[llvm] r340610 - Find PLT entries for x86, x86_64, and AArch64.
Joel Galenson via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 24 08:21:56 PDT 2018
Author: jgalenson
Date: Fri Aug 24 08:21:56 2018
New Revision: 340610
URL: http://llvm.org/viewvc/llvm-project?rev=340610&view=rev
Log:
Find PLT entries for x86, x86_64, and AArch64.
This adds a new method to ELFObjectFileBase that returns the symbols and addresses of PLT entries.
This design was suggested by pcc and eugenis in https://reviews.llvm.org/D49383.
Differential Revision: https://reviews.llvm.org/D50203
Modified:
llvm/trunk/include/llvm/MC/MCInstrAnalysis.h
llvm/trunk/include/llvm/Object/ELFObjectFile.h
llvm/trunk/lib/Object/ELFObjectFile.cpp
llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
Modified: llvm/trunk/include/llvm/MC/MCInstrAnalysis.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCInstrAnalysis.h?rev=340610&r1=340609&r2=340610&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCInstrAnalysis.h (original)
+++ llvm/trunk/include/llvm/MC/MCInstrAnalysis.h Fri Aug 24 08:21:56 2018
@@ -23,6 +23,7 @@
namespace llvm {
class MCRegisterInfo;
+class Triple;
class MCInstrAnalysis {
protected:
@@ -105,6 +106,13 @@ public:
virtual bool
evaluateBranch(const MCInst &Inst, uint64_t Addr, uint64_t Size,
uint64_t &Target) const;
+
+ /// Returns (PLT virtual address, GOT virtual address) pairs for PLT entries.
+ virtual std::vector<std::pair<uint64_t, uint64_t>>
+ findPltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,
+ uint64_t GotPltSectionVA, const Triple &TargetTriple) const {
+ return {};
+ }
};
} // end namespace llvm
Modified: llvm/trunk/include/llvm/Object/ELFObjectFile.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Object/ELFObjectFile.h?rev=340610&r1=340609&r2=340610&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Object/ELFObjectFile.h (original)
+++ llvm/trunk/include/llvm/Object/ELFObjectFile.h Fri Aug 24 08:21:56 2018
@@ -86,6 +86,8 @@ public:
void setARMSubArch(Triple &TheTriple) const override;
virtual uint16_t getEType() const = 0;
+
+ std::vector<std::pair<DataRefImpl, uint64_t>> getPltAddresses() const;
};
class ELFSectionRef : public SectionRef {
Modified: llvm/trunk/lib/Object/ELFObjectFile.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Object/ELFObjectFile.cpp?rev=340610&r1=340609&r2=340610&view=diff
==============================================================================
--- llvm/trunk/lib/Object/ELFObjectFile.cpp (original)
+++ llvm/trunk/lib/Object/ELFObjectFile.cpp Fri Aug 24 08:21:56 2018
@@ -14,6 +14,7 @@
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/ADT/Triple.h"
#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/MC/MCInstrAnalysis.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Object/ELF.h"
#include "llvm/Object/ELFTypes.h"
@@ -23,6 +24,7 @@
#include "llvm/Support/Endian.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/TargetRegistry.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
@@ -327,3 +329,66 @@ void ELFObjectFileBase::setARMSubArch(Tr
TheTriple.setArchName(Triple);
}
+
+std::vector<std::pair<DataRefImpl, uint64_t>>
+ELFObjectFileBase::getPltAddresses() const {
+ std::string Err;
+ const auto Triple = makeTriple();
+ const auto *T = TargetRegistry::lookupTarget(Triple.str(), Err);
+ if (!T)
+ return {};
+ uint64_t JumpSlotReloc = 0;
+ switch (Triple.getArch()) {
+ case Triple::x86:
+ JumpSlotReloc = ELF::R_386_JUMP_SLOT;
+ break;
+ case Triple::x86_64:
+ JumpSlotReloc = ELF::R_X86_64_JUMP_SLOT;
+ break;
+ case Triple::aarch64:
+ JumpSlotReloc = ELF::R_AARCH64_JUMP_SLOT;
+ break;
+ default:
+ return {};
+ }
+ const auto *MIA = T->createMCInstrAnalysis(T->createMCInstrInfo());
+ if (!MIA)
+ return {};
+ Optional<SectionRef> Plt = None, RelaPlt = None, GotPlt = None;
+ for (const SectionRef &Section : sections()) {
+ StringRef Name;
+ if (Section.getName(Name))
+ continue;
+ if (Name == ".plt")
+ Plt = Section;
+ else if (Name == ".rela.plt" || Name == ".rel.plt")
+ RelaPlt = Section;
+ else if (Name == ".got.plt")
+ GotPlt = Section;
+ }
+ if (!Plt || !RelaPlt || !GotPlt)
+ return {};
+ StringRef PltContents;
+ if (Plt->getContents(PltContents))
+ return {};
+ ArrayRef<uint8_t> PltBytes((const uint8_t *)PltContents.data(),
+ Plt->getSize());
+ auto PltEntries = MIA->findPltEntries(Plt->getAddress(), PltBytes,
+ GotPlt->getAddress(), Triple);
+ // Build a map from GOT entry virtual address to PLT entry virtual address.
+ DenseMap<uint64_t, uint64_t> GotToPlt;
+ for (const auto &Entry : PltEntries)
+ GotToPlt.insert(std::make_pair(Entry.second, Entry.first));
+ // Find the relocations in the dynamic relocation table that point to
+ // locations in the GOT for which we know the corresponding PLT entry.
+ std::vector<std::pair<DataRefImpl, uint64_t>> Result;
+ for (const auto &Relocation : RelaPlt->relocations()) {
+ if (Relocation.getType() != JumpSlotReloc)
+ continue;
+ auto PltEntryIter = GotToPlt.find(Relocation.getOffset());
+ if (PltEntryIter != GotToPlt.end())
+ Result.push_back(std::make_pair(
+ Relocation.getSymbol()->getRawDataRefImpl(), PltEntryIter->second));
+ }
+ return Result;
+}
Modified: llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp?rev=340610&r1=340609&r2=340610&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp Fri Aug 24 08:21:56 2018
@@ -24,6 +24,7 @@
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/Support/Endian.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TargetRegistry.h"
@@ -153,6 +154,31 @@ public:
}
return false;
}
+
+ std::vector<std::pair<uint64_t, uint64_t>>
+ findPltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,
+ uint64_t GotPltSectionVA,
+ const Triple &TargetTriple) const override {
+ // Do a lightweight parsing of PLT entries.
+ std::vector<std::pair<uint64_t, uint64_t>> Result;
+ for (uint64_t Byte = 0, End = PltContents.size(); Byte + 7 < End;
+ Byte += 4) {
+ uint32_t Insn = support::endian::read32le(PltContents.data() + Byte);
+ // Check for adrp.
+ if ((Insn & 0x9f000000) != 0x90000000)
+ continue;
+ uint64_t Imm = (((PltSectionVA + Byte) >> 12) << 12) +
+ (((Insn >> 29) & 3) << 12) + (((Insn >> 5) & 0x3ffff) << 14);
+ uint32_t Insn2 = support::endian::read32le(PltContents.data() + Byte + 4);
+ // Check for: ldr Xt, [Xn, #pimm].
+ if (Insn2 >> 22 == 0x3e5) {
+ Imm += ((Insn2 >> 10) & 0xfff) << 3;
+ Result.push_back(std::make_pair(PltSectionVA + Byte, Imm));
+ Byte += 4;
+ }
+ }
+ return Result;
+ }
};
} // end anonymous namespace
Modified: llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp?rev=340610&r1=340609&r2=340610&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp (original)
+++ llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp Fri Aug 24 08:21:56 2018
@@ -384,6 +384,9 @@ public:
const MCInst &Inst) const override;
bool clearsSuperRegisters(const MCRegisterInfo &MRI, const MCInst &Inst,
APInt &Mask) const override;
+ std::vector<std::pair<uint64_t, uint64_t>>
+ findPltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,
+ uint64_t GotSectionVA, const Triple &TargetTriple) const;
};
bool X86MCInstrAnalysis::isDependencyBreaking(const MCSubtargetInfo &STI,
@@ -510,6 +513,64 @@ bool X86MCInstrAnalysis::clearsSuperRegi
return Mask.getBoolValue();
}
+static std::vector<std::pair<uint64_t, uint64_t>>
+findX86PltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,
+ uint64_t GotPltSectionVA) {
+ // Do a lightweight parsing of PLT entries.
+ std::vector<std::pair<uint64_t, uint64_t>> Result;
+ for (uint64_t Byte = 0, End = PltContents.size(); Byte + 6 < End; ) {
+ // Recognize a jmp.
+ if (PltContents[Byte] == 0xff && PltContents[Byte + 1] == 0xa3) {
+ // The jmp instruction at the beginning of each PLT entry jumps to the
+ // address of the base of the .got.plt section plus the immediate.
+ uint32_t Imm = support::endian::read32le(PltContents.data() + Byte + 2);
+ Result.push_back(
+ std::make_pair(PltSectionVA + Byte, GotPltSectionVA + Imm));
+ Byte += 6;
+ } else if (PltContents[Byte] == 0xff && PltContents[Byte + 1] == 0x25) {
+ // The jmp instruction at the beginning of each PLT entry jumps to the
+ // immediate.
+ uint32_t Imm = support::endian::read32le(PltContents.data() + Byte + 2);
+ Result.push_back(std::make_pair(PltSectionVA + Byte, Imm));
+ Byte += 6;
+ } else
+ Byte++;
+ }
+ return Result;
+}
+
+static std::vector<std::pair<uint64_t, uint64_t>>
+findX86_64PltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents) {
+ // Do a lightweight parsing of PLT entries.
+ std::vector<std::pair<uint64_t, uint64_t>> Result;
+ for (uint64_t Byte = 0, End = PltContents.size(); Byte + 6 < End; ) {
+ // Recognize a jmp.
+ if (PltContents[Byte] == 0xff && PltContents[Byte + 1] == 0x25) {
+ // The jmp instruction at the beginning of each PLT entry jumps to the
+ // address of the next instruction plus the immediate.
+ uint32_t Imm = support::endian::read32le(PltContents.data() + Byte + 2);
+ Result.push_back(
+ std::make_pair(PltSectionVA + Byte, PltSectionVA + Byte + 6 + Imm));
+ Byte += 6;
+ } else
+ Byte++;
+ }
+ return Result;
+}
+
+std::vector<std::pair<uint64_t, uint64_t>> X86MCInstrAnalysis::findPltEntries(
+ uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,
+ uint64_t GotPltSectionVA, const Triple &TargetTriple) const {
+ switch (TargetTriple.getArch()) {
+ case Triple::x86:
+ return findX86PltEntries(PltSectionVA, PltContents, GotPltSectionVA);
+ case Triple::x86_64:
+ return findX86_64PltEntries(PltSectionVA, PltContents);
+ default:
+ return {};
+ }
+}
+
} // end of namespace X86_MC
} // end of namespace llvm
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