Source file src/cmd/link/internal/ld/xcoff.go

Documentation: cmd/link/internal/ld

     1  // Copyright 2018 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 ld
     6  
     7  import (
     8  	"bytes"
     9  	"cmd/internal/objabi"
    10  	"cmd/link/internal/loader"
    11  	"cmd/link/internal/sym"
    12  	"encoding/binary"
    13  	"fmt"
    14  	"io/ioutil"
    15  	"math/bits"
    16  	"path/filepath"
    17  	"sort"
    18  	"strings"
    19  	"sync"
    20  )
    21  
    22  // This file handles all algorithms related to XCOFF files generation.
    23  // Most of them are adaptations of the ones in  cmd/link/internal/pe.go
    24  // as PE and XCOFF are based on COFF files.
    25  // XCOFF files generated are 64 bits.
    26  
    27  const (
    28  	// Total amount of space to reserve at the start of the file
    29  	// for File Header, Auxiliary Header, and Section Headers.
    30  	// May waste some.
    31  	XCOFFHDRRESERVE       = FILHSZ_64 + AOUTHSZ_EXEC64 + SCNHSZ_64*23
    32  	XCOFFSECTALIGN  int64 = 32 // base on dump -o
    33  
    34  	// XCOFF binaries should normally have all its sections position-independent.
    35  	// However, this is not yet possible for .text because of some R_ADDR relocations
    36  	// inside RODATA symbols.
    37  	// .data and .bss are position-independent so their address start inside a unreachable
    38  	// segment during execution to force segfault if something is wrong.
    39  	XCOFFTEXTBASE = 0x100000000 // Start of text address
    40  	XCOFFDATABASE = 0x200000000 // Start of data address
    41  )
    42  
    43  // File Header
    44  type XcoffFileHdr64 struct {
    45  	Fmagic   uint16 // Target machine
    46  	Fnscns   uint16 // Number of sections
    47  	Ftimedat int32  // Time and date of file creation
    48  	Fsymptr  uint64 // Byte offset to symbol table start
    49  	Fopthdr  uint16 // Number of bytes in optional header
    50  	Fflags   uint16 // Flags
    51  	Fnsyms   int32  // Number of entries in symbol table
    52  }
    53  
    54  const (
    55  	U64_TOCMAGIC = 0767 // AIX 64-bit XCOFF
    56  )
    57  
    58  // Flags that describe the type of the object file.
    59  const (
    60  	F_RELFLG    = 0x0001
    61  	F_EXEC      = 0x0002
    62  	F_LNNO      = 0x0004
    63  	F_FDPR_PROF = 0x0010
    64  	F_FDPR_OPTI = 0x0020
    65  	F_DSA       = 0x0040
    66  	F_VARPG     = 0x0100
    67  	F_DYNLOAD   = 0x1000
    68  	F_SHROBJ    = 0x2000
    69  	F_LOADONLY  = 0x4000
    70  )
    71  
    72  // Auxiliary Header
    73  type XcoffAoutHdr64 struct {
    74  	Omagic      int16    // Flags - Ignored If Vstamp Is 1
    75  	Ovstamp     int16    // Version
    76  	Odebugger   uint32   // Reserved For Debugger
    77  	Otextstart  uint64   // Virtual Address Of Text
    78  	Odatastart  uint64   // Virtual Address Of Data
    79  	Otoc        uint64   // Toc Address
    80  	Osnentry    int16    // Section Number For Entry Point
    81  	Osntext     int16    // Section Number For Text
    82  	Osndata     int16    // Section Number For Data
    83  	Osntoc      int16    // Section Number For Toc
    84  	Osnloader   int16    // Section Number For Loader
    85  	Osnbss      int16    // Section Number For Bss
    86  	Oalgntext   int16    // Max Text Alignment
    87  	Oalgndata   int16    // Max Data Alignment
    88  	Omodtype    [2]byte  // Module Type Field
    89  	Ocpuflag    uint8    // Bit Flags - Cputypes Of Objects
    90  	Ocputype    uint8    // Reserved for CPU type
    91  	Otextpsize  uint8    // Requested text page size
    92  	Odatapsize  uint8    // Requested data page size
    93  	Ostackpsize uint8    // Requested stack page size
    94  	Oflags      uint8    // Flags And TLS Alignment
    95  	Otsize      uint64   // Text Size In Bytes
    96  	Odsize      uint64   // Data Size In Bytes
    97  	Obsize      uint64   // Bss Size In Bytes
    98  	Oentry      uint64   // Entry Point Address
    99  	Omaxstack   uint64   // Max Stack Size Allowed
   100  	Omaxdata    uint64   // Max Data Size Allowed
   101  	Osntdata    int16    // Section Number For Tdata Section
   102  	Osntbss     int16    // Section Number For Tbss Section
   103  	Ox64flags   uint16   // Additional Flags For 64-Bit Objects
   104  	Oresv3a     int16    // Reserved
   105  	Oresv3      [2]int32 // Reserved
   106  }
   107  
   108  // Section Header
   109  type XcoffScnHdr64 struct {
   110  	Sname    [8]byte // Section Name
   111  	Spaddr   uint64  // Physical Address
   112  	Svaddr   uint64  // Virtual Address
   113  	Ssize    uint64  // Section Size
   114  	Sscnptr  uint64  // File Offset To Raw Data
   115  	Srelptr  uint64  // File Offset To Relocation
   116  	Slnnoptr uint64  // File Offset To Line Numbers
   117  	Snreloc  uint32  // Number Of Relocation Entries
   118  	Snlnno   uint32  // Number Of Line Number Entries
   119  	Sflags   uint32  // flags
   120  }
   121  
   122  // Flags defining the section type.
   123  const (
   124  	STYP_DWARF  = 0x0010
   125  	STYP_TEXT   = 0x0020
   126  	STYP_DATA   = 0x0040
   127  	STYP_BSS    = 0x0080
   128  	STYP_EXCEPT = 0x0100
   129  	STYP_INFO   = 0x0200
   130  	STYP_TDATA  = 0x0400
   131  	STYP_TBSS   = 0x0800
   132  	STYP_LOADER = 0x1000
   133  	STYP_DEBUG  = 0x2000
   134  	STYP_TYPCHK = 0x4000
   135  	STYP_OVRFLO = 0x8000
   136  )
   137  const (
   138  	SSUBTYP_DWINFO  = 0x10000 // DWARF info section
   139  	SSUBTYP_DWLINE  = 0x20000 // DWARF line-number section
   140  	SSUBTYP_DWPBNMS = 0x30000 // DWARF public names section
   141  	SSUBTYP_DWPBTYP = 0x40000 // DWARF public types section
   142  	SSUBTYP_DWARNGE = 0x50000 // DWARF aranges section
   143  	SSUBTYP_DWABREV = 0x60000 // DWARF abbreviation section
   144  	SSUBTYP_DWSTR   = 0x70000 // DWARF strings section
   145  	SSUBTYP_DWRNGES = 0x80000 // DWARF ranges section
   146  	SSUBTYP_DWLOC   = 0x90000 // DWARF location lists section
   147  	SSUBTYP_DWFRAME = 0xA0000 // DWARF frames section
   148  	SSUBTYP_DWMAC   = 0xB0000 // DWARF macros section
   149  )
   150  
   151  // Headers size
   152  const (
   153  	FILHSZ_32      = 20
   154  	FILHSZ_64      = 24
   155  	AOUTHSZ_EXEC32 = 72
   156  	AOUTHSZ_EXEC64 = 120
   157  	SCNHSZ_32      = 40
   158  	SCNHSZ_64      = 72
   159  	LDHDRSZ_32     = 32
   160  	LDHDRSZ_64     = 56
   161  	LDSYMSZ_64     = 24
   162  	RELSZ_64       = 14
   163  )
   164  
   165  // Type representing all XCOFF symbols.
   166  type xcoffSym interface {
   167  }
   168  
   169  // Symbol Table Entry
   170  type XcoffSymEnt64 struct {
   171  	Nvalue  uint64 // Symbol value
   172  	Noffset uint32 // Offset of the name in string table or .debug section
   173  	Nscnum  int16  // Section number of symbol
   174  	Ntype   uint16 // Basic and derived type specification
   175  	Nsclass uint8  // Storage class of symbol
   176  	Nnumaux int8   // Number of auxiliary entries
   177  }
   178  
   179  const SYMESZ = 18
   180  
   181  const (
   182  	// Nscnum
   183  	N_DEBUG = -2
   184  	N_ABS   = -1
   185  	N_UNDEF = 0
   186  
   187  	//Ntype
   188  	SYM_V_INTERNAL  = 0x1000
   189  	SYM_V_HIDDEN    = 0x2000
   190  	SYM_V_PROTECTED = 0x3000
   191  	SYM_V_EXPORTED  = 0x4000
   192  	SYM_TYPE_FUNC   = 0x0020 // is function
   193  )
   194  
   195  // Storage Class.
   196  const (
   197  	C_NULL    = 0   // Symbol table entry marked for deletion
   198  	C_EXT     = 2   // External symbol
   199  	C_STAT    = 3   // Static symbol
   200  	C_BLOCK   = 100 // Beginning or end of inner block
   201  	C_FCN     = 101 // Beginning or end of function
   202  	C_FILE    = 103 // Source file name and compiler information
   203  	C_HIDEXT  = 107 // Unnamed external symbol
   204  	C_BINCL   = 108 // Beginning of include file
   205  	C_EINCL   = 109 // End of include file
   206  	C_WEAKEXT = 111 // Weak external symbol
   207  	C_DWARF   = 112 // DWARF symbol
   208  	C_GSYM    = 128 // Global variable
   209  	C_LSYM    = 129 // Automatic variable allocated on stack
   210  	C_PSYM    = 130 // Argument to subroutine allocated on stack
   211  	C_RSYM    = 131 // Register variable
   212  	C_RPSYM   = 132 // Argument to function or procedure stored in register
   213  	C_STSYM   = 133 // Statically allocated symbol
   214  	C_BCOMM   = 135 // Beginning of common block
   215  	C_ECOML   = 136 // Local member of common block
   216  	C_ECOMM   = 137 // End of common block
   217  	C_DECL    = 140 // Declaration of object
   218  	C_ENTRY   = 141 // Alternate entry
   219  	C_FUN     = 142 // Function or procedure
   220  	C_BSTAT   = 143 // Beginning of static block
   221  	C_ESTAT   = 144 // End of static block
   222  	C_GTLS    = 145 // Global thread-local variable
   223  	C_STTLS   = 146 // Static thread-local variable
   224  )
   225  
   226  // File Auxiliary Entry
   227  type XcoffAuxFile64 struct {
   228  	Xzeroes  uint32 // The name is always in the string table
   229  	Xoffset  uint32 // Offset in the string table
   230  	X_pad1   [6]byte
   231  	Xftype   uint8 // Source file string type
   232  	X_pad2   [2]byte
   233  	Xauxtype uint8 // Type of auxiliary entry
   234  }
   235  
   236  // Function Auxiliary Entry
   237  type XcoffAuxFcn64 struct {
   238  	Xlnnoptr uint64 // File pointer to line number
   239  	Xfsize   uint32 // Size of function in bytes
   240  	Xendndx  uint32 // Symbol table index of next entry
   241  	Xpad     uint8  // Unused
   242  	Xauxtype uint8  // Type of auxiliary entry
   243  }
   244  
   245  // csect Auxiliary Entry.
   246  type XcoffAuxCSect64 struct {
   247  	Xscnlenlo uint32 // Lower 4 bytes of length or symbol table index
   248  	Xparmhash uint32 // Offset of parameter type-check string
   249  	Xsnhash   uint16 // .typchk section number
   250  	Xsmtyp    uint8  // Symbol alignment and type
   251  	Xsmclas   uint8  // Storage-mapping class
   252  	Xscnlenhi uint32 // Upper 4 bytes of length or symbol table index
   253  	Xpad      uint8  // Unused
   254  	Xauxtype  uint8  // Type of auxiliary entry
   255  }
   256  
   257  // DWARF Auxiliary Entry
   258  type XcoffAuxDWARF64 struct {
   259  	Xscnlen  uint64 // Length of this symbol section
   260  	X_pad    [9]byte
   261  	Xauxtype uint8 // Type of auxiliary entry
   262  }
   263  
   264  // Auxiliary type
   265  const (
   266  	_AUX_EXCEPT = 255
   267  	_AUX_FCN    = 254
   268  	_AUX_SYM    = 253
   269  	_AUX_FILE   = 252
   270  	_AUX_CSECT  = 251
   271  	_AUX_SECT   = 250
   272  )
   273  
   274  // Xftype field
   275  const (
   276  	XFT_FN = 0   // Source File Name
   277  	XFT_CT = 1   // Compile Time Stamp
   278  	XFT_CV = 2   // Compiler Version Number
   279  	XFT_CD = 128 // Compiler Defined Information/
   280  
   281  )
   282  
   283  // Symbol type field.
   284  const (
   285  	XTY_ER  = 0    // External reference
   286  	XTY_SD  = 1    // Section definition
   287  	XTY_LD  = 2    // Label definition
   288  	XTY_CM  = 3    // Common csect definition
   289  	XTY_WK  = 0x8  // Weak symbol
   290  	XTY_EXP = 0x10 // Exported symbol
   291  	XTY_ENT = 0x20 // Entry point symbol
   292  	XTY_IMP = 0x40 // Imported symbol
   293  )
   294  
   295  // Storage-mapping class.
   296  const (
   297  	XMC_PR     = 0  // Program code
   298  	XMC_RO     = 1  // Read-only constant
   299  	XMC_DB     = 2  // Debug dictionary table
   300  	XMC_TC     = 3  // TOC entry
   301  	XMC_UA     = 4  // Unclassified
   302  	XMC_RW     = 5  // Read/Write data
   303  	XMC_GL     = 6  // Global linkage
   304  	XMC_XO     = 7  // Extended operation
   305  	XMC_SV     = 8  // 32-bit supervisor call descriptor
   306  	XMC_BS     = 9  // BSS class
   307  	XMC_DS     = 10 // Function descriptor
   308  	XMC_UC     = 11 // Unnamed FORTRAN common
   309  	XMC_TC0    = 15 // TOC anchor
   310  	XMC_TD     = 16 // Scalar data entry in the TOC
   311  	XMC_SV64   = 17 // 64-bit supervisor call descriptor
   312  	XMC_SV3264 = 18 // Supervisor call descriptor for both 32-bit and 64-bit
   313  	XMC_TL     = 20 // Read/Write thread-local data
   314  	XMC_UL     = 21 // Read/Write thread-local data (.tbss)
   315  	XMC_TE     = 22 // TOC entry
   316  )
   317  
   318  // Loader Header
   319  type XcoffLdHdr64 struct {
   320  	Lversion int32  // Loader section version number
   321  	Lnsyms   int32  // Number of symbol table entries
   322  	Lnreloc  int32  // Number of relocation table entries
   323  	Listlen  uint32 // Length of import file ID string table
   324  	Lnimpid  int32  // Number of import file IDs
   325  	Lstlen   uint32 // Length of string table
   326  	Limpoff  uint64 // Offset to start of import file IDs
   327  	Lstoff   uint64 // Offset to start of string table
   328  	Lsymoff  uint64 // Offset to start of symbol table
   329  	Lrldoff  uint64 // Offset to start of relocation entries
   330  }
   331  
   332  // Loader Symbol
   333  type XcoffLdSym64 struct {
   334  	Lvalue  uint64 // Address field
   335  	Loffset uint32 // Byte offset into string table of symbol name
   336  	Lscnum  int16  // Section number containing symbol
   337  	Lsmtype int8   // Symbol type, export, import flags
   338  	Lsmclas int8   // Symbol storage class
   339  	Lifile  int32  // Import file ID; ordinal of import file IDs
   340  	Lparm   uint32 // Parameter type-check field
   341  }
   342  
   343  type xcoffLoaderSymbol struct {
   344  	sym    loader.Sym
   345  	smtype int8
   346  	smclas int8
   347  }
   348  
   349  type XcoffLdImportFile64 struct {
   350  	Limpidpath string
   351  	Limpidbase string
   352  	Limpidmem  string
   353  }
   354  
   355  type XcoffLdRel64 struct {
   356  	Lvaddr  uint64 // Address Field
   357  	Lrtype  uint16 // Relocation Size and Type
   358  	Lrsecnm int16  // Section Number being relocated
   359  	Lsymndx int32  // Loader-Section symbol table index
   360  }
   361  
   362  // xcoffLoaderReloc holds information about a relocation made by the loader.
   363  type xcoffLoaderReloc struct {
   364  	sym    loader.Sym
   365  	roff   int32
   366  	rtype  uint16
   367  	symndx int32
   368  }
   369  
   370  const (
   371  	XCOFF_R_POS = 0x00 // A(sym) Positive Relocation
   372  	XCOFF_R_NEG = 0x01 // -A(sym) Negative Relocation
   373  	XCOFF_R_REL = 0x02 // A(sym-*) Relative to self
   374  	XCOFF_R_TOC = 0x03 // A(sym-TOC) Relative to TOC
   375  	XCOFF_R_TRL = 0x12 // A(sym-TOC) TOC Relative indirect load.
   376  
   377  	XCOFF_R_TRLA = 0x13 // A(sym-TOC) TOC Rel load address. modifiable inst
   378  	XCOFF_R_GL   = 0x05 // A(external TOC of sym) Global Linkage
   379  	XCOFF_R_TCL  = 0x06 // A(local TOC of sym) Local object TOC address
   380  	XCOFF_R_RL   = 0x0C // A(sym) Pos indirect load. modifiable instruction
   381  	XCOFF_R_RLA  = 0x0D // A(sym) Pos Load Address. modifiable instruction
   382  	XCOFF_R_REF  = 0x0F // AL0(sym) Non relocating ref. No garbage collect
   383  	XCOFF_R_BA   = 0x08 // A(sym) Branch absolute. Cannot modify instruction
   384  	XCOFF_R_RBA  = 0x18 // A(sym) Branch absolute. modifiable instruction
   385  	XCOFF_R_BR   = 0x0A // A(sym-*) Branch rel to self. non modifiable
   386  	XCOFF_R_RBR  = 0x1A // A(sym-*) Branch rel to self. modifiable instr
   387  
   388  	XCOFF_R_TLS    = 0x20 // General-dynamic reference to TLS symbol
   389  	XCOFF_R_TLS_IE = 0x21 // Initial-exec reference to TLS symbol
   390  	XCOFF_R_TLS_LD = 0x22 // Local-dynamic reference to TLS symbol
   391  	XCOFF_R_TLS_LE = 0x23 // Local-exec reference to TLS symbol
   392  	XCOFF_R_TLSM   = 0x24 // Module reference to TLS symbol
   393  	XCOFF_R_TLSML  = 0x25 // Module reference to local (own) module
   394  
   395  	XCOFF_R_TOCU = 0x30 // Relative to TOC - high order bits
   396  	XCOFF_R_TOCL = 0x31 // Relative to TOC - low order bits
   397  )
   398  
   399  type XcoffLdStr64 struct {
   400  	size uint16
   401  	name string
   402  }
   403  
   404  // xcoffFile is used to build XCOFF file.
   405  type xcoffFile struct {
   406  	xfhdr           XcoffFileHdr64
   407  	xahdr           XcoffAoutHdr64
   408  	sections        []*XcoffScnHdr64
   409  	sectText        *XcoffScnHdr64
   410  	sectData        *XcoffScnHdr64
   411  	sectBss         *XcoffScnHdr64
   412  	stringTable     xcoffStringTable
   413  	sectNameToScnum map[string]int16
   414  	loaderSize      uint64
   415  	symtabOffset    int64                // offset to the start of symbol table
   416  	symbolCount     uint32               // number of symbol table records written
   417  	symtabSym       []xcoffSym           // XCOFF symbols for the symbol table
   418  	dynLibraries    map[string]int       // Dynamic libraries in .loader section. The integer represents its import file number (- 1)
   419  	loaderSymbols   []*xcoffLoaderSymbol // symbols inside .loader symbol table
   420  	loaderReloc     []*xcoffLoaderReloc  // Reloc that must be made inside loader
   421  	sync.Mutex                           // currently protect loaderReloc
   422  }
   423  
   424  // Var used by XCOFF Generation algorithms
   425  var (
   426  	xfile xcoffFile
   427  )
   428  
   429  // xcoffStringTable is a XCOFF string table.
   430  type xcoffStringTable struct {
   431  	strings    []string
   432  	stringsLen int
   433  }
   434  
   435  // size returns size of string table t.
   436  func (t *xcoffStringTable) size() int {
   437  	// string table starts with 4-byte length at the beginning
   438  	return t.stringsLen + 4
   439  }
   440  
   441  // add adds string str to string table t.
   442  func (t *xcoffStringTable) add(str string) int {
   443  	off := t.size()
   444  	t.strings = append(t.strings, str)
   445  	t.stringsLen += len(str) + 1 // each string will have 0 appended to it
   446  	return off
   447  }
   448  
   449  // write writes string table t into the output file.
   450  func (t *xcoffStringTable) write(out *OutBuf) {
   451  	out.Write32(uint32(t.size()))
   452  	for _, s := range t.strings {
   453  		out.WriteString(s)
   454  		out.Write8(0)
   455  	}
   456  }
   457  
   458  // write writes XCOFF section sect into the output file.
   459  func (sect *XcoffScnHdr64) write(ctxt *Link) {
   460  	binary.Write(ctxt.Out, binary.BigEndian, sect)
   461  	ctxt.Out.Write32(0) // Add 4 empty bytes at the end to match alignment
   462  }
   463  
   464  // addSection adds section to the XCOFF file f.
   465  func (f *xcoffFile) addSection(name string, addr uint64, size uint64, fileoff uint64, flags uint32) *XcoffScnHdr64 {
   466  	sect := &XcoffScnHdr64{
   467  		Spaddr:  addr,
   468  		Svaddr:  addr,
   469  		Ssize:   size,
   470  		Sscnptr: fileoff,
   471  		Sflags:  flags,
   472  	}
   473  	copy(sect.Sname[:], name) // copy string to [8]byte
   474  	f.sections = append(f.sections, sect)
   475  	f.sectNameToScnum[name] = int16(len(f.sections))
   476  	return sect
   477  }
   478  
   479  // addDwarfSection adds a dwarf section to the XCOFF file f.
   480  // This function is similar to addSection, but Dwarf section names
   481  // must be modified to conventional names and they are various subtypes.
   482  func (f *xcoffFile) addDwarfSection(s *sym.Section) *XcoffScnHdr64 {
   483  	newName, subtype := xcoffGetDwarfSubtype(s.Name)
   484  	return f.addSection(newName, 0, s.Length, s.Seg.Fileoff+s.Vaddr-s.Seg.Vaddr, STYP_DWARF|subtype)
   485  }
   486  
   487  // xcoffGetDwarfSubtype returns the XCOFF name of the DWARF section str
   488  // and its subtype constant.
   489  func xcoffGetDwarfSubtype(str string) (string, uint32) {
   490  	switch str {
   491  	default:
   492  		Exitf("unknown DWARF section name for XCOFF: %s", str)
   493  	case ".debug_abbrev":
   494  		return ".dwabrev", SSUBTYP_DWABREV
   495  	case ".debug_info":
   496  		return ".dwinfo", SSUBTYP_DWINFO
   497  	case ".debug_frame":
   498  		return ".dwframe", SSUBTYP_DWFRAME
   499  	case ".debug_line":
   500  		return ".dwline", SSUBTYP_DWLINE
   501  	case ".debug_loc":
   502  		return ".dwloc", SSUBTYP_DWLOC
   503  	case ".debug_pubnames":
   504  		return ".dwpbnms", SSUBTYP_DWPBNMS
   505  	case ".debug_pubtypes":
   506  		return ".dwpbtyp", SSUBTYP_DWPBTYP
   507  	case ".debug_ranges":
   508  		return ".dwrnges", SSUBTYP_DWRNGES
   509  	}
   510  	// never used
   511  	return "", 0
   512  }
   513  
   514  // getXCOFFscnum returns the XCOFF section number of a Go section.
   515  func (f *xcoffFile) getXCOFFscnum(sect *sym.Section) int16 {
   516  	switch sect.Seg {
   517  	case &Segtext:
   518  		return f.sectNameToScnum[".text"]
   519  	case &Segdata:
   520  		if sect.Name == ".noptrbss" || sect.Name == ".bss" {
   521  			return f.sectNameToScnum[".bss"]
   522  		}
   523  		if sect.Name == ".tbss" {
   524  			return f.sectNameToScnum[".tbss"]
   525  		}
   526  		return f.sectNameToScnum[".data"]
   527  	case &Segdwarf:
   528  		name, _ := xcoffGetDwarfSubtype(sect.Name)
   529  		return f.sectNameToScnum[name]
   530  	case &Segrelrodata:
   531  		return f.sectNameToScnum[".data"]
   532  	}
   533  	Errorf(nil, "getXCOFFscnum not implemented for section %s", sect.Name)
   534  	return -1
   535  }
   536  
   537  // Xcoffinit initialised some internal value and setups
   538  // already known header information
   539  func Xcoffinit(ctxt *Link) {
   540  	xfile.dynLibraries = make(map[string]int)
   541  
   542  	HEADR = int32(Rnd(XCOFFHDRRESERVE, XCOFFSECTALIGN))
   543  	if *FlagTextAddr != -1 {
   544  		Errorf(nil, "-T not available on AIX")
   545  	}
   546  	*FlagTextAddr = XCOFFTEXTBASE + int64(HEADR)
   547  	if *FlagRound != -1 {
   548  		Errorf(nil, "-R not available on AIX")
   549  	}
   550  	*FlagRound = int(XCOFFSECTALIGN)
   551  
   552  }
   553  
   554  // SYMBOL TABLE
   555  
   556  // type records C_FILE information needed for genasmsym in XCOFF.
   557  type xcoffSymSrcFile struct {
   558  	name       string
   559  	file       *XcoffSymEnt64   // Symbol of this C_FILE
   560  	csectAux   *XcoffAuxCSect64 // Symbol for the current .csect
   561  	csectSymNb uint64           // Symbol number for the current .csect
   562  	csectSize  int64
   563  }
   564  
   565  var (
   566  	currDwscnoff   = make(map[string]uint64) // Needed to create C_DWARF symbols
   567  	currSymSrcFile xcoffSymSrcFile
   568  	outerSymSize   = make(map[string]int64)
   569  )
   570  
   571  // xcoffUpdateOuterSize stores the size of outer symbols in order to have it
   572  // in the symbol table.
   573  func xcoffUpdateOuterSize(ctxt *Link, size int64, stype sym.SymKind) {
   574  	if size == 0 {
   575  		return
   576  	}
   577  	// TODO: use CarrierSymByType
   578  
   579  	ldr := ctxt.loader
   580  	switch stype {
   581  	default:
   582  		Errorf(nil, "unknown XCOFF outer symbol for type %s", stype.String())
   583  	case sym.SRODATA, sym.SRODATARELRO, sym.SFUNCTAB, sym.SSTRING:
   584  		// Nothing to do
   585  	case sym.STYPERELRO:
   586  		if ctxt.UseRelro() && (ctxt.BuildMode == BuildModeCArchive || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE) {
   587  			// runtime.types size must be removed, as it's a real symbol.
   588  			tsize := ldr.SymSize(ldr.Lookup("runtime.types", 0))
   589  			outerSymSize["typerel.*"] = size - tsize
   590  			return
   591  		}
   592  		fallthrough
   593  	case sym.STYPE:
   594  		if !ctxt.DynlinkingGo() {
   595  			// runtime.types size must be removed, as it's a real symbol.
   596  			tsize := ldr.SymSize(ldr.Lookup("runtime.types", 0))
   597  			outerSymSize["type.*"] = size - tsize
   598  		}
   599  	case sym.SGOSTRING:
   600  		outerSymSize["go.string.*"] = size
   601  	case sym.SGOFUNC:
   602  		if !ctxt.DynlinkingGo() {
   603  			outerSymSize["go.func.*"] = size
   604  		}
   605  	case sym.SGOFUNCRELRO:
   606  		outerSymSize["go.funcrel.*"] = size
   607  	case sym.SGCBITS:
   608  		outerSymSize["runtime.gcbits.*"] = size
   609  	case sym.SPCLNTAB:
   610  		outerSymSize["runtime.pclntab"] = size
   611  	}
   612  }
   613  
   614  // addSymbol writes a symbol or an auxiliary symbol entry on ctxt.out.
   615  func (f *xcoffFile) addSymbol(sym xcoffSym) {
   616  	f.symtabSym = append(f.symtabSym, sym)
   617  	f.symbolCount++
   618  }
   619  
   620  // xcoffAlign returns the log base 2 of the symbol's alignment.
   621  func xcoffAlign(ldr *loader.Loader, x loader.Sym, t SymbolType) uint8 {
   622  	align := ldr.SymAlign(x)
   623  	if align == 0 {
   624  		if t == TextSym {
   625  			align = int32(Funcalign)
   626  		} else {
   627  			align = symalign(ldr, x)
   628  		}
   629  	}
   630  	return logBase2(int(align))
   631  }
   632  
   633  // logBase2 returns the log in base 2 of a.
   634  func logBase2(a int) uint8 {
   635  	return uint8(bits.Len(uint(a)) - 1)
   636  }
   637  
   638  // Write symbols needed when a new file appeared:
   639  // - a C_FILE with one auxiliary entry for its name
   640  // - C_DWARF symbols to provide debug information
   641  // - a C_HIDEXT which will be a csect containing all of its functions
   642  // It needs several parameters to create .csect symbols such as its entry point and its section number.
   643  //
   644  // Currently, a new file is in fact a new package. It seems to be OK, but it might change
   645  // in the future.
   646  func (f *xcoffFile) writeSymbolNewFile(ctxt *Link, name string, firstEntry uint64, extnum int16) {
   647  	ldr := ctxt.loader
   648  	/* C_FILE */
   649  	s := &XcoffSymEnt64{
   650  		Noffset: uint32(f.stringTable.add(".file")),
   651  		Nsclass: C_FILE,
   652  		Nscnum:  N_DEBUG,
   653  		Ntype:   0, // Go isn't inside predefined language.
   654  		Nnumaux: 1,
   655  	}
   656  	f.addSymbol(s)
   657  	currSymSrcFile.file = s
   658  
   659  	// Auxiliary entry for file name.
   660  	auxf := &XcoffAuxFile64{
   661  		Xoffset:  uint32(f.stringTable.add(name)),
   662  		Xftype:   XFT_FN,
   663  		Xauxtype: _AUX_FILE,
   664  	}
   665  	f.addSymbol(auxf)
   666  
   667  	/* Dwarf */
   668  	for _, sect := range Segdwarf.Sections {
   669  		var dwsize uint64
   670  		if ctxt.LinkMode == LinkInternal {
   671  			// Find the size of this corresponding package DWARF compilation unit.
   672  			// This size is set during DWARF generation (see dwarf.go).
   673  			dwsize = getDwsectCUSize(sect.Name, name)
   674  			// .debug_abbrev is common to all packages and not found with the previous function
   675  			if sect.Name == ".debug_abbrev" {
   676  				dwsize = uint64(ldr.SymSize(loader.Sym(sect.Sym)))
   677  
   678  			}
   679  		} else {
   680  			// There is only one .FILE with external linking.
   681  			dwsize = sect.Length
   682  		}
   683  
   684  		// get XCOFF name
   685  		name, _ := xcoffGetDwarfSubtype(sect.Name)
   686  		s := &XcoffSymEnt64{
   687  			Nvalue:  currDwscnoff[sect.Name],
   688  			Noffset: uint32(f.stringTable.add(name)),
   689  			Nsclass: C_DWARF,
   690  			Nscnum:  f.getXCOFFscnum(sect),
   691  			Nnumaux: 1,
   692  		}
   693  
   694  		if currSymSrcFile.csectAux == nil {
   695  			// Dwarf relocations need the symbol number of .dw* symbols.
   696  			// It doesn't need to know it for each package, one is enough.
   697  			// currSymSrcFile.csectAux == nil means first package.
   698  			ldr.SetSymDynid(loader.Sym(sect.Sym), int32(f.symbolCount))
   699  
   700  			if sect.Name == ".debug_frame" && ctxt.LinkMode != LinkExternal {
   701  				// CIE size must be added to the first package.
   702  				dwsize += 48
   703  			}
   704  		}
   705  
   706  		f.addSymbol(s)
   707  
   708  		// update the DWARF section offset in this file
   709  		if sect.Name != ".debug_abbrev" {
   710  			currDwscnoff[sect.Name] += dwsize
   711  		}
   712  
   713  		// Auxiliary dwarf section
   714  		auxd := &XcoffAuxDWARF64{
   715  			Xscnlen:  dwsize,
   716  			Xauxtype: _AUX_SECT,
   717  		}
   718  
   719  		f.addSymbol(auxd)
   720  	}
   721  
   722  	/* .csect */
   723  	// Check if extnum is in text.
   724  	// This is temporary and only here to check if this algorithm is correct.
   725  	if extnum != 1 {
   726  		Exitf("XCOFF symtab: A new file was detected with its first symbol not in .text")
   727  	}
   728  
   729  	currSymSrcFile.csectSymNb = uint64(f.symbolCount)
   730  
   731  	// No offset because no name
   732  	s = &XcoffSymEnt64{
   733  		Nvalue:  firstEntry,
   734  		Nscnum:  extnum,
   735  		Nsclass: C_HIDEXT,
   736  		Ntype:   0, // check visibility ?
   737  		Nnumaux: 1,
   738  	}
   739  	f.addSymbol(s)
   740  
   741  	aux := &XcoffAuxCSect64{
   742  		Xsmclas:  XMC_PR,
   743  		Xsmtyp:   XTY_SD | logBase2(Funcalign)<<3,
   744  		Xauxtype: _AUX_CSECT,
   745  	}
   746  	f.addSymbol(aux)
   747  
   748  	currSymSrcFile.csectAux = aux
   749  	currSymSrcFile.csectSize = 0
   750  }
   751  
   752  // Update values for the previous package.
   753  //  - Svalue of the C_FILE symbol: if it is the last one, this Svalue must be -1
   754  //  - Xsclen of the csect symbol.
   755  func (f *xcoffFile) updatePreviousFile(ctxt *Link, last bool) {
   756  	// first file
   757  	if currSymSrcFile.file == nil {
   758  		return
   759  	}
   760  
   761  	// Update C_FILE
   762  	cfile := currSymSrcFile.file
   763  	if last {
   764  		cfile.Nvalue = 0xFFFFFFFFFFFFFFFF
   765  	} else {
   766  		cfile.Nvalue = uint64(f.symbolCount)
   767  	}
   768  
   769  	// update csect scnlen in this auxiliary entry
   770  	aux := currSymSrcFile.csectAux
   771  	aux.Xscnlenlo = uint32(currSymSrcFile.csectSize & 0xFFFFFFFF)
   772  	aux.Xscnlenhi = uint32(currSymSrcFile.csectSize >> 32)
   773  }
   774  
   775  // Write symbol representing a .text function.
   776  // The symbol table is split with C_FILE corresponding to each package
   777  // and not to each source file as it should be.
   778  func (f *xcoffFile) writeSymbolFunc(ctxt *Link, x loader.Sym) []xcoffSym {
   779  	// New XCOFF symbols which will be written.
   780  	syms := []xcoffSym{}
   781  
   782  	// Check if a new file is detected.
   783  	ldr := ctxt.loader
   784  	name := ldr.SymName(x)
   785  	if strings.Contains(name, "-tramp") || strings.HasPrefix(name, "runtime.text.") {
   786  		// Trampoline don't have a FILE so there are considered
   787  		// in the current file.
   788  		// Same goes for runtime.text.X symbols.
   789  	} else if ldr.SymPkg(x) == "" { // Undefined global symbol
   790  		// If this happens, the algorithm must be redone.
   791  		if currSymSrcFile.name != "" {
   792  			Exitf("undefined global symbol found inside another file")
   793  		}
   794  	} else {
   795  		// Current file has changed. New C_FILE, C_DWARF, etc must be generated.
   796  		if currSymSrcFile.name != ldr.SymPkg(x) {
   797  			if ctxt.LinkMode == LinkInternal {
   798  				// update previous file values
   799  				xfile.updatePreviousFile(ctxt, false)
   800  				currSymSrcFile.name = ldr.SymPkg(x)
   801  				f.writeSymbolNewFile(ctxt, ldr.SymPkg(x), uint64(ldr.SymValue(x)), xfile.getXCOFFscnum(ldr.SymSect(x)))
   802  			} else {
   803  				// With external linking, ld will crash if there is several
   804  				// .FILE and DWARF debugging enable, somewhere during
   805  				// the relocation phase.
   806  				// Therefore, all packages are merged under a fake .FILE
   807  				// "go_functions".
   808  				// TODO(aix); remove once ld has been fixed or the triggering
   809  				// relocation has been found and fixed.
   810  				if currSymSrcFile.name == "" {
   811  					currSymSrcFile.name = ldr.SymPkg(x)
   812  					f.writeSymbolNewFile(ctxt, "go_functions", uint64(ldr.SymValue(x)), xfile.getXCOFFscnum(ldr.SymSect(x)))
   813  				}
   814  			}
   815  
   816  		}
   817  	}
   818  
   819  	s := &XcoffSymEnt64{
   820  		Nsclass: C_EXT,
   821  		Noffset: uint32(xfile.stringTable.add(ldr.SymExtname(x))),
   822  		Nvalue:  uint64(ldr.SymValue(x)),
   823  		Nscnum:  f.getXCOFFscnum(ldr.SymSect(x)),
   824  		Ntype:   SYM_TYPE_FUNC,
   825  		Nnumaux: 2,
   826  	}
   827  
   828  	if ldr.SymVersion(x) != 0 || ldr.AttrVisibilityHidden(x) || ldr.AttrLocal(x) {
   829  		s.Nsclass = C_HIDEXT
   830  	}
   831  
   832  	ldr.SetSymDynid(x, int32(xfile.symbolCount))
   833  	syms = append(syms, s)
   834  
   835  	// Update current csect size
   836  	currSymSrcFile.csectSize += ldr.SymSize(x)
   837  
   838  	// create auxiliary entries
   839  	a2 := &XcoffAuxFcn64{
   840  		Xfsize:   uint32(ldr.SymSize(x)),
   841  		Xlnnoptr: 0,                     // TODO
   842  		Xendndx:  xfile.symbolCount + 3, // this symbol + 2 aux entries
   843  		Xauxtype: _AUX_FCN,
   844  	}
   845  	syms = append(syms, a2)
   846  
   847  	a4 := &XcoffAuxCSect64{
   848  		Xscnlenlo: uint32(currSymSrcFile.csectSymNb & 0xFFFFFFFF),
   849  		Xscnlenhi: uint32(currSymSrcFile.csectSymNb >> 32),
   850  		Xsmclas:   XMC_PR, // Program Code
   851  		Xsmtyp:    XTY_LD, // label definition (based on C)
   852  		Xauxtype:  _AUX_CSECT,
   853  	}
   854  	a4.Xsmtyp |= uint8(xcoffAlign(ldr, x, TextSym) << 3)
   855  
   856  	syms = append(syms, a4)
   857  	return syms
   858  }
   859  
   860  // put function used by genasmsym to write symbol table
   861  func putaixsym(ctxt *Link, x loader.Sym, t SymbolType) {
   862  	// All XCOFF symbols generated by this GO symbols
   863  	// Can be a symbol entry or a auxiliary entry
   864  	syms := []xcoffSym{}
   865  
   866  	ldr := ctxt.loader
   867  	name := ldr.SymName(x)
   868  	if t == UndefinedSym {
   869  		name = ldr.SymExtname(x)
   870  	}
   871  
   872  	switch t {
   873  	default:
   874  		return
   875  
   876  	case TextSym:
   877  		if ldr.SymPkg(x) != "" || strings.Contains(name, "-tramp") || strings.HasPrefix(name, "runtime.text.") {
   878  			// Function within a file
   879  			syms = xfile.writeSymbolFunc(ctxt, x)
   880  		} else {
   881  			// Only runtime.text and runtime.etext come through this way
   882  			if name != "runtime.text" && name != "runtime.etext" && name != "go.buildid" {
   883  				Exitf("putaixsym: unknown text symbol %s", name)
   884  			}
   885  			s := &XcoffSymEnt64{
   886  				Nsclass: C_HIDEXT,
   887  				Noffset: uint32(xfile.stringTable.add(name)),
   888  				Nvalue:  uint64(ldr.SymValue(x)),
   889  				Nscnum:  xfile.getXCOFFscnum(ldr.SymSect(x)),
   890  				Ntype:   SYM_TYPE_FUNC,
   891  				Nnumaux: 1,
   892  			}
   893  			ldr.SetSymDynid(x, int32(xfile.symbolCount))
   894  			syms = append(syms, s)
   895  
   896  			size := uint64(ldr.SymSize(x))
   897  			a4 := &XcoffAuxCSect64{
   898  				Xauxtype:  _AUX_CSECT,
   899  				Xscnlenlo: uint32(size & 0xFFFFFFFF),
   900  				Xscnlenhi: uint32(size >> 32),
   901  				Xsmclas:   XMC_PR,
   902  				Xsmtyp:    XTY_SD,
   903  			}
   904  			a4.Xsmtyp |= uint8(xcoffAlign(ldr, x, TextSym) << 3)
   905  			syms = append(syms, a4)
   906  		}
   907  
   908  	case DataSym, BSSSym:
   909  		s := &XcoffSymEnt64{
   910  			Nsclass: C_EXT,
   911  			Noffset: uint32(xfile.stringTable.add(name)),
   912  			Nvalue:  uint64(ldr.SymValue(x)),
   913  			Nscnum:  xfile.getXCOFFscnum(ldr.SymSect(x)),
   914  			Nnumaux: 1,
   915  		}
   916  
   917  		if ldr.SymVersion(x) != 0 || ldr.AttrVisibilityHidden(x) || ldr.AttrLocal(x) {
   918  			// There is more symbols in the case of a global data
   919  			// which are related to the assembly generated
   920  			// to access such symbols.
   921  			// But as Golang as its own way to check if a symbol is
   922  			// global or local (the capital letter), we don't need to
   923  			// implement them yet.
   924  			s.Nsclass = C_HIDEXT
   925  		}
   926  
   927  		ldr.SetSymDynid(x, int32(xfile.symbolCount))
   928  		syms = append(syms, s)
   929  
   930  		// Create auxiliary entry
   931  
   932  		// Normally, size should be the size of csect containing all
   933  		// the data and bss symbols of one file/package.
   934  		// However, it's easier to just have a csect for each symbol.
   935  		// It might change
   936  		size := uint64(ldr.SymSize(x))
   937  		a4 := &XcoffAuxCSect64{
   938  			Xauxtype:  _AUX_CSECT,
   939  			Xscnlenlo: uint32(size & 0xFFFFFFFF),
   940  			Xscnlenhi: uint32(size >> 32),
   941  		}
   942  
   943  		if ty := ldr.SymType(x); ty >= sym.STYPE && ty <= sym.SPCLNTAB {
   944  			if ctxt.IsExternal() && strings.HasPrefix(ldr.SymSect(x).Name, ".data.rel.ro") {
   945  				// During external linking, read-only datas with relocation
   946  				// must be in .data.
   947  				a4.Xsmclas = XMC_RW
   948  			} else {
   949  				// Read only data
   950  				a4.Xsmclas = XMC_RO
   951  			}
   952  		} else if /*ty == sym.SDATA &&*/ strings.HasPrefix(ldr.SymName(x), "TOC.") && ctxt.IsExternal() {
   953  			a4.Xsmclas = XMC_TC
   954  		} else if ldr.SymName(x) == "TOC" {
   955  			a4.Xsmclas = XMC_TC0
   956  		} else {
   957  			a4.Xsmclas = XMC_RW
   958  		}
   959  		if t == DataSym {
   960  			a4.Xsmtyp |= XTY_SD
   961  		} else {
   962  			a4.Xsmtyp |= XTY_CM
   963  		}
   964  
   965  		a4.Xsmtyp |= uint8(xcoffAlign(ldr, x, t) << 3)
   966  
   967  		syms = append(syms, a4)
   968  
   969  	case UndefinedSym:
   970  		if ty := ldr.SymType(x); ty != sym.SDYNIMPORT && ty != sym.SHOSTOBJ && ty != sym.SUNDEFEXT {
   971  			return
   972  		}
   973  		s := &XcoffSymEnt64{
   974  			Nsclass: C_EXT,
   975  			Noffset: uint32(xfile.stringTable.add(name)),
   976  			Nnumaux: 1,
   977  		}
   978  		ldr.SetSymDynid(x, int32(xfile.symbolCount))
   979  		syms = append(syms, s)
   980  
   981  		a4 := &XcoffAuxCSect64{
   982  			Xauxtype: _AUX_CSECT,
   983  			Xsmclas:  XMC_DS,
   984  			Xsmtyp:   XTY_ER | XTY_IMP,
   985  		}
   986  
   987  		if ldr.SymName(x) == "__n_pthreads" {
   988  			// Currently, all imported symbols made by cgo_import_dynamic are
   989  			// syscall functions, except __n_pthreads which is a variable.
   990  			// TODO(aix): Find a way to detect variables imported by cgo.
   991  			a4.Xsmclas = XMC_RW
   992  		}
   993  
   994  		syms = append(syms, a4)
   995  
   996  	case TLSSym:
   997  		s := &XcoffSymEnt64{
   998  			Nsclass: C_EXT,
   999  			Noffset: uint32(xfile.stringTable.add(name)),
  1000  			Nscnum:  xfile.getXCOFFscnum(ldr.SymSect(x)),
  1001  			Nvalue:  uint64(ldr.SymValue(x)),
  1002  			Nnumaux: 1,
  1003  		}
  1004  
  1005  		ldr.SetSymDynid(x, int32(xfile.symbolCount))
  1006  		syms = append(syms, s)
  1007  
  1008  		size := uint64(ldr.SymSize(x))
  1009  		a4 := &XcoffAuxCSect64{
  1010  			Xauxtype:  _AUX_CSECT,
  1011  			Xsmclas:   XMC_UL,
  1012  			Xsmtyp:    XTY_CM,
  1013  			Xscnlenlo: uint32(size & 0xFFFFFFFF),
  1014  			Xscnlenhi: uint32(size >> 32),
  1015  		}
  1016  
  1017  		syms = append(syms, a4)
  1018  	}
  1019  
  1020  	for _, s := range syms {
  1021  		xfile.addSymbol(s)
  1022  	}
  1023  }
  1024  
  1025  // Generate XCOFF Symbol table.
  1026  // It will be written in out file in Asmbxcoff, because it must be
  1027  // at the very end, especially after relocation sections which needs symbols' index.
  1028  func (f *xcoffFile) asmaixsym(ctxt *Link) {
  1029  	ldr := ctxt.loader
  1030  	// Get correct size for symbols wrapping others symbols like go.string.*
  1031  	// sym.Size can be used directly as the symbols have already been written.
  1032  	for name, size := range outerSymSize {
  1033  		sym := ldr.Lookup(name, 0)
  1034  		if sym == 0 {
  1035  			Errorf(nil, "unknown outer symbol with name %s", name)
  1036  		} else {
  1037  			s := ldr.MakeSymbolUpdater(sym)
  1038  			s.SetSize(size)
  1039  		}
  1040  	}
  1041  
  1042  	// These symbols won't show up in the first loop below because we
  1043  	// skip sym.STEXT symbols. Normal sym.STEXT symbols are emitted by walking textp.
  1044  	s := ldr.Lookup("runtime.text", 0)
  1045  	if ldr.SymType(s) == sym.STEXT {
  1046  		// We've already included this symbol in ctxt.Textp on AIX with external linker.
  1047  		// See data.go:/textaddress
  1048  		if !ctxt.IsExternal() {
  1049  			putaixsym(ctxt, s, TextSym)
  1050  		}
  1051  	}
  1052  
  1053  	n := 1
  1054  	// Generate base addresses for all text sections if there are multiple
  1055  	for _, sect := range Segtext.Sections[1:] {
  1056  		if sect.Name != ".text" || ctxt.IsExternal() {
  1057  			// On AIX, runtime.text.X are symbols already in the symtab.
  1058  			break
  1059  		}
  1060  		s = ldr.Lookup(fmt.Sprintf("runtime.text.%d", n), 0)
  1061  		if s == 0 {
  1062  			break
  1063  		}
  1064  		if ldr.SymType(s) == sym.STEXT {
  1065  			putaixsym(ctxt, s, TextSym)
  1066  		}
  1067  		n++
  1068  	}
  1069  
  1070  	s = ldr.Lookup("runtime.etext", 0)
  1071  	if ldr.SymType(s) == sym.STEXT {
  1072  		// We've already included this symbol in ctxt.Textp
  1073  		// on AIX with external linker.
  1074  		// See data.go:/textaddress
  1075  		if !ctxt.IsExternal() {
  1076  			putaixsym(ctxt, s, TextSym)
  1077  		}
  1078  	}
  1079  
  1080  	shouldBeInSymbolTable := func(s loader.Sym, name string) bool {
  1081  		if name == ".go.buildinfo" {
  1082  			// On AIX, .go.buildinfo must be in the symbol table as
  1083  			// it has relocations.
  1084  			return true
  1085  		}
  1086  		if ldr.AttrNotInSymbolTable(s) {
  1087  			return false
  1088  		}
  1089  		if (name == "" || name[0] == '.') && !ldr.IsFileLocal(s) && name != ".TOC." {
  1090  			return false
  1091  		}
  1092  		return true
  1093  	}
  1094  
  1095  	for s, nsym := loader.Sym(1), loader.Sym(ldr.NSym()); s < nsym; s++ {
  1096  		if !shouldBeInSymbolTable(s, ldr.SymName(s)) {
  1097  			continue
  1098  		}
  1099  		st := ldr.SymType(s)
  1100  		switch {
  1101  		case st == sym.STLSBSS:
  1102  			if ctxt.IsExternal() {
  1103  				putaixsym(ctxt, s, TLSSym)
  1104  			}
  1105  
  1106  		case st == sym.SBSS, st == sym.SNOPTRBSS, st == sym.SLIBFUZZER_EXTRA_COUNTER:
  1107  			if ldr.AttrReachable(s) {
  1108  				data := ldr.Data(s)
  1109  				if len(data) > 0 {
  1110  					ldr.Errorf(s, "should not be bss (size=%d type=%v special=%v)", len(data), ldr.SymType(s), ldr.AttrSpecial(s))
  1111  				}
  1112  				putaixsym(ctxt, s, BSSSym)
  1113  			}
  1114  
  1115  		case st >= sym.SELFRXSECT && st < sym.SXREF: // data sections handled in dodata
  1116  			if ldr.AttrReachable(s) {
  1117  				putaixsym(ctxt, s, DataSym)
  1118  			}
  1119  
  1120  		case st == sym.SUNDEFEXT:
  1121  			putaixsym(ctxt, s, UndefinedSym)
  1122  
  1123  		case st == sym.SDYNIMPORT:
  1124  			if ldr.AttrReachable(s) {
  1125  				putaixsym(ctxt, s, UndefinedSym)
  1126  			}
  1127  		}
  1128  	}
  1129  
  1130  	for _, s := range ctxt.Textp {
  1131  		putaixsym(ctxt, s, TextSym)
  1132  	}
  1133  
  1134  	if ctxt.Debugvlog != 0 || *flagN {
  1135  		ctxt.Logf("symsize = %d\n", uint32(symSize))
  1136  	}
  1137  	xfile.updatePreviousFile(ctxt, true)
  1138  }
  1139  
  1140  func (f *xcoffFile) genDynSym(ctxt *Link) {
  1141  	ldr := ctxt.loader
  1142  	var dynsyms []loader.Sym
  1143  	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
  1144  		if !ldr.AttrReachable(s) {
  1145  			continue
  1146  		}
  1147  		if t := ldr.SymType(s); t != sym.SHOSTOBJ && t != sym.SDYNIMPORT {
  1148  			continue
  1149  		}
  1150  		dynsyms = append(dynsyms, s)
  1151  	}
  1152  
  1153  	for _, s := range dynsyms {
  1154  		f.adddynimpsym(ctxt, s)
  1155  
  1156  		if _, ok := f.dynLibraries[ldr.SymDynimplib(s)]; !ok {
  1157  			f.dynLibraries[ldr.SymDynimplib(s)] = len(f.dynLibraries)
  1158  		}
  1159  	}
  1160  }
  1161  
  1162  // (*xcoffFile)adddynimpsym adds the dynamic symbol "s" to a XCOFF file.
  1163  // A new symbol named s.Extname() is created to be the actual dynamic symbol
  1164  // in the .loader section and in the symbol table as an External Reference.
  1165  // The symbol "s" is transformed to SXCOFFTOC to end up in .data section.
  1166  // However, there is no writing protection on those symbols and
  1167  // it might need to be added.
  1168  // TODO(aix): Handles dynamic symbols without library.
  1169  func (f *xcoffFile) adddynimpsym(ctxt *Link, s loader.Sym) {
  1170  	// Check that library name is given.
  1171  	// Pattern is already checked when compiling.
  1172  	ldr := ctxt.loader
  1173  	if ctxt.IsInternal() && ldr.SymDynimplib(s) == "" {
  1174  		ctxt.Errorf(s, "imported symbol must have a given library")
  1175  	}
  1176  
  1177  	sb := ldr.MakeSymbolUpdater(s)
  1178  	sb.SetReachable(true)
  1179  	sb.SetType(sym.SXCOFFTOC)
  1180  
  1181  	// Create new dynamic symbol
  1182  	extsym := ldr.CreateSymForUpdate(ldr.SymExtname(s), 0)
  1183  	extsym.SetType(sym.SDYNIMPORT)
  1184  	extsym.SetDynimplib(ldr.SymDynimplib(s))
  1185  	extsym.SetExtname(ldr.SymExtname(s))
  1186  	extsym.SetDynimpvers(ldr.SymDynimpvers(s))
  1187  
  1188  	// Add loader symbol
  1189  	lds := &xcoffLoaderSymbol{
  1190  		sym:    extsym.Sym(),
  1191  		smtype: XTY_IMP,
  1192  		smclas: XMC_DS,
  1193  	}
  1194  	if ldr.SymName(s) == "__n_pthreads" {
  1195  		// Currently, all imported symbols made by cgo_import_dynamic are
  1196  		// syscall functions, except __n_pthreads which is a variable.
  1197  		// TODO(aix): Find a way to detect variables imported by cgo.
  1198  		lds.smclas = XMC_RW
  1199  	}
  1200  	f.loaderSymbols = append(f.loaderSymbols, lds)
  1201  
  1202  	// Relocation to retrieve the external address
  1203  	sb.AddBytes(make([]byte, 8))
  1204  	r, _ := sb.AddRel(objabi.R_ADDR)
  1205  	r.SetSym(extsym.Sym())
  1206  	r.SetSiz(uint8(ctxt.Arch.PtrSize))
  1207  	// TODO: maybe this could be
  1208  	// sb.SetSize(0)
  1209  	// sb.SetData(nil)
  1210  	// sb.AddAddr(ctxt.Arch, extsym.Sym())
  1211  	// If the size is not 0 to begin with, I don't think the added 8 bytes
  1212  	// of zeros are necessary.
  1213  }
  1214  
  1215  // Xcoffadddynrel adds a dynamic relocation in a XCOFF file.
  1216  // This relocation will be made by the loader.
  1217  func Xcoffadddynrel(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, r loader.Reloc, rIdx int) bool {
  1218  	if target.IsExternal() {
  1219  		return true
  1220  	}
  1221  	if ldr.SymType(s) <= sym.SPCLNTAB {
  1222  		ldr.Errorf(s, "cannot have a relocation to %s in a text section symbol", ldr.SymName(r.Sym()))
  1223  		return false
  1224  	}
  1225  
  1226  	xldr := &xcoffLoaderReloc{
  1227  		sym:  s,
  1228  		roff: r.Off(),
  1229  	}
  1230  	targ := ldr.ResolveABIAlias(r.Sym())
  1231  	var targType sym.SymKind
  1232  	if targ != 0 {
  1233  		targType = ldr.SymType(targ)
  1234  	}
  1235  
  1236  	switch r.Type() {
  1237  	default:
  1238  		ldr.Errorf(s, "unexpected .loader relocation to symbol: %s (type: %s)", ldr.SymName(targ), r.Type().String())
  1239  		return false
  1240  	case objabi.R_ADDR:
  1241  		if ldr.SymType(s) == sym.SXCOFFTOC && targType == sym.SDYNIMPORT {
  1242  			// Imported symbol relocation
  1243  			for i, dynsym := range xfile.loaderSymbols {
  1244  				if ldr.SymName(dynsym.sym) == ldr.SymName(targ) {
  1245  					xldr.symndx = int32(i + 3) // +3 because of 3 section symbols
  1246  					break
  1247  				}
  1248  			}
  1249  		} else if t := ldr.SymType(s); t == sym.SDATA || t == sym.SNOPTRDATA || t == sym.SBUILDINFO || t == sym.SXCOFFTOC {
  1250  			switch ldr.SymSect(targ).Seg {
  1251  			default:
  1252  				ldr.Errorf(s, "unknown segment for .loader relocation with symbol %s", ldr.SymName(targ))
  1253  			case &Segtext:
  1254  			case &Segrodata:
  1255  				xldr.symndx = 0 // .text
  1256  			case &Segdata:
  1257  				if targType == sym.SBSS || targType == sym.SNOPTRBSS {
  1258  					xldr.symndx = 2 // .bss
  1259  				} else {
  1260  					xldr.symndx = 1 // .data
  1261  				}
  1262  			}
  1263  
  1264  		} else {
  1265  			ldr.Errorf(s, "unexpected type for .loader relocation R_ADDR for symbol %s: %s to %s", ldr.SymName(targ), ldr.SymType(s), ldr.SymType(targ))
  1266  			return false
  1267  		}
  1268  
  1269  		xldr.rtype = 0x3F<<8 + XCOFF_R_POS
  1270  	}
  1271  
  1272  	xfile.Lock()
  1273  	xfile.loaderReloc = append(xfile.loaderReloc, xldr)
  1274  	xfile.Unlock()
  1275  	return true
  1276  }
  1277  
  1278  func (ctxt *Link) doxcoff() {
  1279  	if *FlagD {
  1280  		// All XCOFF files have dynamic symbols because of the syscalls.
  1281  		Exitf("-d is not available on AIX")
  1282  	}
  1283  	ldr := ctxt.loader
  1284  
  1285  	// TOC
  1286  	toc := ldr.CreateSymForUpdate("TOC", 0)
  1287  	toc.SetType(sym.SXCOFFTOC)
  1288  	toc.SetVisibilityHidden(true)
  1289  
  1290  	// Add entry point to .loader symbols.
  1291  	ep := ldr.Lookup(*flagEntrySymbol, 0)
  1292  	if ep == 0 || !ldr.AttrReachable(ep) {
  1293  		Exitf("wrong entry point")
  1294  	}
  1295  
  1296  	xfile.loaderSymbols = append(xfile.loaderSymbols, &xcoffLoaderSymbol{
  1297  		sym:    ep,
  1298  		smtype: XTY_ENT | XTY_SD,
  1299  		smclas: XMC_DS,
  1300  	})
  1301  
  1302  	xfile.genDynSym(ctxt)
  1303  
  1304  	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
  1305  		if strings.HasPrefix(ldr.SymName(s), "TOC.") {
  1306  			sb := ldr.MakeSymbolUpdater(s)
  1307  			sb.SetType(sym.SXCOFFTOC)
  1308  		}
  1309  	}
  1310  
  1311  	if ctxt.IsExternal() {
  1312  		// Change rt0_go name to match name in runtime/cgo:main().
  1313  		rt0 := ldr.Lookup("runtime.rt0_go", 0)
  1314  		ldr.SetSymExtname(rt0, "runtime_rt0_go")
  1315  
  1316  		nsym := loader.Sym(ldr.NSym())
  1317  		for s := loader.Sym(1); s < nsym; s++ {
  1318  			if !ldr.AttrCgoExport(s) {
  1319  				continue
  1320  			}
  1321  			if ldr.SymVersion(s) != 0 { // sanity check
  1322  				panic("cgo_export on non-version 0 symbol")
  1323  			}
  1324  
  1325  			if ldr.SymType(s) == sym.STEXT || ldr.SymType(s) == sym.SABIALIAS {
  1326  				// On AIX, a exported function must have two symbols:
  1327  				// - a .text symbol which must start with a ".".
  1328  				// - a .data symbol which is a function descriptor.
  1329  				//
  1330  				// CgoExport attribute should only be set on a version 0
  1331  				// symbol, which can be TEXT or ABIALIAS.
  1332  				// (before, setupdynexp copies the attribute from the
  1333  				// alias to the aliased. Now we are before setupdynexp.)
  1334  				name := ldr.SymExtname(s)
  1335  				ldr.SetSymExtname(s, "."+name)
  1336  
  1337  				desc := ldr.MakeSymbolUpdater(ldr.CreateExtSym(name, 0))
  1338  				desc.SetReachable(true)
  1339  				desc.SetType(sym.SNOPTRDATA)
  1340  				desc.AddAddr(ctxt.Arch, s)
  1341  				desc.AddAddr(ctxt.Arch, toc.Sym())
  1342  				desc.AddUint64(ctxt.Arch, 0)
  1343  			}
  1344  		}
  1345  	}
  1346  }
  1347  
  1348  // Loader section
  1349  // Currently, this section is created from scratch when assembling the XCOFF file
  1350  // according to information retrieved in xfile object.
  1351  
  1352  // Create loader section and returns its size
  1353  func Loaderblk(ctxt *Link, off uint64) {
  1354  	xfile.writeLdrScn(ctxt, off)
  1355  }
  1356  
  1357  func (f *xcoffFile) writeLdrScn(ctxt *Link, globalOff uint64) {
  1358  	var symtab []*XcoffLdSym64
  1359  	var strtab []*XcoffLdStr64
  1360  	var importtab []*XcoffLdImportFile64
  1361  	var reloctab []*XcoffLdRel64
  1362  	var dynimpreloc []*XcoffLdRel64
  1363  
  1364  	// As the string table is updated in any loader subsection,
  1365  	//  its length must be computed at the same time.
  1366  	stlen := uint32(0)
  1367  
  1368  	// Loader Header
  1369  	hdr := &XcoffLdHdr64{
  1370  		Lversion: 2,
  1371  		Lsymoff:  LDHDRSZ_64,
  1372  	}
  1373  
  1374  	ldr := ctxt.loader
  1375  	/* Symbol table */
  1376  	for _, s := range f.loaderSymbols {
  1377  		lds := &XcoffLdSym64{
  1378  			Loffset: uint32(stlen + 2),
  1379  			Lsmtype: s.smtype,
  1380  			Lsmclas: s.smclas,
  1381  		}
  1382  		sym := s.sym
  1383  		switch s.smtype {
  1384  		default:
  1385  			ldr.Errorf(sym, "unexpected loader symbol type: 0x%x", s.smtype)
  1386  		case XTY_ENT | XTY_SD:
  1387  			lds.Lvalue = uint64(ldr.SymValue(sym))
  1388  			lds.Lscnum = f.getXCOFFscnum(ldr.SymSect(sym))
  1389  		case XTY_IMP:
  1390  			lds.Lifile = int32(f.dynLibraries[ldr.SymDynimplib(sym)] + 1)
  1391  		}
  1392  		ldstr := &XcoffLdStr64{
  1393  			size: uint16(len(ldr.SymName(sym)) + 1), // + null terminator
  1394  			name: ldr.SymName(sym),
  1395  		}
  1396  		stlen += uint32(2 + ldstr.size) // 2 = sizeof ldstr.size
  1397  		symtab = append(symtab, lds)
  1398  		strtab = append(strtab, ldstr)
  1399  
  1400  	}
  1401  
  1402  	hdr.Lnsyms = int32(len(symtab))
  1403  	hdr.Lrldoff = hdr.Lsymoff + uint64(24*hdr.Lnsyms) // 24 = sizeof one symbol
  1404  	off := hdr.Lrldoff                                // current offset is the same of reloc offset
  1405  
  1406  	/* Reloc */
  1407  	// Ensure deterministic order
  1408  	sort.Slice(f.loaderReloc, func(i, j int) bool {
  1409  		r1, r2 := f.loaderReloc[i], f.loaderReloc[j]
  1410  		if r1.sym != r2.sym {
  1411  			return r1.sym < r2.sym
  1412  		}
  1413  		if r1.roff != r2.roff {
  1414  			return r1.roff < r2.roff
  1415  		}
  1416  		if r1.rtype != r2.rtype {
  1417  			return r1.rtype < r2.rtype
  1418  		}
  1419  		return r1.symndx < r2.symndx
  1420  	})
  1421  
  1422  	ep := ldr.Lookup(*flagEntrySymbol, 0)
  1423  	xldr := &XcoffLdRel64{
  1424  		Lvaddr:  uint64(ldr.SymValue(ep)),
  1425  		Lrtype:  0x3F00,
  1426  		Lrsecnm: f.getXCOFFscnum(ldr.SymSect(ep)),
  1427  		Lsymndx: 0,
  1428  	}
  1429  	off += 16
  1430  	reloctab = append(reloctab, xldr)
  1431  
  1432  	off += uint64(16 * len(f.loaderReloc))
  1433  	for _, r := range f.loaderReloc {
  1434  		symp := r.sym
  1435  		if symp == 0 {
  1436  			panic("unexpected 0 sym value")
  1437  		}
  1438  		xldr = &XcoffLdRel64{
  1439  			Lvaddr:  uint64(ldr.SymValue(symp) + int64(r.roff)),
  1440  			Lrtype:  r.rtype,
  1441  			Lsymndx: r.symndx,
  1442  		}
  1443  
  1444  		if ldr.SymSect(symp) != nil {
  1445  			xldr.Lrsecnm = f.getXCOFFscnum(ldr.SymSect(symp))
  1446  		}
  1447  
  1448  		reloctab = append(reloctab, xldr)
  1449  	}
  1450  
  1451  	off += uint64(16 * len(dynimpreloc))
  1452  	reloctab = append(reloctab, dynimpreloc...)
  1453  
  1454  	hdr.Lnreloc = int32(len(reloctab))
  1455  	hdr.Limpoff = off
  1456  
  1457  	/* Import */
  1458  	// Default import: /usr/lib:/lib
  1459  	ldimpf := &XcoffLdImportFile64{
  1460  		Limpidpath: "/usr/lib:/lib",
  1461  	}
  1462  	off += uint64(len(ldimpf.Limpidpath) + len(ldimpf.Limpidbase) + len(ldimpf.Limpidmem) + 3) // + null delimiter
  1463  	importtab = append(importtab, ldimpf)
  1464  
  1465  	// The map created by adddynimpsym associates the name to a number
  1466  	// This number represents the librairie index (- 1) in this import files section
  1467  	// Therefore, they must be sorted before being put inside the section
  1468  	libsOrdered := make([]string, len(f.dynLibraries))
  1469  	for key, val := range f.dynLibraries {
  1470  		if libsOrdered[val] != "" {
  1471  			continue
  1472  		}
  1473  		libsOrdered[val] = key
  1474  	}
  1475  
  1476  	for _, lib := range libsOrdered {
  1477  		// lib string is defined as base.a/mem.o or path/base.a/mem.o
  1478  		n := strings.Split(lib, "/")
  1479  		path := ""
  1480  		base := n[len(n)-2]
  1481  		mem := n[len(n)-1]
  1482  		if len(n) > 2 {
  1483  			path = lib[:len(lib)-len(base)-len(mem)-2]
  1484  
  1485  		}
  1486  		ldimpf = &XcoffLdImportFile64{
  1487  			Limpidpath: path,
  1488  			Limpidbase: base,
  1489  			Limpidmem:  mem,
  1490  		}
  1491  		off += uint64(len(ldimpf.Limpidpath) + len(ldimpf.Limpidbase) + len(ldimpf.Limpidmem) + 3) // + null delimiter
  1492  		importtab = append(importtab, ldimpf)
  1493  	}
  1494  
  1495  	hdr.Lnimpid = int32(len(importtab))
  1496  	hdr.Listlen = uint32(off - hdr.Limpoff)
  1497  	hdr.Lstoff = off
  1498  	hdr.Lstlen = stlen
  1499  
  1500  	/* Writing */
  1501  	ctxt.Out.SeekSet(int64(globalOff))
  1502  	binary.Write(ctxt.Out, ctxt.Arch.ByteOrder, hdr)
  1503  
  1504  	for _, s := range symtab {
  1505  		binary.Write(ctxt.Out, ctxt.Arch.ByteOrder, s)
  1506  
  1507  	}
  1508  	for _, r := range reloctab {
  1509  		binary.Write(ctxt.Out, ctxt.Arch.ByteOrder, r)
  1510  	}
  1511  	for _, f := range importtab {
  1512  		ctxt.Out.WriteString(f.Limpidpath)
  1513  		ctxt.Out.Write8(0)
  1514  		ctxt.Out.WriteString(f.Limpidbase)
  1515  		ctxt.Out.Write8(0)
  1516  		ctxt.Out.WriteString(f.Limpidmem)
  1517  		ctxt.Out.Write8(0)
  1518  	}
  1519  	for _, s := range strtab {
  1520  		ctxt.Out.Write16(s.size)
  1521  		ctxt.Out.WriteString(s.name)
  1522  		ctxt.Out.Write8(0) // null terminator
  1523  	}
  1524  
  1525  	f.loaderSize = off + uint64(stlen)
  1526  }
  1527  
  1528  // XCOFF assembling and writing file
  1529  
  1530  func (f *xcoffFile) writeFileHeader(ctxt *Link) {
  1531  	// File header
  1532  	f.xfhdr.Fmagic = U64_TOCMAGIC
  1533  	f.xfhdr.Fnscns = uint16(len(f.sections))
  1534  	f.xfhdr.Ftimedat = 0
  1535  
  1536  	if !*FlagS {
  1537  		f.xfhdr.Fsymptr = uint64(f.symtabOffset)
  1538  		f.xfhdr.Fnsyms = int32(f.symbolCount)
  1539  	}
  1540  
  1541  	if ctxt.BuildMode == BuildModeExe && ctxt.LinkMode == LinkInternal {
  1542  		ldr := ctxt.loader
  1543  		f.xfhdr.Fopthdr = AOUTHSZ_EXEC64
  1544  		f.xfhdr.Fflags = F_EXEC
  1545  
  1546  		// auxiliary header
  1547  		f.xahdr.Ovstamp = 1 // based on dump -o
  1548  		f.xahdr.Omagic = 0x10b
  1549  		copy(f.xahdr.Omodtype[:], "1L")
  1550  		entry := ldr.Lookup(*flagEntrySymbol, 0)
  1551  		f.xahdr.Oentry = uint64(ldr.SymValue(entry))
  1552  		f.xahdr.Osnentry = f.getXCOFFscnum(ldr.SymSect(entry))
  1553  		toc := ldr.Lookup("TOC", 0)
  1554  		f.xahdr.Otoc = uint64(ldr.SymValue(toc))
  1555  		f.xahdr.Osntoc = f.getXCOFFscnum(ldr.SymSect(toc))
  1556  
  1557  		f.xahdr.Oalgntext = int16(logBase2(int(Funcalign)))
  1558  		f.xahdr.Oalgndata = 0x5
  1559  
  1560  		binary.Write(ctxt.Out, binary.BigEndian, &f.xfhdr)
  1561  		binary.Write(ctxt.Out, binary.BigEndian, &f.xahdr)
  1562  	} else {
  1563  		f.xfhdr.Fopthdr = 0
  1564  		binary.Write(ctxt.Out, binary.BigEndian, &f.xfhdr)
  1565  	}
  1566  
  1567  }
  1568  
  1569  func xcoffwrite(ctxt *Link) {
  1570  	ctxt.Out.SeekSet(0)
  1571  
  1572  	xfile.writeFileHeader(ctxt)
  1573  
  1574  	for _, sect := range xfile.sections {
  1575  		sect.write(ctxt)
  1576  	}
  1577  }
  1578  
  1579  // Generate XCOFF assembly file
  1580  func asmbXcoff(ctxt *Link) {
  1581  	ctxt.Out.SeekSet(0)
  1582  	fileoff := int64(Segdwarf.Fileoff + Segdwarf.Filelen)
  1583  	fileoff = int64(Rnd(int64(fileoff), int64(*FlagRound)))
  1584  
  1585  	xfile.sectNameToScnum = make(map[string]int16)
  1586  
  1587  	// Add sections
  1588  	s := xfile.addSection(".text", Segtext.Vaddr, Segtext.Length, Segtext.Fileoff, STYP_TEXT)
  1589  	xfile.xahdr.Otextstart = s.Svaddr
  1590  	xfile.xahdr.Osntext = xfile.sectNameToScnum[".text"]
  1591  	xfile.xahdr.Otsize = s.Ssize
  1592  	xfile.sectText = s
  1593  
  1594  	segdataVaddr := Segdata.Vaddr
  1595  	segdataFilelen := Segdata.Filelen
  1596  	segdataFileoff := Segdata.Fileoff
  1597  	segbssFilelen := Segdata.Length - Segdata.Filelen
  1598  	if len(Segrelrodata.Sections) > 0 {
  1599  		// Merge relro segment to data segment as
  1600  		// relro data are inside data segment on AIX.
  1601  		segdataVaddr = Segrelrodata.Vaddr
  1602  		segdataFileoff = Segrelrodata.Fileoff
  1603  		segdataFilelen = Segdata.Vaddr + Segdata.Filelen - Segrelrodata.Vaddr
  1604  	}
  1605  
  1606  	s = xfile.addSection(".data", segdataVaddr, segdataFilelen, segdataFileoff, STYP_DATA)
  1607  	xfile.xahdr.Odatastart = s.Svaddr
  1608  	xfile.xahdr.Osndata = xfile.sectNameToScnum[".data"]
  1609  	xfile.xahdr.Odsize = s.Ssize
  1610  	xfile.sectData = s
  1611  
  1612  	s = xfile.addSection(".bss", segdataVaddr+segdataFilelen, segbssFilelen, 0, STYP_BSS)
  1613  	xfile.xahdr.Osnbss = xfile.sectNameToScnum[".bss"]
  1614  	xfile.xahdr.Obsize = s.Ssize
  1615  	xfile.sectBss = s
  1616  
  1617  	if ctxt.LinkMode == LinkExternal {
  1618  		var tbss *sym.Section
  1619  		for _, s := range Segdata.Sections {
  1620  			if s.Name == ".tbss" {
  1621  				tbss = s
  1622  				break
  1623  			}
  1624  		}
  1625  		s = xfile.addSection(".tbss", tbss.Vaddr, tbss.Length, 0, STYP_TBSS)
  1626  	}
  1627  
  1628  	// add dwarf sections
  1629  	for _, sect := range Segdwarf.Sections {
  1630  		xfile.addDwarfSection(sect)
  1631  	}
  1632  
  1633  	// add and write remaining sections
  1634  	if ctxt.LinkMode == LinkInternal {
  1635  		// Loader section
  1636  		if ctxt.BuildMode == BuildModeExe {
  1637  			Loaderblk(ctxt, uint64(fileoff))
  1638  			s = xfile.addSection(".loader", 0, xfile.loaderSize, uint64(fileoff), STYP_LOADER)
  1639  			xfile.xahdr.Osnloader = xfile.sectNameToScnum[".loader"]
  1640  
  1641  			// Update fileoff for symbol table
  1642  			fileoff += int64(xfile.loaderSize)
  1643  		}
  1644  	}
  1645  
  1646  	// Create Symbol table
  1647  	xfile.asmaixsym(ctxt)
  1648  
  1649  	if ctxt.LinkMode == LinkExternal {
  1650  		xfile.emitRelocations(ctxt, fileoff)
  1651  	}
  1652  
  1653  	// Write Symbol table
  1654  	xfile.symtabOffset = ctxt.Out.Offset()
  1655  	for _, s := range xfile.symtabSym {
  1656  		binary.Write(ctxt.Out, ctxt.Arch.ByteOrder, s)
  1657  	}
  1658  	// write string table
  1659  	xfile.stringTable.write(ctxt.Out)
  1660  
  1661  	// write headers
  1662  	xcoffwrite(ctxt)
  1663  }
  1664  
  1665  // emitRelocations emits relocation entries for go.o in external linking.
  1666  func (f *xcoffFile) emitRelocations(ctxt *Link, fileoff int64) {
  1667  	ctxt.Out.SeekSet(fileoff)
  1668  	for ctxt.Out.Offset()&7 != 0 {
  1669  		ctxt.Out.Write8(0)
  1670  	}
  1671  
  1672  	ldr := ctxt.loader
  1673  	// relocsect relocates symbols from first in section sect, and returns
  1674  	// the total number of relocations emitted.
  1675  	relocsect := func(sect *sym.Section, syms []loader.Sym, base uint64) uint32 {
  1676  		// ctxt.Logf("%s 0x%x\n", sect.Name, sect.Vaddr)
  1677  		// If main section has no bits, nothing to relocate.
  1678  		if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen {
  1679  			return 0
  1680  		}
  1681  		sect.Reloff = uint64(ctxt.Out.Offset())
  1682  		for i, s := range syms {
  1683  			if !ldr.AttrReachable(s) {
  1684  				continue
  1685  			}
  1686  			if uint64(ldr.SymValue(s)) >= sect.Vaddr {
  1687  				syms = syms[i:]
  1688  				break
  1689  			}
  1690  		}
  1691  		eaddr := int64(sect.Vaddr + sect.Length)
  1692  		for _, s := range syms {
  1693  			if !ldr.AttrReachable(s) {
  1694  				continue
  1695  			}
  1696  			if ldr.SymValue(s) >= int64(eaddr) {
  1697  				break
  1698  			}
  1699  
  1700  			// Compute external relocations on the go, and pass to Xcoffreloc1 to stream out.
  1701  			// Relocation must be ordered by address, so create a list of sorted indices.
  1702  			relocs := ldr.Relocs(s)
  1703  			sorted := make([]int, relocs.Count())
  1704  			for i := 0; i < relocs.Count(); i++ {
  1705  				sorted[i] = i
  1706  			}
  1707  			sort.Slice(sorted, func(i, j int) bool {
  1708  				return relocs.At(sorted[i]).Off() < relocs.At(sorted[j]).Off()
  1709  			})
  1710  
  1711  			for _, ri := range sorted {
  1712  				r := relocs.At(ri)
  1713  				rr, ok := extreloc(ctxt, ldr, s, r)
  1714  				if !ok {
  1715  					continue
  1716  				}
  1717  				if rr.Xsym == 0 {
  1718  					ldr.Errorf(s, "missing xsym in relocation")
  1719  					continue
  1720  				}
  1721  				if ldr.SymDynid(rr.Xsym) < 0 {
  1722  					ldr.Errorf(s, "reloc %s to non-coff symbol %s (outer=%s) %d %d", r.Type(), ldr.SymName(r.Sym()), ldr.SymName(rr.Xsym), ldr.SymType(r.Sym()), ldr.SymDynid(rr.Xsym))
  1723  				}
  1724  				if !thearch.Xcoffreloc1(ctxt.Arch, ctxt.Out, ldr, s, rr, int64(uint64(ldr.SymValue(s)+int64(r.Off()))-base)) {
  1725  					ldr.Errorf(s, "unsupported obj reloc %d(%s)/%d to %s", r.Type(), r.Type(), r.Siz(), ldr.SymName(r.Sym()))
  1726  				}
  1727  			}
  1728  		}
  1729  		sect.Rellen = uint64(ctxt.Out.Offset()) - sect.Reloff
  1730  		return uint32(sect.Rellen) / RELSZ_64
  1731  	}
  1732  	sects := []struct {
  1733  		xcoffSect *XcoffScnHdr64
  1734  		segs      []*sym.Segment
  1735  	}{
  1736  		{f.sectText, []*sym.Segment{&Segtext}},
  1737  		{f.sectData, []*sym.Segment{&Segrelrodata, &Segdata}},
  1738  	}
  1739  	for _, s := range sects {
  1740  		s.xcoffSect.Srelptr = uint64(ctxt.Out.Offset())
  1741  		n := uint32(0)
  1742  		for _, seg := range s.segs {
  1743  			for _, sect := range seg.Sections {
  1744  				if sect.Name == ".text" {
  1745  					n += relocsect(sect, ctxt.Textp, 0)
  1746  				} else {
  1747  					n += relocsect(sect, ctxt.datap, 0)
  1748  				}
  1749  			}
  1750  		}
  1751  		s.xcoffSect.Snreloc += n
  1752  	}
  1753  
  1754  dwarfLoop:
  1755  	for i := 0; i < len(Segdwarf.Sections); i++ {
  1756  		sect := Segdwarf.Sections[i]
  1757  		si := dwarfp[i]
  1758  		if si.secSym() != loader.Sym(sect.Sym) ||
  1759  			ldr.SymSect(si.secSym()) != sect {
  1760  			panic("inconsistency between dwarfp and Segdwarf")
  1761  		}
  1762  		for _, xcoffSect := range f.sections {
  1763  			_, subtyp := xcoffGetDwarfSubtype(sect.Name)
  1764  			if xcoffSect.Sflags&0xF0000 == subtyp {
  1765  				xcoffSect.Srelptr = uint64(ctxt.Out.Offset())
  1766  				xcoffSect.Snreloc = relocsect(sect, si.syms, sect.Vaddr)
  1767  				continue dwarfLoop
  1768  			}
  1769  		}
  1770  		Errorf(nil, "emitRelocations: could not find %q section", sect.Name)
  1771  	}
  1772  }
  1773  
  1774  // xcoffCreateExportFile creates a file with exported symbols for
  1775  // -Wl,-bE option.
  1776  // ld won't export symbols unless they are listed in an export file.
  1777  func xcoffCreateExportFile(ctxt *Link) (fname string) {
  1778  	fname = filepath.Join(*flagTmpdir, "export_file.exp")
  1779  	var buf bytes.Buffer
  1780  
  1781  	ldr := ctxt.loader
  1782  	for s, nsym := loader.Sym(1), loader.Sym(ldr.NSym()); s < nsym; s++ {
  1783  		if !ldr.AttrCgoExport(s) {
  1784  			continue
  1785  		}
  1786  		extname := ldr.SymExtname(s)
  1787  		if !strings.HasPrefix(extname, "._cgoexp_") {
  1788  			continue
  1789  		}
  1790  		if ldr.SymVersion(s) != 0 {
  1791  			continue // Only export version 0 symbols. See the comment in doxcoff.
  1792  		}
  1793  
  1794  		// Retrieve the name of the initial symbol
  1795  		// exported by cgo.
  1796  		// The corresponding Go symbol is:
  1797  		// _cgoexp_hashcode_symname.
  1798  		name := strings.SplitN(extname, "_", 4)[3]
  1799  
  1800  		buf.Write([]byte(name + "\n"))
  1801  	}
  1802  
  1803  	err := ioutil.WriteFile(fname, buf.Bytes(), 0666)
  1804  	if err != nil {
  1805  		Errorf(nil, "WriteFile %s failed: %v", fname, err)
  1806  	}
  1807  
  1808  	return fname
  1809  }
  1810  

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