(s *LSym, size int64, flag int) {
   148  	if s.OnList() {
   149  		ctxt.Diag("symbol %s listed multiple times", s.Name)
   150  	}
   151  	s.Set(AttrOnList, true)
   152  	ctxt.Data = append(ctxt.Data, s)
   153  	s.Size = size
   154  	if s.Type == 0 {
   155  		s.Type = objabi.SBSS
   156  	}
   157  	if flag&DUPOK != 0 {
   158  		s.Set(AttrDuplicateOK, true)
   159  	}
   160  	if flag&RODATA != 0 {
   161  		s.Type = objabi.SRODATA
   162  	} else if flag&NOPTR != 0 {
   163  		if s.Type == objabi.SDATA {
   164  			s.Type = objabi.SNOPTRDATA
   165  		} else {
   166  			s.Type = objabi.SNOPTRBSS
   167  		}
   168  	} else if flag&TLSBSS != 0 {
   169  		s.Type = objabi.STLSBSS
   170  	}
   171  	if strings.HasPrefix(s.Name, "\"\"."+StaticNamePref) {
   172  		s.Set(AttrStatic, true)
   173  	}
   174  }
   175  
   176  // EmitEntryLiveness generates PCDATA Progs after p to switch to the
   177  // liveness map active at the entry of function s. It returns the last
   178  // Prog generated.
   179  func (ctxt *Link) EmitEntryLiveness(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   180  	pcdata := ctxt.EmitEntryStackMap(s, p, newprog)
   181  	pcdata = ctxt.EmitEntryUnsafePoint(s, pcdata, newprog)
   182  	return pcdata
   183  }
   184  
   185  // Similar to EmitEntryLiveness, but just emit stack map.
   186  func (ctxt *Link) EmitEntryStackMap(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   187  	pcdata := Appendp(p, newprog)
   188  	pcdata.Pos = s.Func().Text.Pos
   189  	pcdata.As = APCDATA
   190  	pcdata.From.Type = TYPE_CONST
   191  	pcdata.From.Offset = objabi.PCDATA_StackMapIndex
   192  	pcdata.To.Type = TYPE_CONST
   193  	pcdata.To.Offset = -1 // pcdata starts at -1 at function entry
   194  
   195  	return pcdata
   196  }
   197  
   198  // Similar to EmitEntryLiveness, but just emit unsafe point map.
   199  func (ctxt *Link) EmitEntryUnsafePoint(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   200  	pcdata := Appendp(p, newprog)
   201  	pcdata.Pos = s.Func().Text.Pos
   202  	pcdata.As = APCDATA
   203  	pcdata.From.Type = TYPE_CONST
   204  	pcdata.From.Offset = objabi.PCDATA_UnsafePoint
   205  	pcdata.To.Type = TYPE_CONST
   206  	pcdata.To.Offset = -1
   207  
   208  	return pcdata
   209  }
   210  
   211  // StartUnsafePoint generates PCDATA Progs after p to mark the
   212  // beginning of an unsafe point. The unsafe point starts immediately
   213  // after p.
   214  // It returns the last Prog generated.
   215  func (ctxt *Link) StartUnsafePoint(p *Prog, newprog ProgAlloc) *Prog {
   216  	pcdata := Appendp(p, newprog)
   217  	pcdata.As = APCDATA
   218  	pcdata.From.Type = TYPE_CONST
   219  	pcdata.From.Offset = objabi.PCDATA_UnsafePoint
   220  	pcdata.To.Type = TYPE_CONST
   221  	pcdata.To.Offset = objabi.PCDATA_UnsafePointUnsafe
   222  
   223  	return pcdata
   224  }
   225  
   226  // EndUnsafePoint generates PCDATA Progs after p to mark the end of an
   227  // unsafe point, restoring the register map index to oldval.
   228  // The unsafe point ends right after p.
   229  // It returns the last Prog generated.
   230  func (ctxt *Link) EndUnsafePoint(p *Prog, newprog ProgAlloc, oldval int64) *Prog {
   231  	pcdata := Appendp(p, newprog)
   232  	pcdata.As = APCDATA
   233  	pcdata.From.Type = TYPE_CONST
   234  	pcdata.From.Offset = objabi.PCDATA_UnsafePoint
   235  	pcdata.To.Type = TYPE_CONST
   236  	pcdata.To.Offset = oldval
   237  
   238  	return pcdata
   239  }
   240  
   241  // MarkUnsafePoints inserts PCDATAs to mark nonpreemptible and restartable
   242  // instruction sequences, based on isUnsafePoint and isRestartable predicate.
   243  // p0 is the start of the instruction stream.
   244  // isUnsafePoint(p) returns true if p is not safe for async preemption.
   245  // isRestartable(p) returns true if we can restart at the start of p (this Prog)
   246  // upon async preemption. (Currently multi-Prog restartable sequence is not
   247  // supported.)
   248  // isRestartable can be nil. In this case it is treated as always returning false.
   249  // If isUnsafePoint(p) and isRestartable(p) are both true, it is treated as
   250  // an unsafe point.
   251  func MarkUnsafePoints(ctxt *Link, p0 *Prog, newprog ProgAlloc, isUnsafePoint, isRestartable func(*Prog) bool) {
   252  	if isRestartable == nil {
   253  		// Default implementation: nothing is restartable.
   254  		isRestartable = func(*Prog) bool { return false }
   255  	}
   256  	prev := p0
   257  	prevPcdata := int64(-1) // entry PC data value
   258  	prevRestart := int64(0)
   259  	for p := prev.Link; p != nil; p, prev = p.Link, p {
   260  		if p.As == APCDATA && p.From.Offset == objabi.PCDATA_UnsafePoint {
   261  			prevPcdata = p.To.Offset
   262  			continue
   263  		}
   264  		if prevPcdata == objabi.PCDATA_UnsafePointUnsafe {
   265  			continue // already unsafe
   266  		}
   267  		if isUnsafePoint(p) {
   268  			q := ctxt.StartUnsafePoint(prev, newprog)
   269  			q.Pc = p.Pc
   270  			q.Link = p
   271  			// Advance to the end of unsafe point.
   272  			for p.Link != nil && isUnsafePoint(p.Link) {
   273  				p = p.Link
   274  			}
   275  			if p.Link == nil {
   276  				break // Reached the end, don't bother marking the end
   277  			}
   278  			p = ctxt.EndUnsafePoint(p, newprog, prevPcdata)
   279  			p.Pc = p.Link.Pc
   280  			continue
   281  		}
   282  		if isRestartable(p) {
   283  			val := int64(objabi.PCDATA_Restart1)
   284  			if val == prevRestart {
   285  				val = objabi.PCDATA_Restart2
   286  			}
   287  			prevRestart = val
   288  			q := Appendp(prev, newprog)
   289  			q.As = APCDATA
   290  			q.From.Type = TYPE_CONST
   291  			q.From.Offset = objabi.PCDATA_UnsafePoint
   292  			q.To.Type = TYPE_CONST
   293  			q.To.Offset = val
   294  			q.Pc = p.Pc
   295  			q.Link = p
   296  
   297  			if p.Link == nil {
   298  				break // Reached the end, don't bother marking the end
   299  			}
   300  			if isRestartable(p.Link) {
   301  				// Next Prog is also restartable. No need to mark the end
   302  				// of this sequence. We'll just go ahead mark the next one.
   303  				continue
   304  			}
   305  			p = Appendp(p, newprog)
   306  			p.As = APCDATA
   307  			p.From.Type = TYPE_CONST
   308  			p.From.Offset = objabi.PCDATA_UnsafePoint
   309  			p.To.Type = TYPE_CONST
   310  			p.To.Offset = prevPcdata
   311  			p.Pc = p.Link.Pc
   312  		}
   313  	}
   314  }
   315  

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