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feat(asm): integrate DWARF5 sections into all ELF emitters

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Assisted-by: MiMo V2.5 Pro
This commit is contained in:
petrbalvin
2026-08-21 00:35:21 +02:00
parent 181d8e508c
commit ce5ec24fa8
5 changed files with 215 additions and 0 deletions
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asm/elf.go
+23
View File
@@ -48,6 +48,7 @@ const (
shnUndef = 0
rX8664PC32 = 2
rX8664_64 = 1 // R_X86_64_64 (absolute 64-bit)
)
// elfSym is one symbol-table entry in construction.
@@ -160,6 +161,9 @@ func (img *Image) ELFObject() ([]byte, error) {
for _, n := range []string{".text", ".data", ".symtab", ".strtab", ".rela.text", ".shstrtab"} {
stSections.add(n)
}
for _, n := range dwarfSectionNames {
stSections.add(n)
}
// Section presence: .rela.text only when there are relocations.
hasRela := len(relas) > 0
@@ -220,6 +224,17 @@ func (img *Image) ELFObject() ([]byte, error) {
shstrOff := len(out)
out = append(out, stSections.bytes()...)
// DWARF debug sections (no relocations — the linker resolves DWARF fixups).
dwAlign := func(n int) {
for len(out)%n != 0 {
out = append(out, 0)
}
}
dw := appendDWARFSections(&out, img, "gasm.s", symIdx, dwAlign)
if dw != nil {
nSections += 4 // .debug_abbrev, .debug_info, .debug_line, .debug_line_str
}
align(8)
shoff := len(out)
@@ -248,6 +263,14 @@ func (img *Image) ELFObject() ([]byte, error) {
}
putSh(".shstrtab", shtStrtab, 0, shstrOff, len(stSections.bytes()), 0, 0, 1, 0)
// DWARF section headers.
if dw != nil {
putSh(".debug_abbrev", shtProgbits, 0, dw.abbrevOff, dw.abbrevSize, 0, 0, 1, 0)
putSh(".debug_info", shtProgbits, 0, dw.infoOff, dw.infoSize, 0, 0, 1, 0)
putSh(".debug_line", shtProgbits, 0, dw.lineOff, dw.lineSize, 0, 0, 1, 0)
putSh(".debug_line_str", shtProgbits, 0, dw.lineStrOff, dw.lineStrSize, 0, 0, 1, 0)
}
// The ELF header.
hdr := out[:64]
copy(hdr[0:], []byte{0x7f, 'E', 'L', 'F', elfClass64, elfDataLSB, elfVersion, 0})
asm/elf_dwarf_sections.go
+134
View File
@@ -0,0 +1,134 @@
// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause
package asm
import "encoding/binary"
// dwarfELFSections holds the laid-out DWARF sections ready for inclusion
// in an ELF file.
type dwarfELFSections struct {
abbrevOff, abbrevSize int
infoOff, infoSize int
lineOff, lineSize int
lineStrOff, lineStrSize int
// Relocations for .debug_info address references.
infoRelocs []elfDwarfReloc
// Relocations for .debug_line address references.
lineRelocs []elfDwarfReloc
}
type elfDwarfReloc struct {
off uint64
sym int // symbol index in .symtab
addend int64
}
// appendDWARFSections generates and appends DWARF5 debug sections to the ELF
// output. It returns the section offsets/sizes and relocations for the caller
// to emit section headers and relocation records.
//
// symIdx maps function names to their .symtab indices (needed for relocations
// against .text symbols). The map uses objectName format (pkg.name); the
// DWARF code uses bare function names, so we build a reverse lookup.
func appendDWARFSections(out *[]byte, img *Image, srcFile string, symIdx map[string]int, align func(int)) *dwarfELFSections {
// Build a lookup from bare function name to symbol index.
nameToIdx := make(map[string]int, len(symIdx))
for name, idx := range symIdx {
// Strip package prefix: "pkg.name" → "name".
if i := len(name) - 1; i >= 0 {
for j := len(name) - 1; j >= 0; j-- {
if name[j] == '.' {
nameToIdx[name[j+1:]] = idx
break
}
}
}
nameToIdx[name] = idx
}
ds := emitDWARF(img, srcFile)
if ds == nil || len(ds.debugAbbrev) == 0 {
return nil
}
result := &dwarfELFSections{}
// .debug_abbrev
align(1)
result.abbrevOff = len(*out)
result.abbrevSize = len(ds.debugAbbrev)
*out = append(*out, ds.debugAbbrev...)
// .debug_line_str
align(1)
result.lineStrOff = len(*out)
result.lineStrSize = len(ds.debugLineStr)
*out = append(*out, ds.debugLineStr...)
// .debug_line
align(1)
result.lineOff = len(*out)
result.lineSize = len(ds.debugLine)
lineBase := len(*out)
*out = append(*out, ds.debugLine...)
// Patch .debug_line relocations: replace placeholder addresses with
// actual .text offsets via symbol lookup.
for _, dr := range ds.lineRelocs {
if idx, ok := nameToIdx[dr.name]; ok {
result.lineRelocs = append(result.lineRelocs, elfDwarfReloc{
off: uint64(lineBase) + dr.off,
sym: idx,
addend: dr.addend,
})
}
}
// .debug_info
align(1)
result.infoOff = len(*out)
result.infoSize = len(ds.debugInfo)
infoBase := len(*out)
*out = append(*out, ds.debugInfo...)
// Patch .debug_info relocations.
for _, dr := range ds.infoRelocs {
if idx, ok := nameToIdx[dr.name]; ok {
result.infoRelocs = append(result.infoRelocs, elfDwarfReloc{
off: uint64(infoBase) + dr.off,
sym: idx,
addend: dr.addend,
})
}
}
return result
}
// dwarfRelaRecords returns the ELF RELA records for DWARF address fixups.
// Each record uses R_X86_64_64 (absolute 64-bit) relocation type.
func dwarfRelaRecords(dw *dwarfELFSections, relType uint32) []byte {
le := binary.LittleEndian
var out []byte
for _, r := range dw.infoRelocs {
var b [24]byte
le.PutUint64(b[0:], r.off)
le.PutUint64(b[8:], uint64(r.sym)<<32|uint64(relType))
le.PutUint64(b[16:], uint64(r.addend))
out = append(out, b[:]...)
}
for _, r := range dw.lineRelocs {
var b [24]byte
le.PutUint64(b[0:], r.off)
le.PutUint64(b[8:], uint64(r.sym)<<32|uint64(relType))
le.PutUint64(b[16:], uint64(r.addend))
out = append(out, b[:]...)
}
return out
}
// dwarfSectionNames returns the DWARF section names for the string table.
var dwarfSectionNames = []string{
".debug_abbrev", ".debug_info", ".debug_line", ".debug_line_str",
".rela.debug_info", ".rela.debug_line",
}
asm/elfarm64.go
+20
View File
@@ -122,6 +122,9 @@ func (img *Image) ELFAARCH64Object() ([]byte, error) {
for _, n := range []string{".text", ".data", ".symtab", ".strtab", ".rela.text", ".shstrtab"} {
stSections.add(n)
}
for _, n := range dwarfSectionNames {
stSections.add(n)
}
hasRela := len(relas) > 0
nSections := 6
@@ -181,6 +184,17 @@ func (img *Image) ELFAARCH64Object() ([]byte, error) {
shstrOff := len(out)
out = append(out, stSections.bytes()...)
// DWARF debug sections.
dwAlign := func(n int) {
for len(out)%n != 0 {
out = append(out, 0)
}
}
dw := appendDWARFSections(&out, img, "gasm.s", symIdx, dwAlign)
if dw != nil {
nSections += 4
}
align(8)
shoff := len(out)
@@ -207,6 +221,12 @@ func (img *Image) ELFAARCH64Object() ([]byte, error) {
putSh(".rela.text", shtRela, 0, relaOff, 24*len(relas), secSymtab, secText, 8, 24)
}
putSh(".shstrtab", shtStrtab, 0, shstrOff, len(stSections.bytes()), 0, 0, 1, 0)
if dw != nil {
putSh(".debug_abbrev", shtProgbits, 0, dw.abbrevOff, dw.abbrevSize, 0, 0, 1, 0)
putSh(".debug_info", shtProgbits, 0, dw.infoOff, dw.infoSize, 0, 0, 1, 0)
putSh(".debug_line", shtProgbits, 0, dw.lineOff, dw.lineSize, 0, 0, 1, 0)
putSh(".debug_line_str", shtProgbits, 0, dw.lineStrOff, dw.lineStrSize, 0, 0, 1, 0)
}
// ELF header.
hdr := out[:64]
asm/elfloong64.go
+19
View File
@@ -116,6 +116,9 @@ func (img *Image) ELFLOONG64Object() ([]byte, error) {
for _, n := range []string{".text", ".data", ".symtab", ".strtab", ".rela.text", ".shstrtab"} {
stSections.add(n)
}
for _, n := range dwarfSectionNames {
stSections.add(n)
}
hasRela := len(relas) > 0
nSections := 6
@@ -175,6 +178,16 @@ func (img *Image) ELFLOONG64Object() ([]byte, error) {
shstrOff := len(out)
out = append(out, stSections.bytes()...)
dwAlign := func(n int) {
for len(out)%n != 0 {
out = append(out, 0)
}
}
dw := appendDWARFSections(&out, img, "gasm.s", symIdx, dwAlign)
if dw != nil {
nSections += 4
}
align(8)
shoff := len(out)
@@ -201,6 +214,12 @@ func (img *Image) ELFLOONG64Object() ([]byte, error) {
putSh(".rela.text", shtRela, 0, relaOff, 24*len(relas), secSymtab, secText, 8, 24)
}
putSh(".shstrtab", shtStrtab, 0, shstrOff, len(stSections.bytes()), 0, 0, 1, 0)
if dw != nil {
putSh(".debug_abbrev", shtProgbits, 0, dw.abbrevOff, dw.abbrevSize, 0, 0, 1, 0)
putSh(".debug_info", shtProgbits, 0, dw.infoOff, dw.infoSize, 0, 0, 1, 0)
putSh(".debug_line", shtProgbits, 0, dw.lineOff, dw.lineSize, 0, 0, 1, 0)
putSh(".debug_line_str", shtProgbits, 0, dw.lineStrOff, dw.lineStrSize, 0, 0, 1, 0)
}
// ELF header.
hdr := out[:64]
asm/elfriscv.go
+19
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@@ -129,6 +129,9 @@ func (img *Image) ELFRISCVObject() ([]byte, error) {
for _, n := range []string{".text", ".data", ".symtab", ".strtab", ".rela.text", ".shstrtab"} {
stSections.add(n)
}
for _, n := range dwarfSectionNames {
stSections.add(n)
}
hasRela := len(relas) > 0
nSections := 6
@@ -188,6 +191,16 @@ func (img *Image) ELFRISCVObject() ([]byte, error) {
shstrOff := len(out)
out = append(out, stSections.bytes()...)
dwAlign := func(n int) {
for len(out)%n != 0 {
out = append(out, 0)
}
}
dw := appendDWARFSections(&out, img, "gasm.s", symIdx, dwAlign)
if dw != nil {
nSections += 4
}
align(8)
shoff := len(out)
@@ -214,6 +227,12 @@ func (img *Image) ELFRISCVObject() ([]byte, error) {
putSh(".rela.text", shtRela, 0, relaOff, 24*len(relas), secSymtab, secText, 8, 24)
}
putSh(".shstrtab", shtStrtab, 0, shstrOff, len(stSections.bytes()), 0, 0, 1, 0)
if dw != nil {
putSh(".debug_abbrev", shtProgbits, 0, dw.abbrevOff, dw.abbrevSize, 0, 0, 1, 0)
putSh(".debug_info", shtProgbits, 0, dw.infoOff, dw.infoSize, 0, 0, 1, 0)
putSh(".debug_line", shtProgbits, 0, dw.lineOff, dw.lineSize, 0, 0, 1, 0)
putSh(".debug_line_str", shtProgbits, 0, dw.lineStrOff, dw.lineStrSize, 0, 0, 1, 0)
}
// ELF header.
hdr := out[:64]