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cmd/link: add support for external linking on linux/riscv64

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Fixes #36739

Change-Id: Id7573b343786360c72524f9f27d2a8f08d379cf3
Reviewed-on: https://go-review.googlesource.com/c/go/+/243517
Trust: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
Joel Sing 2020-08-14 00:13:28 +10:00
parent 515e6a9b12
commit 15eaa870e1
8 changed files with 169 additions and 10 deletions
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2
src/cmd/dist/test.go vendored
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@ -921,7 +921,7 @@ func (t *tester) extLink() bool {
"darwin-amd64", "darwin-arm64",
"dragonfly-amd64",
"freebsd-386", "freebsd-amd64", "freebsd-arm",
"linux-386", "linux-amd64", "linux-arm", "linux-arm64", "linux-ppc64le", "linux-mips64", "linux-mips64le", "linux-mips", "linux-mipsle", "linux-s390x",
"linux-386", "linux-amd64", "linux-arm", "linux-arm64", "linux-ppc64le", "linux-mips64", "linux-mips64le", "linux-mips", "linux-mipsle", "linux-riscv64", "linux-s390x",
"netbsd-386", "netbsd-amd64",
"openbsd-386", "openbsd-amd64",
"windows-386", "windows-amd64":

4
src/cmd/link/internal/ld/config.go
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@ -202,7 +202,7 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
// Internally linking cgo is incomplete on some architectures.
// https://golang.org/issue/14449
// https://golang.org/issue/21961
if iscgo && ctxt.Arch.InFamily(sys.MIPS64, sys.MIPS, sys.PPC64) {
if iscgo && ctxt.Arch.InFamily(sys.MIPS64, sys.MIPS, sys.PPC64, sys.RISCV64) {
return true, objabi.GOARCH + " does not support internal cgo"
}
if iscgo && objabi.GOOS == "android" {
@ -285,8 +285,6 @@ func determineLinkMode(ctxt *Link) {
}
case LinkExternal:
switch {
case objabi.GOARCH == "riscv64":
Exitf("external linking not supported for %s/riscv64", objabi.GOOS)
case objabi.GOARCH == "ppc64" && objabi.GOOS != "aix":
Exitf("external linking not supported for %s/ppc64", objabi.GOOS)
}

3
src/cmd/link/internal/ld/elf.go
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@ -506,6 +506,9 @@ func Elfinit(ctxt *Link) {
if ctxt.Arch.Family == sys.MIPS64 {
ehdr.flags = 0x20000004 /* MIPS 3 CPIC */
}
if ctxt.Arch.Family == sys.RISCV64 {
ehdr.flags = 0x4 /* RISCV Float ABI Double */
}
elf64 = true
ehdr.phoff = ELF64HDRSIZE /* Must be ELF64HDRSIZE: first PHdr must follow ELF header */

6
src/cmd/link/internal/ld/lib.go
View File

@ -247,12 +247,16 @@ type Arch struct {
Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
Gentext func(*Link, *loader.Loader)
Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
// Generate additional symbols for the native symbol table just prior to
// code generation.
GenSymsLate func(*Link, *loader.Loader)
// TLSIEtoLE converts a TLS Initial Executable relocation to
// a TLS Local Executable relocation.
//

8
src/cmd/link/internal/ld/main.go
View File

@ -341,6 +341,14 @@ func Main(arch *sys.Arch, theArch Arch) {
}(f, s)
}
wg.Wait()
// Generate additional symbols for the native symbol table just prior
// to code generation.
bench.Start("GenSymsLate")
if thearch.GenSymsLate != nil {
thearch.GenSymsLate(ctxt, ctxt.loader)
}
bench.Start("Asmb2")
asmb2(ctxt)

5
src/cmd/link/internal/loader/loader.go
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@ -1791,6 +1791,11 @@ func (l *Loader) SortSub(s Sym) Sym {
return sl[0].s
}
// SortSyms sorts a list of symbols by their value.
func (l *Loader) SortSyms(ss []Sym) {
sort.SliceStable(ss, func(i, j int) bool { return l.SymValue(ss[i]) < l.SymValue(ss[j]) })
}
// Insure that reachable bitmap and its siblings have enough size.
func (l *Loader) growAttrBitmaps(reqLen int) {
if reqLen > l.attrReachable.Len() {

146
src/cmd/link/internal/riscv64/asm.go
View File

@ -11,20 +11,138 @@ import (
"cmd/link/internal/ld"
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"debug/elf"
"fmt"
"log"
"sort"
)
// fakeLabelName matches the RISCV_FAKE_LABEL_NAME from binutils.
const fakeLabelName = ".L0 "
func gentext(ctxt *ld.Link, ldr *loader.Loader) {
}
func genSymsLate(ctxt *ld.Link, ldr *loader.Loader) {
if ctxt.LinkMode != ld.LinkExternal {
return
}
// Generate a local text symbol for each relocation target, as the
// R_RISCV_PCREL_LO12_* relocations generated by elfreloc1 need it.
if ctxt.Textp == nil {
log.Fatal("genSymsLate called before Textp has been assigned")
}
var hi20Syms []loader.Sym
for _, s := range ctxt.Textp {
relocs := ldr.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
if r.Type() != objabi.R_RISCV_PCREL_ITYPE && r.Type() != objabi.R_RISCV_PCREL_STYPE {
continue
}
if r.Off() == 0 && ldr.SymType(s) == sym.STEXT {
// Use the symbol for the function instead of creating
// an overlapping symbol.
continue
}
// TODO(jsing): Consider generating ELF symbols without needing
// loader symbols, in order to reduce memory consumption. This
// would require changes to genelfsym so that it called
// putelfsym and putelfsyment as appropriate.
sb := ldr.MakeSymbolBuilder(fakeLabelName)
sb.SetType(sym.STEXT)
sb.SetValue(ldr.SymValue(s) + int64(r.Off()))
sb.SetLocal(true)
sb.SetReachable(true)
sb.SetVisibilityHidden(true)
sb.SetSect(ldr.SymSect(s))
if outer := ldr.OuterSym(s); outer != 0 {
ldr.AddInteriorSym(outer, sb.Sym())
}
hi20Syms = append(hi20Syms, sb.Sym())
}
}
ctxt.Textp = append(ctxt.Textp, hi20Syms...)
ldr.SortSyms(ctxt.Textp)
}
func findHI20Symbol(ctxt *ld.Link, ldr *loader.Loader, val int64) loader.Sym {
idx := sort.Search(len(ctxt.Textp), func(i int) bool { return ldr.SymValue(ctxt.Textp[i]) >= val })
if idx >= len(ctxt.Textp) {
return 0
}
if s := ctxt.Textp[idx]; ldr.SymValue(s) == val && ldr.SymType(s) == sym.STEXT {
return s
}
return 0
}
func elfreloc1(ctxt *ld.Link, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, ri int, sectoff int64) bool {
log.Fatalf("elfreloc1")
elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
switch r.Type {
case objabi.R_ADDR, objabi.R_DWARFSECREF:
out.Write64(uint64(sectoff))
switch r.Size {
case 4:
out.Write64(uint64(elf.R_RISCV_32) | uint64(elfsym)<<32)
case 8:
out.Write64(uint64(elf.R_RISCV_64) | uint64(elfsym)<<32)
default:
ld.Errorf(nil, "unknown size %d for %v relocation", r.Size, r.Type)
return false
}
out.Write64(uint64(r.Xadd))
case objabi.R_CALLRISCV:
// Call relocations are currently handled via R_RISCV_PCREL_ITYPE.
// TODO(jsing): Consider generating elf.R_RISCV_CALL instead of a
// HI20/LO12_I pair.
case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE:
// Find the text symbol for the AUIPC instruction targeted
// by this relocation.
relocs := ldr.Relocs(s)
offset := int64(relocs.At(ri).Off())
hi20Sym := findHI20Symbol(ctxt, ldr, ldr.SymValue(s)+offset)
if hi20Sym == 0 {
ld.Errorf(nil, "failed to find text symbol for HI20 relocation at %d (%x)", sectoff, ldr.SymValue(s)+offset)
return false
}
hi20ElfSym := ld.ElfSymForReloc(ctxt, hi20Sym)
// Emit two relocations - a R_RISCV_PCREL_HI20 relocation and a
// corresponding R_RISCV_PCREL_LO12_I or R_RISCV_PCREL_LO12_S relocation.
// Note that the LO12 relocation must point to a target that has a valid
// HI20 PC-relative relocation text symbol, which in turn points to the
// given symbol. For further details see the ELF specification for RISC-V:
//
// https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#pc-relative-symbol-addresses
//
var hiRel, loRel elf.R_RISCV
switch r.Type {
case objabi.R_RISCV_PCREL_ITYPE:
hiRel, loRel = elf.R_RISCV_PCREL_HI20, elf.R_RISCV_PCREL_LO12_I
case objabi.R_RISCV_PCREL_STYPE:
hiRel, loRel = elf.R_RISCV_PCREL_HI20, elf.R_RISCV_PCREL_LO12_S
}
out.Write64(uint64(sectoff))
out.Write64(uint64(hiRel) | uint64(elfsym)<<32)
out.Write64(uint64(r.Xadd))
out.Write64(uint64(sectoff + 4))
out.Write64(uint64(loRel) | uint64(hi20ElfSym)<<32)
out.Write64(uint64(0))
default:
return false
}
return true
}
func elfsetupplt(ctxt *ld.Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym) {
log.Fatalf("elfsetuplt")
log.Fatalf("elfsetupplt")
}
func machoreloc1(*sys.Arch, *ld.OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool {
@ -33,8 +151,20 @@ func machoreloc1(*sys.Arch, *ld.OutBuf, *loader.Loader, loader.Sym, loader.ExtRe
}
func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loader.Reloc, s loader.Sym, val int64) (o int64, nExtReloc int, ok bool) {
rs := r.Sym()
rs = ldr.ResolveABIAlias(rs)
if target.IsExternal() {
switch r.Type() {
case objabi.R_CALLRISCV:
return val, 0, true
case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE:
return val, 2, true
}
return val, 0, false
}
rs := ldr.ResolveABIAlias(r.Sym())
switch r.Type() {
case objabi.R_CALLRISCV:
// Nothing to do.
@ -89,3 +219,11 @@ func archrelocvariant(*ld.Target, *loader.Loader, loader.Reloc, sym.RelocVariant
log.Fatalf("archrelocvariant")
return -1
}
func extreloc(target *ld.Target, ldr *loader.Loader, r loader.Reloc, s loader.Sym) (loader.ExtReloc, bool) {
switch r.Type() {
case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE:
return ld.ExtrelocViaOuterSym(ldr, r, s), true
}
return loader.ExtReloc{}, false
}

3
src/cmd/link/internal/riscv64/obj.go
View File

@ -23,9 +23,12 @@ func Init() (*sys.Arch, ld.Arch) {
Archinit: archinit,
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
Extreloc: extreloc,
Elfreloc1: elfreloc1,
ElfrelocSize: 24,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
GenSymsLate: genSymsLate,
Machoreloc1: machoreloc1,
Linuxdynld: "/lib/ld.so.1",