RuntimeDyldELF/AArch64: Implement basic GOT support
This patch implements two GOT relocations:
R_AARCH64_ADR_GOT_PAGE and R_AARCH64_LD64_GOT_LO12_NC
Differential revision: https://reviews.llvm.org/D28571
llvm-svn: 294191
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index 63b56f7..9660e1a 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -484,6 +484,14 @@
}
}
+ // Compute Global Offset Table size. If it is not zero we
+ // also update alignment, which is equal to a size of a
+ // single GOT entry.
+ if (unsigned GotSize = computeGOTSize(Obj)) {
+ RWSectionSizes.push_back(GotSize);
+ RWDataAlign = std::max<uint32_t>(RWDataAlign, getGOTEntrySize());
+ }
+
// Compute the size of all common symbols
uint64_t CommonSize = 0;
uint32_t CommonAlign = 1;
@@ -518,6 +526,24 @@
return Error::success();
}
+// compute GOT size
+unsigned RuntimeDyldImpl::computeGOTSize(const ObjectFile &Obj) {
+ size_t GotEntrySize = getGOTEntrySize();
+ if (!GotEntrySize)
+ return 0;
+
+ size_t GotSize = 0;
+ for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
+ SI != SE; ++SI) {
+
+ for (const RelocationRef &Reloc : SI->relocations())
+ if (relocationNeedsGot(Reloc))
+ GotSize += GotEntrySize;
+ }
+
+ return GotSize;
+}
+
// compute stub buffer size for the given section
unsigned RuntimeDyldImpl::computeSectionStubBufSize(const ObjectFile &Obj,
const SectionRef &Section) {
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
index 8e7437a..f780137 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
@@ -961,6 +961,61 @@
return true;
}
+void RuntimeDyldELF::resolveAArch64Branch(unsigned SectionID,
+ const RelocationValueRef &Value,
+ relocation_iterator RelI,
+ StubMap &Stubs) {
+
+ DEBUG(dbgs() << "\t\tThis is an AArch64 branch relocation.");
+ SectionEntry &Section = Sections[SectionID];
+
+ uint64_t Offset = RelI->getOffset();
+ unsigned RelType = RelI->getType();
+ // Look for an existing stub.
+ StubMap::const_iterator i = Stubs.find(Value);
+ if (i != Stubs.end()) {
+ resolveRelocation(Section, Offset,
+ (uint64_t)Section.getAddressWithOffset(i->second),
+ RelType, 0);
+ DEBUG(dbgs() << " Stub function found\n");
+ } else if (!resolveAArch64ShortBranch(SectionID, RelI, Value)) {
+ // Create a new stub function.
+ DEBUG(dbgs() << " Create a new stub function\n");
+ Stubs[Value] = Section.getStubOffset();
+ uint8_t *StubTargetAddr = createStubFunction(
+ Section.getAddressWithOffset(Section.getStubOffset()));
+
+ RelocationEntry REmovz_g3(SectionID, StubTargetAddr - Section.getAddress(),
+ ELF::R_AARCH64_MOVW_UABS_G3, Value.Addend);
+ RelocationEntry REmovk_g2(SectionID,
+ StubTargetAddr - Section.getAddress() + 4,
+ ELF::R_AARCH64_MOVW_UABS_G2_NC, Value.Addend);
+ RelocationEntry REmovk_g1(SectionID,
+ StubTargetAddr - Section.getAddress() + 8,
+ ELF::R_AARCH64_MOVW_UABS_G1_NC, Value.Addend);
+ RelocationEntry REmovk_g0(SectionID,
+ StubTargetAddr - Section.getAddress() + 12,
+ ELF::R_AARCH64_MOVW_UABS_G0_NC, Value.Addend);
+
+ if (Value.SymbolName) {
+ addRelocationForSymbol(REmovz_g3, Value.SymbolName);
+ addRelocationForSymbol(REmovk_g2, Value.SymbolName);
+ addRelocationForSymbol(REmovk_g1, Value.SymbolName);
+ addRelocationForSymbol(REmovk_g0, Value.SymbolName);
+ } else {
+ addRelocationForSection(REmovz_g3, Value.SectionID);
+ addRelocationForSection(REmovk_g2, Value.SectionID);
+ addRelocationForSection(REmovk_g1, Value.SectionID);
+ addRelocationForSection(REmovk_g0, Value.SectionID);
+ }
+ resolveRelocation(Section, Offset,
+ reinterpret_cast<uint64_t>(Section.getAddressWithOffset(
+ Section.getStubOffset())),
+ RelType, 0);
+ Section.advanceStubOffset(getMaxStubSize());
+ }
+}
+
Expected<relocation_iterator>
RuntimeDyldELF::processRelocationRef(
unsigned SectionID, relocation_iterator RelI, const ObjectFile &O,
@@ -1055,55 +1110,22 @@
DEBUG(dbgs() << "\t\tSectionID: " << SectionID << " Offset: " << Offset
<< "\n");
- if ((Arch == Triple::aarch64 || Arch == Triple::aarch64_be) &&
- (RelType == ELF::R_AARCH64_CALL26 || RelType == ELF::R_AARCH64_JUMP26)) {
- // This is an AArch64 branch relocation, need to use a stub function.
- DEBUG(dbgs() << "\t\tThis is an AArch64 branch relocation.");
- SectionEntry &Section = Sections[SectionID];
+ if ((Arch == Triple::aarch64 || Arch == Triple::aarch64_be)) {
+ if (RelType == ELF::R_AARCH64_CALL26 || RelType == ELF::R_AARCH64_JUMP26) {
+ resolveAArch64Branch(SectionID, Value, RelI, Stubs);
+ } else if (RelType == ELF::R_AARCH64_ADR_GOT_PAGE) {
+ // Craete new GOT entry or find existing one. If GOT entry is
+ // to be created, then we also emit ABS64 relocation for it.
+ uint64_t GOTOffset = findOrAllocGOTEntry(Value, ELF::R_AARCH64_ABS64);
+ resolveGOTOffsetRelocation(SectionID, Offset, GOTOffset + Addend,
+ ELF::R_AARCH64_ADR_PREL_PG_HI21);
- // Look for an existing stub.
- StubMap::const_iterator i = Stubs.find(Value);
- if (i != Stubs.end()) {
- resolveRelocation(Section, Offset,
- (uint64_t)Section.getAddressWithOffset(i->second),
- RelType, 0);
- DEBUG(dbgs() << " Stub function found\n");
- } else if (!resolveAArch64ShortBranch(SectionID, RelI, Value)) {
- // Create a new stub function.
- DEBUG(dbgs() << " Create a new stub function\n");
- Stubs[Value] = Section.getStubOffset();
- uint8_t *StubTargetAddr = createStubFunction(
- Section.getAddressWithOffset(Section.getStubOffset()));
-
- RelocationEntry REmovz_g3(SectionID,
- StubTargetAddr - Section.getAddress(),
- ELF::R_AARCH64_MOVW_UABS_G3, Value.Addend);
- RelocationEntry REmovk_g2(SectionID, StubTargetAddr -
- Section.getAddress() + 4,
- ELF::R_AARCH64_MOVW_UABS_G2_NC, Value.Addend);
- RelocationEntry REmovk_g1(SectionID, StubTargetAddr -
- Section.getAddress() + 8,
- ELF::R_AARCH64_MOVW_UABS_G1_NC, Value.Addend);
- RelocationEntry REmovk_g0(SectionID, StubTargetAddr -
- Section.getAddress() + 12,
- ELF::R_AARCH64_MOVW_UABS_G0_NC, Value.Addend);
-
- if (Value.SymbolName) {
- addRelocationForSymbol(REmovz_g3, Value.SymbolName);
- addRelocationForSymbol(REmovk_g2, Value.SymbolName);
- addRelocationForSymbol(REmovk_g1, Value.SymbolName);
- addRelocationForSymbol(REmovk_g0, Value.SymbolName);
- } else {
- addRelocationForSection(REmovz_g3, Value.SectionID);
- addRelocationForSection(REmovk_g2, Value.SectionID);
- addRelocationForSection(REmovk_g1, Value.SectionID);
- addRelocationForSection(REmovk_g0, Value.SectionID);
- }
- resolveRelocation(Section, Offset,
- reinterpret_cast<uint64_t>(Section.getAddressWithOffset(
- Section.getStubOffset())),
- RelType, 0);
- Section.advanceStubOffset(getMaxStubSize());
+ } else if (RelType == ELF::R_AARCH64_LD64_GOT_LO12_NC) {
+ uint64_t GOTOffset = findOrAllocGOTEntry(Value, ELF::R_AARCH64_ABS64);
+ resolveGOTOffsetRelocation(SectionID, Offset, GOTOffset + Addend,
+ ELF::R_AARCH64_LDST64_ABS_LO12_NC);
+ } else {
+ processSimpleRelocation(SectionID, Offset, RelType, Value);
}
} else if (Arch == Triple::arm) {
if (RelType == ELF::R_ARM_PC24 || RelType == ELF::R_ARM_CALL ||
@@ -1252,7 +1274,7 @@
if (i != GOTSymbolOffsets.end())
RE.SymOffset = i->second;
else {
- RE.SymOffset = allocateGOTEntries(SectionID, 1);
+ RE.SymOffset = allocateGOTEntries(1);
GOTSymbolOffsets[TargetName] = RE.SymOffset;
}
}
@@ -1509,14 +1531,15 @@
Section.advanceStubOffset(getMaxStubSize());
// Allocate a GOT Entry
- uint64_t GOTOffset = allocateGOTEntries(SectionID, 1);
+ uint64_t GOTOffset = allocateGOTEntries(1);
// The load of the GOT address has an addend of -4
- resolveGOTOffsetRelocation(SectionID, StubOffset + 2, GOTOffset - 4);
+ resolveGOTOffsetRelocation(SectionID, StubOffset + 2, GOTOffset - 4,
+ ELF::R_X86_64_PC32);
// Fill in the value of the symbol we're targeting into the GOT
addRelocationForSymbol(
- computeGOTOffsetRE(SectionID, GOTOffset, 0, ELF::R_X86_64_64),
+ computeGOTOffsetRE(GOTOffset, 0, ELF::R_X86_64_64),
Value.SymbolName);
}
@@ -1531,11 +1554,13 @@
} else if (RelType == ELF::R_X86_64_GOTPCREL ||
RelType == ELF::R_X86_64_GOTPCRELX ||
RelType == ELF::R_X86_64_REX_GOTPCRELX) {
- uint64_t GOTOffset = allocateGOTEntries(SectionID, 1);
- resolveGOTOffsetRelocation(SectionID, Offset, GOTOffset + Addend);
+ uint64_t GOTOffset = allocateGOTEntries(1);
+ resolveGOTOffsetRelocation(SectionID, Offset, GOTOffset + Addend,
+ ELF::R_X86_64_PC32);
// Fill in the value of the symbol we're targeting into the GOT
- RelocationEntry RE = computeGOTOffsetRE(SectionID, GOTOffset, Value.Offset, ELF::R_X86_64_64);
+ RelocationEntry RE =
+ computeGOTOffsetRE(GOTOffset, Value.Offset, ELF::R_X86_64_64);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
@@ -1593,9 +1618,7 @@
return Result;
}
-uint64_t RuntimeDyldELF::allocateGOTEntries(unsigned SectionID, unsigned no)
-{
- (void)SectionID; // The GOT Section is the same for all section in the object file
+uint64_t RuntimeDyldELF::allocateGOTEntries(unsigned no) {
if (GOTSectionID == 0) {
GOTSectionID = Sections.size();
// Reserve a section id. We'll allocate the section later
@@ -1607,17 +1630,38 @@
return StartOffset;
}
-void RuntimeDyldELF::resolveGOTOffsetRelocation(unsigned SectionID, uint64_t Offset, uint64_t GOTOffset)
-{
+uint64_t RuntimeDyldELF::findOrAllocGOTEntry(const RelocationValueRef &Value,
+ unsigned GOTRelType) {
+ auto E = GOTOffsetMap.insert({Value, 0});
+ if (E.second) {
+ uint64_t GOTOffset = allocateGOTEntries(1);
+
+ // Create relocation for newly created GOT entry
+ RelocationEntry RE =
+ computeGOTOffsetRE(GOTOffset, Value.Offset, GOTRelType);
+ if (Value.SymbolName)
+ addRelocationForSymbol(RE, Value.SymbolName);
+ else
+ addRelocationForSection(RE, Value.SectionID);
+
+ E.first->second = GOTOffset;
+ }
+
+ return E.first->second;
+}
+
+void RuntimeDyldELF::resolveGOTOffsetRelocation(unsigned SectionID,
+ uint64_t Offset,
+ uint64_t GOTOffset,
+ uint32_t Type) {
// Fill in the relative address of the GOT Entry into the stub
- RelocationEntry GOTRE(SectionID, Offset, ELF::R_X86_64_PC32, GOTOffset);
+ RelocationEntry GOTRE(SectionID, Offset, Type, GOTOffset);
addRelocationForSection(GOTRE, GOTSectionID);
}
-RelocationEntry RuntimeDyldELF::computeGOTOffsetRE(unsigned SectionID, uint64_t GOTOffset, uint64_t SymbolOffset,
- uint32_t Type)
-{
- (void)SectionID; // The GOT Section is the same for all section in the object file
+RelocationEntry RuntimeDyldELF::computeGOTOffsetRE(uint64_t GOTOffset,
+ uint64_t SymbolOffset,
+ uint32_t Type) {
return RelocationEntry(GOTSectionID, GOTOffset, Type, SymbolOffset);
}
@@ -1683,6 +1727,19 @@
return Obj.isELF();
}
+bool RuntimeDyldELF::relocationNeedsGot(const RelocationRef &R) const {
+ unsigned RelTy = R.getType();
+ if (Arch == Triple::aarch64 || Arch == Triple::aarch64_be)
+ return RelTy == ELF::R_AARCH64_ADR_GOT_PAGE ||
+ RelTy == ELF::R_AARCH64_LD64_GOT_LO12_NC;
+
+ if (Arch == Triple::x86_64)
+ return RelTy == ELF::R_X86_64_GOTPCREL ||
+ RelTy == ELF::R_X86_64_GOTPCRELX ||
+ RelTy == ELF::R_X86_64_REX_GOTPCRELX;
+ return false;
+}
+
bool RuntimeDyldELF::relocationNeedsStub(const RelocationRef &R) const {
if (Arch != Triple::x86_64)
return true; // Conservative answer
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
index d1867d0..4989797 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
@@ -43,6 +43,9 @@
bool resolveAArch64ShortBranch(unsigned SectionID, relocation_iterator RelI,
const RelocationValueRef &Value);
+ void resolveAArch64Branch(unsigned SectionID, const RelocationValueRef &Value,
+ relocation_iterator RelI, StubMap &Stubs);
+
void resolveARMRelocation(const SectionEntry &Section, uint64_t Offset,
uint32_t Value, uint32_t Type, int32_t Addend);
@@ -88,24 +91,26 @@
ObjSectionToIDMap &LocalSections,
RelocationValueRef &Rel);
protected:
- size_t getGOTEntrySize();
+ size_t getGOTEntrySize() override;
private:
SectionEntry &getSection(unsigned SectionID) { return Sections[SectionID]; }
// Allocate no GOT entries for use in the given section.
- uint64_t allocateGOTEntries(unsigned SectionID, unsigned no);
+ uint64_t allocateGOTEntries(unsigned no);
+
+ // Find GOT entry corresponding to relocation or create new one.
+ uint64_t findOrAllocGOTEntry(const RelocationValueRef &Value,
+ unsigned GOTRelType);
// Resolve the relvative address of GOTOffset in Section ID and place
// it at the given Offset
void resolveGOTOffsetRelocation(unsigned SectionID, uint64_t Offset,
- uint64_t GOTOffset);
+ uint64_t GOTOffset, uint32_t Type);
// For a GOT entry referenced from SectionID, compute a relocation entry
// that will place the final resolved value in the GOT slot
- RelocationEntry computeGOTOffsetRE(unsigned SectionID,
- uint64_t GOTOffset,
- uint64_t SymbolOffset,
+ RelocationEntry computeGOTOffsetRE(uint64_t GOTOffset, uint64_t SymbolOffset,
unsigned Type);
// Compute the address in memory where we can find the placeholder
@@ -146,6 +151,10 @@
SmallVector<SID, 2> UnregisteredEHFrameSections;
SmallVector<SID, 2> RegisteredEHFrameSections;
+ // Map between GOT relocation value and corresponding GOT offset
+ std::map<RelocationValueRef, uint64_t> GOTOffsetMap;
+
+ bool relocationNeedsGot(const RelocationRef &R) const override;
bool relocationNeedsStub(const RelocationRef &R) const override;
public:
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
index 279d0de..f5cc883 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
@@ -213,7 +213,7 @@
}
};
-/// @brief Symbol info for RuntimeDyld.
+/// @brief Symbol info for RuntimeDyld.
class SymbolTableEntry {
public:
SymbolTableEntry()
@@ -426,6 +426,9 @@
uint64_t &RODataSize, uint32_t &RODataAlign,
uint64_t &RWDataSize, uint32_t &RWDataAlign);
+ // \brief Compute GOT size
+ unsigned computeGOTSize(const ObjectFile &Obj);
+
// \brief Compute the stub buffer size required for a section
unsigned computeSectionStubBufSize(const ObjectFile &Obj,
const SectionRef &Section);
@@ -433,6 +436,14 @@
// \brief Implementation of the generic part of the loadObject algorithm.
Expected<ObjSectionToIDMap> loadObjectImpl(const object::ObjectFile &Obj);
+ // \brief Return size of Global Offset Table (GOT) entry
+ virtual size_t getGOTEntrySize() { return 0; }
+
+ // \brief Return true if the relocation R may require allocating a GOT entry.
+ virtual bool relocationNeedsGot(const RelocationRef &R) const {
+ return false;
+ }
+
// \brief Return true if the relocation R may require allocating a stub.
virtual bool relocationNeedsStub(const RelocationRef &R) const {
return true; // Conservative answer