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llvm-project/lld/ELF/Arch/PPC64.cpp

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//===- PPC64.cpp ----------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "SymbolTable.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "Target.h"
#include "Thunks.h"
#include "lld/Common/CommonLinkerContext.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
constexpr uint64_t ppc64TocOffset = 0x8000;
constexpr uint64_t dynamicThreadPointerOffset = 0x8000;
// The instruction encoding of bits 21-30 from the ISA for the Xform and Dform
// instructions that can be used as part of the initial exec TLS sequence.
enum XFormOpcd {
LBZX = 87,
LHZX = 279,
LWZX = 23,
LDX = 21,
STBX = 215,
STHX = 407,
STWX = 151,
STDX = 149,
ADD = 266,
};
enum DFormOpcd {
LBZ = 34,
LBZU = 35,
LHZ = 40,
LHZU = 41,
LHAU = 43,
LWZ = 32,
LWZU = 33,
LFSU = 49,
LD = 58,
LFDU = 51,
STB = 38,
STBU = 39,
STH = 44,
STHU = 45,
STW = 36,
STWU = 37,
STFSU = 53,
STFDU = 55,
STD = 62,
ADDI = 14
};
constexpr uint32_t NOP = 0x60000000;
enum class PPCLegacyInsn : uint32_t {
NOINSN = 0,
// Loads.
LBZ = 0x88000000,
LHZ = 0xa0000000,
LWZ = 0x80000000,
LHA = 0xa8000000,
LWA = 0xe8000002,
LD = 0xe8000000,
LFS = 0xC0000000,
LXSSP = 0xe4000003,
LFD = 0xc8000000,
LXSD = 0xe4000002,
LXV = 0xf4000001,
LXVP = 0x18000000,
// Stores.
STB = 0x98000000,
STH = 0xb0000000,
STW = 0x90000000,
STD = 0xf8000000,
STFS = 0xd0000000,
STXSSP = 0xf4000003,
STFD = 0xd8000000,
STXSD = 0xf4000002,
STXV = 0xf4000005,
STXVP = 0x18000001
};
enum class PPCPrefixedInsn : uint64_t {
NOINSN = 0,
PREFIX_MLS = 0x0610000000000000,
PREFIX_8LS = 0x0410000000000000,
// Loads.
PLBZ = PREFIX_MLS,
PLHZ = PREFIX_MLS,
PLWZ = PREFIX_MLS,
PLHA = PREFIX_MLS,
PLWA = PREFIX_8LS | 0xa4000000,
PLD = PREFIX_8LS | 0xe4000000,
PLFS = PREFIX_MLS,
PLXSSP = PREFIX_8LS | 0xac000000,
PLFD = PREFIX_MLS,
PLXSD = PREFIX_8LS | 0xa8000000,
PLXV = PREFIX_8LS | 0xc8000000,
PLXVP = PREFIX_8LS | 0xe8000000,
// Stores.
PSTB = PREFIX_MLS,
PSTH = PREFIX_MLS,
PSTW = PREFIX_MLS,
PSTD = PREFIX_8LS | 0xf4000000,
PSTFS = PREFIX_MLS,
PSTXSSP = PREFIX_8LS | 0xbc000000,
PSTFD = PREFIX_MLS,
PSTXSD = PREFIX_8LS | 0xb8000000,
PSTXV = PREFIX_8LS | 0xd8000000,
PSTXVP = PREFIX_8LS | 0xf8000000
};
static bool checkPPCLegacyInsn(uint32_t encoding) {
PPCLegacyInsn insn = static_cast<PPCLegacyInsn>(encoding);
if (insn == PPCLegacyInsn::NOINSN)
return false;
#define PCREL_OPT(Legacy, PCRel, InsnMask) \
if (insn == PPCLegacyInsn::Legacy) \
return true;
#include "PPCInsns.def"
#undef PCREL_OPT
return false;
}
// Masks to apply to legacy instructions when converting them to prefixed,
// pc-relative versions. For the most part, the primary opcode is shared
// between the legacy instruction and the suffix of its prefixed version.
// However, there are some instances where that isn't the case (DS-Form and
// DQ-form instructions).
enum class LegacyToPrefixMask : uint64_t {
NOMASK = 0x0,
OPC_AND_RST = 0xffe00000, // Primary opc (0-5) and R[ST] (6-10).
ONLY_RST = 0x3e00000, // [RS]T (6-10).
ST_STX28_TO5 =
0x8000000003e00000, // S/T (6-10) - The [S/T]X bit moves from 28 to 5.
};
uint64_t elf::getPPC64TocBase() {
// The TOC consists of sections .got, .toc, .tocbss, .plt in that order. The
// TOC starts where the first of these sections starts. We always create a
// .got when we see a relocation that uses it, so for us the start is always
// the .got.
uint64_t tocVA = in.got->getVA();
// Per the ppc64-elf-linux ABI, The TOC base is TOC value plus 0x8000
// thus permitting a full 64 Kbytes segment. Note that the glibc startup
// code (crt1.o) assumes that you can get from the TOC base to the
// start of the .toc section with only a single (signed) 16-bit relocation.
return tocVA + ppc64TocOffset;
}
unsigned elf::getPPC64GlobalEntryToLocalEntryOffset(uint8_t stOther) {
// The offset is encoded into the 3 most significant bits of the st_other
// field, with some special values described in section 3.4.1 of the ABI:
// 0 --> Zero offset between the GEP and LEP, and the function does NOT use
// the TOC pointer (r2). r2 will hold the same value on returning from
// the function as it did on entering the function.
// 1 --> Zero offset between the GEP and LEP, and r2 should be treated as a
// caller-saved register for all callers.
// 2-6 --> The binary logarithm of the offset eg:
// 2 --> 2^2 = 4 bytes --> 1 instruction.
// 6 --> 2^6 = 64 bytes --> 16 instructions.
// 7 --> Reserved.
uint8_t gepToLep = (stOther >> 5) & 7;
if (gepToLep < 2)
return 0;
// The value encoded in the st_other bits is the
// log-base-2(offset).
if (gepToLep < 7)
return 1 << gepToLep;
error("reserved value of 7 in the 3 most-significant-bits of st_other");
return 0;
}
void elf::writePrefixedInstruction(uint8_t *loc, uint64_t insn) {
insn = config->isLE ? insn << 32 | insn >> 32 : insn;
write64(loc, insn);
}
static bool addOptional(StringRef name, uint64_t value,
std::vector<Defined *> &defined) {
Symbol *sym = symtab->find(name);
if (!sym || sym->isDefined())
return false;
sym->resolve(Defined{/*file=*/nullptr, StringRef(), STB_GLOBAL, STV_HIDDEN,
STT_FUNC, value,
/*size=*/0, /*section=*/nullptr});
defined.push_back(cast<Defined>(sym));
return true;
}
// If from is 14, write ${prefix}14: firstInsn; ${prefix}15:
// firstInsn+0x200008; ...; ${prefix}31: firstInsn+(31-14)*0x200008; $tail
// The labels are defined only if they exist in the symbol table.
static void writeSequence(MutableArrayRef<uint32_t> buf, const char *prefix,
int from, uint32_t firstInsn,
ArrayRef<uint32_t> tail) {
std::vector<Defined *> defined;
char name[16];
int first;
uint32_t *ptr = buf.data();
for (int r = from; r < 32; ++r) {
format("%s%d", prefix, r).snprint(name, sizeof(name));
if (addOptional(name, 4 * (r - from), defined) && defined.size() == 1)
first = r - from;
write32(ptr++, firstInsn + 0x200008 * (r - from));
}
for (uint32_t insn : tail)
write32(ptr++, insn);
assert(ptr == &*buf.end());
if (defined.empty())
return;
// The full section content has the extent of [begin, end). We drop unused
// instructions and write [first,end).
auto *sec = make<InputSection>(
nullptr, SHF_ALLOC, SHT_PROGBITS, 4,
makeArrayRef(reinterpret_cast<uint8_t *>(buf.data() + first),
4 * (buf.size() - first)),
".text");
inputSections.push_back(sec);
for (Defined *sym : defined) {
sym->section = sec;
sym->value -= 4 * first;
}
}
// Implements some save and restore functions as described by ELF V2 ABI to be
// compatible with GCC. With GCC -Os, when the number of call-saved registers
// exceeds a certain threshold, GCC generates _savegpr0_* _restgpr0_* calls and
// expects the linker to define them. See
// https://sourceware.org/pipermail/binutils/2002-February/017444.html and
// https://sourceware.org/pipermail/binutils/2004-August/036765.html . This is
// weird because libgcc.a would be the natural place. The linker generation
// approach has the advantage that the linker can generate multiple copies to
// avoid long branch thunks. However, we don't consider the advantage
// significant enough to complicate our trunk implementation, so we take the
// simple approach and synthesize .text sections providing the implementation.
void elf::addPPC64SaveRestore() {
static uint32_t savegpr0[20], restgpr0[21], savegpr1[19], restgpr1[19];
constexpr uint32_t blr = 0x4e800020, mtlr_0 = 0x7c0803a6;
// _restgpr0_14: ld 14, -144(1); _restgpr0_15: ld 15, -136(1); ...
// Tail: ld 0, 16(1); mtlr 0; blr
writeSequence(restgpr0, "_restgpr0_", 14, 0xe9c1ff70,
{0xe8010010, mtlr_0, blr});
// _restgpr1_14: ld 14, -144(12); _restgpr1_15: ld 15, -136(12); ...
// Tail: blr
writeSequence(restgpr1, "_restgpr1_", 14, 0xe9ccff70, {blr});
// _savegpr0_14: std 14, -144(1); _savegpr0_15: std 15, -136(1); ...
// Tail: std 0, 16(1); blr
writeSequence(savegpr0, "_savegpr0_", 14, 0xf9c1ff70, {0xf8010010, blr});
// _savegpr1_14: std 14, -144(12); _savegpr1_15: std 15, -136(12); ...
// Tail: blr
writeSequence(savegpr1, "_savegpr1_", 14, 0xf9ccff70, {blr});
}
// Find the R_PPC64_ADDR64 in .rela.toc with matching offset.
template <typename ELFT>
static std::pair<Defined *, int64_t>
getRelaTocSymAndAddend(InputSectionBase *tocSec, uint64_t offset) {
// .rela.toc contains exclusively R_PPC64_ADDR64 relocations sorted by
// r_offset: 0, 8, 16, etc. For a given Offset, Offset / 8 gives us the
// relocation index in most cases.
//
// In rare cases a TOC entry may store a constant that doesn't need an
// R_PPC64_ADDR64, the corresponding r_offset is therefore missing. Offset / 8
// points to a relocation with larger r_offset. Do a linear probe then.
// Constants are extremely uncommon in .toc and the extra number of array
// accesses can be seen as a small constant.
ArrayRef<typename ELFT::Rela> relas =
tocSec->template relsOrRelas<ELFT>().relas;
if (relas.empty())
return {};
uint64_t index = std::min<uint64_t>(offset / 8, relas.size() - 1);
for (;;) {
if (relas[index].r_offset == offset) {
Symbol &sym = tocSec->getFile<ELFT>()->getRelocTargetSym(relas[index]);
return {dyn_cast<Defined>(&sym), getAddend<ELFT>(relas[index])};
}
if (relas[index].r_offset < offset || index == 0)
break;
--index;
}
return {};
}
// When accessing a symbol defined in another translation unit, compilers
// reserve a .toc entry, allocate a local label and generate toc-indirect
// instructions:
//
// addis 3, 2, .LC0@toc@ha # R_PPC64_TOC16_HA
// ld 3, .LC0@toc@l(3) # R_PPC64_TOC16_LO_DS, load the address from a .toc entry
// ld/lwa 3, 0(3) # load the value from the address
//
// .section .toc,"aw",@progbits
// .LC0: .tc var[TC],var
//
// If var is defined, non-preemptable and addressable with a 32-bit signed
// offset from the toc base, the address of var can be computed by adding an
// offset to the toc base, saving a load.
//
// addis 3,2,var@toc@ha # this may be relaxed to a nop,
// addi 3,3,var@toc@l # then this becomes addi 3,2,var@toc
// ld/lwa 3, 0(3) # load the value from the address
//
// Returns true if the relaxation is performed.
bool elf::tryRelaxPPC64TocIndirection(const Relocation &rel, uint8_t *bufLoc) {
assert(config->tocOptimize);
if (rel.addend < 0)
return false;
// If the symbol is not the .toc section, this isn't a toc-indirection.
Defined *defSym = dyn_cast<Defined>(rel.sym);
if (!defSym || !defSym->isSection() || defSym->section->name != ".toc")
return false;
Defined *d;
int64_t addend;
auto *tocISB = cast<InputSectionBase>(defSym->section);
std::tie(d, addend) =
config->isLE ? getRelaTocSymAndAddend<ELF64LE>(tocISB, rel.addend)
: getRelaTocSymAndAddend<ELF64BE>(tocISB, rel.addend);
// Only non-preemptable defined symbols can be relaxed.
if (!d || d->isPreemptible)
return false;
// R_PPC64_ADDR64 should have created a canonical PLT for the non-preemptable
// ifunc and changed its type to STT_FUNC.
assert(!d->isGnuIFunc());
// Two instructions can materialize a 32-bit signed offset from the toc base.
uint64_t tocRelative = d->getVA(addend) - getPPC64TocBase();
if (!isInt<32>(tocRelative))
return false;
// Add PPC64TocOffset that will be subtracted by PPC64::relocate().
target->relaxGot(bufLoc, rel, tocRelative + ppc64TocOffset);
return true;
}
namespace {
class PPC64 final : public TargetInfo {
public:
PPC64();
int getTlsGdRelaxSkip(RelType type) const override;
uint32_t calcEFlags() const override;
RelExpr getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const override;
RelType getDynRel(RelType type) const override;
int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override;
void writePltHeader(uint8_t *buf) const override;
void writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const override;
void writeIplt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const override;
void relocate(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void writeGotHeader(uint8_t *buf) const override;
bool needsThunk(RelExpr expr, RelType type, const InputFile *file,
uint64_t branchAddr, const Symbol &s,
int64_t a) const override;
uint32_t getThunkSectionSpacing() const override;
bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override;
RelExpr adjustTlsExpr(RelType type, RelExpr expr) const override;
RelExpr adjustGotPcExpr(RelType type, int64_t addend,
const uint8_t *loc) const override;
void relaxGot(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
bool adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end,
uint8_t stOther) const override;
};
} // namespace
// Relocation masks following the #lo(value), #hi(value), #ha(value),
// #higher(value), #highera(value), #highest(value), and #highesta(value)
// macros defined in section 4.5.1. Relocation Types of the PPC-elf64abi
// document.
static uint16_t lo(uint64_t v) { return v; }
static uint16_t hi(uint64_t v) { return v >> 16; }
static uint64_t ha(uint64_t v) { return (v + 0x8000) >> 16; }
static uint16_t higher(uint64_t v) { return v >> 32; }
static uint16_t highera(uint64_t v) { return (v + 0x8000) >> 32; }
static uint16_t highest(uint64_t v) { return v >> 48; }
static uint16_t highesta(uint64_t v) { return (v + 0x8000) >> 48; }
// Extracts the 'PO' field of an instruction encoding.
static uint8_t getPrimaryOpCode(uint32_t encoding) { return (encoding >> 26); }
static bool isDQFormInstruction(uint32_t encoding) {
switch (getPrimaryOpCode(encoding)) {
default:
return false;
case 6: // Power10 paired loads/stores (lxvp, stxvp).
case 56:
// The only instruction with a primary opcode of 56 is `lq`.
return true;
case 61:
// There are both DS and DQ instruction forms with this primary opcode.
// Namely `lxv` and `stxv` are the DQ-forms that use it.
// The DS 'XO' bits being set to 01 is restricted to DQ form.
return (encoding & 3) == 0x1;
}
}
static bool isDSFormInstruction(PPCLegacyInsn insn) {
switch (insn) {
default:
return false;
case PPCLegacyInsn::LWA:
case PPCLegacyInsn::LD:
case PPCLegacyInsn::LXSD:
case PPCLegacyInsn::LXSSP:
case PPCLegacyInsn::STD:
case PPCLegacyInsn::STXSD:
case PPCLegacyInsn::STXSSP:
return true;
}
}
static PPCLegacyInsn getPPCLegacyInsn(uint32_t encoding) {
uint32_t opc = encoding & 0xfc000000;
// If the primary opcode is shared between multiple instructions, we need to
// fix it up to match the actual instruction we are after.
if ((opc == 0xe4000000 || opc == 0xe8000000 || opc == 0xf4000000 ||
opc == 0xf8000000) &&
!isDQFormInstruction(encoding))
opc = encoding & 0xfc000003;
else if (opc == 0xf4000000)
opc = encoding & 0xfc000007;
else if (opc == 0x18000000)
opc = encoding & 0xfc00000f;
// If the value is not one of the enumerators in PPCLegacyInsn, we want to
// return PPCLegacyInsn::NOINSN.
if (!checkPPCLegacyInsn(opc))
return PPCLegacyInsn::NOINSN;
return static_cast<PPCLegacyInsn>(opc);
}
static PPCPrefixedInsn getPCRelativeForm(PPCLegacyInsn insn) {
switch (insn) {
#define PCREL_OPT(Legacy, PCRel, InsnMask) \
case PPCLegacyInsn::Legacy: \
return PPCPrefixedInsn::PCRel
#include "PPCInsns.def"
#undef PCREL_OPT
}
return PPCPrefixedInsn::NOINSN;
}
static LegacyToPrefixMask getInsnMask(PPCLegacyInsn insn) {
switch (insn) {
#define PCREL_OPT(Legacy, PCRel, InsnMask) \
case PPCLegacyInsn::Legacy: \
return LegacyToPrefixMask::InsnMask
#include "PPCInsns.def"
#undef PCREL_OPT
}
return LegacyToPrefixMask::NOMASK;
}
static uint64_t getPCRelativeForm(uint32_t encoding) {
PPCLegacyInsn origInsn = getPPCLegacyInsn(encoding);
PPCPrefixedInsn pcrelInsn = getPCRelativeForm(origInsn);
if (pcrelInsn == PPCPrefixedInsn::NOINSN)
return UINT64_C(-1);
LegacyToPrefixMask origInsnMask = getInsnMask(origInsn);
uint64_t pcrelEncoding =
(uint64_t)pcrelInsn | (encoding & (uint64_t)origInsnMask);
// If the mask requires moving bit 28 to bit 5, do that now.
if (origInsnMask == LegacyToPrefixMask::ST_STX28_TO5)
pcrelEncoding |= (encoding & 0x8) << 23;
return pcrelEncoding;
}
static bool isInstructionUpdateForm(uint32_t encoding) {
switch (getPrimaryOpCode(encoding)) {
default:
return false;
case LBZU:
case LHAU:
case LHZU:
case LWZU:
case LFSU:
case LFDU:
case STBU:
case STHU:
case STWU:
case STFSU:
case STFDU:
return true;
// LWA has the same opcode as LD, and the DS bits is what differentiates
// between LD/LDU/LWA
case LD:
case STD:
return (encoding & 3) == 1;
}
}
// Compute the total displacement between the prefixed instruction that gets
// to the start of the data and the load/store instruction that has the offset
// into the data structure.
// For example:
// paddi 3, 0, 1000, 1
// lwz 3, 20(3)
// Should add up to 1020 for total displacement.
static int64_t getTotalDisp(uint64_t prefixedInsn, uint32_t accessInsn) {
int64_t disp34 = llvm::SignExtend64(
((prefixedInsn & 0x3ffff00000000) >> 16) | (prefixedInsn & 0xffff), 34);
int32_t disp16 = llvm::SignExtend32(accessInsn & 0xffff, 16);
// For DS and DQ form instructions, we need to mask out the XO bits.
if (isDQFormInstruction(accessInsn))
disp16 &= ~0xf;
else if (isDSFormInstruction(getPPCLegacyInsn(accessInsn)))
disp16 &= ~0x3;
return disp34 + disp16;
}
// There are a number of places when we either want to read or write an
// instruction when handling a half16 relocation type. On big-endian the buffer
// pointer is pointing into the middle of the word we want to extract, and on
// little-endian it is pointing to the start of the word. These 2 helpers are to
// simplify reading and writing in that context.
static void writeFromHalf16(uint8_t *loc, uint32_t insn) {
write32(config->isLE ? loc : loc - 2, insn);
}
static uint32_t readFromHalf16(const uint8_t *loc) {
return read32(config->isLE ? loc : loc - 2);
}
static uint64_t readPrefixedInstruction(const uint8_t *loc) {
uint64_t fullInstr = read64(loc);
return config->isLE ? (fullInstr << 32 | fullInstr >> 32) : fullInstr;
}
PPC64::PPC64() {
copyRel = R_PPC64_COPY;
gotRel = R_PPC64_GLOB_DAT;
pltRel = R_PPC64_JMP_SLOT;
relativeRel = R_PPC64_RELATIVE;
iRelativeRel = R_PPC64_IRELATIVE;
symbolicRel = R_PPC64_ADDR64;
pltHeaderSize = 60;
pltEntrySize = 4;
ipltEntrySize = 16; // PPC64PltCallStub::size
gotHeaderEntriesNum = 1;
gotPltHeaderEntriesNum = 2;
needsThunks = true;
tlsModuleIndexRel = R_PPC64_DTPMOD64;
tlsOffsetRel = R_PPC64_DTPREL64;
tlsGotRel = R_PPC64_TPREL64;
needsMoreStackNonSplit = false;
// We need 64K pages (at least under glibc/Linux, the loader won't
// set different permissions on a finer granularity than that).
defaultMaxPageSize = 65536;
// The PPC64 ELF ABI v1 spec, says:
//
// It is normally desirable to put segments with different characteristics
// in separate 256 Mbyte portions of the address space, to give the
// operating system full paging flexibility in the 64-bit address space.
//
// And because the lowest non-zero 256M boundary is 0x10000000, PPC64 linkers
// use 0x10000000 as the starting address.
defaultImageBase = 0x10000000;
write32(trapInstr.data(), 0x7fe00008);
}
int PPC64::getTlsGdRelaxSkip(RelType type) const {
// A __tls_get_addr call instruction is marked with 2 relocations:
//
// R_PPC64_TLSGD / R_PPC64_TLSLD: marker relocation
// R_PPC64_REL24: __tls_get_addr
//
// After the relaxation we no longer call __tls_get_addr and should skip both
// relocations to not create a false dependence on __tls_get_addr being
// defined.
if (type == R_PPC64_TLSGD || type == R_PPC64_TLSLD)
return 2;
return 1;
}
static uint32_t getEFlags(InputFile *file) {
if (config->ekind == ELF64BEKind)
return cast<ObjFile<ELF64BE>>(file)->getObj().getHeader().e_flags;
return cast<ObjFile<ELF64LE>>(file)->getObj().getHeader().e_flags;
}
// This file implements v2 ABI. This function makes sure that all
// object files have v2 or an unspecified version as an ABI version.
uint32_t PPC64::calcEFlags() const {
for (InputFile *f : objectFiles) {
uint32_t flag = getEFlags(f);
if (flag == 1)
error(toString(f) + ": ABI version 1 is not supported");
else if (flag > 2)
error(toString(f) + ": unrecognized e_flags: " + Twine(flag));
}
return 2;
}
void PPC64::relaxGot(uint8_t *loc, const Relocation &rel, uint64_t val) const {
switch (rel.type) {
case R_PPC64_TOC16_HA:
// Convert "addis reg, 2, .LC0@toc@h" to "addis reg, 2, var@toc@h" or "nop".
relocate(loc, rel, val);
break;
case R_PPC64_TOC16_LO_DS: {
// Convert "ld reg, .LC0@toc@l(reg)" to "addi reg, reg, var@toc@l" or
// "addi reg, 2, var@toc".
uint32_t insn = readFromHalf16(loc);
if (getPrimaryOpCode(insn) != LD)
error("expected a 'ld' for got-indirect to toc-relative relaxing");
writeFromHalf16(loc, (insn & 0x03ffffff) | 0x38000000);
relocateNoSym(loc, R_PPC64_TOC16_LO, val);
break;
}
case R_PPC64_GOT_PCREL34: {
// Clear the first 8 bits of the prefix and the first 6 bits of the
// instruction (the primary opcode).
uint64_t insn = readPrefixedInstruction(loc);
if ((insn & 0xfc000000) != 0xe4000000)
error("expected a 'pld' for got-indirect to pc-relative relaxing");
insn &= ~0xff000000fc000000;
// Replace the cleared bits with the values for PADDI (0x600000038000000);
insn |= 0x600000038000000;
writePrefixedInstruction(loc, insn);
relocate(loc, rel, val);
break;
}
case R_PPC64_PCREL_OPT: {
// We can only relax this if the R_PPC64_GOT_PCREL34 at this offset can
// be relaxed. The eligibility for the relaxation needs to be determined
// on that relocation since this one does not relocate a symbol.
uint64_t insn = readPrefixedInstruction(loc);
uint32_t accessInsn = read32(loc + rel.addend);
uint64_t pcRelInsn = getPCRelativeForm(accessInsn);
// This error is not necessary for correctness but is emitted for now
// to ensure we don't miss these opportunities in real code. It can be
// removed at a later date.
if (pcRelInsn == UINT64_C(-1)) {
errorOrWarn(
"unrecognized instruction for R_PPC64_PCREL_OPT relaxation: 0x" +
Twine::utohexstr(accessInsn));
break;
}
int64_t totalDisp = getTotalDisp(insn, accessInsn);
if (!isInt<34>(totalDisp))
break; // Displacement doesn't fit.
// Convert the PADDI to the prefixed version of accessInsn and convert
// accessInsn to a nop.
writePrefixedInstruction(loc, pcRelInsn |
((totalDisp & 0x3ffff0000) << 16) |
(totalDisp & 0xffff));
write32(loc + rel.addend, NOP); // nop accessInsn.
break;
}
default:
llvm_unreachable("unexpected relocation type");
}
}
void PPC64::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
// Reference: 3.7.4.2 of the 64-bit ELF V2 abi supplement.
// The general dynamic code sequence for a global `x` will look like:
// Instruction Relocation Symbol
// addis r3, r2, x@got@tlsgd@ha R_PPC64_GOT_TLSGD16_HA x
// addi r3, r3, x@got@tlsgd@l R_PPC64_GOT_TLSGD16_LO x
// bl __tls_get_addr(x@tlsgd) R_PPC64_TLSGD x
// R_PPC64_REL24 __tls_get_addr
// nop None None
// Relaxing to local exec entails converting:
// addis r3, r2, x@got@tlsgd@ha into nop
// addi r3, r3, x@got@tlsgd@l into addis r3, r13, x@tprel@ha
// bl __tls_get_addr(x@tlsgd) into nop
// nop into addi r3, r3, x@tprel@l
switch (rel.type) {
case R_PPC64_GOT_TLSGD16_HA:
writeFromHalf16(loc, NOP);
break;
case R_PPC64_GOT_TLSGD16:
case R_PPC64_GOT_TLSGD16_LO:
writeFromHalf16(loc, 0x3c6d0000); // addis r3, r13
relocateNoSym(loc, R_PPC64_TPREL16_HA, val);
break;
case R_PPC64_GOT_TLSGD_PCREL34:
// Relax from paddi r3, 0, x@got@tlsgd@pcrel, 1 to
// paddi r3, r13, x@tprel, 0
writePrefixedInstruction(loc, 0x06000000386d0000);
relocateNoSym(loc, R_PPC64_TPREL34, val);
break;
case R_PPC64_TLSGD: {
// PC Relative Relaxation:
// Relax from bl __tls_get_addr@notoc(x@tlsgd) to
// nop
// TOC Relaxation:
// Relax from bl __tls_get_addr(x@tlsgd)
// nop
// to
// nop
// addi r3, r3, x@tprel@l
const uintptr_t locAsInt = reinterpret_cast<uintptr_t>(loc);
if (locAsInt % 4 == 0) {
write32(loc, NOP); // nop
write32(loc + 4, 0x38630000); // addi r3, r3
// Since we are relocating a half16 type relocation and Loc + 4 points to
// the start of an instruction we need to advance the buffer by an extra
// 2 bytes on BE.
relocateNoSym(loc + 4 + (config->ekind == ELF64BEKind ? 2 : 0),
R_PPC64_TPREL16_LO, val);
} else if (locAsInt % 4 == 1) {
write32(loc - 1, NOP);
} else {
errorOrWarn("R_PPC64_TLSGD has unexpected byte alignment");
}
break;
}
default:
llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
}
}
void PPC64::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
// Reference: 3.7.4.3 of the 64-bit ELF V2 abi supplement.
// The local dynamic code sequence for a global `x` will look like:
// Instruction Relocation Symbol
// addis r3, r2, x@got@tlsld@ha R_PPC64_GOT_TLSLD16_HA x
// addi r3, r3, x@got@tlsld@l R_PPC64_GOT_TLSLD16_LO x
// bl __tls_get_addr(x@tlsgd) R_PPC64_TLSLD x
// R_PPC64_REL24 __tls_get_addr
// nop None None
// Relaxing to local exec entails converting:
// addis r3, r2, x@got@tlsld@ha into nop
// addi r3, r3, x@got@tlsld@l into addis r3, r13, 0
// bl __tls_get_addr(x@tlsgd) into nop
// nop into addi r3, r3, 4096
switch (rel.type) {
case R_PPC64_GOT_TLSLD16_HA:
writeFromHalf16(loc, NOP);
break;
case R_PPC64_GOT_TLSLD16_LO:
writeFromHalf16(loc, 0x3c6d0000); // addis r3, r13, 0
break;
case R_PPC64_GOT_TLSLD_PCREL34:
// Relax from paddi r3, 0, x1@got@tlsld@pcrel, 1 to
// paddi r3, r13, 0x1000, 0
writePrefixedInstruction(loc, 0x06000000386d1000);
break;
case R_PPC64_TLSLD: {
// PC Relative Relaxation:
// Relax from bl __tls_get_addr@notoc(x@tlsld)
// to
// nop
// TOC Relaxation:
// Relax from bl __tls_get_addr(x@tlsld)
// nop
// to
// nop
// addi r3, r3, 4096
const uintptr_t locAsInt = reinterpret_cast<uintptr_t>(loc);
if (locAsInt % 4 == 0) {
write32(loc, NOP);
write32(loc + 4, 0x38631000); // addi r3, r3, 4096
} else if (locAsInt % 4 == 1) {
write32(loc - 1, NOP);
} else {
errorOrWarn("R_PPC64_TLSLD has unexpected byte alignment");
}
break;
}
case R_PPC64_DTPREL16:
case R_PPC64_DTPREL16_HA:
case R_PPC64_DTPREL16_HI:
case R_PPC64_DTPREL16_DS:
case R_PPC64_DTPREL16_LO:
case R_PPC64_DTPREL16_LO_DS:
case R_PPC64_DTPREL34:
relocate(loc, rel, val);
break;
default:
llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
}
}
unsigned elf::getPPCDFormOp(unsigned secondaryOp) {
switch (secondaryOp) {
case LBZX:
return LBZ;
case LHZX:
return LHZ;
case LWZX:
return LWZ;
case LDX:
return LD;
case STBX:
return STB;
case STHX:
return STH;
case STWX:
return STW;
case STDX:
return STD;
case ADD:
return ADDI;
default:
return 0;
}
}
void PPC64::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
// The initial exec code sequence for a global `x` will look like:
// Instruction Relocation Symbol
// addis r9, r2, x@got@tprel@ha R_PPC64_GOT_TPREL16_HA x
// ld r9, x@got@tprel@l(r9) R_PPC64_GOT_TPREL16_LO_DS x
// add r9, r9, x@tls R_PPC64_TLS x
// Relaxing to local exec entails converting:
// addis r9, r2, x@got@tprel@ha into nop
// ld r9, x@got@tprel@l(r9) into addis r9, r13, x@tprel@ha
// add r9, r9, x@tls into addi r9, r9, x@tprel@l
// x@tls R_PPC64_TLS is a relocation which does not compute anything,
// it is replaced with r13 (thread pointer).
// The add instruction in the initial exec sequence has multiple variations
// that need to be handled. If we are building an address it will use an add
// instruction, if we are accessing memory it will use any of the X-form
// indexed load or store instructions.
unsigned offset = (config->ekind == ELF64BEKind) ? 2 : 0;
switch (rel.type) {
case R_PPC64_GOT_TPREL16_HA:
write32(loc - offset, NOP);
break;
case R_PPC64_GOT_TPREL16_LO_DS:
case R_PPC64_GOT_TPREL16_DS: {
uint32_t regNo = read32(loc - offset) & 0x03E00000; // bits 6-10
write32(loc - offset, 0x3C0D0000 | regNo); // addis RegNo, r13
relocateNoSym(loc, R_PPC64_TPREL16_HA, val);
break;
}
case R_PPC64_GOT_TPREL_PCREL34: {
const uint64_t pldRT = readPrefixedInstruction(loc) & 0x0000000003e00000;
// paddi RT(from pld), r13, symbol@tprel, 0
writePrefixedInstruction(loc, 0x06000000380d0000 | pldRT);
relocateNoSym(loc, R_PPC64_TPREL34, val);
break;
}
case R_PPC64_TLS: {
const uintptr_t locAsInt = reinterpret_cast<uintptr_t>(loc);
if (locAsInt % 4 == 0) {
uint32_t primaryOp = getPrimaryOpCode(read32(loc));
if (primaryOp != 31)
error("unrecognized instruction for IE to LE R_PPC64_TLS");
uint32_t secondaryOp = (read32(loc) & 0x000007FE) >> 1; // bits 21-30
uint32_t dFormOp = getPPCDFormOp(secondaryOp);
if (dFormOp == 0)
error("unrecognized instruction for IE to LE R_PPC64_TLS");
write32(loc, ((dFormOp << 26) | (read32(loc) & 0x03FFFFFF)));
relocateNoSym(loc + offset, R_PPC64_TPREL16_LO, val);
} else if (locAsInt % 4 == 1) {
// If the offset is not 4 byte aligned then we have a PCRel type reloc.
// This version of the relocation is offset by one byte from the
// instruction it references.
uint32_t tlsInstr = read32(loc - 1);
uint32_t primaryOp = getPrimaryOpCode(tlsInstr);
if (primaryOp != 31)
errorOrWarn("unrecognized instruction for IE to LE R_PPC64_TLS");
uint32_t secondaryOp = (tlsInstr & 0x000007FE) >> 1; // bits 21-30
// The add is a special case and should be turned into a nop. The paddi
// that comes before it will already have computed the address of the
// symbol.
if (secondaryOp == 266) {
// Check if the add uses the same result register as the input register.
uint32_t rt = (tlsInstr & 0x03E00000) >> 21; // bits 6-10
uint32_t ra = (tlsInstr & 0x001F0000) >> 16; // bits 11-15
if (ra == rt) {
write32(loc - 1, NOP);
} else {
// mr rt, ra
write32(loc - 1, 0x7C000378 | (rt << 16) | (ra << 21) | (ra << 11));
}
} else {
uint32_t dFormOp = getPPCDFormOp(secondaryOp);
if (dFormOp == 0)
errorOrWarn("unrecognized instruction for IE to LE R_PPC64_TLS");
write32(loc - 1, ((dFormOp << 26) | (tlsInstr & 0x03FF0000)));
}
} else {
errorOrWarn("R_PPC64_TLS must be either 4 byte aligned or one byte "
"offset from 4 byte aligned");
}
break;
}
default:
llvm_unreachable("unknown relocation for IE to LE");
break;
}
}
RelExpr PPC64::getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const {
switch (type) {
case R_PPC64_NONE:
return R_NONE;
case R_PPC64_ADDR16:
case R_PPC64_ADDR16_DS:
case R_PPC64_ADDR16_HA:
case R_PPC64_ADDR16_HI:
case R_PPC64_ADDR16_HIGH:
case R_PPC64_ADDR16_HIGHER:
case R_PPC64_ADDR16_HIGHERA:
case R_PPC64_ADDR16_HIGHEST:
case R_PPC64_ADDR16_HIGHESTA:
case R_PPC64_ADDR16_LO:
case R_PPC64_ADDR16_LO_DS:
case R_PPC64_ADDR32:
case R_PPC64_ADDR64:
return R_ABS;
case R_PPC64_GOT16:
case R_PPC64_GOT16_DS:
case R_PPC64_GOT16_HA:
case R_PPC64_GOT16_HI:
case R_PPC64_GOT16_LO:
case R_PPC64_GOT16_LO_DS:
return R_GOT_OFF;
case R_PPC64_TOC16:
case R_PPC64_TOC16_DS:
case R_PPC64_TOC16_HI:
case R_PPC64_TOC16_LO:
return R_GOTREL;
case R_PPC64_GOT_PCREL34:
case R_PPC64_GOT_TPREL_PCREL34:
case R_PPC64_PCREL_OPT:
return R_GOT_PC;
case R_PPC64_TOC16_HA:
case R_PPC64_TOC16_LO_DS:
return config->tocOptimize ? R_PPC64_RELAX_TOC : R_GOTREL;
case R_PPC64_TOC:
return R_PPC64_TOCBASE;
case R_PPC64_REL14:
case R_PPC64_REL24:
return R_PPC64_CALL_PLT;
case R_PPC64_REL24_NOTOC:
return R_PLT_PC;
case R_PPC64_REL16_LO:
case R_PPC64_REL16_HA:
case R_PPC64_REL16_HI:
case R_PPC64_REL32:
case R_PPC64_REL64:
case R_PPC64_PCREL34:
return R_PC;
case R_PPC64_GOT_TLSGD16:
case R_PPC64_GOT_TLSGD16_HA:
case R_PPC64_GOT_TLSGD16_HI:
case R_PPC64_GOT_TLSGD16_LO:
return R_TLSGD_GOT;
case R_PPC64_GOT_TLSGD_PCREL34:
return R_TLSGD_PC;
case R_PPC64_GOT_TLSLD16:
case R_PPC64_GOT_TLSLD16_HA:
case R_PPC64_GOT_TLSLD16_HI:
case R_PPC64_GOT_TLSLD16_LO:
return R_TLSLD_GOT;
case R_PPC64_GOT_TLSLD_PCREL34:
return R_TLSLD_PC;
case R_PPC64_GOT_TPREL16_HA:
case R_PPC64_GOT_TPREL16_LO_DS:
case R_PPC64_GOT_TPREL16_DS:
case R_PPC64_GOT_TPREL16_HI:
return R_GOT_OFF;
case R_PPC64_GOT_DTPREL16_HA:
case R_PPC64_GOT_DTPREL16_LO_DS:
case R_PPC64_GOT_DTPREL16_DS:
case R_PPC64_GOT_DTPREL16_HI:
return R_TLSLD_GOT_OFF;
case R_PPC64_TPREL16:
case R_PPC64_TPREL16_HA:
case R_PPC64_TPREL16_LO:
case R_PPC64_TPREL16_HI:
case R_PPC64_TPREL16_DS:
case R_PPC64_TPREL16_LO_DS:
case R_PPC64_TPREL16_HIGHER:
case R_PPC64_TPREL16_HIGHERA:
case R_PPC64_TPREL16_HIGHEST:
case R_PPC64_TPREL16_HIGHESTA:
case R_PPC64_TPREL34:
return R_TPREL;
case R_PPC64_DTPREL16:
case R_PPC64_DTPREL16_DS:
case R_PPC64_DTPREL16_HA:
case R_PPC64_DTPREL16_HI:
case R_PPC64_DTPREL16_HIGHER:
case R_PPC64_DTPREL16_HIGHERA:
case R_PPC64_DTPREL16_HIGHEST:
case R_PPC64_DTPREL16_HIGHESTA:
case R_PPC64_DTPREL16_LO:
case R_PPC64_DTPREL16_LO_DS:
case R_PPC64_DTPREL64:
case R_PPC64_DTPREL34:
return R_DTPREL;
case R_PPC64_TLSGD:
return R_TLSDESC_CALL;
case R_PPC64_TLSLD:
return R_TLSLD_HINT;
case R_PPC64_TLS:
return R_TLSIE_HINT;
default:
error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
") against symbol " + toString(s));
return R_NONE;
}
}
RelType PPC64::getDynRel(RelType type) const {
if (type == R_PPC64_ADDR64 || type == R_PPC64_TOC)
return R_PPC64_ADDR64;
return R_PPC64_NONE;
}
int64_t PPC64::getImplicitAddend(const uint8_t *buf, RelType type) const {
switch (type) {
case R_PPC64_NONE:
return 0;
default:
internalLinkerError(getErrorLocation(buf),
"cannot read addend for relocation " + toString(type));
return 0;
}
}
void PPC64::writeGotHeader(uint8_t *buf) const {
write64(buf, getPPC64TocBase());
}
void PPC64::writePltHeader(uint8_t *buf) const {
// The generic resolver stub goes first.
write32(buf + 0, 0x7c0802a6); // mflr r0
write32(buf + 4, 0x429f0005); // bcl 20,4*cr7+so,8 <_glink+0x8>
write32(buf + 8, 0x7d6802a6); // mflr r11
write32(buf + 12, 0x7c0803a6); // mtlr r0
write32(buf + 16, 0x7d8b6050); // subf r12, r11, r12
write32(buf + 20, 0x380cffcc); // subi r0,r12,52
write32(buf + 24, 0x7800f082); // srdi r0,r0,62,2
write32(buf + 28, 0xe98b002c); // ld r12,44(r11)
write32(buf + 32, 0x7d6c5a14); // add r11,r12,r11
write32(buf + 36, 0xe98b0000); // ld r12,0(r11)
write32(buf + 40, 0xe96b0008); // ld r11,8(r11)
write32(buf + 44, 0x7d8903a6); // mtctr r12
write32(buf + 48, 0x4e800420); // bctr
// The 'bcl' instruction will set the link register to the address of the
// following instruction ('mflr r11'). Here we store the offset from that
// instruction to the first entry in the GotPlt section.
int64_t gotPltOffset = in.gotPlt->getVA() - (in.plt->getVA() + 8);
write64(buf + 52, gotPltOffset);
}
void PPC64::writePlt(uint8_t *buf, const Symbol &sym,
uint64_t /*pltEntryAddr*/) const {
int32_t offset = pltHeaderSize + sym.getPltIdx() * pltEntrySize;
// bl __glink_PLTresolve
write32(buf, 0x48000000 | ((-offset) & 0x03FFFFFc));
}
void PPC64::writeIplt(uint8_t *buf, const Symbol &sym,
uint64_t /*pltEntryAddr*/) const {
writePPC64LoadAndBranch(buf, sym.getGotPltVA() - getPPC64TocBase());
}
static std::pair<RelType, uint64_t> toAddr16Rel(RelType type, uint64_t val) {
// Relocations relative to the toc-base need to be adjusted by the Toc offset.
uint64_t tocBiasedVal = val - ppc64TocOffset;
// Relocations relative to dtv[dtpmod] need to be adjusted by the DTP offset.
uint64_t dtpBiasedVal = val - dynamicThreadPointerOffset;
switch (type) {
// TOC biased relocation.
case R_PPC64_GOT16:
case R_PPC64_GOT_TLSGD16:
case R_PPC64_GOT_TLSLD16:
case R_PPC64_TOC16:
return {R_PPC64_ADDR16, tocBiasedVal};
case R_PPC64_GOT16_DS:
case R_PPC64_TOC16_DS:
case R_PPC64_GOT_TPREL16_DS:
case R_PPC64_GOT_DTPREL16_DS:
return {R_PPC64_ADDR16_DS, tocBiasedVal};
case R_PPC64_GOT16_HA:
case R_PPC64_GOT_TLSGD16_HA:
case R_PPC64_GOT_TLSLD16_HA:
case R_PPC64_GOT_TPREL16_HA:
case R_PPC64_GOT_DTPREL16_HA:
case R_PPC64_TOC16_HA:
return {R_PPC64_ADDR16_HA, tocBiasedVal};
case R_PPC64_GOT16_HI:
case R_PPC64_GOT_TLSGD16_HI:
case R_PPC64_GOT_TLSLD16_HI:
case R_PPC64_GOT_TPREL16_HI:
case R_PPC64_GOT_DTPREL16_HI:
case R_PPC64_TOC16_HI:
return {R_PPC64_ADDR16_HI, tocBiasedVal};
case R_PPC64_GOT16_LO:
case R_PPC64_GOT_TLSGD16_LO:
case R_PPC64_GOT_TLSLD16_LO:
case R_PPC64_TOC16_LO:
return {R_PPC64_ADDR16_LO, tocBiasedVal};
case R_PPC64_GOT16_LO_DS:
case R_PPC64_TOC16_LO_DS:
case R_PPC64_GOT_TPREL16_LO_DS:
case R_PPC64_GOT_DTPREL16_LO_DS:
return {R_PPC64_ADDR16_LO_DS, tocBiasedVal};
// Dynamic Thread pointer biased relocation types.
case R_PPC64_DTPREL16:
return {R_PPC64_ADDR16, dtpBiasedVal};
case R_PPC64_DTPREL16_DS:
return {R_PPC64_ADDR16_DS, dtpBiasedVal};
case R_PPC64_DTPREL16_HA:
return {R_PPC64_ADDR16_HA, dtpBiasedVal};
case R_PPC64_DTPREL16_HI:
return {R_PPC64_ADDR16_HI, dtpBiasedVal};
case R_PPC64_DTPREL16_HIGHER:
return {R_PPC64_ADDR16_HIGHER, dtpBiasedVal};
case R_PPC64_DTPREL16_HIGHERA:
return {R_PPC64_ADDR16_HIGHERA, dtpBiasedVal};
case R_PPC64_DTPREL16_HIGHEST:
return {R_PPC64_ADDR16_HIGHEST, dtpBiasedVal};
case R_PPC64_DTPREL16_HIGHESTA:
return {R_PPC64_ADDR16_HIGHESTA, dtpBiasedVal};
case R_PPC64_DTPREL16_LO:
return {R_PPC64_ADDR16_LO, dtpBiasedVal};
case R_PPC64_DTPREL16_LO_DS:
return {R_PPC64_ADDR16_LO_DS, dtpBiasedVal};
case R_PPC64_DTPREL64:
return {R_PPC64_ADDR64, dtpBiasedVal};
default:
return {type, val};
}
}
static bool isTocOptType(RelType type) {
switch (type) {
case R_PPC64_GOT16_HA:
case R_PPC64_GOT16_LO_DS:
case R_PPC64_TOC16_HA:
case R_PPC64_TOC16_LO_DS:
case R_PPC64_TOC16_LO:
return true;
default:
return false;
}
}
void PPC64::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
RelType type = rel.type;
bool shouldTocOptimize = isTocOptType(type);
// For dynamic thread pointer relative, toc-relative, and got-indirect
// relocations, proceed in terms of the corresponding ADDR16 relocation type.
std::tie(type, val) = toAddr16Rel(type, val);
switch (type) {
case R_PPC64_ADDR14: {
checkAlignment(loc, val, 4, rel);
// Preserve the AA/LK bits in the branch instruction
uint8_t aalk = loc[3];
write16(loc + 2, (aalk & 3) | (val & 0xfffc));
break;
}
case R_PPC64_ADDR16:
checkIntUInt(loc, val, 16, rel);
write16(loc, val);
break;
case R_PPC64_ADDR32:
checkIntUInt(loc, val, 32, rel);
write32(loc, val);
break;
case R_PPC64_ADDR16_DS:
case R_PPC64_TPREL16_DS: {
checkInt(loc, val, 16, rel);
// DQ-form instructions use bits 28-31 as part of the instruction encoding
// DS-form instructions only use bits 30-31.
uint16_t mask = isDQFormInstruction(readFromHalf16(loc)) ? 0xf : 0x3;
checkAlignment(loc, lo(val), mask + 1, rel);
write16(loc, (read16(loc) & mask) | lo(val));
} break;
case R_PPC64_ADDR16_HA:
case R_PPC64_REL16_HA:
case R_PPC64_TPREL16_HA:
if (config->tocOptimize && shouldTocOptimize && ha(val) == 0)
writeFromHalf16(loc, NOP);
else {
checkInt(loc, val + 0x8000, 32, rel);
write16(loc, ha(val));
}
break;
case R_PPC64_ADDR16_HI:
case R_PPC64_REL16_HI:
case R_PPC64_TPREL16_HI:
checkInt(loc, val, 32, rel);
write16(loc, hi(val));
break;
case R_PPC64_ADDR16_HIGH:
write16(loc, hi(val));
break;
case R_PPC64_ADDR16_HIGHER:
case R_PPC64_TPREL16_HIGHER:
write16(loc, higher(val));
break;
case R_PPC64_ADDR16_HIGHERA:
case R_PPC64_TPREL16_HIGHERA:
write16(loc, highera(val));
break;
case R_PPC64_ADDR16_HIGHEST:
case R_PPC64_TPREL16_HIGHEST:
write16(loc, highest(val));
break;
case R_PPC64_ADDR16_HIGHESTA:
case R_PPC64_TPREL16_HIGHESTA:
write16(loc, highesta(val));
break;
case R_PPC64_ADDR16_LO:
case R_PPC64_REL16_LO:
case R_PPC64_TPREL16_LO:
// When the high-adjusted part of a toc relocation evaluates to 0, it is
// changed into a nop. The lo part then needs to be updated to use the
// toc-pointer register r2, as the base register.
if (config->tocOptimize && shouldTocOptimize && ha(val) == 0) {
uint32_t insn = readFromHalf16(loc);
if (isInstructionUpdateForm(insn))
error(getErrorLocation(loc) +
"can't toc-optimize an update instruction: 0x" +
utohexstr(insn));
writeFromHalf16(loc, (insn & 0xffe00000) | 0x00020000 | lo(val));
} else {
write16(loc, lo(val));
}
break;
case R_PPC64_ADDR16_LO_DS:
case R_PPC64_TPREL16_LO_DS: {
// DQ-form instructions use bits 28-31 as part of the instruction encoding
// DS-form instructions only use bits 30-31.
uint32_t insn = readFromHalf16(loc);
uint16_t mask = isDQFormInstruction(insn) ? 0xf : 0x3;
checkAlignment(loc, lo(val), mask + 1, rel);
if (config->tocOptimize && shouldTocOptimize && ha(val) == 0) {
// When the high-adjusted part of a toc relocation evaluates to 0, it is
// changed into a nop. The lo part then needs to be updated to use the toc
// pointer register r2, as the base register.
if (isInstructionUpdateForm(insn))
error(getErrorLocation(loc) +
"Can't toc-optimize an update instruction: 0x" +
Twine::utohexstr(insn));
insn &= 0xffe00000 | mask;
writeFromHalf16(loc, insn | 0x00020000 | lo(val));
} else {
write16(loc, (read16(loc) & mask) | lo(val));
}
} break;
case R_PPC64_TPREL16:
checkInt(loc, val, 16, rel);
write16(loc, val);
break;
case R_PPC64_REL32:
checkInt(loc, val, 32, rel);
write32(loc, val);
break;
case R_PPC64_ADDR64:
case R_PPC64_REL64:
case R_PPC64_TOC:
write64(loc, val);
break;
case R_PPC64_REL14: {
uint32_t mask = 0x0000FFFC;
checkInt(loc, val, 16, rel);
checkAlignment(loc, val, 4, rel);
write32(loc, (read32(loc) & ~mask) | (val & mask));
break;
}
case R_PPC64_REL24:
case R_PPC64_REL24_NOTOC: {
uint32_t mask = 0x03FFFFFC;
checkInt(loc, val, 26, rel);
checkAlignment(loc, val, 4, rel);
write32(loc, (read32(loc) & ~mask) | (val & mask));
break;
}
case R_PPC64_DTPREL64:
write64(loc, val - dynamicThreadPointerOffset);
break;
case R_PPC64_DTPREL34:
// The Dynamic Thread Vector actually points 0x8000 bytes past the start
// of the TLS block. Therefore, in the case of R_PPC64_DTPREL34 we first
// need to subtract that value then fallthrough to the general case.
val -= dynamicThreadPointerOffset;
LLVM_FALLTHROUGH;
case R_PPC64_PCREL34:
case R_PPC64_GOT_PCREL34:
case R_PPC64_GOT_TLSGD_PCREL34:
case R_PPC64_GOT_TLSLD_PCREL34:
case R_PPC64_GOT_TPREL_PCREL34:
case R_PPC64_TPREL34: {
const uint64_t si0Mask = 0x00000003ffff0000;
const uint64_t si1Mask = 0x000000000000ffff;
const uint64_t fullMask = 0x0003ffff0000ffff;
checkInt(loc, val, 34, rel);
uint64_t instr = readPrefixedInstruction(loc) & ~fullMask;
writePrefixedInstruction(loc, instr | ((val & si0Mask) << 16) |
(val & si1Mask));
break;
}
// If we encounter a PCREL_OPT relocation that we won't optimize.
case R_PPC64_PCREL_OPT:
break;
default:
llvm_unreachable("unknown relocation");
}
}
bool PPC64::needsThunk(RelExpr expr, RelType type, const InputFile *file,
uint64_t branchAddr, const Symbol &s, int64_t a) const {
if (type != R_PPC64_REL14 && type != R_PPC64_REL24 &&
type != R_PPC64_REL24_NOTOC)
return false;
// If a function is in the Plt it needs to be called with a call-stub.
if (s.isInPlt())
return true;
// This check looks at the st_other bits of the callee with relocation
// R_PPC64_REL14 or R_PPC64_REL24. If the value is 1, then the callee
// clobbers the TOC and we need an R2 save stub.
if (type != R_PPC64_REL24_NOTOC && (s.stOther >> 5) == 1)
return true;
if (type == R_PPC64_REL24_NOTOC && (s.stOther >> 5) > 1)
return true;
// If a symbol is a weak undefined and we are compiling an executable
// it doesn't need a range-extending thunk since it can't be called.
if (s.isUndefWeak() && !config->shared)
return false;
// If the offset exceeds the range of the branch type then it will need
// a range-extending thunk.
// See the comment in getRelocTargetVA() about R_PPC64_CALL.
return !inBranchRange(type, branchAddr,
s.getVA(a) +
getPPC64GlobalEntryToLocalEntryOffset(s.stOther));
}
uint32_t PPC64::getThunkSectionSpacing() const {
// See comment in Arch/ARM.cpp for a more detailed explanation of
// getThunkSectionSpacing(). For PPC64 we pick the constant here based on
// R_PPC64_REL24, which is used by unconditional branch instructions.
// 0x2000000 = (1 << 24-1) * 4
return 0x2000000;
}
bool PPC64::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
int64_t offset = dst - src;
if (type == R_PPC64_REL14)
return isInt<16>(offset);
if (type == R_PPC64_REL24 || type == R_PPC64_REL24_NOTOC)
return isInt<26>(offset);
llvm_unreachable("unsupported relocation type used in branch");
}
RelExpr PPC64::adjustTlsExpr(RelType type, RelExpr expr) const {
if (type != R_PPC64_GOT_TLSGD_PCREL34 && expr == R_RELAX_TLS_GD_TO_IE)
return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
if (expr == R_RELAX_TLS_LD_TO_LE)
return R_RELAX_TLS_LD_TO_LE_ABS;
return expr;
}
RelExpr PPC64::adjustGotPcExpr(RelType type, int64_t addend,
const uint8_t *loc) const {
if ((type == R_PPC64_GOT_PCREL34 || type == R_PPC64_PCREL_OPT) &&
config->pcRelOptimize) {
// It only makes sense to optimize pld since paddi means that the address
// of the object in the GOT is required rather than the object itself.
if ((readPrefixedInstruction(loc) & 0xfc000000) == 0xe4000000)
return R_PPC64_RELAX_GOT_PC;
}
return R_GOT_PC;
}
// Reference: 3.7.4.1 of the 64-bit ELF V2 abi supplement.
// The general dynamic code sequence for a global `x` uses 4 instructions.
// Instruction Relocation Symbol
// addis r3, r2, x@got@tlsgd@ha R_PPC64_GOT_TLSGD16_HA x
// addi r3, r3, x@got@tlsgd@l R_PPC64_GOT_TLSGD16_LO x
// bl __tls_get_addr(x@tlsgd) R_PPC64_TLSGD x
// R_PPC64_REL24 __tls_get_addr
// nop None None
//
// Relaxing to initial-exec entails:
// 1) Convert the addis/addi pair that builds the address of the tls_index
// struct for 'x' to an addis/ld pair that loads an offset from a got-entry.
// 2) Convert the call to __tls_get_addr to a nop.
// 3) Convert the nop following the call to an add of the loaded offset to the
// thread pointer.
// Since the nop must directly follow the call, the R_PPC64_TLSGD relocation is
// used as the relaxation hint for both steps 2 and 3.
void PPC64::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
switch (rel.type) {
case R_PPC64_GOT_TLSGD16_HA:
// This is relaxed from addis rT, r2, sym@got@tlsgd@ha to
// addis rT, r2, sym@got@tprel@ha.
relocateNoSym(loc, R_PPC64_GOT_TPREL16_HA, val);
return;
case R_PPC64_GOT_TLSGD16:
case R_PPC64_GOT_TLSGD16_LO: {
// Relax from addi r3, rA, sym@got@tlsgd@l to
// ld r3, sym@got@tprel@l(rA)
uint32_t ra = (readFromHalf16(loc) & (0x1f << 16));
writeFromHalf16(loc, 0xe8600000 | ra);
relocateNoSym(loc, R_PPC64_GOT_TPREL16_LO_DS, val);
return;
}
case R_PPC64_GOT_TLSGD_PCREL34: {
// Relax from paddi r3, 0, sym@got@tlsgd@pcrel, 1 to
// pld r3, sym@got@tprel@pcrel
writePrefixedInstruction(loc, 0x04100000e4600000);
relocateNoSym(loc, R_PPC64_GOT_TPREL_PCREL34, val);
return;
}
case R_PPC64_TLSGD: {
// PC Relative Relaxation:
// Relax from bl __tls_get_addr@notoc(x@tlsgd) to
// nop
// TOC Relaxation:
// Relax from bl __tls_get_addr(x@tlsgd)
// nop
// to
// nop
// add r3, r3, r13
const uintptr_t locAsInt = reinterpret_cast<uintptr_t>(loc);
if (locAsInt % 4 == 0) {
write32(loc, NOP); // bl __tls_get_addr(sym@tlsgd) --> nop
write32(loc + 4, 0x7c636A14); // nop --> add r3, r3, r13
} else if (locAsInt % 4 == 1) {
// bl __tls_get_addr(sym@tlsgd) --> add r3, r3, r13
write32(loc - 1, 0x7c636a14);
} else {
errorOrWarn("R_PPC64_TLSGD has unexpected byte alignment");
}
return;
}
default:
llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
}
}
// The prologue for a split-stack function is expected to look roughly
// like this:
// .Lglobal_entry_point:
// # TOC pointer initialization.
// ...
// .Llocal_entry_point:
// # load the __private_ss member of the threads tcbhead.
// ld r0,-0x7000-64(r13)
// # subtract the functions stack size from the stack pointer.
// addis r12, r1, ha(-stack-frame size)
// addi r12, r12, l(-stack-frame size)
// # compare needed to actual and branch to allocate_more_stack if more
// # space is needed, otherwise fallthrough to 'normal' function body.
// cmpld cr7,r12,r0
// blt- cr7, .Lallocate_more_stack
//
// -) The allocate_more_stack block might be placed after the split-stack
// prologue and the `blt-` replaced with a `bge+ .Lnormal_func_body`
// instead.
// -) If either the addis or addi is not needed due to the stack size being
// smaller then 32K or a multiple of 64K they will be replaced with a nop,
// but there will always be 2 instructions the linker can overwrite for the
// adjusted stack size.
//
// The linkers job here is to increase the stack size used in the addis/addi
// pair by split-stack-size-adjust.
// addis r12, r1, ha(-stack-frame size - split-stack-adjust-size)
// addi r12, r12, l(-stack-frame size - split-stack-adjust-size)
bool PPC64::adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end,
uint8_t stOther) const {
// If the caller has a global entry point adjust the buffer past it. The start
// of the split-stack prologue will be at the local entry point.
loc += getPPC64GlobalEntryToLocalEntryOffset(stOther);
// At the very least we expect to see a load of some split-stack data from the
// tcb, and 2 instructions that calculate the ending stack address this
// function will require. If there is not enough room for at least 3
// instructions it can't be a split-stack prologue.
if (loc + 12 >= end)
return false;
// First instruction must be `ld r0, -0x7000-64(r13)`
if (read32(loc) != 0xe80d8fc0)
return false;
int16_t hiImm = 0;
int16_t loImm = 0;
// First instruction can be either an addis if the frame size is larger then
// 32K, or an addi if the size is less then 32K.
int32_t firstInstr = read32(loc + 4);
if (getPrimaryOpCode(firstInstr) == 15) {
hiImm = firstInstr & 0xFFFF;
} else if (getPrimaryOpCode(firstInstr) == 14) {
loImm = firstInstr & 0xFFFF;
} else {
return false;
}
// Second instruction is either an addi or a nop. If the first instruction was
// an addi then LoImm is set and the second instruction must be a nop.
uint32_t secondInstr = read32(loc + 8);
if (!loImm && getPrimaryOpCode(secondInstr) == 14) {
loImm = secondInstr & 0xFFFF;
} else if (secondInstr != NOP) {
return false;
}
// The register operands of the first instruction should be the stack-pointer
// (r1) as the input (RA) and r12 as the output (RT). If the second
// instruction is not a nop, then it should use r12 as both input and output.
auto checkRegOperands = [](uint32_t instr, uint8_t expectedRT,
uint8_t expectedRA) {
return ((instr & 0x3E00000) >> 21 == expectedRT) &&
((instr & 0x1F0000) >> 16 == expectedRA);
};
if (!checkRegOperands(firstInstr, 12, 1))
return false;
if (secondInstr != NOP && !checkRegOperands(secondInstr, 12, 12))
return false;
int32_t stackFrameSize = (hiImm * 65536) + loImm;
// Check that the adjusted size doesn't overflow what we can represent with 2
// instructions.
if (stackFrameSize < config->splitStackAdjustSize + INT32_MIN) {
error(getErrorLocation(loc) + "split-stack prologue adjustment overflows");
return false;
}
int32_t adjustedStackFrameSize =
stackFrameSize - config->splitStackAdjustSize;
loImm = adjustedStackFrameSize & 0xFFFF;
hiImm = (adjustedStackFrameSize + 0x8000) >> 16;
if (hiImm) {
write32(loc + 4, 0x3D810000 | (uint16_t)hiImm);
// If the low immediate is zero the second instruction will be a nop.
secondInstr = loImm ? 0x398C0000 | (uint16_t)loImm : NOP;
write32(loc + 8, secondInstr);
} else {
// addi r12, r1, imm
write32(loc + 4, (0x39810000) | (uint16_t)loImm);
write32(loc + 8, NOP);
}
return true;
}
TargetInfo *elf::getPPC64TargetInfo() {
static PPC64 target;
return &target;
}
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