| // Derived from Inferno utils/6l/obj.c and utils/6l/span.c |
| // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/obj.c |
| // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/span.c |
| // |
| // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved. |
| // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net) |
| // Portions Copyright © 1997-1999 Vita Nuova Limited |
| // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com) |
| // Portions Copyright © 2004,2006 Bruce Ellis |
| // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net) |
| // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others |
| // Portions Copyright © 2009 The Go Authors. All rights reserved. |
| // |
| // Permission is hereby granted, free of charge, to any person obtaining a copy |
| // of this software and associated documentation files (the "Software"), to deal |
| // in the Software without restriction, including without limitation the rights |
| // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| // copies of the Software, and to permit persons to whom the Software is |
| // furnished to do so, subject to the following conditions: |
| // |
| // The above copyright notice and this permission notice shall be included in |
| // all copies or substantial portions of the Software. |
| // |
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| // THE SOFTWARE. |
| |
| package ld |
| |
| import ( |
| "bytes" |
| "cmd/internal/gcprog" |
| "cmd/internal/objabi" |
| "cmd/internal/sys" |
| "cmd/link/internal/loader" |
| "cmd/link/internal/sym" |
| "compress/zlib" |
| "encoding/binary" |
| "fmt" |
| "log" |
| "os" |
| "sort" |
| "strconv" |
| "strings" |
| "sync" |
| "sync/atomic" |
| ) |
| |
| // isRuntimeDepPkg reports whether pkg is the runtime package or its dependency |
| func isRuntimeDepPkg(pkg string) bool { |
| switch pkg { |
| case "runtime", |
| "sync/atomic", // runtime may call to sync/atomic, due to go:linkname |
| "internal/bytealg", // for IndexByte |
| "internal/cpu": // for cpu features |
| return true |
| } |
| return strings.HasPrefix(pkg, "runtime/internal/") && !strings.HasSuffix(pkg, "_test") |
| } |
| |
| // Estimate the max size needed to hold any new trampolines created for this function. This |
| // is used to determine when the section can be split if it becomes too large, to ensure that |
| // the trampolines are in the same section as the function that uses them. |
| func maxSizeTrampolinesPPC64(ldr *loader.Loader, s loader.Sym, isTramp bool) uint64 { |
| // If thearch.Trampoline is nil, then trampoline support is not available on this arch. |
| // A trampoline does not need any dependent trampolines. |
| if thearch.Trampoline == nil || isTramp { |
| return 0 |
| } |
| |
| n := uint64(0) |
| relocs := ldr.Relocs(s) |
| for ri := 0; ri < relocs.Count(); ri++ { |
| r := relocs.At(ri) |
| if r.Type().IsDirectCallOrJump() { |
| n++ |
| } |
| } |
| // Trampolines in ppc64 are 4 instructions. |
| return n * 16 |
| } |
| |
| // detect too-far jumps in function s, and add trampolines if necessary |
| // ARM, PPC64 & PPC64LE support trampoline insertion for internal and external linking |
| // On PPC64 & PPC64LE the text sections might be split but will still insert trampolines |
| // where necessary. |
| func trampoline(ctxt *Link, s loader.Sym) { |
| if thearch.Trampoline == nil { |
| return // no need or no support of trampolines on this arch |
| } |
| |
| ldr := ctxt.loader |
| relocs := ldr.Relocs(s) |
| for ri := 0; ri < relocs.Count(); ri++ { |
| r := relocs.At(ri) |
| if !r.Type().IsDirectCallOrJump() { |
| continue |
| } |
| rs := r.Sym() |
| if !ldr.AttrReachable(rs) || ldr.SymType(rs) == sym.Sxxx { |
| continue // something is wrong. skip it here and we'll emit a better error later |
| } |
| rs = ldr.ResolveABIAlias(rs) |
| if ldr.SymValue(rs) == 0 && (ldr.SymType(rs) != sym.SDYNIMPORT && ldr.SymType(rs) != sym.SUNDEFEXT) { |
| if ldr.SymPkg(rs) != ldr.SymPkg(s) { |
| if !isRuntimeDepPkg(ldr.SymPkg(s)) || !isRuntimeDepPkg(ldr.SymPkg(rs)) { |
| ctxt.Errorf(s, "unresolved inter-package jump to %s(%s) from %s", ldr.SymName(rs), ldr.SymPkg(rs), ldr.SymPkg(s)) |
| } |
| // runtime and its dependent packages may call to each other. |
| // they are fine, as they will be laid down together. |
| } |
| continue |
| } |
| |
| thearch.Trampoline(ctxt, ldr, ri, rs, s) |
| } |
| |
| } |
| |
| // FoldSubSymbolOffset computes the offset of symbol s to its top-level outer |
| // symbol. Returns the top-level symbol and the offset. |
| // This is used in generating external relocations. |
| func FoldSubSymbolOffset(ldr *loader.Loader, s loader.Sym) (loader.Sym, int64) { |
| outer := ldr.OuterSym(s) |
| off := int64(0) |
| if outer != 0 { |
| off += ldr.SymValue(s) - ldr.SymValue(outer) |
| s = outer |
| } |
| return s, off |
| } |
| |
| // relocsym resolve relocations in "s", updating the symbol's content |
| // in "P". |
| // The main loop walks through the list of relocations attached to "s" |
| // and resolves them where applicable. Relocations are often |
| // architecture-specific, requiring calls into the 'archreloc' and/or |
| // 'archrelocvariant' functions for the architecture. When external |
| // linking is in effect, it may not be possible to completely resolve |
| // the address/offset for a symbol, in which case the goal is to lay |
| // the groundwork for turning a given relocation into an external reloc |
| // (to be applied by the external linker). For more on how relocations |
| // work in general, see |
| // |
| // "Linkers and Loaders", by John R. Levine (Morgan Kaufmann, 1999), ch. 7 |
| // |
| // This is a performance-critical function for the linker; be careful |
| // to avoid introducing unnecessary allocations in the main loop. |
| func (st *relocSymState) relocsym(s loader.Sym, P []byte) { |
| ldr := st.ldr |
| relocs := ldr.Relocs(s) |
| if relocs.Count() == 0 { |
| return |
| } |
| target := st.target |
| syms := st.syms |
| nExtReloc := 0 // number of external relocations |
| for ri := 0; ri < relocs.Count(); ri++ { |
| r := relocs.At(ri) |
| off := r.Off() |
| siz := int32(r.Siz()) |
| rs := r.Sym() |
| rs = ldr.ResolveABIAlias(rs) |
| rt := r.Type() |
| if off < 0 || off+siz > int32(len(P)) { |
| rname := "" |
| if rs != 0 { |
| rname = ldr.SymName(rs) |
| } |
| st.err.Errorf(s, "invalid relocation %s: %d+%d not in [%d,%d)", rname, off, siz, 0, len(P)) |
| continue |
| } |
| if siz == 0 { // informational relocation - no work to do |
| continue |
| } |
| |
| var rst sym.SymKind |
| if rs != 0 { |
| rst = ldr.SymType(rs) |
| } |
| |
| if rs != 0 && ((rst == sym.Sxxx && !ldr.AttrVisibilityHidden(rs)) || rst == sym.SXREF) { |
| // When putting the runtime but not main into a shared library |
| // these symbols are undefined and that's OK. |
| if target.IsShared() || target.IsPlugin() { |
| if ldr.SymName(rs) == "main.main" || (!target.IsPlugin() && ldr.SymName(rs) == "main..inittask") { |
| sb := ldr.MakeSymbolUpdater(rs) |
| sb.SetType(sym.SDYNIMPORT) |
| } else if strings.HasPrefix(ldr.SymName(rs), "go.info.") { |
| // Skip go.info symbols. They are only needed to communicate |
| // DWARF info between the compiler and linker. |
| continue |
| } |
| } else { |
| st.err.errorUnresolved(ldr, s, rs) |
| continue |
| } |
| } |
| |
| if rt >= objabi.ElfRelocOffset { |
| continue |
| } |
| |
| // We need to be able to reference dynimport symbols when linking against |
| // shared libraries, and Solaris, Darwin and AIX need it always |
| if !target.IsSolaris() && !target.IsDarwin() && !target.IsAIX() && rs != 0 && rst == sym.SDYNIMPORT && !target.IsDynlinkingGo() && !ldr.AttrSubSymbol(rs) { |
| if !(target.IsPPC64() && target.IsExternal() && ldr.SymName(rs) == ".TOC.") { |
| st.err.Errorf(s, "unhandled relocation for %s (type %d (%s) rtype %d (%s))", ldr.SymName(rs), rst, rst, rt, sym.RelocName(target.Arch, rt)) |
| } |
| } |
| if rs != 0 && rst != sym.STLSBSS && rt != objabi.R_WEAKADDROFF && rt != objabi.R_METHODOFF && !ldr.AttrReachable(rs) { |
| st.err.Errorf(s, "unreachable sym in relocation: %s", ldr.SymName(rs)) |
| } |
| |
| var rv sym.RelocVariant |
| if target.IsPPC64() || target.IsS390X() { |
| rv = ldr.RelocVariant(s, ri) |
| } |
| |
| // TODO(mundaym): remove this special case - see issue 14218. |
| if target.IsS390X() { |
| switch rt { |
| case objabi.R_PCRELDBL: |
| rt = objabi.R_PCREL |
| rv = sym.RV_390_DBL |
| case objabi.R_CALL: |
| rv = sym.RV_390_DBL |
| } |
| } |
| |
| var o int64 |
| switch rt { |
| default: |
| switch siz { |
| default: |
| st.err.Errorf(s, "bad reloc size %#x for %s", uint32(siz), ldr.SymName(rs)) |
| case 1: |
| o = int64(P[off]) |
| case 2: |
| o = int64(target.Arch.ByteOrder.Uint16(P[off:])) |
| case 4: |
| o = int64(target.Arch.ByteOrder.Uint32(P[off:])) |
| case 8: |
| o = int64(target.Arch.ByteOrder.Uint64(P[off:])) |
| } |
| out, n, ok := thearch.Archreloc(target, ldr, syms, r, s, o) |
| if target.IsExternal() { |
| nExtReloc += n |
| } |
| if ok { |
| o = out |
| } else { |
| st.err.Errorf(s, "unknown reloc to %v: %d (%s)", ldr.SymName(rs), rt, sym.RelocName(target.Arch, rt)) |
| } |
| case objabi.R_TLS_LE: |
| if target.IsExternal() && target.IsElf() { |
| nExtReloc++ |
| o = 0 |
| if !target.IsAMD64() { |
| o = r.Add() |
| } |
| break |
| } |
| |
| if target.IsElf() && target.IsARM() { |
| // On ELF ARM, the thread pointer is 8 bytes before |
| // the start of the thread-local data block, so add 8 |
| // to the actual TLS offset (r->sym->value). |
| // This 8 seems to be a fundamental constant of |
| // ELF on ARM (or maybe Glibc on ARM); it is not |
| // related to the fact that our own TLS storage happens |
| // to take up 8 bytes. |
| o = 8 + ldr.SymValue(rs) |
| } else if target.IsElf() || target.IsPlan9() || target.IsDarwin() { |
| o = int64(syms.Tlsoffset) + r.Add() |
| } else if target.IsWindows() { |
| o = r.Add() |
| } else { |
| log.Fatalf("unexpected R_TLS_LE relocation for %v", target.HeadType) |
| } |
| case objabi.R_TLS_IE: |
| if target.IsExternal() && target.IsElf() { |
| nExtReloc++ |
| o = 0 |
| if !target.IsAMD64() { |
| o = r.Add() |
| } |
| if target.Is386() { |
| nExtReloc++ // need two ELF relocations on 386, see ../x86/asm.go:elfreloc1 |
| } |
| break |
| } |
| if target.IsPIE() && target.IsElf() { |
| // We are linking the final executable, so we |
| // can optimize any TLS IE relocation to LE. |
| if thearch.TLSIEtoLE == nil { |
| log.Fatalf("internal linking of TLS IE not supported on %v", target.Arch.Family) |
| } |
| thearch.TLSIEtoLE(P, int(off), int(siz)) |
| o = int64(syms.Tlsoffset) |
| } else { |
| log.Fatalf("cannot handle R_TLS_IE (sym %s) when linking internally", ldr.SymName(s)) |
| } |
| case objabi.R_ADDR: |
| if target.IsExternal() { |
| nExtReloc++ |
| |
| // set up addend for eventual relocation via outer symbol. |
| rs := rs |
| rs, off := FoldSubSymbolOffset(ldr, rs) |
| xadd := r.Add() + off |
| rst := ldr.SymType(rs) |
| if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil { |
| st.err.Errorf(s, "missing section for relocation target %s", ldr.SymName(rs)) |
| } |
| |
| o = xadd |
| if target.IsElf() { |
| if target.IsAMD64() { |
| o = 0 |
| } |
| } else if target.IsDarwin() { |
| if ldr.SymType(rs) != sym.SHOSTOBJ { |
| o += ldr.SymValue(rs) |
| } |
| } else if target.IsWindows() { |
| // nothing to do |
| } else if target.IsAIX() { |
| o = ldr.SymValue(rs) + xadd |
| } else { |
| st.err.Errorf(s, "unhandled pcrel relocation to %s on %v", ldr.SymName(rs), target.HeadType) |
| } |
| |
| break |
| } |
| |
| // On AIX, a second relocation must be done by the loader, |
| // as section addresses can change once loaded. |
| // The "default" symbol address is still needed by the loader so |
| // the current relocation can't be skipped. |
| if target.IsAIX() && rst != sym.SDYNIMPORT { |
| // It's not possible to make a loader relocation in a |
| // symbol which is not inside .data section. |
| // FIXME: It should be forbidden to have R_ADDR from a |
| // symbol which isn't in .data. However, as .text has the |
| // same address once loaded, this is possible. |
| if ldr.SymSect(s).Seg == &Segdata { |
| Xcoffadddynrel(target, ldr, syms, s, r, ri) |
| } |
| } |
| |
| o = ldr.SymValue(rs) + r.Add() |
| |
| // On amd64, 4-byte offsets will be sign-extended, so it is impossible to |
| // access more than 2GB of static data; fail at link time is better than |
| // fail at runtime. See https://golang.org/issue/7980. |
| // Instead of special casing only amd64, we treat this as an error on all |
| // 64-bit architectures so as to be future-proof. |
| if int32(o) < 0 && target.Arch.PtrSize > 4 && siz == 4 { |
| st.err.Errorf(s, "non-pc-relative relocation address for %s is too big: %#x (%#x + %#x)", ldr.SymName(rs), uint64(o), ldr.SymValue(rs), r.Add()) |
| errorexit() |
| } |
| case objabi.R_DWARFSECREF: |
| if ldr.SymSect(rs) == nil { |
| st.err.Errorf(s, "missing DWARF section for relocation target %s", ldr.SymName(rs)) |
| } |
| |
| if target.IsExternal() { |
| // On most platforms, the external linker needs to adjust DWARF references |
| // as it combines DWARF sections. However, on Darwin, dsymutil does the |
| // DWARF linking, and it understands how to follow section offsets. |
| // Leaving in the relocation records confuses it (see |
| // https://golang.org/issue/22068) so drop them for Darwin. |
| if !target.IsDarwin() { |
| nExtReloc++ |
| } |
| |
| xadd := r.Add() + ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr) |
| |
| o = xadd |
| if target.IsElf() && target.IsAMD64() { |
| o = 0 |
| } |
| break |
| } |
| o = ldr.SymValue(rs) + r.Add() - int64(ldr.SymSect(rs).Vaddr) |
| case objabi.R_WEAKADDROFF, objabi.R_METHODOFF: |
| if !ldr.AttrReachable(rs) { |
| if rt == objabi.R_METHODOFF { |
| // Set it to a sentinel value. The runtime knows this is not pointing to |
| // anything valid. |
| o = -1 |
| break |
| } |
| continue |
| } |
| fallthrough |
| case objabi.R_ADDROFF: |
| // The method offset tables using this relocation expect the offset to be relative |
| // to the start of the first text section, even if there are multiple. |
| if ldr.SymSect(rs).Name == ".text" { |
| o = ldr.SymValue(rs) - int64(Segtext.Sections[0].Vaddr) + r.Add() |
| } else { |
| o = ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr) + r.Add() |
| } |
| |
| case objabi.R_ADDRCUOFF: |
| // debug_range and debug_loc elements use this relocation type to get an |
| // offset from the start of the compile unit. |
| o = ldr.SymValue(rs) + r.Add() - ldr.SymValue(loader.Sym(ldr.SymUnit(rs).Textp[0])) |
| |
| // r.Sym() can be 0 when CALL $(constant) is transformed from absolute PC to relative PC call. |
| case objabi.R_GOTPCREL: |
| if target.IsDynlinkingGo() && target.IsDarwin() && rs != 0 { |
| nExtReloc++ |
| o = r.Add() |
| break |
| } |
| if target.Is386() && target.IsExternal() && target.IsELF { |
| nExtReloc++ // need two ELF relocations on 386, see ../x86/asm.go:elfreloc1 |
| } |
| fallthrough |
| case objabi.R_CALL, objabi.R_PCREL: |
| if target.IsExternal() && rs != 0 && rst == sym.SUNDEFEXT { |
| // pass through to the external linker. |
| nExtReloc++ |
| o = 0 |
| break |
| } |
| if target.IsExternal() && rs != 0 && (ldr.SymSect(rs) != ldr.SymSect(s) || rt == objabi.R_GOTPCREL) { |
| nExtReloc++ |
| |
| // set up addend for eventual relocation via outer symbol. |
| rs := rs |
| rs, off := FoldSubSymbolOffset(ldr, rs) |
| xadd := r.Add() + off - int64(siz) // relative to address after the relocated chunk |
| rst := ldr.SymType(rs) |
| if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && ldr.SymSect(rs) == nil { |
| st.err.Errorf(s, "missing section for relocation target %s", ldr.SymName(rs)) |
| } |
| |
| o = xadd |
| if target.IsElf() { |
| if target.IsAMD64() { |
| o = 0 |
| } |
| } else if target.IsDarwin() { |
| if rt == objabi.R_CALL { |
| if target.IsExternal() && rst == sym.SDYNIMPORT { |
| if target.IsAMD64() { |
| // AMD64 dynamic relocations are relative to the end of the relocation. |
| o += int64(siz) |
| } |
| } else { |
| if rst != sym.SHOSTOBJ { |
| o += int64(uint64(ldr.SymValue(rs)) - ldr.SymSect(rs).Vaddr) |
| } |
| o -= int64(off) // relative to section offset, not symbol |
| } |
| } else { |
| o += int64(siz) |
| } |
| } else if target.IsWindows() && target.IsAMD64() { // only amd64 needs PCREL |
| // PE/COFF's PC32 relocation uses the address after the relocated |
| // bytes as the base. Compensate by skewing the addend. |
| o += int64(siz) |
| } else { |
| st.err.Errorf(s, "unhandled pcrel relocation to %s on %v", ldr.SymName(rs), target.HeadType) |
| } |
| |
| break |
| } |
| |
| o = 0 |
| if rs != 0 { |
| o = ldr.SymValue(rs) |
| } |
| |
| o += r.Add() - (ldr.SymValue(s) + int64(off) + int64(siz)) |
| case objabi.R_SIZE: |
| o = ldr.SymSize(rs) + r.Add() |
| |
| case objabi.R_XCOFFREF: |
| if !target.IsAIX() { |
| st.err.Errorf(s, "find XCOFF R_REF on non-XCOFF files") |
| } |
| if !target.IsExternal() { |
| st.err.Errorf(s, "find XCOFF R_REF with internal linking") |
| } |
| nExtReloc++ |
| continue |
| |
| case objabi.R_DWARFFILEREF: |
| // We don't renumber files in dwarf.go:writelines anymore. |
| continue |
| |
| case objabi.R_CONST: |
| o = r.Add() |
| |
| case objabi.R_GOTOFF: |
| o = ldr.SymValue(rs) + r.Add() - ldr.SymValue(syms.GOT) |
| } |
| |
| if target.IsPPC64() || target.IsS390X() { |
| if rv != sym.RV_NONE { |
| o = thearch.Archrelocvariant(target, ldr, r, rv, s, o) |
| } |
| } |
| |
| switch siz { |
| default: |
| st.err.Errorf(s, "bad reloc size %#x for %s", uint32(siz), ldr.SymName(rs)) |
| case 1: |
| P[off] = byte(int8(o)) |
| case 2: |
| if o != int64(int16(o)) { |
| st.err.Errorf(s, "relocation address for %s is too big: %#x", ldr.SymName(rs), o) |
| } |
| target.Arch.ByteOrder.PutUint16(P[off:], uint16(o)) |
| case 4: |
| if rt == objabi.R_PCREL || rt == objabi.R_CALL { |
| if o != int64(int32(o)) { |
| st.err.Errorf(s, "pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), o) |
| } |
| } else { |
| if o != int64(int32(o)) && o != int64(uint32(o)) { |
| st.err.Errorf(s, "non-pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), uint64(o)) |
| } |
| } |
| target.Arch.ByteOrder.PutUint32(P[off:], uint32(o)) |
| case 8: |
| target.Arch.ByteOrder.PutUint64(P[off:], uint64(o)) |
| } |
| } |
| if target.IsExternal() { |
| // We'll stream out the external relocations in asmb2 (e.g. elfrelocsect) |
| // and we only need the count here. |
| atomic.AddUint32(&ldr.SymSect(s).Relcount, uint32(nExtReloc)) |
| } |
| } |
| |
| // Convert a Go relocation to an external relocation. |
| func extreloc(ctxt *Link, ldr *loader.Loader, s loader.Sym, r loader.Reloc) (loader.ExtReloc, bool) { |
| var rr loader.ExtReloc |
| target := &ctxt.Target |
| siz := int32(r.Siz()) |
| if siz == 0 { // informational relocation - no work to do |
| return rr, false |
| } |
| |
| rt := r.Type() |
| if rt >= objabi.ElfRelocOffset { |
| return rr, false |
| } |
| rr.Type = rt |
| rr.Size = uint8(siz) |
| |
| // TODO(mundaym): remove this special case - see issue 14218. |
| if target.IsS390X() { |
| switch rt { |
| case objabi.R_PCRELDBL: |
| rt = objabi.R_PCREL |
| } |
| } |
| |
| switch rt { |
| default: |
| return thearch.Extreloc(target, ldr, r, s) |
| |
| case objabi.R_TLS_LE, objabi.R_TLS_IE: |
| if target.IsElf() { |
| rs := ldr.ResolveABIAlias(r.Sym()) |
| rr.Xsym = rs |
| if rr.Xsym == 0 { |
| rr.Xsym = ctxt.Tlsg |
| } |
| rr.Xadd = r.Add() |
| break |
| } |
| return rr, false |
| |
| case objabi.R_ADDR: |
| // set up addend for eventual relocation via outer symbol. |
| rs := ldr.ResolveABIAlias(r.Sym()) |
| rs, off := FoldSubSymbolOffset(ldr, rs) |
| rr.Xadd = r.Add() + off |
| rr.Xsym = rs |
| |
| case objabi.R_DWARFSECREF: |
| // On most platforms, the external linker needs to adjust DWARF references |
| // as it combines DWARF sections. However, on Darwin, dsymutil does the |
| // DWARF linking, and it understands how to follow section offsets. |
| // Leaving in the relocation records confuses it (see |
| // https://golang.org/issue/22068) so drop them for Darwin. |
| if target.IsDarwin() { |
| return rr, false |
| } |
| rs := ldr.ResolveABIAlias(r.Sym()) |
| rr.Xsym = loader.Sym(ldr.SymSect(rs).Sym) |
| rr.Xadd = r.Add() + ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr) |
| |
| // r.Sym() can be 0 when CALL $(constant) is transformed from absolute PC to relative PC call. |
| case objabi.R_GOTPCREL, objabi.R_CALL, objabi.R_PCREL: |
| rs := ldr.ResolveABIAlias(r.Sym()) |
| if rt == objabi.R_GOTPCREL && target.IsDynlinkingGo() && target.IsDarwin() && rs != 0 { |
| rr.Xadd = r.Add() |
| rr.Xadd -= int64(siz) // relative to address after the relocated chunk |
| rr.Xsym = rs |
| break |
| } |
| if rs != 0 && ldr.SymType(rs) == sym.SUNDEFEXT { |
| // pass through to the external linker. |
| rr.Xadd = 0 |
| if target.IsElf() { |
| rr.Xadd -= int64(siz) |
| } |
| rr.Xsym = rs |
| break |
| } |
| if rs != 0 && (ldr.SymSect(rs) != ldr.SymSect(s) || rt == objabi.R_GOTPCREL) { |
| // set up addend for eventual relocation via outer symbol. |
| rs := rs |
| rs, off := FoldSubSymbolOffset(ldr, rs) |
| rr.Xadd = r.Add() + off |
| rr.Xadd -= int64(siz) // relative to address after the relocated chunk |
| rr.Xsym = rs |
| break |
| } |
| return rr, false |
| |
| case objabi.R_XCOFFREF: |
| return ExtrelocSimple(ldr, r), true |
| |
| // These reloc types don't need external relocations. |
| case objabi.R_ADDROFF, objabi.R_WEAKADDROFF, objabi.R_METHODOFF, objabi.R_ADDRCUOFF, |
| objabi.R_SIZE, objabi.R_CONST, objabi.R_GOTOFF: |
| return rr, false |
| } |
| return rr, true |
| } |
| |
| // ExtrelocSimple creates a simple external relocation from r, with the same |
| // symbol and addend. |
| func ExtrelocSimple(ldr *loader.Loader, r loader.Reloc) loader.ExtReloc { |
| var rr loader.ExtReloc |
| rs := ldr.ResolveABIAlias(r.Sym()) |
| rr.Xsym = rs |
| rr.Xadd = r.Add() |
| rr.Type = r.Type() |
| rr.Size = r.Siz() |
| return rr |
| } |
| |
| // ExtrelocViaOuterSym creates an external relocation from r targeting the |
| // outer symbol and folding the subsymbol's offset into the addend. |
| func ExtrelocViaOuterSym(ldr *loader.Loader, r loader.Reloc, s loader.Sym) loader.ExtReloc { |
| // set up addend for eventual relocation via outer symbol. |
| var rr loader.ExtReloc |
| rs := ldr.ResolveABIAlias(r.Sym()) |
| rs, off := FoldSubSymbolOffset(ldr, rs) |
| rr.Xadd = r.Add() + off |
| rst := ldr.SymType(rs) |
| if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil { |
| ldr.Errorf(s, "missing section for %s", ldr.SymName(rs)) |
| } |
| rr.Xsym = rs |
| rr.Type = r.Type() |
| rr.Size = r.Siz() |
| return rr |
| } |
| |
| // relocSymState hold state information needed when making a series of |
| // successive calls to relocsym(). The items here are invariant |
| // (meaning that they are set up once initially and then don't change |
| // during the execution of relocsym), with the exception of a slice |
| // used to facilitate batch allocation of external relocations. Calls |
| // to relocsym happen in parallel; the assumption is that each |
| // parallel thread will have its own state object. |
| type relocSymState struct { |
| target *Target |
| ldr *loader.Loader |
| err *ErrorReporter |
| syms *ArchSyms |
| } |
| |
| // makeRelocSymState creates a relocSymState container object to |
| // pass to relocsym(). If relocsym() calls happen in parallel, |
| // each parallel thread should have its own state object. |
| func (ctxt *Link) makeRelocSymState() *relocSymState { |
| return &relocSymState{ |
| target: &ctxt.Target, |
| ldr: ctxt.loader, |
| err: &ctxt.ErrorReporter, |
| syms: &ctxt.ArchSyms, |
| } |
| } |
| |
| func windynrelocsym(ctxt *Link, rel *loader.SymbolBuilder, s loader.Sym) { |
| var su *loader.SymbolBuilder |
| relocs := ctxt.loader.Relocs(s) |
| for ri := 0; ri < relocs.Count(); ri++ { |
| r := relocs.At(ri) |
| if r.IsMarker() { |
| continue // skip marker relocations |
| } |
| targ := r.Sym() |
| if targ == 0 { |
| continue |
| } |
| rt := r.Type() |
| if !ctxt.loader.AttrReachable(targ) { |
| if rt == objabi.R_WEAKADDROFF { |
| continue |
| } |
| ctxt.Errorf(s, "dynamic relocation to unreachable symbol %s", |
| ctxt.loader.SymName(targ)) |
| } |
| |
| tplt := ctxt.loader.SymPlt(targ) |
| tgot := ctxt.loader.SymGot(targ) |
| if tplt == -2 && tgot != -2 { // make dynimport JMP table for PE object files. |
| tplt := int32(rel.Size()) |
| ctxt.loader.SetPlt(targ, tplt) |
| |
| if su == nil { |
| su = ctxt.loader.MakeSymbolUpdater(s) |
| } |
| r.SetSym(rel.Sym()) |
| r.SetAdd(int64(tplt)) |
| |
| // jmp *addr |
| switch ctxt.Arch.Family { |
| default: |
| ctxt.Errorf(s, "unsupported arch %v", ctxt.Arch.Family) |
| return |
| case sys.I386: |
| rel.AddUint8(0xff) |
| rel.AddUint8(0x25) |
| rel.AddAddrPlus(ctxt.Arch, targ, 0) |
| rel.AddUint8(0x90) |
| rel.AddUint8(0x90) |
| case sys.AMD64: |
| rel.AddUint8(0xff) |
| rel.AddUint8(0x24) |
| rel.AddUint8(0x25) |
| rel.AddAddrPlus4(ctxt.Arch, targ, 0) |
| rel.AddUint8(0x90) |
| } |
| } else if tplt >= 0 { |
| if su == nil { |
| su = ctxt.loader.MakeSymbolUpdater(s) |
| } |
| r.SetSym(rel.Sym()) |
| r.SetAdd(int64(tplt)) |
| } |
| } |
| } |
| |
| // windynrelocsyms generates jump table to C library functions that will be |
| // added later. windynrelocsyms writes the table into .rel symbol. |
| func (ctxt *Link) windynrelocsyms() { |
| if !(ctxt.IsWindows() && iscgo && ctxt.IsInternal()) { |
| return |
| } |
| |
| rel := ctxt.loader.CreateSymForUpdate(".rel", 0) |
| rel.SetType(sym.STEXT) |
| |
| for _, s := range ctxt.Textp { |
| windynrelocsym(ctxt, rel, s) |
| } |
| |
| ctxt.Textp = append(ctxt.Textp, rel.Sym()) |
| } |
| |
| func dynrelocsym(ctxt *Link, s loader.Sym) { |
| target := &ctxt.Target |
| ldr := ctxt.loader |
| syms := &ctxt.ArchSyms |
| relocs := ldr.Relocs(s) |
| for ri := 0; ri < relocs.Count(); ri++ { |
| r := relocs.At(ri) |
| if r.IsMarker() { |
| continue // skip marker relocations |
| } |
| if ctxt.BuildMode == BuildModePIE && ctxt.LinkMode == LinkInternal { |
| // It's expected that some relocations will be done |
| // later by relocsym (R_TLS_LE, R_ADDROFF), so |
| // don't worry if Adddynrel returns false. |
| thearch.Adddynrel(target, ldr, syms, s, r, ri) |
| continue |
| } |
| |
| rSym := r.Sym() |
| if rSym != 0 && ldr.SymType(rSym) == sym.SDYNIMPORT || r.Type() >= objabi.ElfRelocOffset { |
| if rSym != 0 && !ldr.AttrReachable(rSym) { |
| ctxt.Errorf(s, "dynamic relocation to unreachable symbol %s", ldr.SymName(rSym)) |
| } |
| if !thearch.Adddynrel(target, ldr, syms, s, r, ri) { |
| ctxt.Errorf(s, "unsupported dynamic relocation for symbol %s (type=%d (%s) stype=%d (%s))", ldr.SymName(rSym), r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.SymType(rSym), ldr.SymType(rSym)) |
| } |
| } |
| } |
| } |
| |
| func (state *dodataState) dynreloc(ctxt *Link) { |
| if ctxt.HeadType == objabi.Hwindows { |
| return |
| } |
| // -d suppresses dynamic loader format, so we may as well not |
| // compute these sections or mark their symbols as reachable. |
| if *FlagD { |
| return |
| } |
| |
| for _, s := range ctxt.Textp { |
| dynrelocsym(ctxt, s) |
| } |
| for _, syms := range state.data { |
| for _, s := range syms { |
| dynrelocsym(ctxt, s) |
| } |
| } |
| if ctxt.IsELF { |
| elfdynhash(ctxt) |
| } |
| } |
| |
| func CodeblkPad(ctxt *Link, out *OutBuf, addr int64, size int64, pad []byte) { |
| writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, ctxt.Textp, addr, size, pad) |
| } |
| |
| const blockSize = 1 << 20 // 1MB chunks written at a time. |
| |
| // writeBlocks writes a specified chunk of symbols to the output buffer. It |
| // breaks the write up into ≥blockSize chunks to write them out, and schedules |
| // as many goroutines as necessary to accomplish this task. This call then |
| // blocks, waiting on the writes to complete. Note that we use the sem parameter |
| // to limit the number of concurrent writes taking place. |
| func writeBlocks(ctxt *Link, out *OutBuf, sem chan int, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) { |
| for i, s := range syms { |
| if ldr.SymValue(s) >= addr && !ldr.AttrSubSymbol(s) { |
| syms = syms[i:] |
| break |
| } |
| } |
| |
| var wg sync.WaitGroup |
| max, lastAddr, written := int64(blockSize), addr+size, int64(0) |
| for addr < lastAddr { |
| // Find the last symbol we'd write. |
| idx := -1 |
| for i, s := range syms { |
| if ldr.AttrSubSymbol(s) { |
| continue |
| } |
| |
| // If the next symbol's size would put us out of bounds on the total length, |
| // stop looking. |
| end := ldr.SymValue(s) + ldr.SymSize(s) |
| if end > lastAddr { |
| break |
| } |
| |
| // We're gonna write this symbol. |
| idx = i |
| |
| // If we cross over the max size, we've got enough symbols. |
| if end > addr+max { |
| break |
| } |
| } |
| |
| // If we didn't find any symbols to write, we're done here. |
| if idx < 0 { |
| break |
| } |
| |
| // Compute the length to write, including padding. |
| // We need to write to the end address (lastAddr), or the next symbol's |
| // start address, whichever comes first. If there is no more symbols, |
| // just write to lastAddr. This ensures we don't leave holes between the |
| // blocks or at the end. |
| length := int64(0) |
| if idx+1 < len(syms) { |
| // Find the next top-level symbol. |
| // Skip over sub symbols so we won't split a containter symbol |
| // into two blocks. |
| next := syms[idx+1] |
| for ldr.AttrSubSymbol(next) { |
| idx++ |
| next = syms[idx+1] |
| } |
| length = ldr.SymValue(next) - addr |
| } |
| if length == 0 || length > lastAddr-addr { |
| length = lastAddr - addr |
| } |
| |
| // Start the block output operator. |
| if o, err := out.View(uint64(out.Offset() + written)); err == nil { |
| sem <- 1 |
| wg.Add(1) |
| go func(o *OutBuf, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) { |
| writeBlock(ctxt, o, ldr, syms, addr, size, pad) |
| wg.Done() |
| <-sem |
| }(o, ldr, syms, addr, length, pad) |
| } else { // output not mmaped, don't parallelize. |
| writeBlock(ctxt, out, ldr, syms, addr, length, pad) |
| } |
| |
| // Prepare for the next loop. |
| if idx != -1 { |
| syms = syms[idx+1:] |
| } |
| written += length |
| addr += length |
| } |
| wg.Wait() |
| } |
| |
| func writeBlock(ctxt *Link, out *OutBuf, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) { |
| |
| st := ctxt.makeRelocSymState() |
| |
| // This doesn't distinguish the memory size from the file |
| // size, and it lays out the file based on Symbol.Value, which |
| // is the virtual address. DWARF compression changes file sizes, |
| // so dwarfcompress will fix this up later if necessary. |
| eaddr := addr + size |
| for _, s := range syms { |
| if ldr.AttrSubSymbol(s) { |
| continue |
| } |
| val := ldr.SymValue(s) |
| if val >= eaddr { |
| break |
| } |
| if val < addr { |
| ldr.Errorf(s, "phase error: addr=%#x but sym=%#x type=%v sect=%v", addr, val, ldr.SymType(s), ldr.SymSect(s).Name) |
| errorexit() |
| } |
| if addr < val { |
| out.WriteStringPad("", int(val-addr), pad) |
| addr = val |
| } |
| P := out.WriteSym(ldr, s) |
| st.relocsym(s, P) |
| if f, ok := ctxt.generatorSyms[s]; ok { |
| f(ctxt, s) |
| } |
| addr += int64(len(P)) |
| siz := ldr.SymSize(s) |
| if addr < val+siz { |
| out.WriteStringPad("", int(val+siz-addr), pad) |
| addr = val + siz |
| } |
| if addr != val+siz { |
| ldr.Errorf(s, "phase error: addr=%#x value+size=%#x", addr, val+siz) |
| errorexit() |
| } |
| if val+siz >= eaddr { |
| break |
| } |
| } |
| |
| if addr < eaddr { |
| out.WriteStringPad("", int(eaddr-addr), pad) |
| } |
| } |
| |
| type writeFn func(*Link, *OutBuf, int64, int64) |
| |
| // writeParallel handles scheduling parallel execution of data write functions. |
| func writeParallel(wg *sync.WaitGroup, fn writeFn, ctxt *Link, seek, vaddr, length uint64) { |
| if out, err := ctxt.Out.View(seek); err != nil { |
| ctxt.Out.SeekSet(int64(seek)) |
| fn(ctxt, ctxt.Out, int64(vaddr), int64(length)) |
| } else { |
| wg.Add(1) |
| go func() { |
| defer wg.Done() |
| fn(ctxt, out, int64(vaddr), int64(length)) |
| }() |
| } |
| } |
| |
| func datblk(ctxt *Link, out *OutBuf, addr, size int64) { |
| writeDatblkToOutBuf(ctxt, out, addr, size) |
| } |
| |
| // Used only on Wasm for now. |
| func DatblkBytes(ctxt *Link, addr int64, size int64) []byte { |
| buf := make([]byte, size) |
| out := &OutBuf{heap: buf} |
| writeDatblkToOutBuf(ctxt, out, addr, size) |
| return buf |
| } |
| |
| func writeDatblkToOutBuf(ctxt *Link, out *OutBuf, addr int64, size int64) { |
| writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, ctxt.datap, addr, size, zeros[:]) |
| } |
| |
| func dwarfblk(ctxt *Link, out *OutBuf, addr int64, size int64) { |
| // Concatenate the section symbol lists into a single list to pass |
| // to writeBlocks. |
| // |
| // NB: ideally we would do a separate writeBlocks call for each |
| // section, but this would run the risk of undoing any file offset |
| // adjustments made during layout. |
| n := 0 |
| for i := range dwarfp { |
| n += len(dwarfp[i].syms) |
| } |
| syms := make([]loader.Sym, 0, n) |
| for i := range dwarfp { |
| syms = append(syms, dwarfp[i].syms...) |
| } |
| writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, syms, addr, size, zeros[:]) |
| } |
| |
| var zeros [512]byte |
| |
| var ( |
| strdata = make(map[string]string) |
| strnames []string |
| ) |
| |
| func addstrdata1(ctxt *Link, arg string) { |
| eq := strings.Index(arg, "=") |
| dot := strings.LastIndex(arg[:eq+1], ".") |
| if eq < 0 || dot < 0 { |
| Exitf("-X flag requires argument of the form importpath.name=value") |
| } |
| pkg := arg[:dot] |
| if ctxt.BuildMode == BuildModePlugin && pkg == "main" { |
| pkg = *flagPluginPath |
| } |
| pkg = objabi.PathToPrefix(pkg) |
| name := pkg + arg[dot:eq] |
| value := arg[eq+1:] |
| if _, ok := strdata[name]; !ok { |
| strnames = append(strnames, name) |
| } |
| strdata[name] = value |
| } |
| |
| // addstrdata sets the initial value of the string variable name to value. |
| func addstrdata(arch *sys.Arch, l *loader.Loader, name, value string) { |
| s := l.Lookup(name, 0) |
| if s == 0 { |
| return |
| } |
| if goType := l.SymGoType(s); goType == 0 { |
| return |
| } else if typeName := l.SymName(goType); typeName != "type.string" { |
| Errorf(nil, "%s: cannot set with -X: not a var of type string (%s)", name, typeName) |
| return |
| } |
| if !l.AttrReachable(s) { |
| return // don't bother setting unreachable variable |
| } |
| bld := l.MakeSymbolUpdater(s) |
| if bld.Type() == sym.SBSS { |
| bld.SetType(sym.SDATA) |
| } |
| |
| p := fmt.Sprintf("%s.str", name) |
| sbld := l.CreateSymForUpdate(p, 0) |
| sbld.Addstring(value) |
| sbld.SetType(sym.SRODATA) |
| |
| bld.SetSize(0) |
| bld.SetData(make([]byte, 0, arch.PtrSize*2)) |
| bld.SetReadOnly(false) |
| bld.ResetRelocs() |
| bld.AddAddrPlus(arch, sbld.Sym(), 0) |
| bld.AddUint(arch, uint64(len(value))) |
| } |
| |
| func (ctxt *Link) dostrdata() { |
| for _, name := range strnames { |
| addstrdata(ctxt.Arch, ctxt.loader, name, strdata[name]) |
| } |
| } |
| |
| // addgostring adds str, as a Go string value, to s. symname is the name of the |
| // symbol used to define the string data and must be unique per linked object. |
| func addgostring(ctxt *Link, ldr *loader.Loader, s *loader.SymbolBuilder, symname, str string) { |
| sdata := ldr.CreateSymForUpdate(symname, 0) |
| if sdata.Type() != sym.Sxxx { |
| ctxt.Errorf(s.Sym(), "duplicate symname in addgostring: %s", symname) |
| } |
| sdata.SetLocal(true) |
| sdata.SetType(sym.SRODATA) |
| sdata.SetSize(int64(len(str))) |
| sdata.SetData([]byte(str)) |
| s.AddAddr(ctxt.Arch, sdata.Sym()) |
| s.AddUint(ctxt.Arch, uint64(len(str))) |
| } |
| |
| func addinitarrdata(ctxt *Link, ldr *loader.Loader, s loader.Sym) { |
| p := ldr.SymName(s) + ".ptr" |
| sp := ldr.CreateSymForUpdate(p, 0) |
| sp.SetType(sym.SINITARR) |
| sp.SetSize(0) |
| sp.SetDuplicateOK(true) |
| sp.AddAddr(ctxt.Arch, s) |
| } |
| |
| // symalign returns the required alignment for the given symbol s. |
| func symalign(ldr *loader.Loader, s loader.Sym) int32 { |
| min := int32(thearch.Minalign) |
| align := ldr.SymAlign(s) |
| if align >= min { |
| return align |
| } else if align != 0 { |
| return min |
| } |
| // FIXME: figure out a way to avoid checking by name here. |
| sname := ldr.SymName(s) |
| if strings.HasPrefix(sname, "go.string.") || strings.HasPrefix(sname, "type..namedata.") { |
| // String data is just bytes. |
| // If we align it, we waste a lot of space to padding. |
| return min |
| } |
| align = int32(thearch.Maxalign) |
| ssz := ldr.SymSize(s) |
| for int64(align) > ssz && align > min { |
| align >>= 1 |
| } |
| ldr.SetSymAlign(s, align) |
| return align |
| } |
| |
| func aligndatsize(state *dodataState, datsize int64, s loader.Sym) int64 { |
| return Rnd(datsize, int64(symalign(state.ctxt.loader, s))) |
| } |
| |
| const debugGCProg = false |
| |
| type GCProg struct { |
| ctxt *Link |
| sym *loader.SymbolBuilder |
| w gcprog.Writer |
| } |
| |
| func (p *GCProg) Init(ctxt *Link, name string) { |
| p.ctxt = ctxt |
| p.sym = ctxt.loader.CreateSymForUpdate(name, 0) |
| p.w.Init(p.writeByte()) |
| if debugGCProg { |
| fmt.Fprintf(os.Stderr, "ld: start GCProg %s\n", name) |
| p.w.Debug(os.Stderr) |
| } |
| } |
| |
| func (p *GCProg) writeByte() func(x byte) { |
| return func(x byte) { |
| p.sym.AddUint8(x) |
| } |
| } |
| |
| func (p *GCProg) End(size int64) { |
| p.w.ZeroUntil(size / int64(p.ctxt.Arch.PtrSize)) |
| p.w.End() |
| if debugGCProg { |
| fmt.Fprintf(os.Stderr, "ld: end GCProg\n") |
| } |
| } |
| |
| func (p *GCProg) AddSym(s loader.Sym) { |
| ldr := p.ctxt.loader |
| typ := ldr.SymGoType(s) |
| |
| // Things without pointers should be in sym.SNOPTRDATA or sym.SNOPTRBSS; |
| // everything we see should have pointers and should therefore have a type. |
| if typ == 0 { |
| switch ldr.SymName(s) { |
| case "runtime.data", "runtime.edata", "runtime.bss", "runtime.ebss": |
| // Ignore special symbols that are sometimes laid out |
| // as real symbols. See comment about dyld on darwin in |
| // the address function. |
| return |
| } |
| p.ctxt.Errorf(p.sym.Sym(), "missing Go type information for global symbol %s: size %d", ldr.SymName(s), ldr.SymSize(s)) |
| return |
| } |
| |
| ptrsize := int64(p.ctxt.Arch.PtrSize) |
| typData := ldr.Data(typ) |
| nptr := decodetypePtrdata(p.ctxt.Arch, typData) / ptrsize |
| |
| if debugGCProg { |
| fmt.Fprintf(os.Stderr, "gcprog sym: %s at %d (ptr=%d+%d)\n", ldr.SymName(s), ldr.SymValue(s), ldr.SymValue(s)/ptrsize, nptr) |
| } |
| |
| sval := ldr.SymValue(s) |
| if decodetypeUsegcprog(p.ctxt.Arch, typData) == 0 { |
| // Copy pointers from mask into program. |
| mask := decodetypeGcmask(p.ctxt, typ) |
| for i := int64(0); i < nptr; i++ { |
| if (mask[i/8]>>uint(i%8))&1 != 0 { |
| p.w.Ptr(sval/ptrsize + i) |
| } |
| } |
| return |
| } |
| |
| // Copy program. |
| prog := decodetypeGcprog(p.ctxt, typ) |
| p.w.ZeroUntil(sval / ptrsize) |
| p.w.Append(prog[4:], nptr) |
| } |
| |
| // cutoff is the maximum data section size permitted by the linker |
| // (see issue #9862). |
| const cutoff = 2e9 // 2 GB (or so; looks better in errors than 2^31) |
| |
| func (state *dodataState) checkdatsize(symn sym.SymKind) { |
| if state.datsize > cutoff { |
| Errorf(nil, "too much data in section %v (over %v bytes)", symn, cutoff) |
| } |
| } |
| |
| // fixZeroSizedSymbols gives a few special symbols with zero size some space. |
| func fixZeroSizedSymbols(ctxt *Link) { |
| // The values in moduledata are filled out by relocations |
| // pointing to the addresses of these special symbols. |
| // Typically these symbols have no size and are not laid |
| // out with their matching section. |
| // |
| // However on darwin, dyld will find the special symbol |
| // in the first loaded module, even though it is local. |
| // |
| // (An hypothesis, formed without looking in the dyld sources: |
| // these special symbols have no size, so their address |
| // matches a real symbol. The dynamic linker assumes we |
| // want the normal symbol with the same address and finds |
| // it in the other module.) |
| // |
| // To work around this we lay out the symbls whose |
| // addresses are vital for multi-module programs to work |
| // as normal symbols, and give them a little size. |
| // |
| // On AIX, as all DATA sections are merged together, ld might not put |
| // these symbols at the beginning of their respective section if there |
| // aren't real symbols, their alignment might not match the |
| // first symbol alignment. Therefore, there are explicitly put at the |
| // beginning of their section with the same alignment. |
| if !(ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin) && !(ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) { |
| return |
| } |
| |
| ldr := ctxt.loader |
| bss := ldr.CreateSymForUpdate("runtime.bss", 0) |
| bss.SetSize(8) |
| ldr.SetAttrSpecial(bss.Sym(), false) |
| |
| ebss := ldr.CreateSymForUpdate("runtime.ebss", 0) |
| ldr.SetAttrSpecial(ebss.Sym(), false) |
| |
| data := ldr.CreateSymForUpdate("runtime.data", 0) |
| data.SetSize(8) |
| ldr.SetAttrSpecial(data.Sym(), false) |
| |
| edata := ldr.CreateSymForUpdate("runtime.edata", 0) |
| ldr.SetAttrSpecial(edata.Sym(), false) |
| |
| if ctxt.HeadType == objabi.Haix { |
| // XCOFFTOC symbols are part of .data section. |
| edata.SetType(sym.SXCOFFTOC) |
| } |
| |
| types := ldr.CreateSymForUpdate("runtime.types", 0) |
| types.SetType(sym.STYPE) |
| types.SetSize(8) |
| ldr.SetAttrSpecial(types.Sym(), false) |
| |
| etypes := ldr.CreateSymForUpdate("runtime.etypes", 0) |
| etypes.SetType(sym.SFUNCTAB) |
| ldr.SetAttrSpecial(etypes.Sym(), false) |
| |
| if ctxt.HeadType == objabi.Haix { |
| rodata := ldr.CreateSymForUpdate("runtime.rodata", 0) |
| rodata.SetType(sym.SSTRING) |
| rodata.SetSize(8) |
| ldr.SetAttrSpecial(rodata.Sym(), false) |
| |
| erodata := ldr.CreateSymForUpdate("runtime.erodata", 0) |
| ldr.SetAttrSpecial(erodata.Sym(), false) |
| } |
| } |
| |
| // makeRelroForSharedLib creates a section of readonly data if necessary. |
| func (state *dodataState) makeRelroForSharedLib(target *Link) { |
| if !target.UseRelro() { |
| return |
| } |
| |
| // "read only" data with relocations needs to go in its own section |
| // when building a shared library. We do this by boosting objects of |
| // type SXXX with relocations to type SXXXRELRO. |
| ldr := target.loader |
| for _, symnro := range sym.ReadOnly { |
| symnrelro := sym.RelROMap[symnro] |
| |
| ro := []loader.Sym{} |
| relro := state.data[symnrelro] |
| |
| for _, s := range state.data[symnro] { |
| relocs := ldr.Relocs(s) |
| isRelro := relocs.Count() > 0 |
| switch state.symType(s) { |
| case sym.STYPE, sym.STYPERELRO, sym.SGOFUNCRELRO: |
| // Symbols are not sorted yet, so it is possible |
| // that an Outer symbol has been changed to a |
| // relro Type before it reaches here. |
| isRelro = true |
| case sym.SFUNCTAB: |
| if ldr.SymName(s) == "runtime.etypes" { |
| // runtime.etypes must be at the end of |
| // the relro data. |
| isRelro = true |
| } |
| } |
| if isRelro { |
| state.setSymType(s, symnrelro) |
| if outer := ldr.OuterSym(s); outer != 0 { |
| state.setSymType(outer, symnrelro) |
| } |
| relro = append(relro, s) |
| } else { |
| ro = append(ro, s) |
| } |
| } |
| |
| // Check that we haven't made two symbols with the same .Outer into |
| // different types (because references two symbols with non-nil Outer |
| // become references to the outer symbol + offset it's vital that the |
| // symbol and the outer end up in the same section). |
| for _, s := range relro { |
| if outer := ldr.OuterSym(s); outer != 0 { |
| st := state.symType(s) |
| ost := state.symType(outer) |
| if st != ost { |
| state.ctxt.Errorf(s, "inconsistent types for symbol and its Outer %s (%v != %v)", |
| ldr.SymName(outer), st, ost) |
| } |
| } |
| } |
| |
| state.data[symnro] = ro |
| state.data[symnrelro] = relro |
| } |
| } |
| |
| // dodataState holds bits of state information needed by dodata() and the |
| // various helpers it calls. The lifetime of these items should not extend |
| // past the end of dodata(). |
| type dodataState struct { |
| // Link context |
| ctxt *Link |
| // Data symbols bucketed by type. |
| data [sym.SXREF][]loader.Sym |
| // Max alignment for each flavor of data symbol. |
| dataMaxAlign [sym.SXREF]int32 |
| // Overridden sym type |
| symGroupType []sym.SymKind |
| // Current data size so far. |
| datsize int64 |
| } |
| |
| // A note on symType/setSymType below: |
| // |
| // In the legacy linker, the types of symbols (notably data symbols) are |
| // changed during the symtab() phase so as to insure that similar symbols |
| // are bucketed together, then their types are changed back again during |
| // dodata. Symbol to section assignment also plays tricks along these lines |
| // in the case where a relro segment is needed. |
| // |
| // The value returned from setType() below reflects the effects of |
| // any overrides made by symtab and/or dodata. |
| |
| // symType returns the (possibly overridden) type of 's'. |
| func (state *dodataState) symType(s loader.Sym) sym.SymKind { |
| if int(s) < len(state.symGroupType) { |
| if override := state.symGroupType[s]; override != 0 { |
| return override |
| } |
| } |
| return state.ctxt.loader.SymType(s) |
| } |
| |
| // setSymType sets a new override type for 's'. |
| func (state *dodataState) setSymType(s loader.Sym, kind sym.SymKind) { |
| if s == 0 { |
| panic("bad") |
| } |
| if int(s) < len(state.symGroupType) { |
| state.symGroupType[s] = kind |
| } else { |
| su := state.ctxt.loader.MakeSymbolUpdater(s) |
| su.SetType(kind) |
| } |
| } |
| |
| func (ctxt *Link) dodata(symGroupType []sym.SymKind) { |
| |
| // Give zeros sized symbols space if necessary. |
| fixZeroSizedSymbols(ctxt) |
| |
| // Collect data symbols by type into data. |
| state := dodataState{ctxt: ctxt, symGroupType: symGroupType} |
| ldr := ctxt.loader |
| for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ { |
| if !ldr.AttrReachable(s) || ldr.AttrSpecial(s) || ldr.AttrSubSymbol(s) || |
| !ldr.TopLevelSym(s) { |
| continue |
| } |
| |
| st := state.symType(s) |
| |
| if st <= sym.STEXT || st >= sym.SXREF { |
| continue |
| } |
| state.data[st] = append(state.data[st], s) |
| |
| // Similarly with checking the onlist attr. |
| if ldr.AttrOnList(s) { |
| log.Fatalf("symbol %s listed multiple times", ldr.SymName(s)) |
| } |
| ldr.SetAttrOnList(s, true) |
| } |
| |
| // Now that we have the data symbols, but before we start |
| // to assign addresses, record all the necessary |
| // dynamic relocations. These will grow the relocation |
| // symbol, which is itself data. |
| // |
| // On darwin, we need the symbol table numbers for dynreloc. |
| if ctxt.HeadType == objabi.Hdarwin { |
| machosymorder(ctxt) |
| } |
| state.dynreloc(ctxt) |
| |
| // Move any RO data with relocations to a separate section. |
| state.makeRelroForSharedLib(ctxt) |
| |
| // Set alignment for the symbol with the largest known index, |
| // so as to trigger allocation of the loader's internal |
| // alignment array. This will avoid data races in the parallel |
| // section below. |
| lastSym := loader.Sym(ldr.NSym() - 1) |
| ldr.SetSymAlign(lastSym, ldr.SymAlign(lastSym)) |
| |
| // Sort symbols. |
| var wg sync.WaitGroup |
| for symn := range state.data { |
| symn := sym.SymKind(symn) |
| wg.Add(1) |
| go func() { |
| state.data[symn], state.dataMaxAlign[symn] = state.dodataSect(ctxt, symn, state.data[symn]) |
| wg.Done() |
| }() |
| } |
| wg.Wait() |
| |
| if ctxt.IsELF { |
| // Make .rela and .rela.plt contiguous, the ELF ABI requires this |
| // and Solaris actually cares. |
| syms := state.data[sym.SELFROSECT] |
| reli, plti := -1, -1 |
| for i, s := range syms { |
| switch ldr.SymName(s) { |
| case ".rel.plt", ".rela.plt": |
| plti = i |
| case ".rel", ".rela": |
| reli = i |
| } |
| } |
| if reli >= 0 && plti >= 0 && plti != reli+1 { |
| var first, second int |
| if plti > reli { |
| first, second = reli, plti |
| } else { |
| first, second = plti, reli |
| } |
| rel, plt := syms[reli], syms[plti] |
| copy(syms[first+2:], syms[first+1:second]) |
| syms[first+0] = rel |
| syms[first+1] = plt |
| |
| // Make sure alignment doesn't introduce a gap. |
| // Setting the alignment explicitly prevents |
| // symalign from basing it on the size and |
| // getting it wrong. |
| ldr.SetSymAlign(rel, int32(ctxt.Arch.RegSize)) |
| ldr.SetSymAlign(plt, int32(ctxt.Arch.RegSize)) |
| } |
| state.data[sym.SELFROSECT] = syms |
| } |
| |
| if ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal { |
| // These symbols must have the same alignment as their section. |
| // Otherwize, ld might change the layout of Go sections. |
| ldr.SetSymAlign(ldr.Lookup("runtime.data", 0), state.dataMaxAlign[sym.SDATA]) |
| ldr.SetSymAlign(ldr.Lookup("runtime.bss", 0), state.dataMaxAlign[sym.SBSS]) |
| } |
| |
| // Create *sym.Section objects and assign symbols to sections for |
| // data/rodata (and related) symbols. |
| state.allocateDataSections(ctxt) |
| |
| // Create *sym.Section objects and assign symbols to sections for |
| // DWARF symbols. |
| state.allocateDwarfSections(ctxt) |
| |
| /* number the sections */ |
| n := int16(1) |
| |
| for _, sect := range Segtext.Sections { |
| sect.Extnum = n |
| n++ |
| } |
| for _, sect := range Segrodata.Sections { |
| sect.Extnum = n |
| n++ |
| } |
| for _, sect := range Segrelrodata.Sections { |
| sect.Extnum = n |
| n++ |
| } |
| for _, sect := range Segdata.Sections { |
| sect.Extnum = n |
| n++ |
| } |
| for _, sect := range Segdwarf.Sections { |
| sect.Extnum = n |
| n++ |
| } |
| } |
| |
| // allocateDataSectionForSym creates a new sym.Section into which a a |
| // single symbol will be placed. Here "seg" is the segment into which |
| // the section will go, "s" is the symbol to be placed into the new |
| // section, and "rwx" contains permissions for the section. |
| func (state *dodataState) allocateDataSectionForSym(seg *sym.Segment, s loader.Sym, rwx int) *sym.Section { |
| ldr := state.ctxt.loader |
| sname := ldr.SymName(s) |
| sect := addsection(ldr, state.ctxt.Arch, seg, sname, rwx) |
| sect.Align = symalign(ldr, s) |
| state.datsize = Rnd(state.datsize, int64(sect.Align)) |
| sect.Vaddr = uint64(state.datsize) |
| return sect |
| } |
| |
| // allocateNamedDataSection creates a new sym.Section for a category |
| // of data symbols. Here "seg" is the segment into which the section |
| // will go, "sName" is the name to give to the section, "types" is a |
| // range of symbol types to be put into the section, and "rwx" |
| // contains permissions for the section. |
| func (state *dodataState) allocateNamedDataSection(seg *sym.Segment, sName string, types []sym.SymKind, rwx int) *sym.Section { |
| sect := addsection(state.ctxt.loader, state.ctxt.Arch, seg, sName, rwx) |
| if len(types) == 0 { |
| sect.Align = 1 |
| } else if len(types) == 1 { |
| sect.Align = state.dataMaxAlign[types[0]] |
| } else { |
| for _, symn := range types { |
| align := state.dataMaxAlign[symn] |
| if sect.Align < align { |
| sect.Align = align |
| } |
| } |
| } |
| state.datsize = Rnd(state.datsize, int64(sect.Align)) |
| sect.Vaddr = uint64(state.datsize) |
| return sect |
| } |
| |
| // assignDsymsToSection assigns a collection of data symbols to a |
| // newly created section. "sect" is the section into which to place |
| // the symbols, "syms" holds the list of symbols to assign, |
| // "forceType" (if non-zero) contains a new sym type to apply to each |
| // sym during the assignment, and "aligner" is a hook to call to |
| // handle alignment during the assignment process. |
| func (state *dodataState) assignDsymsToSection(sect *sym.Section, syms []loader.Sym, forceType sym.SymKind, aligner func(state *dodataState, datsize int64, s loader.Sym) int64) { |
| ldr := state.ctxt.loader |
| for _, s := range syms { |
| state.datsize = aligner(state, state.datsize, s) |
| ldr.SetSymSect(s, sect) |
| if forceType != sym.Sxxx { |
| state.setSymType(s, forceType) |
| } |
| ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr)) |
| state.datsize += ldr.SymSize(s) |
| } |
| sect.Length = uint64(state.datsize) - sect.Vaddr |
| } |
| |
| func (state *dodataState) assignToSection(sect *sym.Section, symn sym.SymKind, forceType sym.SymKind) { |
| state.assignDsymsToSection(sect, state.data[symn], forceType, aligndatsize) |
| state.checkdatsize(symn) |
| } |
| |
| // allocateSingleSymSections walks through the bucketed data symbols |
| // with type 'symn', creates a new section for each sym, and assigns |
| // the sym to a newly created section. Section name is set from the |
| // symbol name. "Seg" is the segment into which to place the new |
| // section, "forceType" is the new sym.SymKind to assign to the symbol |
| // within the section, and "rwx" holds section permissions. |
| func (state *dodataState) allocateSingleSymSections(seg *sym.Segment, symn sym.SymKind, forceType sym.SymKind, rwx int) { |
| ldr := state.ctxt.loader |
| for _, s := range state.data[symn] { |
| sect := state.allocateDataSectionForSym(seg, s, rwx) |
| ldr.SetSymSect(s, sect) |
| state.setSymType(s, forceType) |
| ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr)) |
| state.datsize += ldr.SymSize(s) |
| sect.Length = uint64(state.datsize) - sect.Vaddr |
| } |
| state.checkdatsize(symn) |
| } |
| |
| // allocateNamedSectionAndAssignSyms creates a new section with the |
| // specified name, then walks through the bucketed data symbols with |
| // type 'symn' and assigns each of them to this new section. "Seg" is |
| // the segment into which to place the new section, "secName" is the |
| // name to give to the new section, "forceType" (if non-zero) contains |
| // a new sym type to apply to each sym during the assignment, and |
| // "rwx" holds section permissions. |
| func (state *dodataState) allocateNamedSectionAndAssignSyms(seg *sym.Segment, secName string, symn sym.SymKind, forceType sym.SymKind, rwx int) *sym.Section { |
| |
| sect := state.allocateNamedDataSection(seg, secName, []sym.SymKind{symn}, rwx) |
| state.assignDsymsToSection(sect, state.data[symn], forceType, aligndatsize) |
| return sect |
| } |
| |
| // allocateDataSections allocates sym.Section objects for data/rodata |
| // (and related) symbols, and then assigns symbols to those sections. |
| func (state *dodataState) allocateDataSections(ctxt *Link) { |
| // Allocate sections. |
| // Data is processed before segtext, because we need |
| // to see all symbols in the .data and .bss sections in order |
| // to generate garbage collection information. |
| |
| // Writable data sections that do not need any specialized handling. |
| writable := []sym.SymKind{ |
| sym.SBUILDINFO, |
| sym.SELFSECT, |
| sym.SMACHO, |
| sym.SMACHOGOT, |
| sym.SWINDOWS, |
| } |
| for _, symn := range writable { |
| state.allocateSingleSymSections(&Segdata, symn, sym.SDATA, 06) |
| } |
| ldr := ctxt.loader |
| |
| // .got (and .toc on ppc64) |
| if len(state.data[sym.SELFGOT]) > 0 { |
| sect := state.allocateNamedSectionAndAssignSyms(&Segdata, ".got", sym.SELFGOT, sym.SDATA, 06) |
| if ctxt.IsPPC64() { |
| for _, s := range state.data[sym.SELFGOT] { |
| // Resolve .TOC. symbol for this object file (ppc64) |
| |
| toc := ldr.Lookup(".TOC.", int(ldr.SymVersion(s))) |
| if toc != 0 { |
| ldr.SetSymSect(toc, sect) |
| ldr.AddInteriorSym(s, toc) |
| ldr.SetSymValue(toc, 0x8000) |
| } |
| } |
| } |
| } |
| |
| /* pointer-free data */ |
| sect := state.allocateNamedSectionAndAssignSyms(&Segdata, ".noptrdata", sym.SNOPTRDATA, sym.SDATA, 06) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.noptrdata", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.enoptrdata", 0), sect) |
| |
| hasinitarr := ctxt.linkShared |
| |
| /* shared library initializer */ |
| switch ctxt.BuildMode { |
| case BuildModeCArchive, BuildModeCShared, BuildModeShared, BuildModePlugin: |
| hasinitarr = true |
| } |
| |
| if ctxt.HeadType == objabi.Haix { |
| if len(state.data[sym.SINITARR]) > 0 { |
| Errorf(nil, "XCOFF format doesn't allow .init_array section") |
| } |
| } |
| |
| if hasinitarr && len(state.data[sym.SINITARR]) > 0 { |
| state.allocateNamedSectionAndAssignSyms(&Segdata, ".init_array", sym.SINITARR, sym.Sxxx, 06) |
| } |
| |
| /* data */ |
| sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".data", sym.SDATA, sym.SDATA, 06) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.data", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.edata", 0), sect) |
| dataGcEnd := state.datsize - int64(sect.Vaddr) |
| |
| // On AIX, TOC entries must be the last of .data |
| // These aren't part of gc as they won't change during the runtime. |
| state.assignToSection(sect, sym.SXCOFFTOC, sym.SDATA) |
| state.checkdatsize(sym.SDATA) |
| sect.Length = uint64(state.datsize) - sect.Vaddr |
| |
| /* bss */ |
| sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".bss", sym.SBSS, sym.Sxxx, 06) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.bss", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.ebss", 0), sect) |
| bssGcEnd := state.datsize - int64(sect.Vaddr) |
| |
| // Emit gcdata for bss symbols now that symbol values have been assigned. |
| gcsToEmit := []struct { |
| symName string |
| symKind sym.SymKind |
| gcEnd int64 |
| }{ |
| {"runtime.gcdata", sym.SDATA, dataGcEnd}, |
| {"runtime.gcbss", sym.SBSS, bssGcEnd}, |
| } |
| for _, g := range gcsToEmit { |
| var gc GCProg |
| gc.Init(ctxt, g.symName) |
| for _, s := range state.data[g.symKind] { |
| gc.AddSym(s) |
| } |
| gc.End(g.gcEnd) |
| } |
| |
| /* pointer-free bss */ |
| sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".noptrbss", sym.SNOPTRBSS, sym.Sxxx, 06) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.noptrbss", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.enoptrbss", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.end", 0), sect) |
| |
| // Coverage instrumentation counters for libfuzzer. |
| if len(state.data[sym.SLIBFUZZER_EXTRA_COUNTER]) > 0 { |
| state.allocateNamedSectionAndAssignSyms(&Segdata, "__libfuzzer_extra_counters", sym.SLIBFUZZER_EXTRA_COUNTER, sym.Sxxx, 06) |
| } |
| |
| if len(state.data[sym.STLSBSS]) > 0 { |
| var sect *sym.Section |
| // FIXME: not clear why it is sometimes necessary to suppress .tbss section creation. |
| if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && (ctxt.LinkMode == LinkExternal || !*FlagD) { |
| sect = addsection(ldr, ctxt.Arch, &Segdata, ".tbss", 06) |
| sect.Align = int32(ctxt.Arch.PtrSize) |
| // FIXME: why does this need to be set to zero? |
| sect.Vaddr = 0 |
| } |
| state.datsize = 0 |
| |
| for _, s := range state.data[sym.STLSBSS] { |
| state.datsize = aligndatsize(state, state.datsize, s) |
| if sect != nil { |
| ldr.SetSymSect(s, sect) |
| } |
| ldr.SetSymValue(s, state.datsize) |
| state.datsize += ldr.SymSize(s) |
| } |
| state.checkdatsize(sym.STLSBSS) |
| |
| if sect != nil { |
| sect.Length = uint64(state.datsize) |
| } |
| } |
| |
| /* |
| * We finished data, begin read-only data. |
| * Not all systems support a separate read-only non-executable data section. |
| * ELF and Windows PE systems do. |
| * OS X and Plan 9 do not. |
| * And if we're using external linking mode, the point is moot, |
| * since it's not our decision; that code expects the sections in |
| * segtext. |
| */ |
| var segro *sym.Segment |
| if ctxt.IsELF && ctxt.LinkMode == LinkInternal { |
| segro = &Segrodata |
| } else if ctxt.HeadType == objabi.Hwindows { |
| segro = &Segrodata |
| } else { |
| segro = &Segtext |
| } |
| |
| state.datsize = 0 |
| |
| /* read-only executable ELF, Mach-O sections */ |
| if len(state.data[sym.STEXT]) != 0 { |
| culprit := ldr.SymName(state.data[sym.STEXT][0]) |
| Errorf(nil, "dodata found an sym.STEXT symbol: %s", culprit) |
| } |
| state.allocateSingleSymSections(&Segtext, sym.SELFRXSECT, sym.SRODATA, 05) |
| state.allocateSingleSymSections(&Segtext, sym.SMACHOPLT, sym.SRODATA, 05) |
| |
| /* read-only data */ |
| sect = state.allocateNamedDataSection(segro, ".rodata", sym.ReadOnly, 04) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.rodata", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.erodata", 0), sect) |
| if !ctxt.UseRelro() { |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.types", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.etypes", 0), sect) |
| } |
| for _, symn := range sym.ReadOnly { |
| symnStartValue := state.datsize |
| state.assignToSection(sect, symn, sym.SRODATA) |
| if ctxt.HeadType == objabi.Haix { |
| // Read-only symbols might be wrapped inside their outer |
| // symbol. |
| // XCOFF symbol table needs to know the size of |
| // these outer symbols. |
| xcoffUpdateOuterSize(ctxt, state.datsize-symnStartValue, symn) |
| } |
| } |
| |
| /* read-only ELF, Mach-O sections */ |
| state.allocateSingleSymSections(segro, sym.SELFROSECT, sym.SRODATA, 04) |
| |
| // There is some data that are conceptually read-only but are written to by |
| // relocations. On GNU systems, we can arrange for the dynamic linker to |
| // mprotect sections after relocations are applied by giving them write |
| // permissions in the object file and calling them ".data.rel.ro.FOO". We |
| // divide the .rodata section between actual .rodata and .data.rel.ro.rodata, |
| // but for the other sections that this applies to, we just write a read-only |
| // .FOO section or a read-write .data.rel.ro.FOO section depending on the |
| // situation. |
| // TODO(mwhudson): It would make sense to do this more widely, but it makes |
| // the system linker segfault on darwin. |
| const relroPerm = 06 |
| const fallbackPerm = 04 |
| relroSecPerm := fallbackPerm |
| genrelrosecname := func(suffix string) string { |
| if suffix == "" { |
| return ".rodata" |
| } |
| return suffix |
| } |
| seg := segro |
| |
| if ctxt.UseRelro() { |
| segrelro := &Segrelrodata |
| if ctxt.LinkMode == LinkExternal && !ctxt.IsAIX() && !ctxt.IsDarwin() { |
| // Using a separate segment with an external |
| // linker results in some programs moving |
| // their data sections unexpectedly, which |
| // corrupts the moduledata. So we use the |
| // rodata segment and let the external linker |
| // sort out a rel.ro segment. |
| segrelro = segro |
| } else { |
| // Reset datsize for new segment. |
| state.datsize = 0 |
| } |
| |
| if !ctxt.IsDarwin() { // We don't need the special names on darwin. |
| genrelrosecname = func(suffix string) string { |
| return ".data.rel.ro" + suffix |
| } |
| } |
| |
| relroReadOnly := []sym.SymKind{} |
| for _, symnro := range sym.ReadOnly { |
| symn := sym.RelROMap[symnro] |
| relroReadOnly = append(relroReadOnly, symn) |
| } |
| seg = segrelro |
| relroSecPerm = relroPerm |
| |
| /* data only written by relocations */ |
| sect = state.allocateNamedDataSection(segrelro, genrelrosecname(""), relroReadOnly, relroSecPerm) |
| |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.types", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.etypes", 0), sect) |
| |
| for i, symnro := range sym.ReadOnly { |
| if i == 0 && symnro == sym.STYPE && ctxt.HeadType != objabi.Haix { |
| // Skip forward so that no type |
| // reference uses a zero offset. |
| // This is unlikely but possible in small |
| // programs with no other read-only data. |
| state.datsize++ |
| } |
| |
| symn := sym.RelROMap[symnro] |
| symnStartValue := state.datsize |
| |
| for _, s := range state.data[symn] { |
| outer := ldr.OuterSym(s) |
| if s != 0 && ldr.SymSect(outer) != nil && ldr.SymSect(outer) != sect { |
| ctxt.Errorf(s, "s.Outer (%s) in different section from s, %s != %s", ldr.SymName(outer), ldr.SymSect(outer).Name, sect.Name) |
| } |
| } |
| state.assignToSection(sect, symn, sym.SRODATA) |
| if ctxt.HeadType == objabi.Haix { |
| // Read-only symbols might be wrapped inside their outer |
| // symbol. |
| // XCOFF symbol table needs to know the size of |
| // these outer symbols. |
| xcoffUpdateOuterSize(ctxt, state.datsize-symnStartValue, symn) |
| } |
| } |
| |
| sect.Length = uint64(state.datsize) - sect.Vaddr |
| } |
| |
| /* typelink */ |
| sect = state.allocateNamedDataSection(seg, genrelrosecname(".typelink"), []sym.SymKind{sym.STYPELINK}, relroSecPerm) |
| |
| typelink := ldr.CreateSymForUpdate("runtime.typelink", 0) |
| ldr.SetSymSect(typelink.Sym(), sect) |
| typelink.SetType(sym.SRODATA) |
| state.datsize += typelink.Size() |
| state.checkdatsize(sym.STYPELINK) |
| sect.Length = uint64(state.datsize) - sect.Vaddr |
| |
| /* itablink */ |
| sect = state.allocateNamedDataSection(seg, genrelrosecname(".itablink"), []sym.SymKind{sym.SITABLINK}, relroSecPerm) |
| |
| itablink := ldr.CreateSymForUpdate("runtime.itablink", 0) |
| ldr.SetSymSect(itablink.Sym(), sect) |
| itablink.SetType(sym.SRODATA) |
| state.datsize += itablink.Size() |
| state.checkdatsize(sym.SITABLINK) |
| sect.Length = uint64(state.datsize) - sect.Vaddr |
| |
| /* gosymtab */ |
| sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gosymtab"), sym.SSYMTAB, sym.SRODATA, relroSecPerm) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.symtab", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.esymtab", 0), sect) |
| |
| /* gopclntab */ |
| sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gopclntab"), sym.SPCLNTAB, sym.SRODATA, relroSecPerm) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pcheader", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.funcnametab", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.cutab", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.filetab", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pctab", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.functab", 0), sect) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.epclntab", 0), sect) |
| if ctxt.HeadType == objabi.Haix { |
| xcoffUpdateOuterSize(ctxt, int64(sect.Length), sym.SPCLNTAB) |
| } |
| |
| // 6g uses 4-byte relocation offsets, so the entire segment must fit in 32 bits. |
| if state.datsize != int64(uint32(state.datsize)) { |
| Errorf(nil, "read-only data segment too large: %d", state.datsize) |
| } |
| |
| siz := 0 |
| for symn := sym.SELFRXSECT; symn < sym.SXREF; symn++ { |
| siz += len(state.data[symn]) |
| } |
| ctxt.datap = make([]loader.Sym, 0, siz) |
| for symn := sym.SELFRXSECT; symn < sym.SXREF; symn++ { |
| ctxt.datap = append(ctxt.datap, state.data[symn]...) |
| } |
| } |
| |
| // allocateDwarfSections allocates sym.Section objects for DWARF |
| // symbols, and assigns symbols to sections. |
| func (state *dodataState) allocateDwarfSections(ctxt *Link) { |
| |
| alignOne := func(state *dodataState, datsize int64, s loader.Sym) int64 { return datsize } |
| |
| ldr := ctxt.loader |
| for i := 0; i < len(dwarfp); i++ { |
| // First the section symbol. |
| s := dwarfp[i].secSym() |
| sect := state.allocateNamedDataSection(&Segdwarf, ldr.SymName(s), []sym.SymKind{}, 04) |
| ldr.SetSymSect(s, sect) |
| sect.Sym = sym.LoaderSym(s) |
| curType := ldr.SymType(s) |
| state.setSymType(s, sym.SRODATA) |
| ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr)) |
| state.datsize += ldr.SymSize(s) |
| |
| // Then any sub-symbols for the section symbol. |
| subSyms := dwarfp[i].subSyms() |
| state.assignDsymsToSection(sect, subSyms, sym.SRODATA, alignOne) |
| |
| for j := 0; j < len(subSyms); j++ { |
| s := subSyms[j] |
| if ctxt.HeadType == objabi.Haix && curType == sym.SDWARFLOC { |
| // Update the size of .debug_loc for this symbol's |
| // package. |
| addDwsectCUSize(".debug_loc", ldr.SymPkg(s), uint64(ldr.SymSize(s))) |
| } |
| } |
| sect.Length = uint64(state.datsize) - sect.Vaddr |
| state.checkdatsize(curType) |
| } |
| } |
| |
| type symNameSize struct { |
| name string |
| sz int64 |
| val int64 |
| sym loader.Sym |
| } |
| |
| func (state *dodataState) dodataSect(ctxt *Link, symn sym.SymKind, syms []loader.Sym) (result []loader.Sym, maxAlign int32) { |
| var head, tail loader.Sym |
| ldr := ctxt.loader |
| sl := make([]symNameSize, len(syms)) |
| for k, s := range syms { |
| ss := ldr.SymSize(s) |
| sl[k] = symNameSize{name: ldr.SymName(s), sz: ss, sym: s} |
| ds := int64(len(ldr.Data(s))) |
| switch { |
| case ss < ds: |
| ctxt.Errorf(s, "initialize bounds (%d < %d)", ss, ds) |
| case ss < 0: |
| ctxt.Errorf(s, "negative size (%d bytes)", ss) |
| case ss > cutoff: |
| ctxt.Errorf(s, "symbol too large (%d bytes)", ss) |
| } |
| |
| // If the usually-special section-marker symbols are being laid |
| // out as regular symbols, put them either at the beginning or |
| // end of their section. |
| if (ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin) || (ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) { |
| switch ldr.SymName(s) { |
| case "runtime.text", "runtime.bss", "runtime.data", "runtime.types", "runtime.rodata": |
| head = s |
| continue |
| case "runtime.etext", "runtime.ebss", "runtime.edata", "runtime.etypes", "runtime.erodata": |
| tail = s |
| continue |
| } |
| } |
| } |
| |
| // For ppc64, we want to interleave the .got and .toc sections |
| // from input files. Both are type sym.SELFGOT, so in that case |
| // we skip size comparison and fall through to the name |
| // comparison (conveniently, .got sorts before .toc). |
| checkSize := symn != sym.SELFGOT |
| |
| // Perform the sort. |
| if symn != sym.SPCLNTAB { |
| sort.Slice(sl, func(i, j int) bool { |
| si, sj := sl[i].sym, sl[j].sym |
| switch { |
| case si == head, sj == tail: |
| return true |
| case sj == head, si == tail: |
| return false |
| } |
| if checkSize { |
| isz := sl[i].sz |
| jsz := sl[j].sz |
| if isz != jsz { |
| return isz < jsz |
| } |
| } |
| iname := sl[i].name |
| jname := sl[j].name |
| if iname != jname { |
| return iname < jname |
| } |
| return si < sj |
| }) |
| } else { |
| // PCLNTAB was built internally, and has the proper order based on value. |
| // Sort the symbols as such. |
| for k, s := range syms { |
| sl[k].val = ldr.SymValue(s) |
| } |
| sort.Slice(sl, func(i, j int) bool { return sl[i].val < sl[j].val }) |
| } |
| |
| // Set alignment, construct result |
| syms = syms[:0] |
| for k := range sl { |
| s := sl[k].sym |
| if s != head && s != tail { |
| align := symalign(ldr, s) |
| if maxAlign < align { |
| maxAlign = align |
| } |
| } |
| syms = append(syms, s) |
| } |
| |
| return syms, maxAlign |
| } |
| |
| // Add buildid to beginning of text segment, on non-ELF systems. |
| // Non-ELF binary formats are not always flexible enough to |
| // give us a place to put the Go build ID. On those systems, we put it |
| // at the very beginning of the text segment. |
| // This ``header'' is read by cmd/go. |
| func (ctxt *Link) textbuildid() { |
| if ctxt.IsELF || ctxt.BuildMode == BuildModePlugin || *flagBuildid == "" { |
| return |
| } |
| |
| ldr := ctxt.loader |
| s := ldr.CreateSymForUpdate("go.buildid", 0) |
| // The \xff is invalid UTF-8, meant to make it less likely |
| // to find one of these accidentally. |
| data := "\xff Go build ID: " + strconv.Quote(*flagBuildid) + "\n \xff" |
| s.SetType(sym.STEXT) |
| s.SetData([]byte(data)) |
| s.SetSize(int64(len(data))) |
| |
| ctxt.Textp = append(ctxt.Textp, 0) |
| copy(ctxt.Textp[1:], ctxt.Textp) |
| ctxt.Textp[0] = s.Sym() |
| } |
| |
| func (ctxt *Link) buildinfo() { |
| if ctxt.linkShared || ctxt.BuildMode == BuildModePlugin { |
| // -linkshared and -buildmode=plugin get confused |
| // about the relocations in go.buildinfo |
| // pointing at the other data sections. |
| // The version information is only available in executables. |
| return |
| } |
| |
| ldr := ctxt.loader |
| s := ldr.CreateSymForUpdate(".go.buildinfo", 0) |
| // On AIX, .go.buildinfo must be in the symbol table as |
| // it has relocations. |
| s.SetNotInSymbolTable(!ctxt.IsAIX()) |
| s.SetType(sym.SBUILDINFO) |
| s.SetAlign(16) |
| // The \xff is invalid UTF-8, meant to make it less likely |
| // to find one of these accidentally. |
| const prefix = "\xff Go buildinf:" // 14 bytes, plus 2 data bytes filled in below |
| data := make([]byte, 32) |
| copy(data, prefix) |
| data[len(prefix)] = byte(ctxt.Arch.PtrSize) |
| data[len(prefix)+1] = 0 |
| if ctxt.Arch.ByteOrder == binary.BigEndian { |
| data[len(prefix)+1] = 1 |
| } |
| s.SetData(data) |
| s.SetSize(int64(len(data))) |
| r, _ := s.AddRel(objabi.R_ADDR) |
| r.SetOff(16) |
| r.SetSiz(uint8(ctxt.Arch.PtrSize)) |
| r.SetSym(ldr.LookupOrCreateSym("runtime.buildVersion", 0)) |
| r, _ = s.AddRel(objabi.R_ADDR) |
| r.SetOff(16 + int32(ctxt.Arch.PtrSize)) |
| r.SetSiz(uint8(ctxt.Arch.PtrSize)) |
| r.SetSym(ldr.LookupOrCreateSym("runtime.modinfo", 0)) |
| } |
| |
| // assign addresses to text |
| func (ctxt *Link) textaddress() { |
| addsection(ctxt.loader, ctxt.Arch, &Segtext, ".text", 05) |
| |
| // Assign PCs in text segment. |
| // Could parallelize, by assigning to text |
| // and then letting threads copy down, but probably not worth it. |
| sect := Segtext.Sections[0] |
| |
| sect.Align = int32(Funcalign) |
| |
| ldr := ctxt.loader |
| |
| text := ctxt.xdefine("runtime.text", sym.STEXT, 0) |
| etext := ctxt.xdefine("runtime.etext", sym.STEXT, 0) |
| ldr.SetSymSect(text, sect) |
| if ctxt.IsAIX() && ctxt.IsExternal() { |
| // Setting runtime.text has a real symbol prevents ld to |
| // change its base address resulting in wrong offsets for |
| // reflect methods. |
| u := ldr.MakeSymbolUpdater(text) |
| u.SetAlign(sect.Align) |
| u.SetSize(8) |
| } |
| |
| if (ctxt.DynlinkingGo() && ctxt.IsDarwin()) || (ctxt.IsAIX() && ctxt.IsExternal()) { |
| ldr.SetSymSect(etext, sect) |
| ctxt.Textp = append(ctxt.Textp, etext, 0) |
| copy(ctxt.Textp[1:], ctxt.Textp) |
| ctxt.Textp[0] = text |
| } |
| |
| va := uint64(Rnd(*FlagTextAddr, int64(Funcalign))) |
| n := 1 |
| sect.Vaddr = va |
| ntramps := 0 |
| for _, s := range ctxt.Textp { |
| sect, n, va = assignAddress(ctxt, sect, n, s, va, false) |
| |
| trampoline(ctxt, s) // resolve jumps, may add trampolines if jump too far |
| |
| // lay down trampolines after each function |
| for ; ntramps < len(ctxt.tramps); ntramps++ { |
| tramp := ctxt.tramps[ntramps] |
| if ctxt.IsAIX() && strings.HasPrefix(ldr.SymName(tramp), "runtime.text.") { |
| // Already set in assignAddress |
| continue |
| } |
| sect, n, va = assignAddress(ctxt, sect, n, tramp, va, true) |
| } |
| } |
| |
| sect.Length = va - sect.Vaddr |
| ldr.SetSymSect(etext, sect) |
| if ldr.SymValue(etext) == 0 { |
| // Set the address of the start/end symbols, if not already |
| // (i.e. not darwin+dynlink or AIX+external, see above). |
| ldr.SetSymValue(etext, int64(va)) |
| ldr.SetSymValue(text, int64(Segtext.Sections[0].Vaddr)) |
| } |
| |
| // merge tramps into Textp, keeping Textp in address order |
| if ntramps != 0 { |
| newtextp := make([]loader.Sym, 0, len(ctxt.Textp)+ntramps) |
| i := 0 |
| for _, s := range ctxt.Textp { |
| for ; i < ntramps && ldr.SymValue(ctxt.tramps[i]) < ldr.SymValue(s); i++ { |
| newtextp = append(newtextp, ctxt.tramps[i]) |
| } |
| newtextp = append(newtextp, s) |
| } |
| newtextp = append(newtextp, ctxt.tramps[i:ntramps]...) |
| |
| ctxt.Textp = newtextp |
| } |
| } |
| |
| // assigns address for a text symbol, returns (possibly new) section, its number, and the address |
| func assignAddress(ctxt *Link, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64) { |
| ldr := ctxt.loader |
| if thearch.AssignAddress != nil { |
| return thearch.AssignAddress(ldr, sect, n, s, va, isTramp) |
| } |
| |
| ldr.SetSymSect(s, sect) |
| if ldr.AttrSubSymbol(s) { |
| return sect, n, va |
| } |
| |
| align := ldr.SymAlign(s) |
| if align == 0 { |
| align = int32(Funcalign) |
| } |
| va = uint64(Rnd(int64(va), int64(align))) |
| if sect.Align < align { |
| sect.Align = align |
| } |
| |
| funcsize := uint64(MINFUNC) // spacing required for findfunctab |
| if ldr.SymSize(s) > MINFUNC { |
| funcsize = uint64(ldr.SymSize(s)) |
| } |
| |
| // On ppc64x a text section should not be larger than 2^26 bytes due to the size of |
| // call target offset field in the bl instruction. Splitting into smaller text |
| // sections smaller than this limit allows the GNU linker to modify the long calls |
| // appropriately. The limit allows for the space needed for tables inserted by the linker. |
| |
| // If this function doesn't fit in the current text section, then create a new one. |
| |
| // Only break at outermost syms. |
| |
| // For debugging purposes, allow text size limit to be cranked down, |
| // so as to stress test the code that handles multiple text sections. |
| var textSizelimit uint64 = 0x1c00000 |
| if *FlagDebugTextSize != 0 { |
| textSizelimit = uint64(*FlagDebugTextSize) |
| } |
| |
| if ctxt.Arch.InFamily(sys.PPC64) && ldr.OuterSym(s) == 0 && ctxt.IsExternal() { |
| // Sanity check: make sure the limit is larger than any |
| // individual text symbol. |
| if funcsize > textSizelimit { |
| panic(fmt.Sprintf("error: ppc64 text size limit %d less than text symbol %s size of %d", textSizelimit, ldr.SymName(s), funcsize)) |
| } |
| |
| if va-sect.Vaddr+funcsize+maxSizeTrampolinesPPC64(ldr, s, isTramp) > textSizelimit { |
| // Set the length for the previous text section |
| sect.Length = va - sect.Vaddr |
| |
| // Create new section, set the starting Vaddr |
| sect = addsection(ctxt.loader, ctxt.Arch, &Segtext, ".text", 05) |
| sect.Vaddr = va |
| ldr.SetSymSect(s, sect) |
| |
| // Create a symbol for the start of the secondary text sections |
| ntext := ldr.CreateSymForUpdate(fmt.Sprintf("runtime.text.%d", n), 0) |
| ntext.SetSect(sect) |
| if ctxt.IsAIX() { |
| // runtime.text.X must be a real symbol on AIX. |
| // Assign its address directly in order to be the |
| // first symbol of this new section. |
| ntext.SetType(sym.STEXT) |
| ntext.SetSize(int64(MINFUNC)) |
| ntext.SetOnList(true) |
| ctxt.tramps = append(ctxt.tramps, ntext.Sym()) |
| |
| ntext.SetValue(int64(va)) |
| va += uint64(ntext.Size()) |
| |
| if align := ldr.SymAlign(s); align != 0 { |
| va = uint64(Rnd(int64(va), int64(align))) |
| } else { |
| va = uint64(Rnd(int64(va), int64(Funcalign))) |
| } |
| } |
| n++ |
| } |
| } |
| |
| ldr.SetSymValue(s, 0) |
| for sub := s; sub != 0; sub = ldr.SubSym(sub) { |
| ldr.SetSymValue(sub, ldr.SymValue(sub)+int64(va)) |
| } |
| |
| va += funcsize |
| |
| return sect, n, va |
| } |
| |
| // address assigns virtual addresses to all segments and sections and |
| // returns all segments in file order. |
| func (ctxt *Link) address() []*sym.Segment { |
| var order []*sym.Segment // Layout order |
| |
| va := uint64(*FlagTextAddr) |
| order = append(order, &Segtext) |
| Segtext.Rwx = 05 |
| Segtext.Vaddr = va |
| for _, s := range Segtext.Sections { |
| va = uint64(Rnd(int64(va), int64(s.Align))) |
| s.Vaddr = va |
| va += s.Length |
| } |
| |
| Segtext.Length = va - uint64(*FlagTextAddr) |
| |
| if len(Segrodata.Sections) > 0 { |
| // align to page boundary so as not to mix |
| // rodata and executable text. |
| // |
| // Note: gold or GNU ld will reduce the size of the executable |
| // file by arranging for the relro segment to end at a page |
| // boundary, and overlap the end of the text segment with the |
| // start of the relro segment in the file. The PT_LOAD segments |
| // will be such that the last page of the text segment will be |
| // mapped twice, once r-x and once starting out rw- and, after |
| // relocation processing, changed to r--. |
| // |
| // Ideally the last page of the text segment would not be |
| // writable even for this short period. |
| va = uint64(Rnd(int64(va), int64(*FlagRound))) |
| |
| order = append(order, &Segrodata) |
| Segrodata.Rwx = 04 |
| Segrodata.Vaddr = va |
| for _, s := range Segrodata.Sections { |
| va = uint64(Rnd(int64(va), int64(s.Align))) |
| s.Vaddr = va |
| va += s.Length |
| } |
| |
| Segrodata.Length = va - Segrodata.Vaddr |
| } |
| if len(Segrelrodata.Sections) > 0 { |
| // align to page boundary so as not to mix |
| // rodata, rel-ro data, and executable text. |
| va = uint64(Rnd(int64(va), int64(*FlagRound))) |
| if ctxt.HeadType == objabi.Haix { |
| // Relro data are inside data segment on AIX. |
| va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE) |
| } |
| |
| order = append(order, &Segrelrodata) |
| Segrelrodata.Rwx = 06 |
| Segrelrodata.Vaddr = va |
| for _, s := range Segrelrodata.Sections { |
| va = uint64(Rnd(int64(va), int64(s.Align))) |
| s.Vaddr = va |
| va += s.Length |
| } |
| |
| Segrelrodata.Length = va - Segrelrodata.Vaddr |
| } |
| |
| va = uint64(Rnd(int64(va), int64(*FlagRound))) |
| if ctxt.HeadType == objabi.Haix && len(Segrelrodata.Sections) == 0 { |
| // Data sections are moved to an unreachable segment |
| // to ensure that they are position-independent. |
| // Already done if relro sections exist. |
| va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE) |
| } |
| order = append(order, &Segdata) |
| Segdata.Rwx = 06 |
| Segdata.Vaddr = va |
| var data *sym.Section |
| var noptr *sym.Section |
| var bss *sym.Section |
| var noptrbss *sym.Section |
| for i, s := range Segdata.Sections { |
| if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && s.Name == ".tbss" { |
| continue |
| } |
| vlen := int64(s.Length) |
| if i+1 < len(Segdata.Sections) && !((ctxt.IsELF || ctxt.HeadType == objabi.Haix) && Segdata.Sections[i+1].Name == ".tbss") { |
| vlen = int64(Segdata.Sections[i+1].Vaddr - s.Vaddr) |
| } |
| s.Vaddr = va |
| va += uint64(vlen) |
| Segdata.Length = va - Segdata.Vaddr |
| if s.Name == ".data" { |
| data = s |
| } |
| if s.Name == ".noptrdata" { |
| noptr = s |
| } |
| if s.Name == ".bss" { |
| bss = s |
| } |
| if s.Name == ".noptrbss" { |
| noptrbss = s |
| } |
| } |
| |
| // Assign Segdata's Filelen omitting the BSS. We do this here |
| // simply because right now we know where the BSS starts. |
| Segdata.Filelen = bss.Vaddr - Segdata.Vaddr |
| |
| va = uint64(Rnd(int64(va), int64(*FlagRound))) |
| order = append(order, &Segdwarf) |
| Segdwarf.Rwx = 06 |
| Segdwarf.Vaddr = va |
| for i, s := range Segdwarf.Sections { |
| vlen := int64(s.Length) |
| if i+1 < len(Segdwarf.Sections) { |
| vlen = int64(Segdwarf.Sections[i+1].Vaddr - s.Vaddr) |
| } |
| s.Vaddr = va |
| va += uint64(vlen) |
| if ctxt.HeadType == objabi.Hwindows { |
| va = uint64(Rnd(int64(va), PEFILEALIGN)) |
| } |
| Segdwarf.Length = va - Segdwarf.Vaddr |
| } |
| |
| ldr := ctxt.loader |
| var ( |
| rodata = ldr.SymSect(ldr.LookupOrCreateSym("runtime.rodata", 0)) |
| symtab = ldr.SymSect(ldr.LookupOrCreateSym("runtime.symtab", 0)) |
| pclntab = ldr.SymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0)) |
| types = ldr.SymSect(ldr.LookupOrCreateSym("runtime.types", 0)) |
| ) |
| |
| for _, s := range ctxt.datap { |
| if sect := ldr.SymSect(s); sect != nil { |
| ldr.AddToSymValue(s, int64(sect.Vaddr)) |
| } |
| v := ldr.SymValue(s) |
| for sub := ldr.SubSym(s); sub != 0; sub = ldr.SubSym(sub) { |
| ldr.AddToSymValue(sub, v) |
| } |
| } |
| |
| for _, si := range dwarfp { |
| for _, s := range si.syms { |
| if sect := ldr.SymSect(s); sect != nil { |
| ldr.AddToSymValue(s, int64(sect.Vaddr)) |
| } |
| sub := ldr.SubSym(s) |
| if sub != 0 { |
| panic(fmt.Sprintf("unexpected sub-sym for %s %s", ldr.SymName(s), ldr.SymType(s).String())) |
| } |
| v := ldr.SymValue(s) |
| for ; sub != 0; sub = ldr.SubSym(sub) { |
| ldr.AddToSymValue(s, v) |
| } |
| } |
| } |
| |
| if ctxt.BuildMode == BuildModeShared { |
| s := ldr.LookupOrCreateSym("go.link.abihashbytes", 0) |
| sect := ldr.SymSect(ldr.LookupOrCreateSym(".note.go.abihash", 0)) |
| ldr.SetSymSect(s, sect) |
| ldr.SetSymValue(s, int64(sect.Vaddr+16)) |
| } |
| |
| // If there are multiple text sections, create runtime.text.n for |
| // their section Vaddr, using n for index |
| n := 1 |
| for _, sect := range Segtext.Sections[1:] { |
| if sect.Name != ".text" { |
| break |
| } |
| symname := fmt.Sprintf("runtime.text.%d", n) |
| if ctxt.HeadType != objabi.Haix || ctxt.LinkMode != LinkExternal { |
| // Addresses are already set on AIX with external linker |
| // because these symbols are part of their sections. |
| ctxt.xdefine(symname, sym.STEXT, int64(sect.Vaddr)) |
| } |
| n++ |
| } |
| |
| ctxt.xdefine("runtime.rodata", sym.SRODATA, int64(rodata.Vaddr)) |
| ctxt.xdefine("runtime.erodata", sym.SRODATA, int64(rodata.Vaddr+rodata.Length)) |
| ctxt.xdefine("runtime.types", sym.SRODATA, int64(types.Vaddr)) |
| ctxt.xdefine("runtime.etypes", sym.SRODATA, int64(types.Vaddr+types.Length)) |
| |
| s := ldr.Lookup("runtime.gcdata", 0) |
| ldr.SetAttrLocal(s, true) |
| ctxt.xdefine("runtime.egcdata", sym.SRODATA, ldr.SymAddr(s)+ldr.SymSize(s)) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.egcdata", 0), ldr.SymSect(s)) |
| |
| s = ldr.LookupOrCreateSym("runtime.gcbss", 0) |
| ldr.SetAttrLocal(s, true) |
| ctxt.xdefine("runtime.egcbss", sym.SRODATA, ldr.SymAddr(s)+ldr.SymSize(s)) |
| ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.egcbss", 0), ldr.SymSect(s)) |
| |
| ctxt.xdefine("runtime.symtab", sym.SRODATA, int64(symtab.Vaddr)) |
| ctxt.xdefine("runtime.esymtab", sym.SRODATA, int64(symtab.Vaddr+symtab.Length)) |
| ctxt.xdefine("runtime.pclntab", sym.SRODATA, int64(pclntab.Vaddr)) |
| ctxt.defineInternal("runtime.pcheader", sym.SRODATA) |
| ctxt.defineInternal("runtime.funcnametab", sym.SRODATA) |
| ctxt.defineInternal("runtime.cutab", sym.SRODATA) |
| ctxt.defineInternal("runtime.filetab", sym.SRODATA) |
| ctxt.defineInternal("runtime.pctab", sym.SRODATA) |
| ctxt.defineInternal("runtime.functab", sym.SRODATA) |
| ctxt.xdefine("runtime.epclntab", sym.SRODATA, int64(pclntab.Vaddr+pclntab.Length)) |
| ctxt.xdefine("runtime.noptrdata", sym.SNOPTRDATA, int64(noptr.Vaddr)) |
| ctxt.xdefine("runtime.enoptrdata", sym.SNOPTRDATA, int64(noptr.Vaddr+noptr.Length)) |
| ctxt.xdefine("runtime.bss", sym.SBSS, int64(bss.Vaddr)) |
| ctxt.xdefine("runtime.ebss", sym.SBSS, int64(bss.Vaddr+bss.Length)) |
| ctxt.xdefine("runtime.data", sym.SDATA, int64(data.Vaddr)) |
| ctxt.xdefine("runtime.edata", sym.SDATA, int64(data.Vaddr+data.Length)) |
| ctxt.xdefine("runtime.noptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr)) |
| ctxt.xdefine("runtime.enoptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr+noptrbss.Length)) |
| ctxt.xdefine("runtime.end", sym.SBSS, int64(Segdata.Vaddr+Segdata.Length)) |
| |
| if ctxt.IsSolaris() { |
| // On Solaris, in the runtime it sets the external names of the |
| // end symbols. Unset them and define separate symbols, so we |
| // keep both. |
| etext := ldr.Lookup("runtime.etext", 0) |
| edata := ldr.Lookup("runtime.edata", 0) |
| end := ldr.Lookup("runtime.end", 0) |
| ldr.SetSymExtname(etext, "runtime.etext") |
| ldr.SetSymExtname(edata, "runtime.edata") |
| ldr.SetSymExtname(end, "runtime.end") |
| ctxt.xdefine("_etext", ldr.SymType(etext), ldr.SymValue(etext)) |
| ctxt.xdefine("_edata", ldr.SymType(edata), ldr.SymValue(edata)) |
| ctxt.xdefine("_end", ldr.SymType(end), ldr.SymValue(end)) |
| ldr.SetSymSect(ldr.Lookup("_etext", 0), ldr.SymSect(etext)) |
| ldr.SetSymSect(ldr.Lookup("_edata", 0), ldr.SymSect(edata)) |
| ldr.SetSymSect(ldr.Lookup("_end", 0), ldr.SymSect(end)) |
| } |
| |
| return order |
| } |
| |
| // layout assigns file offsets and lengths to the segments in order. |
| // Returns the file size containing all the segments. |
| func (ctxt *Link) layout(order []*sym.Segment) uint64 { |
| var prev *sym.Segment |
| for _, seg := range order { |
| if prev == nil { |
| seg.Fileoff = uint64(HEADR) |
| } else { |
| switch ctxt.HeadType { |
| default: |
| // Assuming the previous segment was |
| // aligned, the following rounding |
| // should ensure that this segment's |
| // VA ≡ Fileoff mod FlagRound. |
| seg.Fileoff = uint64(Rnd(int64(prev.Fileoff+prev.Filelen), int64(*FlagRound))) |
| if seg.Vaddr%uint64(*FlagRound) != seg.Fileoff%uint64(*FlagRound) { |
| Exitf("bad segment rounding (Vaddr=%#x Fileoff=%#x FlagRound=%#x)", seg.Vaddr, seg.Fileoff, *FlagRound) |
| } |
| case objabi.Hwindows: |
| seg.Fileoff = prev.Fileoff + uint64(Rnd(int64(prev.Filelen), PEFILEALIGN)) |
| case objabi.Hplan9: |
| seg.Fileoff = prev.Fileoff + prev.Filelen |
| } |
| } |
| if seg != &Segdata { |
| // Link.address already set Segdata.Filelen to |
| // account for BSS. |
| seg.Filelen = seg.Length |
| } |
| prev = seg |
| } |
| return prev.Fileoff + prev.Filelen |
| } |
| |
| // add a trampoline with symbol s (to be laid down after the current function) |
| func (ctxt *Link) AddTramp(s *loader.SymbolBuilder) { |
| s.SetType(sym.STEXT) |
| s.SetReachable(true) |
| s.SetOnList(true) |
| ctxt.tramps = append(ctxt.tramps, s.Sym()) |
| if *FlagDebugTramp > 0 && ctxt.Debugvlog > 0 { |
| ctxt.Logf("trampoline %s inserted\n", s.Name()) |
| } |
| } |
| |
| // compressSyms compresses syms and returns the contents of the |
| // compressed section. If the section would get larger, it returns nil. |
| func compressSyms(ctxt *Link, syms []loader.Sym) []byte { |
| ldr := ctxt.loader |
| var total int64 |
| for _, sym := range syms { |
| total += ldr.SymSize(sym) |
| } |
| |
| var buf bytes.Buffer |
| buf.Write([]byte("ZLIB")) |
| var sizeBytes [8]byte |
| binary.BigEndian.PutUint64(sizeBytes[:], uint64(total)) |
| buf.Write(sizeBytes[:]) |
| |
| var relocbuf []byte // temporary buffer for applying relocations |
| |
| // Using zlib.BestSpeed achieves very nearly the same |
| // compression levels of zlib.DefaultCompression, but takes |
| // substantially less time. This is important because DWARF |
| // compression can be a significant fraction of link time. |
| z, err := zlib.NewWriterLevel(&buf, zlib.BestSpeed) |
| if err != nil { |
| log.Fatalf("NewWriterLevel failed: %s", err) |
| } |
| st := ctxt.makeRelocSymState() |
| for _, s := range syms { |
| // Symbol data may be read-only. Apply relocations in a |
| // temporary buffer, and immediately write it out. |
| P := ldr.Data(s) |
| relocs := ldr.Relocs(s) |
| if relocs.Count() != 0 { |
| relocbuf = append(relocbuf[:0], P...) |
| P = relocbuf |
| st.relocsym(s, P) |
| } |
| if _, err := z.Write(P); err != nil { |
| log.Fatalf("compression failed: %s", err) |
| } |
| for i := ldr.SymSize(s) - int64(len(P)); i > 0; { |
| b := zeros[:] |
| if i < int64(len(b)) { |
| b = b[:i] |
| } |
| n, err := z.Write(b) |
| if err != nil { |
| log.Fatalf("compression failed: %s", err) |
| } |
| i -= int64(n) |
| } |
| } |
| if err := z.Close(); err != nil { |
| log.Fatalf("compression failed: %s", err) |
| } |
| if int64(buf.Len()) >= total { |
| // Compression didn't save any space. |
| return nil |
| } |
| return buf.Bytes() |
| } |
