[llvm] r213491 - [PowerPC] ELFv2 dynamic loader support
Ulrich Weigand
ulrich.weigand at de.ibm.com
Sun Jul 20 16:53:14 PDT 2014
Author: uweigand
Date: Sun Jul 20 18:53:14 2014
New Revision: 213491
URL: http://llvm.org/viewvc/llvm-project?rev=213491&view=rev
Log:
[PowerPC] ELFv2 dynamic loader support
This patch enables the new ELFv2 ABI in the runtime dynamic loader.
The loader has to implement the following features:
- In the ELFv2 ABI, do not look up a function descriptor in .opd, but
instead use the local entry point when resolving a direct call.
- Update the TOC restore code to use the new TOC slot linkage area
offset.
- Create PLT stubs appropriate for the ELFv2 ABI.
Note that this patch also adds common-code changes. These are necessary
because the loader must check the newly added ELF flags: the e_flags
header bits encoding the ABI version, and the st_other symbol table
entry bits encoding the local entry point offset. There is currently
no way to access these, so I've added ObjectFile::getPlatformFlags and
SymbolRef::getOther accessors.
Reviewed by Hal Finkel.
Modified:
llvm/trunk/include/llvm/Object/ELFObjectFile.h
llvm/trunk/include/llvm/Object/ObjectFile.h
llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
Modified: llvm/trunk/include/llvm/Object/ELFObjectFile.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Object/ELFObjectFile.h?rev=213491&r1=213490&r2=213491&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Object/ELFObjectFile.h (original)
+++ llvm/trunk/include/llvm/Object/ELFObjectFile.h Sun Jul 20 18:53:14 2014
@@ -65,6 +65,7 @@ protected:
uint32_t &Res) const override;
std::error_code getSymbolSize(DataRefImpl Symb, uint64_t &Res) const override;
uint32_t getSymbolFlags(DataRefImpl Symb) const override;
+ std::error_code getSymbolOther(DataRefImpl Symb, uint8_t &Res) const override;
std::error_code getSymbolType(DataRefImpl Symb,
SymbolRef::Type &Res) const override;
std::error_code getSymbolSection(DataRefImpl Symb,
@@ -202,6 +203,11 @@ public:
unsigned getArch() const override;
StringRef getLoadName() const override;
+ std::error_code getPlatformFlags(unsigned &Result) const override {
+ Result = EF.getHeader()->e_flags;
+ return object_error::success;
+ }
+
const ELFFile<ELFT> *getELFFile() const { return &EF; }
bool isDyldType() const { return isDyldELFObject; }
@@ -294,6 +300,13 @@ std::error_code ELFObjectFile<ELFT>::get
return object_error::success;
}
+template <class ELFT>
+std::error_code ELFObjectFile<ELFT>::getSymbolOther(DataRefImpl Symb,
+ uint8_t &Result) const {
+ Result = toELFSymIter(Symb)->st_other;
+ return object_error::success;
+}
+
template <class ELFT>
std::error_code
ELFObjectFile<ELFT>::getSymbolType(DataRefImpl Symb,
Modified: llvm/trunk/include/llvm/Object/ObjectFile.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Object/ObjectFile.h?rev=213491&r1=213490&r2=213491&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Object/ObjectFile.h (original)
+++ llvm/trunk/include/llvm/Object/ObjectFile.h Sun Jul 20 18:53:14 2014
@@ -149,6 +149,7 @@ public:
std::error_code getAlignment(uint32_t &Result) const;
std::error_code getSize(uint64_t &Result) const;
std::error_code getType(SymbolRef::Type &Result) const;
+ std::error_code getOther(uint8_t &Result) const;
/// @brief Get section this symbol is defined in reference to. Result is
/// end_sections() if it is undefined or is an absolute symbol.
@@ -237,6 +238,10 @@ protected:
SymbolRef::Type &Res) const = 0;
virtual std::error_code getSymbolSection(DataRefImpl Symb,
section_iterator &Res) const = 0;
+ virtual std::error_code getSymbolOther(DataRefImpl Symb,
+ uint8_t &Res) const {
+ return object_error::invalid_file_type;
+ }
// Same as above for SectionRef.
friend class SectionRef;
@@ -328,6 +333,12 @@ public:
/// LC_ID_DYLIB (install name) on MachO.
virtual StringRef getLoadName() const = 0;
+ /// Returns platform-specific object flags, if any.
+ virtual std::error_code getPlatformFlags(unsigned &Result) const {
+ Result = 0;
+ return object_error::invalid_file_type;
+ }
+
/// @returns Pointer to ObjectFile subclass to handle this type of object.
/// @param ObjectPath The path to the object file. ObjectPath.isObject must
/// return true.
@@ -383,6 +394,10 @@ inline std::error_code SymbolRef::getTyp
return getObject()->getSymbolType(getRawDataRefImpl(), Result);
}
+inline std::error_code SymbolRef::getOther(uint8_t &Result) const {
+ return getObject()->getSymbolOther(getRawDataRefImpl(), Result);
+}
+
inline const ObjectFile *SymbolRef::getObject() const {
const SymbolicFile *O = BasicSymbolRef::getObject();
return cast<ObjectFile>(O);
Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=213491&r1=213490&r2=213491&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Sun Jul 20 18:53:14 2014
@@ -517,7 +517,8 @@ void RuntimeDyldImpl::addRelocationForSy
}
}
-uint8_t *RuntimeDyldImpl::createStubFunction(uint8_t *Addr) {
+uint8_t *RuntimeDyldImpl::createStubFunction(uint8_t *Addr,
+ unsigned AbiVariant) {
if (Arch == Triple::aarch64 || Arch == Triple::aarch64_be ||
Arch == Triple::arm64 || Arch == Triple::arm64_be) {
// This stub has to be able to access the full address space,
@@ -561,22 +562,31 @@ uint8_t *RuntimeDyldImpl::createStubFunc
*StubAddr = NopInstr;
return Addr;
} else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
- // PowerPC64 stub: the address points to a function descriptor
- // instead of the function itself. Load the function address
- // on r11 and sets it to control register. Also loads the function
- // TOC in r2 and environment pointer to r11.
+ // Depending on which version of the ELF ABI is in use, we need to
+ // generate one of two variants of the stub. They both start with
+ // the same sequence to load the target address into r12.
writeInt32BE(Addr, 0x3D800000); // lis r12, highest(addr)
writeInt32BE(Addr+4, 0x618C0000); // ori r12, higher(addr)
writeInt32BE(Addr+8, 0x798C07C6); // sldi r12, r12, 32
writeInt32BE(Addr+12, 0x658C0000); // oris r12, r12, h(addr)
writeInt32BE(Addr+16, 0x618C0000); // ori r12, r12, l(addr)
- writeInt32BE(Addr+20, 0xF8410028); // std r2, 40(r1)
- writeInt32BE(Addr+24, 0xE96C0000); // ld r11, 0(r12)
- writeInt32BE(Addr+28, 0xE84C0008); // ld r2, 0(r12)
- writeInt32BE(Addr+32, 0x7D6903A6); // mtctr r11
- writeInt32BE(Addr+36, 0xE96C0010); // ld r11, 16(r2)
- writeInt32BE(Addr+40, 0x4E800420); // bctr
-
+ if (AbiVariant == 2) {
+ // PowerPC64 stub ELFv2 ABI: The address points to the function itself.
+ // The address is already in r12 as required by the ABI. Branch to it.
+ writeInt32BE(Addr+20, 0xF8410018); // std r2, 24(r1)
+ writeInt32BE(Addr+24, 0x7D8903A6); // mtctr r12
+ writeInt32BE(Addr+28, 0x4E800420); // bctr
+ } else {
+ // PowerPC64 stub ELFv1 ABI: The address points to a function descriptor.
+ // Load the function address on r11 and sets it to control register. Also
+ // loads the function TOC in r2 and environment pointer to r11.
+ writeInt32BE(Addr+20, 0xF8410028); // std r2, 40(r1)
+ writeInt32BE(Addr+24, 0xE96C0000); // ld r11, 0(r12)
+ writeInt32BE(Addr+28, 0xE84C0008); // ld r2, 0(r12)
+ writeInt32BE(Addr+32, 0x7D6903A6); // mtctr r11
+ writeInt32BE(Addr+36, 0xE96C0010); // ld r11, 16(r2)
+ writeInt32BE(Addr+40, 0x4E800420); // bctr
+ }
return Addr;
} else if (Arch == Triple::systemz) {
writeInt16BE(Addr, 0xC418); // lgrl %r1,.+8
Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp?rev=213491&r1=213490&r2=213491&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp Sun Jul 20 18:53:14 2014
@@ -1141,6 +1141,10 @@ relocation_iterator RuntimeDyldELF::proc
}
} else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
if (RelType == ELF::R_PPC64_REL24) {
+ // Determine ABI variant in use for this object.
+ unsigned AbiVariant;
+ Obj.getObjectFile()->getPlatformFlags(AbiVariant);
+ AbiVariant &= ELF::EF_PPC64_ABI;
// A PPC branch relocation will need a stub function if the target is
// an external symbol (Symbol::ST_Unknown) or if the target address
// is not within the signed 24-bits branch address.
@@ -1148,10 +1152,18 @@ relocation_iterator RuntimeDyldELF::proc
uint8_t *Target = Section.Address + Offset;
bool RangeOverflow = false;
if (SymType != SymbolRef::ST_Unknown) {
- // A function call may points to the .opd entry, so the final symbol
- // value
- // in calculated based in the relocation values in .opd section.
- findOPDEntrySection(Obj, ObjSectionToID, Value);
+ if (AbiVariant != 2) {
+ // In the ELFv1 ABI, a function call may point to the .opd entry,
+ // so the final symbol value is calculated based on the relocation
+ // values in the .opd section.
+ findOPDEntrySection(Obj, ObjSectionToID, Value);
+ } else {
+ // In the ELFv2 ABI, a function symbol may provide a local entry
+ // point, which must be used for direct calls.
+ uint8_t SymOther;
+ Symbol->getOther(SymOther);
+ Value.Addend += ELF::decodePPC64LocalEntryOffset(SymOther);
+ }
uint8_t *RelocTarget = Sections[Value.SectionID].Address + Value.Addend;
int32_t delta = static_cast<int32_t>(Target - RelocTarget);
// If it is within 24-bits branch range, just set the branch target
@@ -1179,7 +1191,8 @@ relocation_iterator RuntimeDyldELF::proc
DEBUG(dbgs() << " Create a new stub function\n");
Stubs[Value] = Section.StubOffset;
uint8_t *StubTargetAddr =
- createStubFunction(Section.Address + Section.StubOffset);
+ createStubFunction(Section.Address + Section.StubOffset,
+ AbiVariant);
RelocationEntry RE(SectionID, StubTargetAddr - Section.Address,
ELF::R_PPC64_ADDR64, Value.Addend);
@@ -1217,9 +1230,13 @@ relocation_iterator RuntimeDyldELF::proc
RelType, 0);
Section.StubOffset += getMaxStubSize();
}
- if (SymType == SymbolRef::ST_Unknown)
+ if (SymType == SymbolRef::ST_Unknown) {
// Restore the TOC for external calls
- writeInt32BE(Target + 4, 0xE8410028); // ld r2,40(r1)
+ if (AbiVariant == 2)
+ writeInt32BE(Target + 4, 0xE8410018); // ld r2,28(r1)
+ else
+ writeInt32BE(Target + 4, 0xE8410028); // ld r2,40(r1)
+ }
}
} else if (RelType == ELF::R_PPC64_TOC16 ||
RelType == ELF::R_PPC64_TOC16_DS ||
Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h?rev=213491&r1=213490&r2=213491&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h Sun Jul 20 18:53:14 2014
@@ -312,7 +312,7 @@ protected:
/// \brief Emits long jump instruction to Addr.
/// \return Pointer to the memory area for emitting target address.
- uint8_t *createStubFunction(uint8_t *Addr);
+ uint8_t *createStubFunction(uint8_t *Addr, unsigned AbiVariant = 0);
/// \brief Resolves relocations from Relocs list with address from Value.
void resolveRelocationList(const RelocationList &Relocs, uint64_t Value);
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