func writeinfo(ctxt *Link, syms []*Symbol, funcs []*Symbol) []*Symbol {
if infosec == nil {
infosec = Linklookup(ctxt, ".debug_info", 0)
}
infosec.R = infosec.R[:0]
infosec.Type = obj.SDWARFINFO
infosec.Attr |= AttrReachable
syms = append(syms, infosec)
if arangessec == nil {
arangessec = Linklookup(ctxt, ".dwarfaranges", 0)
}
arangessec.R = arangessec.R[:0]
var dwarfctxt dwarf.Context = dwctxt{ctxt}
for compunit := dwroot.Child; compunit != nil; compunit = compunit.Link {
s := dtolsym(compunit.Sym)
// Write .debug_info Compilation Unit Header (sec 7.5.1)
// Fields marked with (*) must be changed for 64-bit dwarf
// This must match COMPUNITHEADERSIZE above.
Adduint32(ctxt, s, 0) // unit_length (*), will be filled in later.
Adduint16(ctxt, s, 2) // dwarf version (appendix F)
// debug_abbrev_offset (*)
adddwarfref(ctxt, s, abbrevsym, 4)
Adduint8(ctxt, s, uint8(SysArch.PtrSize)) // address_size
dwarf.Uleb128put(dwarfctxt, s, int64(compunit.Abbrev))
dwarf.PutAttrs(dwarfctxt, s, compunit.Abbrev, compunit.Attr)
cu := []*Symbol{s}
if funcs != nil {
cu = append(cu, funcs...)
funcs = nil
}
cu = putdies(ctxt, dwarfctxt, cu, compunit.Child)
var cusize int64
for _, child := range cu {
cusize += child.Size
}
cusize -= 4 // exclude the length field.
setuint32(ctxt, s, 0, uint32(cusize))
newattr(compunit, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, cusize, 0)
syms = append(syms, cu...)
}
return syms
}
func putdie(linkctxt *Link, ctxt dwarf.Context, syms []*Symbol, die *dwarf.DWDie) []*Symbol {
s := dtolsym(die.Sym)
if s == nil {
s = syms[len(syms)-1]
} else {
if s.Attr.OnList() {
log.Fatalf("symbol %s listed multiple times", s.Name)
}
s.Attr |= AttrOnList
syms = append(syms, s)
}
dwarf.Uleb128put(ctxt, s, int64(die.Abbrev))
dwarf.PutAttrs(ctxt, s, die.Abbrev, die.Attr)
if dwarf.HasChildren(die) {
return putdies(linkctxt, ctxt, syms, die.Child)
}
return syms
}
func writelines(ctxt *Link, syms []*Symbol) ([]*Symbol, []*Symbol) {
var dwarfctxt dwarf.Context = dwctxt{ctxt}
if linesec == nil {
linesec = Linklookup(ctxt, ".debug_line", 0)
}
linesec.Type = obj.SDWARFSECT
linesec.R = linesec.R[:0]
ls := linesec
syms = append(syms, ls)
var funcs []*Symbol
unitstart := int64(-1)
headerstart := int64(-1)
headerend := int64(-1)
epc := int64(0)
var epcs *Symbol
var dwinfo *dwarf.DWDie
lang := dwarf.DW_LANG_Go
s := ctxt.Textp[0]
dwinfo = newdie(ctxt, &dwroot, dwarf.DW_ABRV_COMPUNIT, "go", 0)
newattr(dwinfo, dwarf.DW_AT_language, dwarf.DW_CLS_CONSTANT, int64(lang), 0)
newattr(dwinfo, dwarf.DW_AT_stmt_list, dwarf.DW_CLS_PTR, 0, linesec)
newattr(dwinfo, dwarf.DW_AT_low_pc, dwarf.DW_CLS_ADDRESS, s.Value, s)
// OS X linker requires compilation dir or absolute path in comp unit name to output debug info.
compDir := getCompilationDir()
newattr(dwinfo, dwarf.DW_AT_comp_dir, dwarf.DW_CLS_STRING, int64(len(compDir)), compDir)
// Write .debug_line Line Number Program Header (sec 6.2.4)
// Fields marked with (*) must be changed for 64-bit dwarf
unit_length_offset := ls.Size
Adduint32(ctxt, ls, 0) // unit_length (*), filled in at end.
unitstart = ls.Size
Adduint16(ctxt, ls, 2) // dwarf version (appendix F)
header_length_offset := ls.Size
Adduint32(ctxt, ls, 0) // header_length (*), filled in at end.
headerstart = ls.Size
// cpos == unitstart + 4 + 2 + 4
Adduint8(ctxt, ls, 1) // minimum_instruction_length
Adduint8(ctxt, ls, 1) // default_is_stmt
Adduint8(ctxt, ls, LINE_BASE&0xFF) // line_base
Adduint8(ctxt, ls, LINE_RANGE) // line_range
Adduint8(ctxt, ls, OPCODE_BASE) // opcode_base
Adduint8(ctxt, ls, 0) // standard_opcode_lengths[1]
Adduint8(ctxt, ls, 1) // standard_opcode_lengths[2]
Adduint8(ctxt, ls, 1) // standard_opcode_lengths[3]
Adduint8(ctxt, ls, 1) // standard_opcode_lengths[4]
Adduint8(ctxt, ls, 1) // standard_opcode_lengths[5]
Adduint8(ctxt, ls, 0) // standard_opcode_lengths[6]
Adduint8(ctxt, ls, 0) // standard_opcode_lengths[7]
Adduint8(ctxt, ls, 0) // standard_opcode_lengths[8]
Adduint8(ctxt, ls, 1) // standard_opcode_lengths[9]
Adduint8(ctxt, ls, 0) // include_directories (empty)
for _, f := range ctxt.Filesyms {
Addstring(ctxt, ls, f.Name)
Adduint8(ctxt, ls, 0)
Adduint8(ctxt, ls, 0)
Adduint8(ctxt, ls, 0)
}
// 4 zeros: the string termination + 3 fields.
Adduint8(ctxt, ls, 0)
// terminate file_names.
headerend = ls.Size
Adduint8(ctxt, ls, 0) // start extended opcode
dwarf.Uleb128put(dwarfctxt, ls, 1+int64(SysArch.PtrSize))
Adduint8(ctxt, ls, dwarf.DW_LNE_set_address)
pc := s.Value
line := 1
file := 1
Addaddr(ctxt, ls, s)
var pcfile Pciter
var pcline Pciter
for _, ctxt.Cursym = range ctxt.Textp {
s := ctxt.Cursym
epc = s.Value + s.Size
epcs = s
dsym := Linklookup(ctxt, dwarf.InfoPrefix+s.Name, int(s.Version))
dsym.Attr |= AttrHidden
dsym.Type = obj.SDWARFINFO
for _, r := range dsym.R {
if r.Type == obj.R_DWARFREF && r.Sym.Size == 0 {
if Buildmode == BuildmodeShared {
// These type symbols may not be present in BuildmodeShared. Skip.
continue
}
n := nameFromDIESym(r.Sym)
defgotype(ctxt, Linklookup(ctxt, "type."+n, 0))
}
}
funcs = append(funcs, dsym)
if s.FuncInfo == nil {
continue
}
finddebugruntimepath(s)
pciterinit(ctxt, &pcfile, &s.FuncInfo.Pcfile)
pciterinit(ctxt, &pcline, &s.FuncInfo.Pcline)
epc = pc
for pcfile.done == 0 && pcline.done == 0 {
if epc-s.Value >= int64(pcfile.nextpc) {
pciternext(&pcfile)
continue
}
if epc-s.Value >= int64(pcline.nextpc) {
pciternext(&pcline)
continue
}
if int32(file) != pcfile.value {
Adduint8(ctxt, ls, dwarf.DW_LNS_set_file)
dwarf.Uleb128put(dwarfctxt, ls, int64(pcfile.value))
file = int(pcfile.value)
}
putpclcdelta(ctxt, dwarfctxt, ls, s.Value+int64(pcline.pc)-pc, int64(pcline.value)-int64(line))
pc = s.Value + int64(pcline.pc)
line = int(pcline.value)
if pcfile.nextpc < pcline.nextpc {
epc = int64(pcfile.nextpc)
} else {
epc = int64(pcline.nextpc)
}
epc += s.Value
}
}
Adduint8(ctxt, ls, 0) // start extended opcode
dwarf.Uleb128put(dwarfctxt, ls, 1)
Adduint8(ctxt, ls, dwarf.DW_LNE_end_sequence)
newattr(dwinfo, dwarf.DW_AT_high_pc, dwarf.DW_CLS_ADDRESS, epc+1, epcs)
setuint32(ctxt, ls, unit_length_offset, uint32(ls.Size-unitstart))
setuint32(ctxt, ls, header_length_offset, uint32(headerend-headerstart))
return syms, funcs
}
func writeframes(ctxt *Link, syms []*Symbol) []*Symbol {
var dwarfctxt dwarf.Context = dwctxt{ctxt}
if framesec == nil {
framesec = Linklookup(ctxt, ".debug_frame", 0)
}
framesec.Type = obj.SDWARFSECT
framesec.R = framesec.R[:0]
fs := framesec
syms = append(syms, fs)
// Emit the CIE, Section 6.4.1
cieReserve := uint32(16)
if haslinkregister(ctxt) {
cieReserve = 32
}
Adduint32(ctxt, fs, cieReserve) // initial length, must be multiple of thearch.ptrsize
Adduint32(ctxt, fs, 0xffffffff) // cid.
Adduint8(ctxt, fs, 3) // dwarf version (appendix F)
Adduint8(ctxt, fs, 0) // augmentation ""
dwarf.Uleb128put(dwarfctxt, fs, 1) // code_alignment_factor
dwarf.Sleb128put(dwarfctxt, fs, dataAlignmentFactor) // all CFI offset calculations include multiplication with this factor
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfreglr)) // return_address_register
Adduint8(ctxt, fs, dwarf.DW_CFA_def_cfa) // Set the current frame address..
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfregsp)) // ...to use the value in the platform's SP register (defined in l.go)...
if haslinkregister(ctxt) {
dwarf.Uleb128put(dwarfctxt, fs, int64(0)) // ...plus a 0 offset.
Adduint8(ctxt, fs, dwarf.DW_CFA_same_value) // The platform's link register is unchanged during the prologue.
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfreglr))
Adduint8(ctxt, fs, dwarf.DW_CFA_val_offset) // The previous value...
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfregsp)) // ...of the platform's SP register...
dwarf.Uleb128put(dwarfctxt, fs, int64(0)) // ...is CFA+0.
} else {
dwarf.Uleb128put(dwarfctxt, fs, int64(SysArch.PtrSize)) // ...plus the word size (because the call instruction implicitly adds one word to the frame).
Adduint8(ctxt, fs, dwarf.DW_CFA_offset_extended) // The previous value...
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfreglr)) // ...of the return address...
dwarf.Uleb128put(dwarfctxt, fs, int64(-SysArch.PtrSize)/dataAlignmentFactor) // ...is saved at [CFA - (PtrSize/4)].
}
// 4 is to exclude the length field.
pad := int64(cieReserve) + 4 - fs.Size
if pad < 0 {
Exitf("dwarf: cieReserve too small by %d bytes.", -pad)
}
Addbytes(ctxt, fs, zeros[:pad])
var deltaBuf []byte
var pcsp Pciter
for _, ctxt.Cursym = range ctxt.Textp {
s := ctxt.Cursym
if s.FuncInfo == nil {
continue
}
// Emit a FDE, Section 6.4.1.
// First build the section contents into a byte buffer.
deltaBuf = deltaBuf[:0]
for pciterinit(ctxt, &pcsp, &s.FuncInfo.Pcsp); pcsp.done == 0; pciternext(&pcsp) {
nextpc := pcsp.nextpc
// pciterinit goes up to the end of the function,
// but DWARF expects us to stop just before the end.
if int64(nextpc) == s.Size {
nextpc--
if nextpc < pcsp.pc {
continue
}
}
if haslinkregister(ctxt) {
// TODO(bryanpkc): This is imprecise. In general, the instruction
// that stores the return address to the stack frame is not the
// same one that allocates the frame.
if pcsp.value > 0 {
// The return address is preserved at (CFA-frame_size)
// after a stack frame has been allocated.
deltaBuf = append(deltaBuf, dwarf.DW_CFA_offset_extended_sf)
deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(Thearch.Dwarfreglr))
deltaBuf = dwarf.AppendSleb128(deltaBuf, -int64(pcsp.value)/dataAlignmentFactor)
} else {
// The return address is restored into the link register
// when a stack frame has been de-allocated.
deltaBuf = append(deltaBuf, dwarf.DW_CFA_same_value)
deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(Thearch.Dwarfreglr))
}
deltaBuf = appendPCDeltaCFA(deltaBuf, int64(nextpc)-int64(pcsp.pc), int64(pcsp.value))
} else {
deltaBuf = appendPCDeltaCFA(deltaBuf, int64(nextpc)-int64(pcsp.pc), int64(SysArch.PtrSize)+int64(pcsp.value))
}
}
pad := int(Rnd(int64(len(deltaBuf)), int64(SysArch.PtrSize))) - len(deltaBuf)
deltaBuf = append(deltaBuf, zeros[:pad]...)
// Emit the FDE header, Section 6.4.1.
// 4 bytes: length, must be multiple of thearch.ptrsize
// 4 bytes: Pointer to the CIE above, at offset 0
// ptrsize: initial location
// ptrsize: address range
Adduint32(ctxt, fs, uint32(4+2*SysArch.PtrSize+len(deltaBuf))) // length (excludes itself)
if Linkmode == LinkExternal {
adddwarfref(ctxt, fs, framesec, 4)
} else {
Adduint32(ctxt, fs, 0) // CIE offset
}
Addaddr(ctxt, fs, s)
adduintxx(ctxt, fs, uint64(s.Size), SysArch.PtrSize) // address range
Addbytes(ctxt, fs, deltaBuf)
}
return syms
}
func putpclcdelta(linkctxt *Link, ctxt dwarf.Context, s *Symbol, deltaPC uint64, deltaLC int64) {
// Choose a special opcode that minimizes the number of bytes needed to
// encode the remaining PC delta and LC delta.
var opcode int64
if deltaLC < LINE_BASE {
if deltaPC >= PC_RANGE {
opcode = OPCODE_BASE + (LINE_RANGE * PC_RANGE)
} else {
opcode = OPCODE_BASE + (LINE_RANGE * int64(deltaPC))
}
} else if deltaLC < LINE_BASE+LINE_RANGE {
if deltaPC >= PC_RANGE {
opcode = OPCODE_BASE + (deltaLC - LINE_BASE) + (LINE_RANGE * PC_RANGE)
if opcode > 255 {
opcode -= LINE_RANGE
}
} else {
opcode = OPCODE_BASE + (deltaLC - LINE_BASE) + (LINE_RANGE * int64(deltaPC))
}
} else {
if deltaPC <= PC_RANGE {
opcode = OPCODE_BASE + (LINE_RANGE - 1) + (LINE_RANGE * int64(deltaPC))
if opcode > 255 {
opcode = 255
}
} else {
// Use opcode 249 (pc+=23, lc+=5) or 255 (pc+=24, lc+=1).
//
// Let x=deltaPC-PC_RANGE. If we use opcode 255, x will be the remaining
// deltaPC that we need to encode separately before emitting 255. If we
// use opcode 249, we will need to encode x+1. If x+1 takes one more
// byte to encode than x, then we use opcode 255.
//
// In all other cases x and x+1 take the same number of bytes to encode,
// so we use opcode 249, which may save us a byte in encoding deltaLC,
// for similar reasons.
switch deltaPC - PC_RANGE {
// PC_RANGE is the largest deltaPC we can encode in one byte, using
// DW_LNS_const_add_pc.
//
// (1<<16)-1 is the largest deltaPC we can encode in three bytes, using
// DW_LNS_fixed_advance_pc.
//
// (1<<(7n))-1 is the largest deltaPC we can encode in n+1 bytes for
// n=1,3,4,5,..., using DW_LNS_advance_pc.
case PC_RANGE, (1 << 7) - 1, (1 << 16) - 1, (1 << 21) - 1, (1 << 28) - 1,
(1 << 35) - 1, (1 << 42) - 1, (1 << 49) - 1, (1 << 56) - 1, (1 << 63) - 1:
opcode = 255
default:
opcode = OPCODE_BASE + LINE_RANGE*PC_RANGE - 1 // 249
}
}
}
if opcode < OPCODE_BASE || opcode > 255 {
panic(fmt.Sprintf("produced invalid special opcode %d", opcode))
}
// Subtract from deltaPC and deltaLC the amounts that the opcode will add.
deltaPC -= uint64((opcode - OPCODE_BASE) / LINE_RANGE)
deltaLC -= int64((opcode-OPCODE_BASE)%LINE_RANGE + LINE_BASE)
// Encode deltaPC.
if deltaPC != 0 {
if deltaPC <= PC_RANGE {
// Adjust the opcode so that we can use the 1-byte DW_LNS_const_add_pc
// instruction.
opcode -= LINE_RANGE * int64(PC_RANGE-deltaPC)
if opcode < OPCODE_BASE {
panic(fmt.Sprintf("produced invalid special opcode %d", opcode))
}
Adduint8(linkctxt, s, dwarf.DW_LNS_const_add_pc)
} else if (1<<14) <= deltaPC && deltaPC < (1<<16) {
Adduint8(linkctxt, s, dwarf.DW_LNS_fixed_advance_pc)
Adduint16(linkctxt, s, uint16(deltaPC))
} else {
Adduint8(linkctxt, s, dwarf.DW_LNS_advance_pc)
dwarf.Uleb128put(ctxt, s, int64(deltaPC))
}
}
// Encode deltaLC.
if deltaLC != 0 {
Adduint8(linkctxt, s, dwarf.DW_LNS_advance_line)
dwarf.Sleb128put(ctxt, s, deltaLC)
}
// Output the special opcode.
Adduint8(linkctxt, s, uint8(opcode))
}