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cmd/link: enable DWARF combining on macOS ARM64

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It appears the machoCalcStart function is meant to align the
segment, but it doesn't. Replace it with an actual alignment
calculation. Also, use the alignment from the configuration,
instead of hardcode.

With this fix we could enable DWARF combining on macOS ARM64.

Change-Id: I19ec771b77d752b83a54c53b6ee65af78a31b8ae
Reviewed-on: https://go-review.googlesource.com/c/go/+/253558
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang 2020-09-04 14:35:57 -04:00
parent a52a5d8a43
commit 1e6ad65b43
3 changed files with 5 additions and 18 deletions
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2
src/cmd/link/internal/arm64/obj.go
View file

@ -105,7 +105,7 @@ func archinit(ctxt *ld.Link) {
*ld.FlagTextAddr = 4096 + int64(ld.HEADR) *ld.FlagTextAddr = 4096 + int64(ld.HEADR)
} }
if *ld.FlagRound == -1 { if *ld.FlagRound == -1 {
*ld.FlagRound = 4096 *ld.FlagRound = 16384 // 16K page alignment
} }
} }
} }

4
src/cmd/link/internal/ld/lib.go
View file

@ -1240,11 +1240,11 @@ func (ctxt *Link) hostlink() {
// On darwin, whether to combine DWARF into executable. // On darwin, whether to combine DWARF into executable.
// Only macOS supports unmapped segments such as our __DWARF segment. // Only macOS supports unmapped segments such as our __DWARF segment.
combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
switch ctxt.HeadType { switch ctxt.HeadType {
case objabi.Hdarwin: case objabi.Hdarwin:
if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() { if combineDwarf {
// Leave room for DWARF combining. // Leave room for DWARF combining.
// -headerpad is incompatible with -fembed-bitcode. // -headerpad is incompatible with -fembed-bitcode.
argv = append(argv, "-Wl,-headerpad,1144") argv = append(argv, "-Wl,-headerpad,1144")

17
src/cmd/link/internal/ld/macho_combine_dwarf.go
View file

@ -16,10 +16,6 @@ import (
"unsafe" "unsafe"
) )
const (
pageAlign = 12 // 4096 = 1 << 12
)
type loadCmd struct { type loadCmd struct {
Cmd macho.LoadCmd Cmd macho.LoadCmd
Len uint32 Len uint32
@ -138,7 +134,7 @@ func machoCombineDwarf(ctxt *Link, exef *os.File, exem *macho.File, dsym, outexe
// Now copy the dwarf data into the output. // Now copy the dwarf data into the output.
// Kernel requires all loaded segments to be page-aligned in the file, // Kernel requires all loaded segments to be page-aligned in the file,
// even though we mark this one as being 0 bytes of virtual address space. // even though we mark this one as being 0 bytes of virtual address space.
dwarfstart := machoCalcStart(realdwarf.Offset, linkseg.Offset, pageAlign) dwarfstart := Rnd(int64(linkseg.Offset), int64(*FlagRound))
if _, err := outf.Seek(dwarfstart, 0); err != nil { if _, err := outf.Seek(dwarfstart, 0); err != nil {
return err return err
} }
@ -166,7 +162,7 @@ func machoCombineDwarf(ctxt *Link, exef *os.File, exem *macho.File, dsym, outexe
if _, err := exef.Seek(int64(linkseg.Offset), 0); err != nil { if _, err := exef.Seek(int64(linkseg.Offset), 0); err != nil {
return err return err
} }
linkstart := machoCalcStart(linkseg.Offset, uint64(dwarfstart)+dwarfsize, pageAlign) linkstart := Rnd(dwarfstart+int64(dwarfsize), int64(*FlagRound))
if _, err := outf.Seek(linkstart, 0); err != nil { if _, err := outf.Seek(linkstart, 0); err != nil {
return err return err
} }
@ -432,12 +428,3 @@ func machoUpdateLoadCommand(r loadCmdReader, linkseg *macho.Segment, linkoffset
} }
return nil return nil
} }
func machoCalcStart(origAddr, newAddr uint64, alignExp uint32) int64 {
align := uint64(1 << alignExp)
origMod, newMod := origAddr%align, newAddr%align
if origMod == newMod {
return int64(newAddr)
}
return int64(newAddr + align + origMod - newMod)
}