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-rw-r--r--lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp312
1 files changed, 290 insertions, 22 deletions
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
index cd99c3c..f2c69fc 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
@@ -22,7 +22,7 @@
#include "llvm/ADT/Triple.h"
#include "llvm/ExecutionEngine/ObjectBuffer.h"
#include "llvm/ExecutionEngine/ObjectImage.h"
-#include "llvm/Object/ELF.h"
+#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/ELF.h"
using namespace llvm;
@@ -151,12 +151,31 @@ void DyldELFObject<ELFT>::updateSymbolAddress(const SymbolRef &SymRef,
namespace llvm {
-StringRef RuntimeDyldELF::getEHFrameSection() {
- for (int i = 0, e = Sections.size(); i != e; ++i) {
- if (Sections[i].Name == ".eh_frame")
- return StringRef((const char*)Sections[i].Address, Sections[i].Size);
+void RuntimeDyldELF::registerEHFrames() {
+ if (!MemMgr)
+ return;
+ for (int i = 0, e = UnregisteredEHFrameSections.size(); i != e; ++i) {
+ SID EHFrameSID = UnregisteredEHFrameSections[i];
+ uint8_t *EHFrameAddr = Sections[EHFrameSID].Address;
+ uint64_t EHFrameLoadAddr = Sections[EHFrameSID].LoadAddress;
+ size_t EHFrameSize = Sections[EHFrameSID].Size;
+ MemMgr->registerEHFrames(EHFrameAddr, EHFrameLoadAddr, EHFrameSize);
+ RegisteredEHFrameSections.push_back(EHFrameSID);
}
- return StringRef();
+ UnregisteredEHFrameSections.clear();
+}
+
+void RuntimeDyldELF::deregisterEHFrames() {
+ if (!MemMgr)
+ return;
+ for (int i = 0, e = RegisteredEHFrameSections.size(); i != e; ++i) {
+ SID EHFrameSID = RegisteredEHFrameSections[i];
+ uint8_t *EHFrameAddr = Sections[EHFrameSID].Address;
+ uint64_t EHFrameLoadAddr = Sections[EHFrameSID].LoadAddress;
+ size_t EHFrameSize = Sections[EHFrameSID].Size;
+ MemMgr->deregisterEHFrames(EHFrameAddr, EHFrameLoadAddr, EHFrameSize);
+ }
+ RegisteredEHFrameSections.clear();
}
ObjectImage *RuntimeDyldELF::createObjectImage(ObjectBuffer *Buffer) {
@@ -202,7 +221,8 @@ void RuntimeDyldELF::resolveX86_64Relocation(const SectionEntry &Section,
uint64_t Offset,
uint64_t Value,
uint32_t Type,
- int64_t Addend) {
+ int64_t Addend,
+ uint64_t SymOffset) {
switch (Type) {
default:
llvm_unreachable("Relocation type not implemented yet!");
@@ -227,6 +247,21 @@ void RuntimeDyldELF::resolveX86_64Relocation(const SectionEntry &Section,
<< " at " << format("%p\n",Target));
break;
}
+ case ELF::R_X86_64_GOTPCREL: {
+ // findGOTEntry returns the 'G + GOT' part of the relocation calculation
+ // based on the load/target address of the GOT (not the current/local addr).
+ uint64_t GOTAddr = findGOTEntry(Value, SymOffset);
+ uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
+ uint64_t FinalAddress = Section.LoadAddress + Offset;
+ // The processRelocationRef method combines the symbol offset and the addend
+ // and in most cases that's what we want. For this relocation type, we need
+ // the raw addend, so we subtract the symbol offset to get it.
+ int64_t RealOffset = GOTAddr + Addend - SymOffset - FinalAddress;
+ assert(RealOffset <= INT32_MAX && RealOffset >= INT32_MIN);
+ int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
+ *Target = TruncOffset;
+ break;
+ }
case ELF::R_X86_64_PC32: {
// Get the placeholder value from the generated object since
// a previous relocation attempt may have overwritten the loaded version
@@ -240,6 +275,16 @@ void RuntimeDyldELF::resolveX86_64Relocation(const SectionEntry &Section,
*Target = TruncOffset;
break;
}
+ case ELF::R_X86_64_PC64: {
+ // Get the placeholder value from the generated object since
+ // a previous relocation attempt may have overwritten the loaded version
+ uint64_t *Placeholder = reinterpret_cast<uint64_t*>(Section.ObjAddress
+ + Offset);
+ uint64_t *Target = reinterpret_cast<uint64_t*>(Section.Address + Offset);
+ uint64_t FinalAddress = Section.LoadAddress + Offset;
+ *Target = *Placeholder + Value + Addend - FinalAddress;
+ break;
+ }
}
}
@@ -304,7 +349,7 @@ void RuntimeDyldELF::resolveAArch64Relocation(const SectionEntry &Section,
}
case ELF::R_AARCH64_PREL32: {
uint64_t Result = Value + Addend - FinalAddress;
- assert(static_cast<int64_t>(Result) >= INT32_MIN &&
+ assert(static_cast<int64_t>(Result) >= INT32_MIN &&
static_cast<int64_t>(Result) <= UINT32_MAX);
*TargetPtr = static_cast<uint32_t>(Result & 0xffffffffU);
break;
@@ -316,7 +361,7 @@ void RuntimeDyldELF::resolveAArch64Relocation(const SectionEntry &Section,
uint64_t BranchImm = Value + Addend - FinalAddress;
// "Check that -2^27 <= result < 2^27".
- assert(-(1LL << 27) <= static_cast<int64_t>(BranchImm) &&
+ assert(-(1LL << 27) <= static_cast<int64_t>(BranchImm) &&
static_cast<int64_t>(BranchImm) < (1LL << 27));
// AArch64 code is emitted with .rela relocations. The data already in any
@@ -341,7 +386,6 @@ void RuntimeDyldELF::resolveAArch64Relocation(const SectionEntry &Section,
case ELF::R_AARCH64_MOVW_UABS_G2_NC: {
uint64_t Result = Value + Addend;
-
// AArch64 code is emitted with .rela relocations. The data already in any
// bits affected by the relocation on entry is garbage.
*TargetPtr &= 0xffe0001fU;
@@ -585,7 +629,7 @@ void RuntimeDyldELF::findOPDEntrySection(ObjectImage &Obj,
// Finally compares the Symbol value and the target symbol offset
// to check if this .opd entry refers to the symbol the relocation
// points to.
- if (Rel.Addend != (intptr_t)TargetSymbolOffset)
+ if (Rel.Addend != (int64_t)TargetSymbolOffset)
continue;
section_iterator tsi(Obj.end_sections());
@@ -735,20 +779,42 @@ void RuntimeDyldELF::resolveSystemZRelocation(const SectionEntry &Section,
}
}
+// The target location for the relocation is described by RE.SectionID and
+// RE.Offset. RE.SectionID can be used to find the SectionEntry. Each
+// SectionEntry has three members describing its location.
+// SectionEntry::Address is the address at which the section has been loaded
+// into memory in the current (host) process. SectionEntry::LoadAddress is the
+// address that the section will have in the target process.
+// SectionEntry::ObjAddress is the address of the bits for this section in the
+// original emitted object image (also in the current address space).
+//
+// Relocations will be applied as if the section were loaded at
+// SectionEntry::LoadAddress, but they will be applied at an address based
+// on SectionEntry::Address. SectionEntry::ObjAddress will be used to refer to
+// Target memory contents if they are required for value calculations.
+//
+// The Value parameter here is the load address of the symbol for the
+// relocation to be applied. For relocations which refer to symbols in the
+// current object Value will be the LoadAddress of the section in which
+// the symbol resides (RE.Addend provides additional information about the
+// symbol location). For external symbols, Value will be the address of the
+// symbol in the target address space.
void RuntimeDyldELF::resolveRelocation(const RelocationEntry &RE,
- uint64_t Value) {
+ uint64_t Value) {
const SectionEntry &Section = Sections[RE.SectionID];
- return resolveRelocation(Section, RE.Offset, Value, RE.RelType, RE.Addend);
+ return resolveRelocation(Section, RE.Offset, Value, RE.RelType, RE.Addend,
+ RE.SymOffset);
}
void RuntimeDyldELF::resolveRelocation(const SectionEntry &Section,
uint64_t Offset,
uint64_t Value,
uint32_t Type,
- int64_t Addend) {
+ int64_t Addend,
+ uint64_t SymOffset) {
switch (Arch) {
case Triple::x86_64:
- resolveX86_64Relocation(Section, Offset, Value, Type, Addend);
+ resolveX86_64Relocation(Section, Offset, Value, Type, Addend, SymOffset);
break;
case Triple::x86:
resolveX86Relocation(Section, Offset,
@@ -811,6 +877,7 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
}
if (lsi != Symbols.end()) {
Value.SectionID = lsi->second.first;
+ Value.Offset = lsi->second.second;
Value.Addend = lsi->second.second + Addend;
} else {
// Search for the symbol in the global symbol table
@@ -819,6 +886,7 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
gsi = GlobalSymbolTable.find(TargetName.data());
if (gsi != GlobalSymbolTable.end()) {
Value.SectionID = gsi->second.first;
+ Value.Offset = gsi->second.second;
Value.Addend = gsi->second.second + Addend;
} else {
switch (SymType) {
@@ -841,9 +909,17 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
Value.Addend = Addend;
break;
}
+ case SymbolRef::ST_Data:
case SymbolRef::ST_Unknown: {
Value.SymbolName = TargetName.data();
Value.Addend = Addend;
+
+ // Absolute relocations will have a zero symbol ID (STN_UNDEF), which
+ // will manifest here as a NULL symbol name.
+ // We can set this as a valid (but empty) symbol name, and rely
+ // on addRelocationForSymbol to handle this.
+ if (!Value.SymbolName)
+ Value.SymbolName = "";
break;
}
default:
@@ -955,8 +1031,8 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
// Look up for existing stub.
StubMap::const_iterator i = Stubs.find(Value);
if (i != Stubs.end()) {
- resolveRelocation(Section, Offset,
- (uint64_t)Section.Address + i->second, RelType, 0);
+ RelocationEntry RE(SectionID, Offset, RelType, i->second);
+ addRelocationForSection(RE, SectionID);
DEBUG(dbgs() << " Stub function found\n");
} else {
// Create a new stub function.
@@ -981,9 +1057,8 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
addRelocationForSection(RELo, Value.SectionID);
}
- resolveRelocation(Section, Offset,
- (uint64_t)Section.Address + Section.StubOffset,
- RelType, 0);
+ RelocationEntry RE(SectionID, Offset, RelType, Section.StubOffset);
+ addRelocationForSection(RE, SectionID);
Section.StubOffset += getMaxStubSize();
}
} else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
@@ -1069,7 +1144,10 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
RelocationEntry RE(SectionID, Offset, RelType, Value.Addend);
// Extra check to avoid relocation againt empty symbols (usually
// the R_PPC64_TOC).
- if (Value.SymbolName && !TargetName.empty())
+ if (SymType != SymbolRef::ST_Unknown && TargetName.empty())
+ Value.SymbolName = NULL;
+
+ if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
addRelocationForSection(RE, Value.SectionID);
@@ -1121,8 +1199,67 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
ELF::R_390_PC32DBL, Addend);
else
resolveRelocation(Section, Offset, StubAddress, RelType, Addend);
+ } else if (Arch == Triple::x86_64 && RelType == ELF::R_X86_64_PLT32) {
+ // The way the PLT relocations normally work is that the linker allocates the
+ // PLT and this relocation makes a PC-relative call into the PLT. The PLT
+ // entry will then jump to an address provided by the GOT. On first call, the
+ // GOT address will point back into PLT code that resolves the symbol. After
+ // the first call, the GOT entry points to the actual function.
+ //
+ // For local functions we're ignoring all of that here and just replacing
+ // the PLT32 relocation type with PC32, which will translate the relocation
+ // into a PC-relative call directly to the function. For external symbols we
+ // can't be sure the function will be within 2^32 bytes of the call site, so
+ // we need to create a stub, which calls into the GOT. This case is
+ // equivalent to the usual PLT implementation except that we use the stub
+ // mechanism in RuntimeDyld (which puts stubs at the end of the section)
+ // rather than allocating a PLT section.
+ if (Value.SymbolName) {
+ // This is a call to an external function.
+ // Look for an existing stub.
+ SectionEntry &Section = Sections[SectionID];
+ StubMap::const_iterator i = Stubs.find(Value);
+ uintptr_t StubAddress;
+ if (i != Stubs.end()) {
+ StubAddress = uintptr_t(Section.Address) + i->second;
+ DEBUG(dbgs() << " Stub function found\n");
+ } else {
+ // Create a new stub function (equivalent to a PLT entry).
+ DEBUG(dbgs() << " Create a new stub function\n");
+
+ uintptr_t BaseAddress = uintptr_t(Section.Address);
+ uintptr_t StubAlignment = getStubAlignment();
+ StubAddress = (BaseAddress + Section.StubOffset +
+ StubAlignment - 1) & -StubAlignment;
+ unsigned StubOffset = StubAddress - BaseAddress;
+ Stubs[Value] = StubOffset;
+ createStubFunction((uint8_t *)StubAddress);
+
+ // Create a GOT entry for the external function.
+ GOTEntries.push_back(Value);
+
+ // Make our stub function a relative call to the GOT entry.
+ RelocationEntry RE(SectionID, StubOffset + 2,
+ ELF::R_X86_64_GOTPCREL, -4);
+ addRelocationForSymbol(RE, Value.SymbolName);
+
+ // Bump our stub offset counter
+ Section.StubOffset = StubOffset + getMaxStubSize();
+ }
+
+ // Make the target call a call into the stub table.
+ resolveRelocation(Section, Offset, StubAddress,
+ ELF::R_X86_64_PC32, Addend);
+ } else {
+ RelocationEntry RE(SectionID, Offset, ELF::R_X86_64_PC32, Value.Addend,
+ Value.Offset);
+ addRelocationForSection(RE, Value.SectionID);
+ }
} else {
- RelocationEntry RE(SectionID, Offset, RelType, Value.Addend);
+ if (Arch == Triple::x86_64 && RelType == ELF::R_X86_64_GOTPCREL) {
+ GOTEntries.push_back(Value);
+ }
+ RelocationEntry RE(SectionID, Offset, RelType, Value.Addend, Value.Offset);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
@@ -1130,6 +1267,137 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
}
}
+void RuntimeDyldELF::updateGOTEntries(StringRef Name, uint64_t Addr) {
+
+ SmallVectorImpl<std::pair<SID, GOTRelocations> >::iterator it;
+ SmallVectorImpl<std::pair<SID, GOTRelocations> >::iterator end = GOTs.end();
+
+ for (it = GOTs.begin(); it != end; ++it) {
+ GOTRelocations &GOTEntries = it->second;
+ for (int i = 0, e = GOTEntries.size(); i != e; ++i) {
+ if (GOTEntries[i].SymbolName != 0 && GOTEntries[i].SymbolName == Name) {
+ GOTEntries[i].Offset = Addr;
+ }
+ }
+ }
+}
+
+size_t RuntimeDyldELF::getGOTEntrySize() {
+ // We don't use the GOT in all of these cases, but it's essentially free
+ // to put them all here.
+ size_t Result = 0;
+ switch (Arch) {
+ case Triple::x86_64:
+ case Triple::aarch64:
+ case Triple::ppc64:
+ case Triple::ppc64le:
+ case Triple::systemz:
+ Result = sizeof(uint64_t);
+ break;
+ case Triple::x86:
+ case Triple::arm:
+ case Triple::thumb:
+ case Triple::mips:
+ case Triple::mipsel:
+ Result = sizeof(uint32_t);
+ break;
+ default: llvm_unreachable("Unsupported CPU type!");
+ }
+ return Result;
+}
+
+uint64_t RuntimeDyldELF::findGOTEntry(uint64_t LoadAddress,
+ uint64_t Offset) {
+
+ const size_t GOTEntrySize = getGOTEntrySize();
+
+ SmallVectorImpl<std::pair<SID, GOTRelocations> >::const_iterator it;
+ SmallVectorImpl<std::pair<SID, GOTRelocations> >::const_iterator end = GOTs.end();
+
+ int GOTIndex = -1;
+ for (it = GOTs.begin(); it != end; ++it) {
+ SID GOTSectionID = it->first;
+ const GOTRelocations &GOTEntries = it->second;
+
+ // Find the matching entry in our vector.
+ uint64_t SymbolOffset = 0;
+ for (int i = 0, e = GOTEntries.size(); i != e; ++i) {
+ if (GOTEntries[i].SymbolName == 0) {
+ if (getSectionLoadAddress(GOTEntries[i].SectionID) == LoadAddress &&
+ GOTEntries[i].Offset == Offset) {
+ GOTIndex = i;
+ SymbolOffset = GOTEntries[i].Offset;
+ break;
+ }
+ } else {
+ // GOT entries for external symbols use the addend as the address when
+ // the external symbol has been resolved.
+ if (GOTEntries[i].Offset == LoadAddress) {
+ GOTIndex = i;
+ // Don't use the Addend here. The relocation handler will use it.
+ break;
+ }
+ }
+ }
+
+ if (GOTIndex != -1) {
+ if (GOTEntrySize == sizeof(uint64_t)) {
+ uint64_t *LocalGOTAddr = (uint64_t*)getSectionAddress(GOTSectionID);
+ // Fill in this entry with the address of the symbol being referenced.
+ LocalGOTAddr[GOTIndex] = LoadAddress + SymbolOffset;
+ } else {
+ uint32_t *LocalGOTAddr = (uint32_t*)getSectionAddress(GOTSectionID);
+ // Fill in this entry with the address of the symbol being referenced.
+ LocalGOTAddr[GOTIndex] = (uint32_t)(LoadAddress + SymbolOffset);
+ }
+
+ // Calculate the load address of this entry
+ return getSectionLoadAddress(GOTSectionID) + (GOTIndex * GOTEntrySize);
+ }
+ }
+
+ assert(GOTIndex != -1 && "Unable to find requested GOT entry.");
+ return 0;
+}
+
+void RuntimeDyldELF::finalizeLoad(ObjSectionToIDMap &SectionMap) {
+ // If necessary, allocate the global offset table
+ if (MemMgr) {
+ // Allocate the GOT if necessary
+ size_t numGOTEntries = GOTEntries.size();
+ if (numGOTEntries != 0) {
+ // Allocate memory for the section
+ unsigned SectionID = Sections.size();
+ size_t TotalSize = numGOTEntries * getGOTEntrySize();
+ uint8_t *Addr = MemMgr->allocateDataSection(TotalSize, getGOTEntrySize(),
+ SectionID, ".got", false);
+ if (!Addr)
+ report_fatal_error("Unable to allocate memory for GOT!");
+
+ GOTs.push_back(std::make_pair(SectionID, GOTEntries));
+ Sections.push_back(SectionEntry(".got", Addr, TotalSize, 0));
+ // For now, initialize all GOT entries to zero. We'll fill them in as
+ // needed when GOT-based relocations are applied.
+ memset(Addr, 0, TotalSize);
+ }
+ }
+ else {
+ report_fatal_error("Unable to allocate memory for GOT!");
+ }
+
+ // Look for and record the EH frame section.
+ ObjSectionToIDMap::iterator i, e;
+ for (i = SectionMap.begin(), e = SectionMap.end(); i != e; ++i) {
+ const SectionRef &Section = i->first;
+ StringRef Name;
+ Section.getName(Name);
+ if (Name == ".eh_frame") {
+ UnregisteredEHFrameSections.push_back(i->second);
+ break;
+ }
+ }
+}
+
bool RuntimeDyldELF::isCompatibleFormat(const ObjectBuffer *Buffer) const {
if (Buffer->getBufferSize() < strlen(ELF::ElfMagic))
return false;
generated by cgit v1.1 at 2024-05-21 05:32:11 +0000