357 changes: 170 additions & 187 deletions llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -247,29 +247,16 @@ void RuntimeDyldELF::resolveX86_64Relocation(const SectionEntry &Section,
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
support::ulittle32_t::ref Placeholder(
(void *)(Section.ObjAddress + Offset));
uint64_t FinalAddress = Section.LoadAddress + Offset;
int64_t RealOffset = Value + Addend - FinalAddress;
// Don't add the placeholder if this is a stub
if (Offset < Section.Size)
RealOffset += Placeholder;
assert(RealOffset <= INT32_MAX && RealOffset >= INT32_MIN);
int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
support::ulittle32_t::ref(Section.Address + Offset) = 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
support::ulittle64_t::ref Placeholder(
(void *)(Section.ObjAddress + Offset));
uint64_t FinalAddress = Section.LoadAddress + Offset;
int64_t RealOffset = Value + Addend - FinalAddress;
if (Offset < Section.Size)
RealOffset += Placeholder;
support::ulittle64_t::ref(Section.Address + Offset) = RealOffset;
break;
}
Expand All @@ -281,21 +268,12 @@ void RuntimeDyldELF::resolveX86Relocation(const SectionEntry &Section,
uint32_t Type, int32_t Addend) {
switch (Type) {
case ELF::R_386_32: {
// Get the placeholder value from the generated object since
// a previous relocation attempt may have overwritten the loaded version
support::ulittle32_t::ref Placeholder(
(void *)(Section.ObjAddress + Offset));
support::ulittle32_t::ref(Section.Address + Offset) =
Placeholder + Value + Addend;
support::ulittle32_t::ref(Section.Address + Offset) = Value + Addend;
break;
}
case ELF::R_386_PC32: {
// Get the placeholder value from the generated object since
// a previous relocation attempt may have overwritten the loaded version
support::ulittle32_t::ref Placeholder(
(void *)(Section.ObjAddress + Offset));
uint32_t FinalAddress = ((Section.LoadAddress + Offset) & 0xFFFFFFFF);
uint32_t RealOffset = Placeholder + Value + Addend - FinalAddress;
uint32_t RealOffset = Value + Addend - FinalAddress;
support::ulittle32_t::ref(Section.Address + Offset) = RealOffset;
break;
}
Expand Down Expand Up @@ -452,8 +430,6 @@ void RuntimeDyldELF::resolveARMRelocation(const SectionEntry &Section,
uint64_t Offset, uint32_t Value,
uint32_t Type, int32_t Addend) {
// TODO: Add Thumb relocations.
uint32_t *Placeholder =
reinterpret_cast<uint32_t *>(Section.ObjAddress + Offset);
uint32_t *TargetPtr = (uint32_t *)(Section.Address + Offset);
uint32_t FinalAddress = ((Section.LoadAddress + Offset) & 0xFFFFFFFF);
Value += Addend;
Expand All @@ -470,61 +446,39 @@ void RuntimeDyldELF::resolveARMRelocation(const SectionEntry &Section,

case ELF::R_ARM_NONE:
break;
// Write a 32bit value to relocation address, taking into account the
// implicit addend encoded in the target.
case ELF::R_ARM_PREL31:
case ELF::R_ARM_TARGET1:
case ELF::R_ARM_ABS32:
*TargetPtr = *Placeholder + Value;
*TargetPtr = Value;
break;
// Write first 16 bit of 32 bit value to the mov instruction.
// Last 4 bit should be shifted.
// Write first 16 bit of 32 bit value to the mov instruction.
// Last 4 bit should be shifted.
case ELF::R_ARM_MOVW_ABS_NC:
// We are not expecting any other addend in the relocation address.
// Using 0x000F0FFF because MOVW has its 16 bit immediate split into 2
// non-contiguous fields.
assert((*Placeholder & 0x000F0FFF) == 0);
Value = Value & 0xFFFF;
*TargetPtr = *Placeholder | (Value & 0xFFF);
*TargetPtr |= ((Value >> 12) & 0xF) << 16;
break;
// Write last 16 bit of 32 bit value to the mov instruction.
// Last 4 bit should be shifted.
case ELF::R_ARM_MOVT_ABS:
// We are not expecting any other addend in the relocation address.
// Use 0x000F0FFF for the same reason as R_ARM_MOVW_ABS_NC.
assert((*Placeholder & 0x000F0FFF) == 0);

Value = (Value >> 16) & 0xFFFF;
*TargetPtr = *Placeholder | (Value & 0xFFF);
if (Type == ELF::R_ARM_MOVW_ABS_NC)
Value = Value & 0xFFFF;
else if (Type == ELF::R_ARM_MOVT_ABS)
Value = (Value >> 16) & 0xFFFF;
*TargetPtr &= ~0x000F0FFF;
*TargetPtr = Value & 0xFFF;
*TargetPtr |= ((Value >> 12) & 0xF) << 16;
break;
// Write 24 bit relative value to the branch instruction.
// Write 24 bit relative value to the branch instruction.
case ELF::R_ARM_PC24: // Fall through.
case ELF::R_ARM_CALL: // Fall through.
case ELF::R_ARM_JUMP24: {
case ELF::R_ARM_JUMP24:
int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
RelValue = (RelValue & 0x03FFFFFC) >> 2;
assert((*TargetPtr & 0xFFFFFF) == 0xFFFFFE);
*TargetPtr &= 0xFF000000;
*TargetPtr |= RelValue;
break;
}
case ELF::R_ARM_PRIVATE_0:
// This relocation is reserved by the ARM ELF ABI for internal use. We
// appropriate it here to act as an R_ARM_ABS32 without any addend for use
// in the stubs created during JIT (which can't put an addend into the
// original object file).
*TargetPtr = Value;
break;
}
}

void RuntimeDyldELF::resolveMIPSRelocation(const SectionEntry &Section,
uint64_t Offset, uint32_t Value,
uint32_t Type, int32_t Addend) {
uint32_t *Placeholder =
reinterpret_cast<uint32_t *>(Section.ObjAddress + Offset);
uint32_t *TargetPtr = (uint32_t *)(Section.Address + Offset);
Value += Addend;

Expand All @@ -539,30 +493,17 @@ void RuntimeDyldELF::resolveMIPSRelocation(const SectionEntry &Section,
llvm_unreachable("Not implemented relocation type!");
break;
case ELF::R_MIPS_32:
*TargetPtr = Value + (*Placeholder);
*TargetPtr = Value;
break;
case ELF::R_MIPS_26:
*TargetPtr = ((*Placeholder) & 0xfc000000) | ((Value & 0x0fffffff) >> 2);
*TargetPtr = ((*TargetPtr) & 0xfc000000) | ((Value & 0x0fffffff) >> 2);
break;
case ELF::R_MIPS_HI16:
// Get the higher 16-bits. Also add 1 if bit 15 is 1.
Value += ((*Placeholder) & 0x0000ffff) << 16;
*TargetPtr =
((*Placeholder) & 0xffff0000) | (((Value + 0x8000) >> 16) & 0xffff);
((*TargetPtr) & 0xffff0000) | (((Value + 0x8000) >> 16) & 0xffff);
break;
case ELF::R_MIPS_LO16:
Value += ((*Placeholder) & 0x0000ffff);
*TargetPtr = ((*Placeholder) & 0xffff0000) | (Value & 0xffff);
break;
case ELF::R_MIPS_UNUSED1:
// Similar to ELF::R_ARM_PRIVATE_0, R_MIPS_UNUSED1 and R_MIPS_UNUSED2
// are used for internal JIT purpose. These relocations are similar to
// R_MIPS_HI16 and R_MIPS_LO16, but they do not take any addend into
// account.
*TargetPtr =
((*TargetPtr) & 0xffff0000) | (((Value + 0x8000) >> 16) & 0xffff);
break;
case ELF::R_MIPS_UNUSED2:
*TargetPtr = ((*TargetPtr) & 0xffff0000) | (Value & 0xffff);
break;
}
Expand Down Expand Up @@ -888,6 +829,18 @@ void RuntimeDyldELF::resolveRelocation(const SectionEntry &Section,
}
}

void *RuntimeDyldELF::computePlaceholderAddress(unsigned SectionID, uint64_t Offset) const {
return (void*)(Sections[SectionID].ObjAddress + Offset);
}

void RuntimeDyldELF::processSimpleRelocation(unsigned SectionID, uint64_t Offset, unsigned RelType, RelocationValueRef Value) {
RelocationEntry RE(SectionID, Offset, RelType, Value.Addend, Value.Offset);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
addRelocationForSection(RE, Value.SectionID);
}

relocation_iterator RuntimeDyldELF::processRelocationRef(
unsigned SectionID, relocation_iterator RelI,
const ObjectFile &Obj,
Expand Down Expand Up @@ -1005,80 +958,101 @@ relocation_iterator RuntimeDyldELF::processRelocationRef(
0);
Section.StubOffset += getMaxStubSize();
}
} else if (Arch == Triple::arm &&
(RelType == ELF::R_ARM_PC24 || RelType == ELF::R_ARM_CALL ||
RelType == ELF::R_ARM_JUMP24)) {
// This is an ARM branch relocation, need to use a stub function.
DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
SectionEntry &Section = Sections[SectionID];
} else if (Arch == Triple::arm) {
if (RelType == ELF::R_ARM_PC24 || RelType == ELF::R_ARM_CALL ||
RelType == ELF::R_ARM_JUMP24) {
// This is an ARM branch relocation, need to use a stub function.
DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
SectionEntry &Section = Sections[SectionID];

// Look for an existing stub.
StubMap::const_iterator i = Stubs.find(Value);
if (i != Stubs.end()) {
resolveRelocation(Section, Offset, (uint64_t)Section.Address + i->second,
RelType, 0);
DEBUG(dbgs() << " Stub function found\n");
} else {
// Create a new stub function.
DEBUG(dbgs() << " Create a new stub function\n");
Stubs[Value] = Section.StubOffset;
uint8_t *StubTargetAddr =
// Look for an existing stub.
StubMap::const_iterator i = Stubs.find(Value);
if (i != Stubs.end()) {
resolveRelocation(Section, Offset, (uint64_t)Section.Address + i->second,
RelType, 0);
DEBUG(dbgs() << " Stub function found\n");
} else {
// Create a new stub function.
DEBUG(dbgs() << " Create a new stub function\n");
Stubs[Value] = Section.StubOffset;
uint8_t *StubTargetAddr =
createStubFunction(Section.Address + Section.StubOffset);
RelocationEntry RE(SectionID, StubTargetAddr - Section.Address,
ELF::R_ARM_PRIVATE_0, Value.Addend);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
addRelocationForSection(RE, Value.SectionID);

resolveRelocation(Section, Offset,
(uint64_t)Section.Address + Section.StubOffset, RelType,
0);
Section.StubOffset += getMaxStubSize();
RelocationEntry RE(SectionID, StubTargetAddr - Section.Address,
ELF::R_ARM_ABS32, Value.Addend);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
addRelocationForSection(RE, Value.SectionID);

resolveRelocation(Section, Offset,
(uint64_t)Section.Address + Section.StubOffset, RelType,
0);
Section.StubOffset += getMaxStubSize();
}
} else {
uint32_t *Placeholder =
reinterpret_cast<uint32_t*>(computePlaceholderAddress(SectionID, Offset));
if (RelType == ELF::R_ARM_PREL31 || RelType == ELF::R_ARM_TARGET1 ||
RelType == ELF::R_ARM_ABS32) {
Value.Addend += *Placeholder;
} else if (RelType == ELF::R_ARM_MOVW_ABS_NC || RelType == ELF::R_ARM_MOVT_ABS) {
// See ELF for ARM documentation
Value.Addend += (int16_t)((*Placeholder & 0xFFF) | (((*Placeholder >> 16) & 0xF) << 12));
}
processSimpleRelocation(SectionID, Offset, RelType, Value);
}
} else if ((Arch == Triple::mipsel || Arch == Triple::mips) &&
RelType == ELF::R_MIPS_26) {
// This is an Mips branch relocation, need to use a stub function.
DEBUG(dbgs() << "\t\tThis is a Mips branch relocation.");
SectionEntry &Section = Sections[SectionID];
uint8_t *Target = Section.Address + Offset;
uint32_t *TargetAddress = (uint32_t *)Target;
} else if ((Arch == Triple::mipsel || Arch == Triple::mips)) {
uint32_t *Placeholder = reinterpret_cast<uint32_t*>(computePlaceholderAddress(SectionID, Offset));
if (RelType == ELF::R_MIPS_26) {
// This is an Mips branch relocation, need to use a stub function.
DEBUG(dbgs() << "\t\tThis is a Mips branch relocation.");
SectionEntry &Section = Sections[SectionID];

// Extract the addend from the instruction.
uint32_t Addend = ((*TargetAddress) & 0x03ffffff) << 2;
// Extract the addend from the instruction.
// We shift up by two since the Value will be down shifted again
// when applying the relocation.
uint32_t Addend = ((*Placeholder) & 0x03ffffff) << 2;

Value.Addend += Addend;
Value.Addend += Addend;

// Look up for existing stub.
StubMap::const_iterator i = Stubs.find(Value);
if (i != Stubs.end()) {
RelocationEntry RE(SectionID, Offset, RelType, i->second);
addRelocationForSection(RE, SectionID);
DEBUG(dbgs() << " Stub function found\n");
} else {
// Create a new stub function.
DEBUG(dbgs() << " Create a new stub function\n");
Stubs[Value] = Section.StubOffset;
uint8_t *StubTargetAddr =
// Look up for existing stub.
StubMap::const_iterator i = Stubs.find(Value);
if (i != Stubs.end()) {
RelocationEntry RE(SectionID, Offset, RelType, i->second);
addRelocationForSection(RE, SectionID);
DEBUG(dbgs() << " Stub function found\n");
} else {
// Create a new stub function.
DEBUG(dbgs() << " Create a new stub function\n");
Stubs[Value] = Section.StubOffset;
uint8_t *StubTargetAddr =
createStubFunction(Section.Address + Section.StubOffset);

// Creating Hi and Lo relocations for the filled stub instructions.
RelocationEntry REHi(SectionID, StubTargetAddr - Section.Address,
ELF::R_MIPS_UNUSED1, Value.Addend);
RelocationEntry RELo(SectionID, StubTargetAddr - Section.Address + 4,
ELF::R_MIPS_UNUSED2, Value.Addend);
// Creating Hi and Lo relocations for the filled stub instructions.
RelocationEntry REHi(SectionID, StubTargetAddr - Section.Address,
ELF::R_MIPS_HI16, Value.Addend);
RelocationEntry RELo(SectionID, StubTargetAddr - Section.Address + 4,
ELF::R_MIPS_LO16, Value.Addend);

if (Value.SymbolName) {
addRelocationForSymbol(REHi, Value.SymbolName);
addRelocationForSymbol(RELo, Value.SymbolName);
} else {
addRelocationForSection(REHi, Value.SectionID);
addRelocationForSection(RELo, Value.SectionID);
}
if (Value.SymbolName) {
addRelocationForSymbol(REHi, Value.SymbolName);
addRelocationForSymbol(RELo, Value.SymbolName);
}
else {
addRelocationForSection(REHi, Value.SectionID);
addRelocationForSection(RELo, Value.SectionID);
}

RelocationEntry RE(SectionID, Offset, RelType, Section.StubOffset);
addRelocationForSection(RE, SectionID);
Section.StubOffset += getMaxStubSize();
RelocationEntry RE(SectionID, Offset, RelType, Section.StubOffset);
addRelocationForSection(RE, SectionID);
Section.StubOffset += getMaxStubSize();
}
} else {
if (RelType == ELF::R_MIPS_HI16)
Value.Addend += ((*Placeholder) & 0x0000ffff) << 16;
else if (RelType == ELF::R_MIPS_LO16)
Value.Addend += ((*Placeholder) & 0x0000ffff);
processSimpleRelocation(SectionID, Offset, RelType, Value);
}
} else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
if (RelType == ELF::R_PPC64_REL24) {
Expand Down Expand Up @@ -1277,40 +1251,41 @@ relocation_iterator RuntimeDyldELF::processRelocationRef(
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()) {
} else if (Arch == Triple::x86_64) {
if (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 {
} 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;
-StubAlignment;
unsigned StubOffset = StubAddress - BaseAddress;
Stubs[Value] = StubOffset;
createStubFunction((uint8_t *)StubAddress);
Expand All @@ -1326,33 +1301,41 @@ relocation_iterator RuntimeDyldELF::processRelocationRef(

// Fill in the value of the symbol we're targeting into the GOT
addRelocationForSymbol(computeGOTOffsetRE(SectionID,GOTOffset,0,ELF::R_X86_64_64),
Value.SymbolName);
Value.SymbolName);
}

// 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 if (RelType == ELF::R_X86_64_GOTPCREL) {
uint64_t GOTOffset = allocateGOTEntries(SectionID, 1);
resolveGOTOffsetRelocation(SectionID, Offset, GOTOffset + Addend);

// Make the target call a call into the stub table.
resolveRelocation(Section, Offset, StubAddress, ELF::R_X86_64_PC32,
Addend);
// 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);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
addRelocationForSection(RE, Value.SectionID);
} else if (RelType == ELF::R_X86_64_PC32) {
Value.Addend += support::ulittle32_t::ref(computePlaceholderAddress(SectionID, Offset));
processSimpleRelocation(SectionID, Offset, RelType, Value);
} else if (RelType == ELF::R_X86_64_PC64) {
Value.Addend += support::ulittle64_t::ref(computePlaceholderAddress(SectionID, Offset));
processSimpleRelocation(SectionID, Offset, RelType, Value);
} else {
RelocationEntry RE(SectionID, Offset, ELF::R_X86_64_PC32, Value.Addend,
Value.Offset);
addRelocationForSection(RE, Value.SectionID);
processSimpleRelocation(SectionID, Offset, RelType, Value);
}
} else if (Arch == Triple::x86_64 && RelType == ELF::R_X86_64_GOTPCREL) {
uint64_t GOTOffset = allocateGOTEntries(SectionID, 1);
resolveGOTOffsetRelocation(SectionID, Offset, GOTOffset + Addend);

// 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);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
addRelocationForSection(RE, Value.SectionID);
} else {
RelocationEntry RE(SectionID, Offset, RelType, Value.Addend, Value.Offset);
if (Value.SymbolName)
addRelocationForSymbol(RE, Value.SymbolName);
else
addRelocationForSection(RE, Value.SectionID);
if (Arch == Triple::x86) {
Value.Addend += support::ulittle32_t::ref(computePlaceholderAddress(SectionID, Offset));
}
processSimpleRelocation(SectionID, Offset, RelType, Value);
}
return ++RelI;
}
Expand Down
7 changes: 7 additions & 0 deletions llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,13 @@ class RuntimeDyldELF : public RuntimeDyldImpl {
uint64_t SymbolOffset,
unsigned Type);

// Compute the address in memory where we can find the placeholder
void *computePlaceholderAddress(unsigned SectionID, uint64_t Offset) const;

// Split out common case for createing the RelocationEntry for when the relocation requires
// no particular advanced processing.
void processSimpleRelocation(unsigned SectionID, uint64_t Offset, unsigned RelType, RelocationValueRef Value);

// The tentative ID for the GOT section
unsigned GOTSectionID;

Expand Down