// Copyright 2018 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 ld
import (
"bytes"
"cmd/internal/objabi"
"cmd/link/internal/sym"
"encoding/binary"
"strings"
)
// This file handles all algorithms related to XCOFF files generation.
// Most of them are adaptations of the ones in cmd/link/internal/pe.go
// as PE and XCOFF are based on COFF files.
// XCOFF files generated are 64 bits.
const (
// Total amount of space to reserve at the start of the file
// for File Header, Auxiliary Header, and Section Headers.
// May waste some.
XCOFFHDRRESERVE = FILHSZ_64 + AOUTHSZ_EXEC64 + SCNHSZ_64*23
XCOFFSECTALIGN int64 = 32 // base on dump -o
// XCOFF binaries should normally have all its sections position-independent.
// However, this is not yet possible for .text because of some R_ADDR relocations
// inside RODATA symbols.
// .data and .bss are position-independent so their address start inside a unreachable
// segment during execution to force segfault if something is wrong.
XCOFFTEXTBASE = 0x100000000 // Start of text address
XCOFFDATABASE = 0x200000000 // Start of data address
)
// File Header
type XcoffFileHdr64 struct {
Fmagic uint16 // Target machine
Fnscns uint16 // Number of sections
Ftimedat int32 // Time and date of file creation
Fsymptr uint64 // Byte offset to symbol table start
Fopthdr uint16 // Number of bytes in optional header
Fflags uint16 // Flags
Fnsyms int32 // Number of entries in symbol table
}
const (
U64_TOCMAGIC = 0767 // AIX 64-bit XCOFF
)
// Flags that describe the type of the object file.
const (
F_RELFLG = 0x0001
F_EXEC = 0x0002
F_LNNO = 0x0004
F_FDPR_PROF = 0x0010
F_FDPR_OPTI = 0x0020
F_DSA = 0x0040
F_VARPG = 0x0100
F_DYNLOAD = 0x1000
F_SHROBJ = 0x2000
F_LOADONLY = 0x4000
)
// Auxiliary Header
type XcoffAoutHdr64 struct {
Omagic int16 // Flags - Ignored If Vstamp Is 1
Ovstamp int16 // Version
Odebugger uint32 // Reserved For Debugger
Otextstart uint64 // Virtual Address Of Text
Odatastart uint64 // Virtual Address Of Data
Otoc uint64 // Toc Address
Osnentry int16 // Section Number For Entry Point
Osntext int16 // Section Number For Text
Osndata int16 // Section Number For Data
Osntoc int16 // Section Number For Toc
Osnloader int16 // Section Number For Loader
Osnbss int16 // Section Number For Bss
Oalgntext int16 // Max Text Alignment
Oalgndata int16 // Max Data Alignment
Omodtype [2]byte // Module Type Field
Ocpuflag uint8 // Bit Flags - Cputypes Of Objects
Ocputype uint8 // Reserved for CPU type
Otextpsize uint8 // Requested text page size
Odatapsize uint8 // Requested data page size
Ostackpsize uint8 // Requested stack page size
Oflags uint8 // Flags And TLS Alignment
Otsize uint64 // Text Size In Bytes
Odsize uint64 // Data Size In Bytes
Obsize uint64 // Bss Size In Bytes
Oentry uint64 // Entry Point Address
Omaxstack uint64 // Max Stack Size Allowed
Omaxdata uint64 // Max Data Size Allowed
Osntdata int16 // Section Number For Tdata Section
Osntbss int16 // Section Number For Tbss Section
Ox64flags uint16 // Additional Flags For 64-Bit Objects
Oresv3a int16 // Reserved
Oresv3 [2]int32 // Reserved
}
// Section Header
type XcoffScnHdr64 struct {
Sname [8]byte // Section Name
Spaddr uint64 // Physical Address
Svaddr uint64 // Virtual Address
Ssize uint64 // Section Size
Sscnptr uint64 // File Offset To Raw Data
Srelptr uint64 // File Offset To Relocation
Slnnoptr uint64 // File Offset To Line Numbers
Snreloc uint32 // Number Of Relocation Entries
Snlnno uint32 // Number Of Line Number Entries
Sflags uint32 // flags
}
// Flags defining the section type.
const (
STYP_DWARF = 0x0010
STYP_TEXT = 0x0020
STYP_DATA = 0x0040
STYP_BSS = 0x0080
STYP_EXCEPT = 0x0100
STYP_INFO = 0x0200
STYP_TDATA = 0x0400
STYP_TBSS = 0x0800
STYP_LOADER = 0x1000
STYP_DEBUG = 0x2000
STYP_TYPCHK = 0x4000
STYP_OVRFLO = 0x8000
)
const (
SSUBTYP_DWINFO = 0x10000 // DWARF info section
SSUBTYP_DWLINE = 0x20000 // DWARF line-number section
SSUBTYP_DWPBNMS = 0x30000 // DWARF public names section
SSUBTYP_DWPBTYP = 0x40000 // DWARF public types section
SSUBTYP_DWARNGE = 0x50000 // DWARF aranges section
SSUBTYP_DWABREV = 0x60000 // DWARF abbreviation section
SSUBTYP_DWSTR = 0x70000 // DWARF strings section
SSUBTYP_DWRNGES = 0x80000 // DWARF ranges section
SSUBTYP_DWLOC = 0x90000 // DWARF location lists section
SSUBTYP_DWFRAME = 0xA0000 // DWARF frames section
SSUBTYP_DWMAC = 0xB0000 // DWARF macros section
)
// Headers size
const (
FILHSZ_32 = 20
FILHSZ_64 = 24
AOUTHSZ_EXEC32 = 72
AOUTHSZ_EXEC64 = 120
SCNHSZ_32 = 40
SCNHSZ_64 = 72
LDHDRSZ_32 = 32
LDHDRSZ_64 = 56
LDSYMSZ_64 = 24
)
// Symbol Table Entry
type XcoffSymEnt64 struct {
Nvalue uint64 // Symbol value
Noffset uint32 // Offset of the name in string table or .debug section
Nscnum int16 // Section number of symbol
Ntype uint16 // Basic and derived type specification
Nsclass uint8 // Storage class of symbol
Nnumaux int8 // Number of auxiliary entries
}
const SYMESZ = 18
const (
// Nscnum
N_DEBUG = -2
N_ABS = -1
N_UNDEF = 0
//Ntype
SYM_V_INTERNAL = 0x1000
SYM_V_HIDDEN = 0x2000
SYM_V_PROTECTED = 0x3000
SYM_V_EXPORTED = 0x4000
SYM_TYPE_FUNC = 0x0020 // is function
)
// Storage Class.
const (
C_NULL = 0 // Symbol table entry marked for deletion
C_EXT = 2 // External symbol
C_STAT = 3 // Static symbol
C_BLOCK = 100 // Beginning or end of inner block
C_FCN = 101 // Beginning or end of function
C_FILE = 103 // Source file name and compiler information
C_HIDEXT = 107 // Unnamed external symbol
C_BINCL = 108 // Beginning of include file
C_EINCL = 109 // End of include file
C_WEAKEXT = 111 // Weak external symbol
C_DWARF = 112 // DWARF symbol
C_GSYM = 128 // Global variable
C_LSYM = 129 // Automatic variable allocated on stack
C_PSYM = 130 // Argument to subroutine allocated on stack
C_RSYM = 131 // Register variable
C_RPSYM = 132 // Argument to function or procedure stored in register
C_STSYM = 133 // Statically allocated symbol
C_BCOMM = 135 // Beginning of common block
C_ECOML = 136 // Local member of common block
C_ECOMM = 137 // End of common block
C_DECL = 140 // Declaration of object
C_ENTRY = 141 // Alternate entry
C_FUN = 142 // Function or procedure
C_BSTAT = 143 // Beginning of static block
C_ESTAT = 144 // End of static block
C_GTLS = 145 // Global thread-local variable
C_STTLS = 146 // Static thread-local variable
)
// File Auxiliary Entry
type XcoffAuxFile64 struct {
Xfname [8]byte // Name or offset inside string table
Xftype uint8 // Source file string type
Xauxtype uint8 // Type of auxiliary entry
}
// Function Auxiliary Entry
type XcoffAuxFcn64 struct {
Xlnnoptr uint64 // File pointer to line number
Xfsize uint32 // Size of function in bytes
Xendndx uint32 // Symbol table index of next entry
Xpad uint8 // Unused
Xauxtype uint8 // Type of auxiliary entry
}
// csect Auxiliary Entry.
type XcoffAuxCSect64 struct {
Xscnlenlo uint32 // Lower 4 bytes of length or symbol table index
Xparmhash uint32 // Offset of parameter type-check string
Xsnhash uint16 // .typchk section number
Xsmtyp uint8 // Symbol alignment and type
Xsmclas uint8 // Storage-mapping class
Xscnlenhi uint32 // Upper 4 bytes of length or symbol table index
Xpad uint8 // Unused
Xauxtype uint8 // Type of auxiliary entry
}
// Auxiliary type
const (
_AUX_EXCEPT = 255
_AUX_FCN = 254
_AUX_SYM = 253
_AUX_FILE = 252
_AUX_CSECT = 251
_AUX_SECT = 250
)
// Xftype field
const (
XFT_FN = 0 // Source File Name
XFT_CT = 1 // Compile Time Stamp
XFT_CV = 2 // Compiler Version Number
XFT_CD = 128 // Compiler Defined Information/
)
// Symbol type field.
const (
XTY_ER = 0 // External reference
XTY_SD = 1 // Section definition
XTY_LD = 2 // Label definition
XTY_CM = 3 // Common csect definition
XTY_WK = 0x8 // Weak symbol
XTY_EXP = 0x10 // Exported symbol
XTY_ENT = 0x20 // Entry point symbol
XTY_IMP = 0x40 // Imported symbol
)
// Storage-mapping class.
const (
XMC_PR = 0 // Program code
XMC_RO = 1 // Read-only constant
XMC_DB = 2 // Debug dictionary table
XMC_TC = 3 // TOC entry
XMC_UA = 4 // Unclassified
XMC_RW = 5 // Read/Write data
XMC_GL = 6 // Global linkage
XMC_XO = 7 // Extended operation
XMC_SV = 8 // 32-bit supervisor call descriptor
XMC_BS = 9 // BSS class
XMC_DS = 10 // Function descriptor
XMC_UC = 11 // Unnamed FORTRAN common
XMC_TC0 = 15 // TOC anchor
XMC_TD = 16 // Scalar data entry in the TOC
XMC_SV64 = 17 // 64-bit supervisor call descriptor
XMC_SV3264 = 18 // Supervisor call descriptor for both 32-bit and 64-bit
XMC_TL = 20 // Read/Write thread-local data
XMC_UL = 21 // Read/Write thread-local data (.tbss)
XMC_TE = 22 // TOC entry
)
// Loader Header
type XcoffLdHdr64 struct {
Lversion int32 // Loader section version number
Lnsyms int32 // Number of symbol table entries
Lnreloc int32 // Number of relocation table entries
Listlen uint32 // Length of import file ID string table
Lnimpid int32 // Number of import file IDs
Lstlen uint32 // Length of string table
Limpoff uint64 // Offset to start of import file IDs
Lstoff uint64 // Offset to start of string table
Lsymoff uint64 // Offset to start of symbol table
Lrldoff uint64 // Offset to start of relocation entries
}
// Loader Symbol
type XcoffLdSym64 struct {
Lvalue uint64 // Address field
Loffset uint32 // Byte offset into string table of symbol name
Lscnum int16 // Section number containing symbol
Lsmtype int8 // Symbol type, export, import flags
Lsmclas int8 // Symbol storage class
Lifile int32 // Import file ID; ordinal of import file IDs
Lparm uint32 // Parameter type-check field
}
type xcoffLoaderSymbol struct {
sym *sym.Symbol
smtype int8
smclas int8
}
type XcoffLdImportFile64 struct {
Limpidpath string
Limpidbase string
Limpidmem string
}
type XcoffLdRel64 struct {
Lvaddr uint64 // Address Field
Lrtype uint16 // Relocation Size and Type
Lrsecnm int16 // Section Number being relocated
Lsymndx int32 // Loader-Section symbol table index
}
// xcoffLoaderReloc holds information about a relocation made by the loader.
type xcoffLoaderReloc struct {
sym *sym.Symbol
rel *sym.Reloc
rtype uint16
symndx int32
}
const (
XCOFF_R_POS = 0x00 // A(sym) Positive Relocation
)
type XcoffLdStr64 struct {
size uint16
name string
}
// xcoffFile is used to build XCOFF file.
type xcoffFile struct {
xfhdr XcoffFileHdr64
xahdr XcoffAoutHdr64
sections []*XcoffScnHdr64
stringTable xcoffStringTable
sectNameToScnum map[string]int16
loaderSize uint64
symtabOffset int64 // offset to the start of symbol table
symbolCount uint32 // number of symbol table records written
dynLibraries map[string]int // Dynamic libraries in .loader section. The integer represents its import file number (- 1)
loaderSymbols []*xcoffLoaderSymbol // symbols inside .loader symbol table
loaderReloc []*xcoffLoaderReloc // Reloc that must be made inside loader
}
// Var used by XCOFF Generation algorithms
var (
xfile xcoffFile
)
// xcoffStringTable is a XCOFF string table.
type xcoffStringTable struct {
strings []string
stringsLen int
}
// size returns size of string table t.
func (t *xcoffStringTable) size() int {
// string table starts with 4-byte length at the beginning
return t.stringsLen + 4
}
// add adds string str to string table t.
func (t *xcoffStringTable) add(str string) int {
off := t.size()
t.strings = append(t.strings, str)
t.stringsLen += len(str) + 1 // each string will have 0 appended to it
return off
}
// write writes string table t into the output file.
func (t *xcoffStringTable) write(out *OutBuf) {
out.Write32(uint32(t.size()))
for _, s := range t.strings {
out.WriteString(s)
out.Write8(0)
}
}
// write writes XCOFF section sect into the output file.
func (sect *XcoffScnHdr64) write(ctxt *Link) {
binary.Write(ctxt.Out, binary.BigEndian, sect)
ctxt.Out.Write32(0) // Add 4 empty bytes at the end to match alignment
}
// addSection adds section to the XCOFF file f.
func (f *xcoffFile) addSection(name string, addr uint64, size uint64, fileoff uint64, flags uint32) *XcoffScnHdr64 {
sect := &XcoffScnHdr64{
Spaddr: addr,
Svaddr: addr,
Ssize: size,
Sscnptr: fileoff,
Sflags: flags,
}
copy(sect.Sname[:], name) // copy string to [8]byte
f.sections = append(f.sections, sect)
f.sectNameToScnum[name] = int16(len(f.sections))
return sect
}
// addDwarfSection adds a dwarf section to the XCOFF file f.
// This function is similar to addSection, but Dwarf section names
// must be modified to conventional names and they are various subtypes.
func (f *xcoffFile) addDwarfSection(s *sym.Section) *XcoffScnHdr64 {
newName, subtype := xcoffGetDwarfSubtype(s.Name)
return f.addSection(newName, 0, s.Length, s.Seg.Fileoff+s.Vaddr-s.Seg.Vaddr, STYP_DWARF|subtype)
}
// xcoffGetDwarfSubtype returns the XCOFF name of the DWARF section str
// and its subtype constant.
func xcoffGetDwarfSubtype(str string) (string, uint32) {
switch str {
default:
Exitf("unknown DWARF section name for XCOFF: %s", str)
case ".debug_abbrev":
return ".dwabrev", SSUBTYP_DWABREV
case ".debug_info":
return ".dwinfo", SSUBTYP_DWINFO
case ".debug_frame":
return ".dwframe", SSUBTYP_DWFRAME
case ".debug_line":
return ".dwline", SSUBTYP_DWLINE
case ".debug_loc":
return ".dwloc", SSUBTYP_DWLOC
case ".debug_pubnames":
return ".dwpbnms", SSUBTYP_DWPBNMS
case ".debug_pubtypes":
return ".dwpbtyp", SSUBTYP_DWPBTYP
case ".debug_ranges":
return ".dwrnge", SSUBTYP_DWRNGES
}
// never used
return "", 0
}
// getXCOFFscnum returns the XCOFF section number of a Go section.
func (f *xcoffFile) getXCOFFscnum(sect *sym.Section) int16 {
switch sect.Seg {
case &Segtext:
return f.sectNameToScnum[".text"]
case &Segdata:
if sect.Name == ".noptrdata" || sect.Name == ".data" {
return f.sectNameToScnum[".data"]
}
if sect.Name == ".noptrbss" || sect.Name == ".bss" {
return f.sectNameToScnum[".bss"]
}
Errorf(nil, "unknown XCOFF segment data section: %s", sect.Name)
case &Segdwarf:
name, _ := xcoffGetDwarfSubtype(sect.Name)
return f.sectNameToScnum[name]
}
Errorf(nil, "getXCOFFscnum not implemented for section %s", sect.Name)
return -1
}
// Xcoffinit initialised some internal value and setups
// already known header information
func Xcoffinit(ctxt *Link) {
xfile.dynLibraries = make(map[string]int)
HEADR = int32(Rnd(XCOFFHDRRESERVE, XCOFFSECTALIGN))
if *FlagTextAddr != -1 {
Errorf(nil, "-T not available on AIX")
}
*FlagTextAddr = XCOFFTEXTBASE + int64(HEADR)
*FlagDataAddr = 0
if *FlagRound != -1 {
Errorf(nil, "-R not available on AIX")
}
*FlagRound = int(XCOFFSECTALIGN)
}
// SYMBOL TABLE
// type records C_FILE information needed for genasmsym in XCOFF.
type xcoffSymSrcFile struct {
name string
fileSymNb uint32 // Symbol number of this C_FILE
csectSymNb uint64 // Symbol number for the current .csect
csectSize int64
}
var (
currDwscnoff = make(map[string]uint64) // Needed to create C_DWARF symbols
currSymSrcFile xcoffSymSrcFile
)
// writeSymbol writes a symbol or an auxiliary symbol entry on ctxt.out.
func (f *xcoffFile) writeSymbol(out *OutBuf, byteOrder binary.ByteOrder, sym interface{}) {
binary.Write(out, byteOrder, sym)
f.symbolCount++
}
// Write symbols needed when a new file appared :
// - a C_FILE with one auxiliary entry for its name
// - C_DWARF symbols to provide debug information
// - a C_HIDEXT which will be a csect containing all of its functions
// It needs several parameters to create .csect symbols such as its entry point and its section number.
//
// Currently, a new file is in fact a new package. It seems to be OK, but it might change
// in the future.
func (f *xcoffFile) writeSymbolNewFile(ctxt *Link, name string, firstEntry uint64, extnum int16) {
/* C_FILE */
s := &XcoffSymEnt64{
Noffset: uint32(f.stringTable.add(".file")),
Nsclass: C_FILE,
Nscnum: N_DEBUG,
Ntype: 0, // Go isn't inside predefined language.
Nnumaux: 1,
}
f.writeSymbol(ctxt.Out, ctxt.Arch.ByteOrder, s)
// Auxiliary entry for file name.
ctxt.Out.Write32(0)
ctxt.Out.Write32(uint32(f.stringTable.add(name)))
ctxt.Out.Write32(0) // 6 bytes empty
ctxt.Out.Write16(0)
ctxt.Out.Write8(XFT_FN)
ctxt.Out.Write16(0) // 2 bytes empty
ctxt.Out.Write8(_AUX_FILE)
f.symbolCount++
/* Dwarf */
for _, sect := range Segdwarf.Sections {
// Find the size of this corresponding package DWARF compilation unit.
// This size is set during DWARF generation (see dwarf.go).
dwsize := getDwsectCUSize(sect.Name, name)
// .debug_abbrev is commun to all packages and not found with the previous function
if sect.Name == ".debug_abbrev" {
s := ctxt.Syms.Lookup(sect.Name, 0)
dwsize = uint64(s.Size)
}
// get XCOFF name
name, _ := xcoffGetDwarfSubtype(sect.Name)
s := &XcoffSymEnt64{
Nvalue: currDwscnoff[sect.Name],
Noffset: uint32(f.stringTable.add(name)),
Nsclass: C_DWARF,
Nscnum: f.getXCOFFscnum(sect),
Nnumaux: 1,
}
f.writeSymbol(ctxt.Out, ctxt.Arch.ByteOrder, s)
// update the DWARF section offset in this file
if sect.Name != ".debug_abbrev" {
currDwscnoff[sect.Name] += dwsize
}
// Auxiliary dwarf section
ctxt.Out.Write64(dwsize) // section length
ctxt.Out.Write64(0) // nreloc
ctxt.Out.Write8(0) // pad
ctxt.Out.Write8(_AUX_SECT)
f.symbolCount++
}
/* .csect */
// Check if extnum is in text.
// This is temporary and only here to check if this algorithm is correct.
if extnum != 1 {
Exitf("XCOFF symtab: A new file was detected with its first symbol not in .text")
}
currSymSrcFile.csectSymNb = uint64(f.symbolCount)
currSymSrcFile.csectSize = 0
// No offset because no name
s = &XcoffSymEnt64{
Nvalue: firstEntry,
Nscnum: extnum,
Nsclass: C_HIDEXT,
Ntype: 0, // check visibility ?
Nnumaux: 1,
}
f.writeSymbol(ctxt.Out, ctxt.Arch.ByteOrder, s)
aux := &XcoffAuxCSect64{
Xsmclas: XMC_PR,
Xsmtyp: XTY_SD | 5<<3, // align = 5
Xauxtype: _AUX_CSECT,
}
f.writeSymbol(ctxt.Out, ctxt.Arch.ByteOrder, aux)
}
// Update values for the previous package.
// - Svalue of the C_FILE symbol: if it is the last one, this Svalue must be -1
// - Xsclen of the csect symbol.
func (f *xcoffFile) updatePreviousFile(ctxt *Link, last bool) {
// first file
if currSymSrcFile.fileSymNb == 0 {
return
}
prevOff := f.symtabOffset + int64(currSymSrcFile.fileSymNb*SYMESZ)
currOff := ctxt.Out.Offset()
// Update C_FILE
ctxt.Out.SeekSet(prevOff)
if last {
ctxt.Out.Write64(0xFFFFFFFFFFFFFFFF)
} else {
ctxt.Out.Write64(uint64(f.symbolCount))
}
// update csect scnlen in this auxiliary entry
prevOff = f.symtabOffset + int64((currSymSrcFile.csectSymNb+1)*SYMESZ)
ctxt.Out.SeekSet(prevOff)
ctxt.Out.Write32(uint32(currSymSrcFile.csectSize & 0xFFFFFFFF))
prevOff += 12
ctxt.Out.SeekSet(prevOff)
ctxt.Out.Write32(uint32(currSymSrcFile.csectSize >> 32))
ctxt.Out.SeekSet(currOff)
}
// Write symbol representing a .text function.
// The symbol table is split with C_FILE corresponding to each package
// and not to each source file as it should be.
func (f *xcoffFile) writeSymbolFunc(ctxt *Link, x *sym.Symbol) []interface{} {
// New XCOFF symbols which will be written.
syms := []interface{}{}
// Check if a new file is detected.
if x.File == "" { // Undefined global symbol
// If this happens, the algorithme must be redone.
if currSymSrcFile.name != "" {
Exitf("undefined global symbol found inside another file")
}
} else {
// Current file has changed. New C_FILE, C_DWARF, etc must be generated.
if currSymSrcFile.name != x.File {
// update previous file values
xfile.updatePreviousFile(ctxt, false)
currSymSrcFile.name = x.File
currSymSrcFile.fileSymNb = f.symbolCount
f.writeSymbolNewFile(ctxt, x.File, uint64(x.Value), xfile.getXCOFFscnum(x.Sect))
}
}
s := &XcoffSymEnt64{
Nsclass: C_EXT,
Noffset: uint32(xfile.stringTable.add(x.Name)),
Nvalue: uint64(x.Value),
Nscnum: f.getXCOFFscnum(x.Sect),
Ntype: SYM_TYPE_FUNC,
Nnumaux: 2,
}
if x.Version != 0 || x.Attr.VisibilityHidden() || x.Attr.Local() {
s.Nsclass = C_HIDEXT
}
syms = append(syms, s)
// Update current csect size
currSymSrcFile.csectSize += x.Size
// create auxiliary entries
a2 := &XcoffAuxFcn64{
Xfsize: uint32(x.Size),
Xlnnoptr: 0, // TODO
Xendndx: xfile.symbolCount + 3, // this symbol + 2 aux entries
Xauxtype: _AUX_FCN,
}
syms = append(syms, a2)
a4 := &XcoffAuxCSect64{
Xscnlenlo: uint32(currSymSrcFile.csectSymNb & 0xFFFFFFFF),
Xscnlenhi: uint32(currSymSrcFile.csectSymNb >> 32),
Xsmclas: XMC_PR, // Program Code
Xsmtyp: XTY_LD, // label definition (based on C)
Xauxtype: _AUX_CSECT,
}
syms = append(syms, a4)
return syms
}
// put function used by genasmsym to write symbol table
func putaixsym(ctxt *Link, x *sym.Symbol, str string, t SymbolType, addr int64, go_ *sym.Symbol) {
// All XCOFF symbols generated by this GO symbols
// Can be a symbol entry or a auxiliary entry
syms := []interface{}{}
switch t {
default:
return
case TextSym:
if x.FuncInfo != nil {
// Function within a file
syms = xfile.writeSymbolFunc(ctxt, x)
} else {
// Only runtime.text and runtime.etext come through this way
if x.Name != "runtime.text" && x.Name != "runtime.etext" && x.Name != "go.buildid" {
Exitf("putaixsym: unknown text symbol %s", x.Name)
}
s := &XcoffSymEnt64{
Nsclass: C_HIDEXT,
Noffset: uint32(xfile.stringTable.add(str)),
Nvalue: uint64(x.Value),
Nscnum: xfile.getXCOFFscnum(x.Sect),
Ntype: SYM_TYPE_FUNC,
Nnumaux: 1,
}
syms = append(syms, s)
size := uint64(x.Size)
a4 := &XcoffAuxCSect64{
Xauxtype: _AUX_CSECT,
Xscnlenlo: uint32(size & 0xFFFFFFFF),
Xscnlenhi: uint32(size >> 32),
Xsmclas: XMC_PR,
Xsmtyp: XTY_SD,
}
syms = append(syms, a4)
}
case DataSym, BSSSym:
s := &XcoffSymEnt64{
Nsclass: C_EXT,
Noffset: uint32(xfile.stringTable.add(str)),
Nvalue: uint64(x.Value),
Nscnum: xfile.getXCOFFscnum(x.Sect),
Nnumaux: 1,
}
if x.Version != 0 || x.Attr.VisibilityHidden() || x.Attr.Local() {
// There is more symbols in the case of a global data
// which are related to the assembly generated
// to access such symbols.
// But as Golang as its own way to check if a symbol is
// global or local (the capital letter), we don't need to
// implement them yet.
s.Nsclass = C_HIDEXT
}
syms = append(syms, s)
// Create auxiliary entry
// Normally, size should be the size of csect containing all
// the data and bss symbols of one file/package.
// However, it's easier to just have a csect for each symbol.
// It might change
size := uint64(x.Size)
a4 := &XcoffAuxCSect64{
Xauxtype: _AUX_CSECT,
Xscnlenlo: uint32(size & 0xFFFFFFFF),
Xscnlenhi: uint32(size >> 32),
}
// Read only data
if x.Type >= sym.STYPE && x.Type <= sym.SPCLNTAB {
a4.Xsmclas = XMC_RO
} else {
a4.Xsmclas = XMC_RW
}
if t == DataSym {
a4.Xsmtyp |= XTY_SD
} else {
a4.Xsmtyp |= XTY_CM
}
syms = append(syms, a4)
case UndefinedSym:
if x.Type != sym.SDYNIMPORT && x.Type != sym.SHOSTOBJ {
return
}
s := &XcoffSymEnt64{
Nsclass: C_EXT,
Noffset: uint32(xfile.stringTable.add(str)),
Nnumaux: 1,
}
syms = append(syms, s)
a4 := &XcoffAuxCSect64{
Xauxtype: _AUX_CSECT,
Xsmclas: XMC_DS,
Xsmtyp: XTY_ER | XTY_IMP,
}
if x.Name == "__n_pthreads" {
// Currently, all imported symbols made by cgo_import_dynamic are
// syscall functions, except __n_pthreads which is a variable.
// TODO(aix): Find a way to detect variables imported by cgo.
a4.Xsmclas = XMC_RW
}
syms = append(syms, a4)
}
for _, s := range syms {
xfile.writeSymbol(ctxt.Out, ctxt.Arch.ByteOrder, s)
}
}
// Generate XCOFF Symbol table and XCOFF String table
func (f *xcoffFile) asmaixsym(ctxt *Link) {
// write symbol table
genasmsym(ctxt, putaixsym)
// update last file Svalue
xfile.updatePreviousFile(ctxt, true)
// write string table
xfile.stringTable.write(ctxt.Out)
}
func (f *xcoffFile) genDynSym(ctxt *Link) {
var dynsyms []*sym.Symbol
for _, s := range ctxt.Syms.Allsym {
if s.Type != sym.SHOSTOBJ && s.Type != sym.SDYNIMPORT {
continue
}
dynsyms = append(dynsyms, s)
}
for _, s := range dynsyms {
f.adddynimpsym(ctxt, s)
if _, ok := f.dynLibraries[s.Dynimplib()]; !ok {
f.dynLibraries[s.Dynimplib()] = len(f.dynLibraries)
}
}
}
// (*xcoffFile)adddynimpsym adds the dynamic symbol "s" to a XCOFF file.
// A new symbol named s.Extname() is created to be the actual dynamic symbol
// in the .loader section and in the symbol table as an External Reference.
// The symbol "s" is transformed to SXCOFFTOC to end up in .data section.
// However, there is no writing protection on those symbols and
// it might need to be added.
// TODO(aix): Handles dynamic symbols without library.
func (f *xcoffFile) adddynimpsym(ctxt *Link, s *sym.Symbol) {
// Check that library name is given.
// Pattern is already checked when compiling.
if s.Dynimplib() == "" {
Errorf(s, "imported symbol must have a given library")
}
s.Type = sym.SXCOFFTOC
// Create new dynamic symbol
extsym := ctxt.Syms.Lookup(s.Extname(), 0)
extsym.Type = sym.SDYNIMPORT
extsym.Attr |= sym.AttrReachable
extsym.SetDynimplib(s.Dynimplib())
extsym.SetExtname(s.Extname())
extsym.SetDynimpvers(s.Dynimpvers())
// Add loader symbol
lds := &xcoffLoaderSymbol{
sym: extsym,
smtype: XTY_IMP,
smclas: XMC_DS,
}
if s.Name == "__n_pthreads" {
// Currently, all imported symbols made by cgo_import_dynamic are
// syscall functions, except __n_pthreads which is a variable.
// TODO(aix): Find a way to detect variables imported by cgo.
lds.smclas = XMC_RW
}
f.loaderSymbols = append(f.loaderSymbols, lds)
// Relocation to retrieve the external address
s.AddBytes(make([]byte, 8))
s.SetAddr(ctxt.Arch, 0, extsym)
}
// Xcoffadddynrel adds a dynamic relocation in a XCOFF file.
// This relocation will be made by the loader.
func Xcoffadddynrel(ctxt *Link, s *sym.Symbol, r *sym.Reloc) bool {
if s.Type <= sym.SPCLNTAB {
Errorf(s, "cannot have a relocation to %s in a text section symbol", r.Sym.Name)
return false
}
ldr := &xcoffLoaderReloc{
sym: s,
rel: r,
}
switch r.Type {
default:
Errorf(s, "unexpected .loader relocation to symbol: %s (type: %s)", r.Sym.Name, r.Type.String())
return false
case objabi.R_ADDR:
if s.Type == sym.SXCOFFTOC && r.Sym.Type == sym.SDYNIMPORT {
// Imported symbol relocation
for i, dynsym := range xfile.loaderSymbols {
if dynsym.sym.Name == r.Sym.Name {
ldr.symndx = int32(i + 3) // +3 because of 3 section symbols
break
}
}
} else if s.Type == sym.SDATA {
switch r.Sym.Sect.Seg {
default:
Errorf(s, "unknown segment for .loader relocation with symbol %s", r.Sym.Name)
case &Segtext:
case &Segrodata:
ldr.symndx = 0 // .text
case &Segdata:
if r.Sym.Type == sym.SBSS || r.Sym.Type == sym.SNOPTRBSS {
ldr.symndx = 2 // .bss
} else {
ldr.symndx = 1 // .data
}
}
} else {
Errorf(s, "unexpected type for .loader relocation R_ADDR for symbol %s: %s to %s", r.Sym.Name, s.Type, r.Sym.Type)
return false
}
ldr.rtype = 0x3F<<8 + XCOFF_R_POS
}
xfile.loaderReloc = append(xfile.loaderReloc, ldr)
return true
}
func (ctxt *Link) doxcoff() {
if *FlagD {
// All XCOFF files have dynamic symbols because of the syscalls.
Exitf("-d is not available on AIX")
}
// Initial map used to store compilation unit size for each DWARF section (see dwarf.go).
dwsectCUSize = make(map[string]uint64)
// TOC
toc := ctxt.Syms.Lookup("TOC", 0)
toc.Type = sym.SXCOFFTOC
toc.Attr |= sym.AttrReachable
// XCOFF does not allow relocations of data symbol address to a text symbol.
// Such case occurs when a RODATA symbol retrieves a data symbol address.
// When it happens, this RODATA symbol is moved to .data section.
// runtime.algarray is a readonly symbol but stored inside .data section.
// If it stays in .data, all type symbols will be moved to .data which
// cannot be done.
algarray := ctxt.Syms.Lookup("runtime.algarray", 0)
algarray.Type = sym.SRODATA
for {
again := false
for _, s := range ctxt.Syms.Allsym {
if s.Type != sym.SRODATA {
continue
}
for ri := range s.R {
r := &s.R[ri]
if r.Type != objabi.R_ADDR {
continue
}
if r.Sym.Type != sym.Sxxx && r.Sym.Type != sym.STEXT && r.Sym.Type != sym.SRODATA {
s.Type = sym.SDATA
again = true
break
}
}
}
if !again {
break
}
}
// Add entry point to .loader symbols.
ep := ctxt.Syms.ROLookup(*flagEntrySymbol, 0)
if !ep.Attr.Reachable() {
Exitf("wrong entry point")
}
xfile.loaderSymbols = append(xfile.loaderSymbols, &xcoffLoaderSymbol{
sym: ep,
smtype: XTY_ENT | XTY_SD,
smclas: XMC_DS,
})
xfile.genDynSym(ctxt)
for _, s := range ctxt.Syms.Allsym {
if strings.HasPrefix(s.Name, "TOC.") {
s.Type = sym.SXCOFFTOC
}
}
}
// Loader section
// Currently, this section is created from scratch when assembling the XCOFF file
// according to information retrieved in xfile object.
// Create loader section and returns its size
func Loaderblk(ctxt *Link, off uint64) {
xfile.writeLdrScn(ctxt, off)
}
func (f *xcoffFile) writeLdrScn(ctxt *Link, globalOff uint64) {
var symtab []*XcoffLdSym64
var strtab []*XcoffLdStr64
var importtab []*XcoffLdImportFile64
var reloctab []*XcoffLdRel64
var dynimpreloc []*XcoffLdRel64
// As the string table is updated in any loader subsection,
// its length must be computed at the same time.
stlen := uint32(0)
// Loader Header
hdr := &XcoffLdHdr64{
Lversion: 2,
Lsymoff: LDHDRSZ_64,
}
/* Symbol table */
for _, s := range f.loaderSymbols {
lds := &XcoffLdSym64{
Loffset: uint32(stlen + 2),
Lsmtype: s.smtype,
Lsmclas: s.smclas,
}
switch s.smtype {
default:
Errorf(s.sym, "unexpected loader symbol type: 0x%x", s.smtype)
case XTY_ENT | XTY_SD:
lds.Lvalue = uint64(s.sym.Value)
lds.Lscnum = f.getXCOFFscnum(s.sym.Sect)
case XTY_IMP:
lds.Lifile = int32(f.dynLibraries[s.sym.Dynimplib()] + 1)
}
ldstr := &XcoffLdStr64{
size: uint16(len(s.sym.Name) + 1), // + null terminator
name: s.sym.Name,
}
stlen += uint32(2 + ldstr.size) // 2 = sizeof ldstr.size
symtab = append(symtab, lds)
strtab = append(strtab, ldstr)
}
hdr.Lnsyms = int32(len(symtab))
hdr.Lrldoff = hdr.Lsymoff + uint64(24*hdr.Lnsyms) // 24 = sizeof one symbol
off := hdr.Lrldoff // current offset is the same of reloc offset
/* Reloc */
ep := ctxt.Syms.ROLookup(*flagEntrySymbol, 0)
ldr := &XcoffLdRel64{
Lvaddr: uint64(ep.Value),
Lrtype: 0x3F00,
Lrsecnm: f.getXCOFFscnum(ep.Sect),
Lsymndx: 0,
}
off += 16
reloctab = append(reloctab, ldr)
off += uint64(16 * len(f.loaderReloc))
for _, r := range f.loaderReloc {
ldr = &XcoffLdRel64{
Lvaddr: uint64(r.sym.Value + int64(r.rel.Off)),
Lrtype: r.rtype,
Lsymndx: r.symndx,
}
if r.sym.Sect != nil {
ldr.Lrsecnm = f.getXCOFFscnum(r.sym.Sect)
}
reloctab = append(reloctab, ldr)
}
off += uint64(16 * len(dynimpreloc))
reloctab = append(reloctab, dynimpreloc...)
hdr.Lnreloc = int32(len(reloctab))
hdr.Limpoff = off
/* Import */
// Default import: /usr/lib:/lib
ldimpf := &XcoffLdImportFile64{
Limpidpath: "/usr/lib:/lib",
}
off += uint64(len(ldimpf.Limpidpath) + len(ldimpf.Limpidbase) + len(ldimpf.Limpidmem) + 3) // + null delimiter
importtab = append(importtab, ldimpf)
// The map created by adddynimpsym associates the name to a number
// This number represents the librairie index (- 1) in this import files section
// Therefore, they must be sorted before being put inside the section
libsOrdered := make([]string, len(f.dynLibraries))
for key, val := range f.dynLibraries {
if libsOrdered[val] != "" {
continue
}
libsOrdered[val] = key
}
for _, lib := range libsOrdered {
// lib string is defined as base.a/mem.o or path/base.a/mem.o
n := strings.Split(lib, "/")
path := ""
base := n[len(n)-2]
mem := n[len(n)-1]
if len(n) > 2 {
path = lib[:len(lib)-len(base)-len(mem)-2]
}
ldimpf = &XcoffLdImportFile64{
Limpidpath: path,
Limpidbase: base,
Limpidmem: mem,
}
off += uint64(len(ldimpf.Limpidpath) + len(ldimpf.Limpidbase) + len(ldimpf.Limpidmem) + 3) // + null delimiter
importtab = append(importtab, ldimpf)
}
hdr.Lnimpid = int32(len(importtab))
hdr.Listlen = uint32(off - hdr.Limpoff)
hdr.Lstoff = off
hdr.Lstlen = stlen
/* Writing */
ctxt.Out.SeekSet(int64(globalOff))
binary.Write(ctxt.Out, ctxt.Arch.ByteOrder, hdr)
for _, s := range symtab {
binary.Write(ctxt.Out, ctxt.Arch.ByteOrder, s)
}
for _, r := range reloctab {
binary.Write(ctxt.Out, ctxt.Arch.ByteOrder, r)
}
for _, f := range importtab {
ctxt.Out.WriteString(f.Limpidpath)
ctxt.Out.Write8(0)
ctxt.Out.WriteString(f.Limpidbase)
ctxt.Out.Write8(0)
ctxt.Out.WriteString(f.Limpidmem)
ctxt.Out.Write8(0)
}
for _, s := range strtab {
ctxt.Out.Write16(s.size)
ctxt.Out.WriteString(s.name)
ctxt.Out.Write8(0) // null terminator
}
f.loaderSize = off + uint64(stlen)
ctxt.Out.Flush()
/* again for printing */
if !*flagA {
return
}
ctxt.Logf("\n.loader section")
// write in buf
var buf bytes.Buffer
binary.Write(&buf, ctxt.Arch.ByteOrder, hdr)
for _, s := range symtab {
binary.Write(&buf, ctxt.Arch.ByteOrder, s)
}
for _, f := range importtab {
buf.WriteString(f.Limpidpath)
buf.WriteByte(0)
buf.WriteString(f.Limpidbase)
buf.WriteByte(0)
buf.WriteString(f.Limpidmem)
buf.WriteByte(0)
}
for _, s := range strtab {
binary.Write(&buf, ctxt.Arch.ByteOrder, s.size)
buf.WriteString(s.name)
buf.WriteByte(0) // null terminator
}
// Log buffer
ctxt.Logf("\n\t%.8x|", globalOff)
for i, b := range buf.Bytes() {
if i > 0 && i%16 == 0 {
ctxt.Logf("\n\t%.8x|", uint64(globalOff)+uint64(i))
}
ctxt.Logf(" %.2x", b)
}
ctxt.Logf("\n")
}
// XCOFF assembling and writing file
func (f *xcoffFile) writeFileHeader(ctxt *Link) {
// File header
f.xfhdr.Fmagic = U64_TOCMAGIC
f.xfhdr.Fnscns = uint16(len(f.sections))
f.xfhdr.Ftimedat = 0
if !*FlagS {
f.xfhdr.Fsymptr = uint64(f.symtabOffset)
f.xfhdr.Fnsyms = int32(f.symbolCount)
}
if ctxt.BuildMode == BuildModeExe {
f.xfhdr.Fopthdr = AOUTHSZ_EXEC64
f.xfhdr.Fflags = F_EXEC
// auxiliary header
f.xahdr.Ovstamp = 1 // based on dump -o
f.xahdr.Omagic = 0x10b
copy(f.xahdr.Omodtype[:], "1L")
entry := ctxt.Syms.ROLookup(*flagEntrySymbol, 0)
f.xahdr.Oentry = uint64(entry.Value)
f.xahdr.Osnentry = f.getXCOFFscnum(entry.Sect)
toc := ctxt.Syms.ROLookup("TOC", 0)
f.xahdr.Otoc = uint64(toc.Value)
f.xahdr.Osntoc = f.getXCOFFscnum(toc.Sect)
// Based on dump -o
f.xahdr.Oalgntext = 0x5
f.xahdr.Oalgndata = 0x5
binary.Write(ctxt.Out, binary.BigEndian, &f.xfhdr)
binary.Write(ctxt.Out, binary.BigEndian, &f.xahdr)
} else {
f.xfhdr.Fopthdr = 0
binary.Write(ctxt.Out, binary.BigEndian, &f.xfhdr)
}
}
func xcoffwrite(ctxt *Link) {
ctxt.Out.SeekSet(0)
xfile.writeFileHeader(ctxt)
for _, sect := range xfile.sections {
sect.write(ctxt)
}
}
// Generate XCOFF assembly file
func Asmbxcoff(ctxt *Link, fileoff int64) {
xfile.sectNameToScnum = make(map[string]int16)
// Add sections
s := xfile.addSection(".text", Segtext.Vaddr, Segtext.Length, Segtext.Fileoff, STYP_TEXT)
xfile.xahdr.Otextstart = s.Svaddr
xfile.xahdr.Osntext = xfile.sectNameToScnum[".text"]
xfile.xahdr.Otsize = s.Ssize
s = xfile.addSection(".data", Segdata.Vaddr, Segdata.Filelen, Segdata.Fileoff, STYP_DATA)
xfile.xahdr.Odatastart = s.Svaddr
xfile.xahdr.Osndata = xfile.sectNameToScnum[".data"]
xfile.xahdr.Odsize = s.Ssize
s = xfile.addSection(".bss", Segdata.Vaddr+Segdata.Filelen, Segdata.Length-Segdata.Filelen, 0, STYP_BSS)
xfile.xahdr.Osnbss = xfile.sectNameToScnum[".bss"]
xfile.xahdr.Obsize = s.Ssize
// add dwarf sections
for _, sect := range Segdwarf.Sections {
xfile.addDwarfSection(sect)
}
// add and write remaining sections
if ctxt.LinkMode == LinkInternal {
// Loader section
if ctxt.BuildMode == BuildModeExe {
Loaderblk(ctxt, uint64(fileoff))
s = xfile.addSection(".loader", 0, xfile.loaderSize, uint64(fileoff), STYP_LOADER)
xfile.xahdr.Osnloader = xfile.sectNameToScnum[".loader"]
}
} else {
// TODO: Relocation
}
// Write symbol table
symo := Rnd(ctxt.Out.Offset(), int64(*FlagRound))
xfile.symtabOffset = symo
ctxt.Out.SeekSet(int64(symo))
xfile.asmaixsym(ctxt)
// write headers
xcoffwrite(ctxt)
}