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llvm-project/lld/ELF/Arch/SystemZ.cpp
Fangrui Song c1a6defd9f [ELF] Make RelType a struct type 
otherwise operator<<(const ELFSyncStream &s, RelType type) applies to
non-reloc-type uint32_t, which can be confusing.
2024-11-16 20:26:34 -08:00

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//===- SystemZ.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 "OutputSections.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "Target.h"
#include "lld/Common/ErrorHandler.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
namespace {
class SystemZ : public TargetInfo {
public:
SystemZ(Ctx &);
int getTlsGdRelaxSkip(RelType type) const override;
RelExpr getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const override;
RelType getDynRel(RelType type) const override;
void writeGotHeader(uint8_t *buf) const override;
void writeGotPlt(uint8_t *buf, const Symbol &s) const override;
void writeIgotPlt(uint8_t *buf, const Symbol &s) const override;
void writePltHeader(uint8_t *buf) const override;
void addPltHeaderSymbols(InputSection &isd) const override;
void writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const override;
RelExpr adjustTlsExpr(RelType type, RelExpr expr) const override;
RelExpr adjustGotPcExpr(RelType type, int64_t addend,
const uint8_t *loc) const override;
bool relaxOnce(int pass) const override;
void relocate(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override;
private:
void relaxGot(uint8_t *loc, const Relocation &rel, uint64_t val) const;
void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
};
} // namespace
SystemZ::SystemZ(Ctx &ctx) : TargetInfo(ctx) {
copyRel = R_390_COPY;
gotRel = R_390_GLOB_DAT;
pltRel = R_390_JMP_SLOT;
relativeRel = R_390_RELATIVE;
iRelativeRel = R_390_IRELATIVE;
symbolicRel = R_390_64;
tlsGotRel = R_390_TLS_TPOFF;
tlsModuleIndexRel = R_390_TLS_DTPMOD;
tlsOffsetRel = R_390_TLS_DTPOFF;
gotHeaderEntriesNum = 3;
gotPltHeaderEntriesNum = 0;
gotEntrySize = 8;
pltHeaderSize = 32;
pltEntrySize = 32;
ipltEntrySize = 32;
// This "trap instruction" is used to fill gaps between sections.
// On SystemZ, the behavior of the GNU ld is to fill those gaps
// with nop instructions instead - and unfortunately the default
// glibc crt object files (used to) rely on that behavior since
// they use an alignment on the .init section fragments that causes
// gaps which must be filled with nops as they are being executed.
// Therefore, we provide a nop instruction as "trapInstr" here.
trapInstr = {0x07, 0x07, 0x07, 0x07};
defaultImageBase = 0x1000000;
}
RelExpr SystemZ::getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const {
switch (type) {
case R_390_NONE:
return R_NONE;
// Relocations targeting the symbol value.
case R_390_8:
case R_390_12:
case R_390_16:
case R_390_20:
case R_390_32:
case R_390_64:
return R_ABS;
case R_390_PC16:
case R_390_PC32:
case R_390_PC64:
case R_390_PC12DBL:
case R_390_PC16DBL:
case R_390_PC24DBL:
case R_390_PC32DBL:
return R_PC;
case R_390_GOTOFF16:
case R_390_GOTOFF: // a.k.a. R_390_GOTOFF32
case R_390_GOTOFF64:
return R_GOTREL;
// Relocations targeting the PLT associated with the symbol.
case R_390_PLT32:
case R_390_PLT64:
case R_390_PLT12DBL:
case R_390_PLT16DBL:
case R_390_PLT24DBL:
case R_390_PLT32DBL:
return R_PLT_PC;
case R_390_PLTOFF16:
case R_390_PLTOFF32:
case R_390_PLTOFF64:
return R_PLT_GOTREL;
// Relocations targeting the GOT entry associated with the symbol.
case R_390_GOTENT:
return R_GOT_PC;
case R_390_GOT12:
case R_390_GOT16:
case R_390_GOT20:
case R_390_GOT32:
case R_390_GOT64:
return R_GOT_OFF;
// Relocations targeting the GOTPLT entry associated with the symbol.
case R_390_GOTPLTENT:
return R_GOTPLT_PC;
case R_390_GOTPLT12:
case R_390_GOTPLT16:
case R_390_GOTPLT20:
case R_390_GOTPLT32:
case R_390_GOTPLT64:
return R_GOTPLT_GOTREL;
// Relocations targeting _GLOBAL_OFFSET_TABLE_.
case R_390_GOTPC:
case R_390_GOTPCDBL:
return R_GOTONLY_PC;
// TLS-related relocations.
case R_390_TLS_LOAD:
return R_NONE;
case R_390_TLS_GDCALL:
return R_TLSGD_PC;
case R_390_TLS_LDCALL:
return R_TLSLD_PC;
case R_390_TLS_GD32:
case R_390_TLS_GD64:
return R_TLSGD_GOT;
case R_390_TLS_LDM32:
case R_390_TLS_LDM64:
return R_TLSLD_GOT;
case R_390_TLS_LDO32:
case R_390_TLS_LDO64:
return R_DTPREL;
case R_390_TLS_LE32:
case R_390_TLS_LE64:
return R_TPREL;
case R_390_TLS_IE32:
case R_390_TLS_IE64:
return R_GOT;
case R_390_TLS_GOTIE12:
case R_390_TLS_GOTIE20:
case R_390_TLS_GOTIE32:
case R_390_TLS_GOTIE64:
return R_GOT_OFF;
case R_390_TLS_IEENT:
return R_GOT_PC;
default:
Err(ctx) << getErrorLoc(ctx, loc) << "unknown relocation (" << type.v
<< ") against symbol " << &s;
return R_NONE;
}
}
void SystemZ::writeGotHeader(uint8_t *buf) const {
// _GLOBAL_OFFSET_TABLE_[0] holds the value of _DYNAMIC.
// _GLOBAL_OFFSET_TABLE_[1] and [2] are reserved.
write64be(buf, ctx.mainPart->dynamic->getVA());
}
void SystemZ::writeGotPlt(uint8_t *buf, const Symbol &s) const {
write64be(buf, s.getPltVA(ctx) + 14);
}
void SystemZ::writeIgotPlt(uint8_t *buf, const Symbol &s) const {
if (ctx.arg.writeAddends)
write64be(buf, s.getVA(ctx));
}
void SystemZ::writePltHeader(uint8_t *buf) const {
const uint8_t pltData[] = {
0xe3, 0x10, 0xf0, 0x38, 0x00, 0x24, // stg %r1,56(%r15)
0xc0, 0x10, 0x00, 0x00, 0x00, 0x00, // larl %r1,_GLOBAL_OFFSET_TABLE_
0xd2, 0x07, 0xf0, 0x30, 0x10, 0x08, // mvc 48(8,%r15),8(%r1)
0xe3, 0x10, 0x10, 0x10, 0x00, 0x04, // lg %r1,16(%r1)
0x07, 0xf1, // br %r1
0x07, 0x00, // nopr
0x07, 0x00, // nopr
0x07, 0x00, // nopr
};
memcpy(buf, pltData, sizeof(pltData));
uint64_t got = ctx.in.got->getVA();
uint64_t plt = ctx.in.plt->getVA();
write32be(buf + 8, (got - plt - 6) >> 1);
}
void SystemZ::addPltHeaderSymbols(InputSection &isec) const {
// The PLT header needs a reference to _GLOBAL_OFFSET_TABLE_, so we
// must ensure the .got section is created even if otherwise unused.
ctx.in.got->hasGotOffRel.store(true, std::memory_order_relaxed);
}
void SystemZ::writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const {
const uint8_t inst[] = {
0xc0, 0x10, 0x00, 0x00, 0x00, 0x00, // larl %r1,<.got.plt slot>
0xe3, 0x10, 0x10, 0x00, 0x00, 0x04, // lg %r1,0(%r1)
0x07, 0xf1, // br %r1
0x0d, 0x10, // basr %r1,%r0
0xe3, 0x10, 0x10, 0x0c, 0x00, 0x14, // lgf %r1,12(%r1)
0xc0, 0xf4, 0x00, 0x00, 0x00, 0x00, // jg <plt header>
0x00, 0x00, 0x00, 0x00, // <relocation offset>
};
memcpy(buf, inst, sizeof(inst));
write32be(buf + 2, (sym.getGotPltVA(ctx) - pltEntryAddr) >> 1);
write32be(buf + 24, (ctx.in.plt->getVA() - pltEntryAddr - 22) >> 1);
write32be(buf + 28, ctx.in.relaPlt->entsize * sym.getPltIdx(ctx));
}
int64_t SystemZ::getImplicitAddend(const uint8_t *buf, RelType type) const {
switch (type) {
case R_390_8:
return SignExtend64<8>(*buf);
case R_390_16:
case R_390_PC16:
return SignExtend64<16>(read16be(buf));
case R_390_PC16DBL:
return SignExtend64<16>(read16be(buf)) << 1;
case R_390_32:
case R_390_PC32:
return SignExtend64<32>(read32be(buf));
case R_390_PC32DBL:
return SignExtend64<32>(read32be(buf)) << 1;
case R_390_64:
case R_390_PC64:
case R_390_TLS_DTPMOD:
case R_390_TLS_DTPOFF:
case R_390_TLS_TPOFF:
case R_390_GLOB_DAT:
case R_390_RELATIVE:
case R_390_IRELATIVE:
return read64be(buf);
case R_390_COPY:
case R_390_JMP_SLOT:
case R_390_NONE:
// These relocations are defined as not having an implicit addend.
return 0;
default:
InternalErr(ctx, buf) << "cannot read addend for relocation " << type;
return 0;
}
}
RelType SystemZ::getDynRel(RelType type) const {
if (type == R_390_64 || type == R_390_PC64)
return type;
return R_390_NONE;
}
RelExpr SystemZ::adjustTlsExpr(RelType type, RelExpr expr) const {
if (expr == R_RELAX_TLS_GD_TO_IE)
return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
return expr;
}
int SystemZ::getTlsGdRelaxSkip(RelType type) const {
// A __tls_get_offset call instruction is marked with 2 relocations:
//
// R_390_TLS_GDCALL / R_390_TLS_LDCALL: marker relocation
// R_390_PLT32DBL: __tls_get_offset
//
// After the relaxation we no longer call __tls_get_offset and should skip
// both relocations to not create a false dependence on __tls_get_offset
// being defined.
//
// Note that this mechanism only works correctly if the R_390_TLS_[GL]DCALL
// is seen immediately *before* the R_390_PLT32DBL. Unfortunately, current
// compilers on the platform will typically generate the inverse sequence.
// To fix this, we sort relocations by offset in RelocationScanner::scan;
// this ensures the correct sequence as the R_390_TLS_[GL]DCALL applies to
// the first byte of the brasl instruction, while the R_390_PLT32DBL applies
// to its third byte (the relative displacement).
if (type == R_390_TLS_GDCALL || type == R_390_TLS_LDCALL)
return 2;
return 1;
}
void SystemZ::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
// The general-dynamic code sequence for a global `x`:
//
// Instruction Relocation Symbol
// ear %rX,%a0
// sllg %rX,%rX,32
// ear %rX,%a1
// larl %r12,_GLOBAL_OFFSET_TABLE_ R_390_GOTPCDBL _GLOBAL_OFFSET_TABLE_
// lgrl %r2,.LC0 R_390_PC32DBL .LC0
// brasl %r14,__tls_get_offset@plt R_390_TLS_GDCALL x
// :tls_gdcall:x R_390_PLT32DBL __tls_get_offset
// la %r2,0(%r2,%rX)
//
// .LC0:
// .quad x@TLSGD R_390_TLS_GD64 x
//
// Relaxing to initial-exec entails:
// 1) Replacing the call by a load from the GOT.
// 2) Replacing the relocation on the constant LC0 by R_390_TLS_GOTIE64.
switch (rel.type) {
case R_390_TLS_GDCALL:
// brasl %r14,__tls_get_offset@plt -> lg %r2,0(%r2,%r12)
write16be(loc, 0xe322);
write32be(loc + 2, 0xc0000004);
break;
case R_390_TLS_GD64:
relocateNoSym(loc, R_390_TLS_GOTIE64, val);
break;
default:
llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
}
}
void SystemZ::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
// The general-dynamic code sequence for a global `x`:
//
// Instruction Relocation Symbol
// ear %rX,%a0
// sllg %rX,%rX,32
// ear %rX,%a1
// larl %r12,_GLOBAL_OFFSET_TABLE_ R_390_GOTPCDBL _GLOBAL_OFFSET_TABLE_
// lgrl %r2,.LC0 R_390_PC32DBL .LC0
// brasl %r14,__tls_get_offset@plt R_390_TLS_GDCALL x
// :tls_gdcall:x R_390_PLT32DBL __tls_get_offset
// la %r2,0(%r2,%rX)
//
// .LC0:
// .quad x@tlsgd R_390_TLS_GD64 x
//
// Relaxing to local-exec entails:
// 1) Replacing the call by a nop.
// 2) Replacing the relocation on the constant LC0 by R_390_TLS_LE64.
switch (rel.type) {
case R_390_TLS_GDCALL:
// brasl %r14,__tls_get_offset@plt -> brcl 0,.
write16be(loc, 0xc004);
write32be(loc + 2, 0x00000000);
break;
case R_390_TLS_GD64:
relocateNoSym(loc, R_390_TLS_LE64, val);
break;
default:
llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
}
}
void SystemZ::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
// The local-dynamic code sequence for a global `x`:
//
// Instruction Relocation Symbol
// ear %rX,%a0
// sllg %rX,%rX,32
// ear %rX,%a1
// larl %r12,_GLOBAL_OFFSET_TABLE_ R_390_GOTPCDBL _GLOBAL_OFFSET_TABLE_
// lgrl %r2,.LC0 R_390_PC32DBL .LC0
// brasl %r14,__tls_get_offset@plt R_390_TLS_LDCALL <sym>
// :tls_ldcall:<sym> R_390_PLT32DBL __tls_get_offset
// la %r2,0(%r2,%rX)
// lgrl %rY,.LC1 R_390_PC32DBL .LC1
// la %r2,0(%r2,%rY)
//
// .LC0:
// .quad <sym>@tlsldm R_390_TLS_LDM64 <sym>
// .LC1:
// .quad x@dtpoff R_390_TLS_LDO64 x
//
// Relaxing to local-exec entails:
// 1) Replacing the call by a nop.
// 2) Replacing the constant LC0 by 0 (i.e. ignoring the relocation).
// 3) Replacing the relocation on the constant LC1 by R_390_TLS_LE64.
switch (rel.type) {
case R_390_TLS_LDCALL:
// brasl %r14,__tls_get_offset@plt -> brcl 0,.
write16be(loc, 0xc004);
write32be(loc + 2, 0x00000000);
break;
case R_390_TLS_LDM64:
break;
case R_390_TLS_LDO64:
relocateNoSym(loc, R_390_TLS_LE64, val);
break;
default:
llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
}
}
RelExpr SystemZ::adjustGotPcExpr(RelType type, int64_t addend,
const uint8_t *loc) const {
// Only R_390_GOTENT with addend 2 can be relaxed.
if (!ctx.arg.relax || addend != 2 || type != R_390_GOTENT)
return R_GOT_PC;
const uint16_t op = read16be(loc - 2);
// lgrl rx,sym@GOTENT -> larl rx, sym
// This relaxation is legal if "sym" binds locally (which was already
// verified by our caller) and is in-range and properly aligned for a
// LARL instruction. We cannot verify the latter constraint here, so
// we assume it is true and revert the decision later on in relaxOnce
// if necessary.
if ((op & 0xff0f) == 0xc408)
return R_RELAX_GOT_PC;
return R_GOT_PC;
}
bool SystemZ::relaxOnce(int pass) const {
// If we decided in adjustGotPcExpr to relax a R_390_GOTENT,
// we need to validate the target symbol is in-range and aligned.
SmallVector<InputSection *, 0> storage;
bool changed = false;
for (OutputSection *osec : ctx.outputSections) {
if (!(osec->flags & SHF_EXECINSTR))
continue;
for (InputSection *sec : getInputSections(*osec, storage)) {
for (Relocation &rel : sec->relocs()) {
if (rel.expr != R_RELAX_GOT_PC)
continue;
uint64_t v = sec->getRelocTargetVA(
ctx, rel, sec->getOutputSection()->addr + rel.offset);
if (isInt<33>(v) && !(v & 1))
continue;
if (rel.sym->auxIdx == 0) {
rel.sym->allocateAux(ctx);
addGotEntry(ctx, *rel.sym);
changed = true;
}
rel.expr = R_GOT_PC;
}
}
}
return changed;
}
void SystemZ::relaxGot(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
assert(isInt<33>(val) &&
"R_390_GOTENT should not have been relaxed if it overflows");
assert(!(val & 1) &&
"R_390_GOTENT should not have been relaxed if it is misaligned");
const uint16_t op = read16be(loc - 2);
// lgrl rx,sym@GOTENT -> larl rx, sym
if ((op & 0xff0f) == 0xc408) {
write16be(loc - 2, 0xc000 | (op & 0x00f0));
write32be(loc, val >> 1);
}
}
void SystemZ::relocate(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
switch (rel.expr) {
case R_RELAX_GOT_PC:
return relaxGot(loc, rel, val);
case R_RELAX_TLS_GD_TO_IE_GOT_OFF:
return relaxTlsGdToIe(loc, rel, val);
case R_RELAX_TLS_GD_TO_LE:
return relaxTlsGdToLe(loc, rel, val);
case R_RELAX_TLS_LD_TO_LE:
return relaxTlsLdToLe(loc, rel, val);
default:
break;
}
switch (rel.type) {
case R_390_8:
checkIntUInt(ctx, loc, val, 8, rel);
*loc = val;
break;
case R_390_12:
case R_390_GOT12:
case R_390_GOTPLT12:
case R_390_TLS_GOTIE12:
checkUInt(ctx, loc, val, 12, rel);
write16be(loc, (read16be(loc) & 0xF000) | val);
break;
case R_390_PC12DBL:
case R_390_PLT12DBL:
checkInt(ctx, loc, val, 13, rel);
checkAlignment(ctx, loc, val, 2, rel);
write16be(loc, (read16be(loc) & 0xF000) | ((val >> 1) & 0x0FFF));
break;
case R_390_16:
case R_390_GOT16:
case R_390_GOTPLT16:
case R_390_GOTOFF16:
case R_390_PLTOFF16:
checkIntUInt(ctx, loc, val, 16, rel);
write16be(loc, val);
break;
case R_390_PC16:
checkInt(ctx, loc, val, 16, rel);
write16be(loc, val);
break;
case R_390_PC16DBL:
case R_390_PLT16DBL:
checkInt(ctx, loc, val, 17, rel);
checkAlignment(ctx, loc, val, 2, rel);
write16be(loc, val >> 1);
break;
case R_390_20:
case R_390_GOT20:
case R_390_GOTPLT20:
case R_390_TLS_GOTIE20:
checkInt(ctx, loc, val, 20, rel);
write32be(loc, (read32be(loc) & 0xF00000FF) | ((val & 0xFFF) << 16) |
((val & 0xFF000) >> 4));
break;
case R_390_PC24DBL:
case R_390_PLT24DBL:
checkInt(ctx, loc, val, 25, rel);
checkAlignment(ctx, loc, val, 2, rel);
loc[0] = val >> 17;
loc[1] = val >> 9;
loc[2] = val >> 1;
break;
case R_390_32:
case R_390_GOT32:
case R_390_GOTPLT32:
case R_390_GOTOFF:
case R_390_PLTOFF32:
case R_390_TLS_IE32:
case R_390_TLS_GOTIE32:
case R_390_TLS_GD32:
case R_390_TLS_LDM32:
case R_390_TLS_LDO32:
case R_390_TLS_LE32:
checkIntUInt(ctx, loc, val, 32, rel);
write32be(loc, val);
break;
case R_390_PC32:
case R_390_PLT32:
checkInt(ctx, loc, val, 32, rel);
write32be(loc, val);
break;
case R_390_PC32DBL:
case R_390_PLT32DBL:
case R_390_GOTPCDBL:
case R_390_GOTENT:
case R_390_GOTPLTENT:
case R_390_TLS_IEENT:
checkInt(ctx, loc, val, 33, rel);
checkAlignment(ctx, loc, val, 2, rel);
write32be(loc, val >> 1);
break;
case R_390_64:
case R_390_PC64:
case R_390_PLT64:
case R_390_GOT64:
case R_390_GOTPLT64:
case R_390_GOTOFF64:
case R_390_PLTOFF64:
case R_390_GOTPC:
case R_390_TLS_IE64:
case R_390_TLS_GOTIE64:
case R_390_TLS_GD64:
case R_390_TLS_LDM64:
case R_390_TLS_LDO64:
case R_390_TLS_LE64:
case R_390_TLS_DTPMOD:
case R_390_TLS_DTPOFF:
case R_390_TLS_TPOFF:
write64be(loc, val);
break;
case R_390_TLS_LOAD:
case R_390_TLS_GDCALL:
case R_390_TLS_LDCALL:
break;
default:
llvm_unreachable("unknown relocation");
}
}
void elf::setSystemZTargetInfo(Ctx &ctx) { ctx.target.reset(new SystemZ(ctx)); }
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