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cmd/link: implement windows/arm64 external linking
Change-Id: Ia73309ec7013138b37028e669d7ae5eac81126e8 Reviewed-on: https://go-review.googlesource.com/c/go/+/312044 Trust: Russ Cox <rsc@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Russ Cox
parent
bf9216055b
commit
8e368708c5
@ -464,8 +464,9 @@ func elfreloc1(ctxt *ld.Link, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
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return true
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}
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// sign-extends from 24-bit.
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func signext24(x int64) int64 { return x << 40 >> 40 }
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// sign-extends from 21, 24-bit.
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func signext21(x int64) int64 { return x << (64 - 21) >> (64 - 21) }
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func signext24(x int64) int64 { return x << (64 - 24) >> (64 - 24) }
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func machoreloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, sectoff int64) bool {
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var v uint32
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@ -478,7 +479,7 @@ func machoreloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sy
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if xadd != signext24(xadd) {
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// If the relocation target would overflow the addend, then target
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// a linker-manufactured label symbol with a smaller addend instead.
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label := ldr.Lookup(machoLabelName(ldr, rs, xadd), ldr.SymVersion(rs))
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label := ldr.Lookup(offsetLabelName(ldr, rs, xadd/machoRelocLimit*machoRelocLimit), ldr.SymVersion(rs))
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if label != 0 {
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xadd = ldr.SymValue(rs) + xadd - ldr.SymValue(label)
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rs = label
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@ -569,35 +570,67 @@ func machoreloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sy
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}
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func pereloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, sectoff int64) bool {
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var v uint32
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rs := r.Xsym
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rt := r.Type
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if ldr.SymDynid(rs) < 0 {
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if r.Xadd != signext21(r.Xadd) {
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// If the relocation target would overflow the addend, then target
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// a linker-manufactured label symbol with a smaller addend instead.
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label := ldr.Lookup(offsetLabelName(ldr, rs, r.Xadd/peRelocLimit*peRelocLimit), ldr.SymVersion(rs))
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if label == 0 {
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ldr.Errorf(s, "invalid relocation: %v %s+0x%x", rt, ldr.SymName(rs), r.Xadd)
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return false
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}
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rs = label
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}
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if rt == objabi.R_CALLARM64 && r.Xadd != 0 {
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label := ldr.Lookup(offsetLabelName(ldr, rs, r.Xadd), ldr.SymVersion(rs))
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if label == 0 {
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ldr.Errorf(s, "invalid relocation: %v %s+0x%x", rt, ldr.SymName(rs), r.Xadd)
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return false
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}
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rs = label
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}
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symdynid := ldr.SymDynid(rs)
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if symdynid < 0 {
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ldr.Errorf(s, "reloc %d (%s) to non-coff symbol %s type=%d (%s)", rt, sym.RelocName(arch, rt), ldr.SymName(rs), ldr.SymType(rs), ldr.SymType(rs))
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return false
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}
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out.Write32(uint32(sectoff))
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out.Write32(uint32(ldr.SymDynid(rs)))
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switch rt {
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default:
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return false
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case objabi.R_DWARFSECREF:
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v = ld.IMAGE_REL_ARM64_SECREL
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out.Write32(uint32(sectoff))
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out.Write32(uint32(symdynid))
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out.Write16(ld.IMAGE_REL_ARM64_SECREL)
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case objabi.R_ADDR:
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out.Write32(uint32(sectoff))
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out.Write32(uint32(symdynid))
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if r.Size == 8 {
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v = ld.IMAGE_REL_ARM64_ADDR64
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out.Write16(ld.IMAGE_REL_ARM64_ADDR64)
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} else {
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v = ld.IMAGE_REL_ARM64_ADDR32
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out.Write16(ld.IMAGE_REL_ARM64_ADDR32)
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}
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}
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out.Write16(uint16(v))
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case objabi.R_ADDRARM64:
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// Note: r.Xadd has been taken care of below, in archreloc.
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out.Write32(uint32(sectoff))
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out.Write32(uint32(symdynid))
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out.Write16(ld.IMAGE_REL_ARM64_PAGEBASE_REL21)
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out.Write32(uint32(sectoff + 4))
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out.Write32(uint32(symdynid))
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out.Write16(ld.IMAGE_REL_ARM64_PAGEOFFSET_12A)
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case objabi.R_CALLARM64:
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// Note: r.Xadd has been taken care of above, by using a label pointing into the middle of the function.
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out.Write32(uint32(sectoff))
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out.Write32(uint32(symdynid))
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out.Write16(ld.IMAGE_REL_ARM64_BRANCH26)
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}
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return true
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}
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@ -628,14 +661,8 @@ func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loade
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nExtReloc = 4 // need another two relocations for non-zero addend
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}
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// Note: ld64 currently has a bug that any non-zero addend for BR26 relocation
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// will make the linking fail because it thinks the code is not PIC even though
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// the BR26 relocation should be fully resolved at link time.
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// That is the reason why the next if block is disabled. When the bug in ld64
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// is fixed, we can enable this block and also enable duff's device in cmd/7g.
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if false && target.IsDarwin() {
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if target.IsWindows() {
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var o0, o1 uint32
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if target.IsBigEndian() {
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o0 = uint32(val >> 32)
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o1 = uint32(val)
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@ -643,15 +670,20 @@ func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loade
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o0 = uint32(val)
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o1 = uint32(val >> 32)
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}
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// Mach-O wants the addend to be encoded in the instruction
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// Note that although Mach-O supports ARM64_RELOC_ADDEND, it
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// can only encode 24-bit of signed addend, but the instructions
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// supports 33-bit of signed addend, so we always encode the
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// addend in place.
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o0 |= (uint32((xadd>>12)&3) << 29) | (uint32((xadd>>12>>2)&0x7ffff) << 5)
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o1 |= uint32(xadd&0xfff) << 10
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// when laid out, the instruction order must always be o1, o2.
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// The first instruction (ADRP) has a 21-bit immediate field,
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// and the second (ADD) has a 12-bit immediate field.
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// The first instruction is only for high bits, but to get the carry bits right we have
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// to put the full addend, including the bottom 12 bits again.
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// That limits the distance of any addend to only 21 bits.
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// But we assume that LDRP's top bit will be interpreted as a sign bit,
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// so we only use 20 bits.
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// pereloc takes care of introducing new symbol labels
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// every megabyte for longer relocations.
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xadd := uint32(xadd)
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o0 |= (xadd&3)<<29 | (xadd&0xffffc)<<3
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o1 |= (xadd & 0xfff) << 10
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if target.IsBigEndian() {
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val = int64(o0)<<32 | int64(o1)
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} else {
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@ -668,6 +700,18 @@ func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loade
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nExtReloc = 2 // need two ELF relocations. see elfreloc1
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}
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return val, nExtReloc, isOk
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case objabi.R_ADDR:
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if target.IsWindows() && r.Add() != 0 {
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if r.Siz() == 8 {
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val = r.Add()
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} else if target.IsBigEndian() {
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val = int64(uint32(val)) | int64(r.Add())<<32
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} else {
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val = val>>32<<32 | int64(uint32(r.Add()))
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}
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return val, 1, true
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}
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}
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}
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@ -1018,37 +1062,54 @@ func addpltsym(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loade
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}
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}
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const machoRelocLimit = 1 << 23
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const (
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machoRelocLimit = 1 << 23
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peRelocLimit = 1 << 20
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)
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func gensymlate(ctxt *ld.Link, ldr *loader.Loader) {
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// When external linking on darwin, Mach-O relocation has only signed 24-bit
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// addend. For large symbols, we generate "label" symbols in the middle, so
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// that relocations can target them with smaller addends.
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if !ctxt.IsDarwin() || !ctxt.IsExternal() {
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// On Windows, we only get 21 bits, again (presumably) signed.
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if !ctxt.IsDarwin() && !ctxt.IsWindows() || !ctxt.IsExternal() {
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return
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}
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big := false
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for _, seg := range ld.Segments {
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if seg.Length >= machoRelocLimit {
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big = true
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break
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}
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}
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if !big {
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return // skip work if nothing big
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limit := int64(machoRelocLimit)
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if ctxt.IsWindows() {
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limit = peRelocLimit
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}
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// addLabelSyms adds "label" symbols at s+machoRelocLimit, s+2*machoRelocLimit, etc.
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addLabelSyms := func(s loader.Sym, sz int64) {
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if ctxt.IsDarwin() {
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big := false
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for _, seg := range ld.Segments {
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if seg.Length >= machoRelocLimit {
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big = true
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break
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}
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}
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if !big {
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return // skip work if nothing big
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}
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}
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// addLabelSyms adds "label" symbols at s+limit, s+2*limit, etc.
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addLabelSyms := func(s loader.Sym, limit, sz int64) {
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v := ldr.SymValue(s)
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for off := int64(machoRelocLimit); off < sz; off += machoRelocLimit {
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p := ldr.LookupOrCreateSym(machoLabelName(ldr, s, off), ldr.SymVersion(s))
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for off := limit; off < sz; off += limit {
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p := ldr.LookupOrCreateSym(offsetLabelName(ldr, s, off), ldr.SymVersion(s))
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ldr.SetAttrReachable(p, true)
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ldr.SetSymValue(p, v+off)
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ldr.SetSymSect(p, ldr.SymSect(s))
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ld.AddMachoSym(ldr, p)
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//fmt.Printf("gensymlate %s %x\n", ldr.SymName(p), ldr.SymValue(p))
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if ctxt.IsDarwin() {
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ld.AddMachoSym(ldr, p)
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} else if ctxt.IsWindows() {
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ld.AddPELabelSym(ldr, p)
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} else {
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panic("missing case in gensymlate")
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}
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// fmt.Printf("gensymlate %s %x\n", ldr.SymName(p), ldr.SymValue(p))
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}
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}
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@ -1057,26 +1118,39 @@ func gensymlate(ctxt *ld.Link, ldr *loader.Loader) {
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continue
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}
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if ldr.SymType(s) == sym.STEXT {
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continue // we don't target the middle of a function
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if ctxt.IsDarwin() || ctxt.IsWindows() {
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// Cannot relocate into middle of function.
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// Generate symbol names for every offset we need in duffcopy/duffzero (only 64 each).
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switch ldr.SymName(s) {
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case "runtime.duffcopy":
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addLabelSyms(s, 8, 8*64)
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case "runtime.duffzero":
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addLabelSyms(s, 4, 4*64)
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}
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}
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continue // we don't target the middle of other functions
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}
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sz := ldr.SymSize(s)
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if sz <= machoRelocLimit {
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if sz <= limit {
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continue
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}
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addLabelSyms(s, sz)
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addLabelSyms(s, limit, sz)
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}
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// Also for carrier symbols (for which SymSize is 0)
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for _, ss := range ld.CarrierSymByType {
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if ss.Sym != 0 && ss.Size > machoRelocLimit {
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addLabelSyms(ss.Sym, ss.Size)
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if ss.Sym != 0 && ss.Size > limit {
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addLabelSyms(ss.Sym, limit, ss.Size)
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}
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}
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}
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// machoLabelName returns the name of the "label" symbol used for a
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// relocation targeting s+off. The label symbols is used on darwin
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// when external linking, so that the addend fits in a Mach-O relocation.
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func machoLabelName(ldr *loader.Loader, s loader.Sym, off int64) string {
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return fmt.Sprintf("%s.%d", ldr.SymExtname(s), off/machoRelocLimit)
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// offsetLabelName returns the name of the "label" symbol used for a
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// relocation targeting s+off. The label symbols is used on Darwin/Windows
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// when external linking, so that the addend fits in a Mach-O/PE relocation.
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func offsetLabelName(ldr *loader.Loader, s loader.Sym, off int64) string {
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if off>>20<<20 == off {
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return fmt.Sprintf("%s+%dMB", ldr.SymExtname(s), off>>20)
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}
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return fmt.Sprintf("%s+%d", ldr.SymExtname(s), off)
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}
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@ -704,6 +704,12 @@ func (f *peFile) mapToPESection(ldr *loader.Loader, s loader.Sym, linkmode LinkM
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return f.bssSect.index, int64(v - Segdata.Filelen), nil
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}
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var isLabel = make(map[loader.Sym]bool)
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func AddPELabelSym(ldr *loader.Loader, s loader.Sym) {
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isLabel[s] = true
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}
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// writeSymbols writes all COFF symbol table records.
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func (f *peFile) writeSymbols(ctxt *Link) {
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ldr := ctxt.loader
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@ -800,6 +806,10 @@ func (f *peFile) writeSymbols(ctxt *Link) {
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switch t {
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case sym.SDYNIMPORT, sym.SHOSTOBJ, sym.SUNDEFEXT:
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addsym(s)
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default:
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if len(isLabel) > 0 && isLabel[s] {
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addsym(s)
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}
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}
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}
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}
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