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47008fdea7
The way prelink used to work was * The compiler decides if a given section only has relocations that are know to point to the same DSO. If so, it names it .data.rel.ro.local<something>. * The static linker puts all of these together. * The prelinker program assigns addresses to each library and resolves the local relocations. There are many problems with this: * It is incompatible with address space randomization. * The information passed by the compiler is redundant. The linker knows if a given relocation is in the same DSO or not. If could sort by that if so desired. * There are newer ways of speeding up DSO (gnu hash for example). * Even if we want to implement this again in the compiler, the previous implementation is pretty broken. It talks about relocations that are "resolved by the static linker". If they are resolved, there are none left for the prelinker. What one needs to track is if an expression will require only dynamic relocations that point to the same DSO. At this point it looks like the prelinker is an historical curiosity. For example, fedora has retired it because it failed to build for two releases (http://pkgs.fedoraproject.org/cgit/prelink.git/commit/?id=eb43100a8331d91c801ee3dcdb0a0bb9babfdc1f) This patch removes support for it. That is, it stops printing the ".local" sections. llvm-svn: 253280
62 lines
2.5 KiB
C++
62 lines
2.5 KiB
C++
//===-- PPCTargetObjectFile.cpp - PPC Object Info -------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "PPCTargetObjectFile.h"
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#include "llvm/IR/Mangler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCSectionELF.h"
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using namespace llvm;
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void
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PPC64LinuxTargetObjectFile::
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Initialize(MCContext &Ctx, const TargetMachine &TM) {
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TargetLoweringObjectFileELF::Initialize(Ctx, TM);
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InitializeELF(TM.Options.UseInitArray);
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}
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MCSection *PPC64LinuxTargetObjectFile::SelectSectionForGlobal(
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const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
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const TargetMachine &TM) const {
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// Here override ReadOnlySection to DataRelROSection for PPC64 SVR4 ABI
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// when we have a constant that contains global relocations. This is
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// necessary because of this ABI's handling of pointers to functions in
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// a shared library. The address of a function is actually the address
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// of a function descriptor, which resides in the .opd section. Generated
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// code uses the descriptor directly rather than going via the GOT as some
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// other ABIs do, which means that initialized function pointers must
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// reference the descriptor. The linker must convert copy relocs of
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// pointers to functions in shared libraries into dynamic relocations,
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// because of an ordering problem with initialization of copy relocs and
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// PLT entries. The dynamic relocation will be initialized by the dynamic
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// linker, so we must use DataRelROSection instead of ReadOnlySection.
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// For more information, see the description of ELIMINATE_COPY_RELOCS in
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// GNU ld.
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if (Kind.isReadOnly()) {
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const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
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if (GVar && GVar->isConstant() && GVar->getInitializer()->needsRelocation())
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Kind = SectionKind::getReadOnlyWithRel();
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}
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return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind,
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Mang, TM);
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}
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const MCExpr *PPC64LinuxTargetObjectFile::
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getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
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const MCExpr *Expr =
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MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_PPC_DTPREL, getContext());
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return MCBinaryExpr::createAdd(Expr,
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MCConstantExpr::create(0x8000, getContext()),
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getContext());
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}
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