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llvm / llvm-project / lld / 5aa0cff7e964df5e9d3fb634706407a58ec45575 / . / ELF / Arch / RISCV.cpp
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//===- RISCV.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 "InputFiles.h"
#include "OutputSections.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "Target.h"
#include "llvm/Support/ELFAttributes.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/RISCVAttributeParser.h"
#include "llvm/Support/RISCVAttributes.h"
#include "llvm/Support/RISCVISAInfo.h"
#include "llvm/Support/TimeProfiler.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
namespace {
class RISCV final : public TargetInfo {
public:
RISCV();
uint32_t calcEFlags() const override;
int64_t getImplicitAddend(const uint8_t *buf, 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 writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const override;
RelType getDynRel(RelType type) const override;
RelExpr getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const override;
void relocate(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relocateAlloc(InputSectionBase &sec, uint8_t *buf) const override;
bool relaxOnce(int pass) const override;
void finalizeRelax(int passes) const override;
};
} // end anonymous namespace
// These are internal relocation numbers for GP relaxation. They aren't part
// of the psABI spec.
#define INTERNAL_R_RISCV_GPREL_I 256
#define INTERNAL_R_RISCV_GPREL_S 257
const uint64_t dtpOffset = 0x800;
namespace {
enum Op {
ADDI = 0x13,
AUIPC = 0x17,
JALR = 0x67,
LD = 0x3003,
LUI = 0x37,
LW = 0x2003,
SRLI = 0x5013,
SUB = 0x40000033,
};
enum Reg {
X_RA = 1,
X_GP = 3,
X_TP = 4,
X_T0 = 5,
X_T1 = 6,
X_T2 = 7,
X_A0 = 10,
X_T3 = 28,
};
} // namespace
static uint32_t hi20(uint32_t val) { return (val + 0x800) >> 12; }
static uint32_t lo12(uint32_t val) { return val & 4095; }
static uint32_t itype(uint32_t op, uint32_t rd, uint32_t rs1, uint32_t imm) {
return op | (rd << 7) | (rs1 << 15) | (imm << 20);
}
static uint32_t rtype(uint32_t op, uint32_t rd, uint32_t rs1, uint32_t rs2) {
return op | (rd << 7) | (rs1 << 15) | (rs2 << 20);
}
static uint32_t utype(uint32_t op, uint32_t rd, uint32_t imm) {
return op | (rd << 7) | (imm << 12);
}
// Extract bits v[begin:end], where range is inclusive, and begin must be < 63.
static uint32_t extractBits(uint64_t v, uint32_t begin, uint32_t end) {
return (v & ((1ULL << (begin + 1)) - 1)) >> end;
}
static uint32_t setLO12_I(uint32_t insn, uint32_t imm) {
return (insn & 0xfffff) | (imm << 20);
}
static uint32_t setLO12_S(uint32_t insn, uint32_t imm) {
return (insn & 0x1fff07f) | (extractBits(imm, 11, 5) << 25) |
(extractBits(imm, 4, 0) << 7);
}
RISCV::RISCV() {
copyRel = R_RISCV_COPY;
pltRel = R_RISCV_JUMP_SLOT;
relativeRel = R_RISCV_RELATIVE;
iRelativeRel = R_RISCV_IRELATIVE;
if (config->is64) {
symbolicRel = R_RISCV_64;
tlsModuleIndexRel = R_RISCV_TLS_DTPMOD64;
tlsOffsetRel = R_RISCV_TLS_DTPREL64;
tlsGotRel = R_RISCV_TLS_TPREL64;
} else {
symbolicRel = R_RISCV_32;
tlsModuleIndexRel = R_RISCV_TLS_DTPMOD32;
tlsOffsetRel = R_RISCV_TLS_DTPREL32;
tlsGotRel = R_RISCV_TLS_TPREL32;
}
gotRel = symbolicRel;
tlsDescRel = R_RISCV_TLSDESC;
// .got[0] = _DYNAMIC
gotHeaderEntriesNum = 1;
// .got.plt[0] = _dl_runtime_resolve, .got.plt[1] = link_map
gotPltHeaderEntriesNum = 2;
pltHeaderSize = 32;
pltEntrySize = 16;
ipltEntrySize = 16;
}
static uint32_t getEFlags(InputFile *f) {
if (config->is64)
return cast<ObjFile<ELF64LE>>(f)->getObj().getHeader().e_flags;
return cast<ObjFile<ELF32LE>>(f)->getObj().getHeader().e_flags;
}
uint32_t RISCV::calcEFlags() const {
// If there are only binary input files (from -b binary), use a
// value of 0 for the ELF header flags.
if (ctx.objectFiles.empty())
return 0;
uint32_t target = getEFlags(ctx.objectFiles.front());
for (InputFile *f : ctx.objectFiles) {
uint32_t eflags = getEFlags(f);
if (eflags & EF_RISCV_RVC)
target |= EF_RISCV_RVC;
if ((eflags & EF_RISCV_FLOAT_ABI) != (target & EF_RISCV_FLOAT_ABI))
error(
toString(f) +
": cannot link object files with different floating-point ABI from " +
toString(ctx.objectFiles[0]));
if ((eflags & EF_RISCV_RVE) != (target & EF_RISCV_RVE))
error(toString(f) +
": cannot link object files with different EF_RISCV_RVE");
}
return target;
}
int64_t RISCV::getImplicitAddend(const uint8_t *buf, RelType type) const {
switch (type) {
default:
internalLinkerError(getErrorLocation(buf),
"cannot read addend for relocation " + toString(type));
return 0;
case R_RISCV_32:
case R_RISCV_TLS_DTPMOD32:
case R_RISCV_TLS_DTPREL32:
case R_RISCV_TLS_TPREL32:
return SignExtend64<32>(read32le(buf));
case R_RISCV_64:
case R_RISCV_TLS_DTPMOD64:
case R_RISCV_TLS_DTPREL64:
case R_RISCV_TLS_TPREL64:
return read64le(buf);
case R_RISCV_RELATIVE:
case R_RISCV_IRELATIVE:
return config->is64 ? read64le(buf) : read32le(buf);
case R_RISCV_NONE:
case R_RISCV_JUMP_SLOT:
// These relocations are defined as not having an implicit addend.
return 0;
case R_RISCV_TLSDESC:
return config->is64 ? read64le(buf + 8) : read32le(buf + 4);
}
}
void RISCV::writeGotHeader(uint8_t *buf) const {
if (config->is64)
write64le(buf, mainPart->dynamic->getVA());
else
write32le(buf, mainPart->dynamic->getVA());
}
void RISCV::writeGotPlt(uint8_t *buf, const Symbol &s) const {
if (config->is64)
write64le(buf, in.plt->getVA());
else
write32le(buf, in.plt->getVA());
}
void RISCV::writeIgotPlt(uint8_t *buf, const Symbol &s) const {
if (config->writeAddends) {
if (config->is64)
write64le(buf, s.getVA());
else
write32le(buf, s.getVA());
}
}
void RISCV::writePltHeader(uint8_t *buf) const {
// 1: auipc t2, %pcrel_hi(.got.plt)
// sub t1, t1, t3
// l[wd] t3, %pcrel_lo(1b)(t2); t3 = _dl_runtime_resolve
// addi t1, t1, -pltHeaderSize-12; t1 = &.plt[i] - &.plt[0]
// addi t0, t2, %pcrel_lo(1b)
// srli t1, t1, (rv64?1:2); t1 = &.got.plt[i] - &.got.plt[0]
// l[wd] t0, Wordsize(t0); t0 = link_map
// jr t3
uint32_t offset = in.gotPlt->getVA() - in.plt->getVA();
uint32_t load = config->is64 ? LD : LW;
write32le(buf + 0, utype(AUIPC, X_T2, hi20(offset)));
write32le(buf + 4, rtype(SUB, X_T1, X_T1, X_T3));
write32le(buf + 8, itype(load, X_T3, X_T2, lo12(offset)));
write32le(buf + 12, itype(ADDI, X_T1, X_T1, -target->pltHeaderSize - 12));
write32le(buf + 16, itype(ADDI, X_T0, X_T2, lo12(offset)));
write32le(buf + 20, itype(SRLI, X_T1, X_T1, config->is64 ? 1 : 2));
write32le(buf + 24, itype(load, X_T0, X_T0, config->wordsize));
write32le(buf + 28, itype(JALR, 0, X_T3, 0));
}
void RISCV::writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const {
// 1: auipc t3, %pcrel_hi(f@.got.plt)
// l[wd] t3, %pcrel_lo(1b)(t3)
// jalr t1, t3
// nop
uint32_t offset = sym.getGotPltVA() - pltEntryAddr;
write32le(buf + 0, utype(AUIPC, X_T3, hi20(offset)));
write32le(buf + 4, itype(config->is64 ? LD : LW, X_T3, X_T3, lo12(offset)));
write32le(buf + 8, itype(JALR, X_T1, X_T3, 0));
write32le(buf + 12, itype(ADDI, 0, 0, 0));
}
RelType RISCV::getDynRel(RelType type) const {
return type == target->symbolicRel ? type
: static_cast<RelType>(R_RISCV_NONE);
}
RelExpr RISCV::getRelExpr(const RelType type, const Symbol &s,
const uint8_t *loc) const {
switch (type) {
case R_RISCV_NONE:
return R_NONE;
case R_RISCV_32:
case R_RISCV_64:
case R_RISCV_HI20:
case R_RISCV_LO12_I:
case R_RISCV_LO12_S:
case R_RISCV_RVC_LUI:
return R_ABS;
case R_RISCV_ADD8:
case R_RISCV_ADD16:
case R_RISCV_ADD32:
case R_RISCV_ADD64:
case R_RISCV_SET6:
case R_RISCV_SET8:
case R_RISCV_SET16:
case R_RISCV_SET32:
case R_RISCV_SUB6:
case R_RISCV_SUB8:
case R_RISCV_SUB16:
case R_RISCV_SUB32:
case R_RISCV_SUB64:
return R_RISCV_ADD;
case R_RISCV_JAL:
case R_RISCV_BRANCH:
case R_RISCV_PCREL_HI20:
case R_RISCV_RVC_BRANCH:
case R_RISCV_RVC_JUMP:
case R_RISCV_32_PCREL:
return R_PC;
case R_RISCV_CALL:
case R_RISCV_CALL_PLT:
case R_RISCV_PLT32:
return R_PLT_PC;
case R_RISCV_GOT_HI20:
case R_RISCV_GOT32_PCREL:
return R_GOT_PC;
case R_RISCV_PCREL_LO12_I:
case R_RISCV_PCREL_LO12_S:
return R_RISCV_PC_INDIRECT;
case R_RISCV_TLSDESC_HI20:
case R_RISCV_TLSDESC_LOAD_LO12:
case R_RISCV_TLSDESC_ADD_LO12:
return R_TLSDESC_PC;
case R_RISCV_TLSDESC_CALL:
return R_TLSDESC_CALL;
case R_RISCV_TLS_GD_HI20:
return R_TLSGD_PC;
case R_RISCV_TLS_GOT_HI20:
return R_GOT_PC;
case R_RISCV_TPREL_HI20:
case R_RISCV_TPREL_LO12_I:
case R_RISCV_TPREL_LO12_S:
return R_TPREL;
case R_RISCV_ALIGN:
return R_RELAX_HINT;
case R_RISCV_TPREL_ADD:
case R_RISCV_RELAX:
return config->relax ? R_RELAX_HINT : R_NONE;
case R_RISCV_SET_ULEB128:
case R_RISCV_SUB_ULEB128:
return R_RISCV_LEB128;
default:
error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
") against symbol " + toString(s));
return R_NONE;
}
}
void RISCV::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
const unsigned bits = config->wordsize * 8;
switch (rel.type) {
case R_RISCV_32:
write32le(loc, val);
return;
case R_RISCV_64:
write64le(loc, val);
return;
case R_RISCV_RVC_BRANCH: {
checkInt(loc, val, 9, rel);
checkAlignment(loc, val, 2, rel);
uint16_t insn = read16le(loc) & 0xE383;
uint16_t imm8 = extractBits(val, 8, 8) << 12;
uint16_t imm4_3 = extractBits(val, 4, 3) << 10;
uint16_t imm7_6 = extractBits(val, 7, 6) << 5;
uint16_t imm2_1 = extractBits(val, 2, 1) << 3;
uint16_t imm5 = extractBits(val, 5, 5) << 2;
insn |= imm8 | imm4_3 | imm7_6 | imm2_1 | imm5;
write16le(loc, insn);
return;
}
case R_RISCV_RVC_JUMP: {
checkInt(loc, val, 12, rel);
checkAlignment(loc, val, 2, rel);
uint16_t insn = read16le(loc) & 0xE003;
uint16_t imm11 = extractBits(val, 11, 11) << 12;
uint16_t imm4 = extractBits(val, 4, 4) << 11;
uint16_t imm9_8 = extractBits(val, 9, 8) << 9;
uint16_t imm10 = extractBits(val, 10, 10) << 8;
uint16_t imm6 = extractBits(val, 6, 6) << 7;
uint16_t imm7 = extractBits(val, 7, 7) << 6;
uint16_t imm3_1 = extractBits(val, 3, 1) << 3;
uint16_t imm5 = extractBits(val, 5, 5) << 2;
insn |= imm11 | imm4 | imm9_8 | imm10 | imm6 | imm7 | imm3_1 | imm5;
write16le(loc, insn);
return;
}
case R_RISCV_RVC_LUI: {
int64_t imm = SignExtend64(val + 0x800, bits) >> 12;
checkInt(loc, imm, 6, rel);
if (imm == 0) { // `c.lui rd, 0` is illegal, convert to `c.li rd, 0`
write16le(loc, (read16le(loc) & 0x0F83) | 0x4000);
} else {
uint16_t imm17 = extractBits(val + 0x800, 17, 17) << 12;
uint16_t imm16_12 = extractBits(val + 0x800, 16, 12) << 2;
write16le(loc, (read16le(loc) & 0xEF83) | imm17 | imm16_12);
}
return;
}
case R_RISCV_JAL: {
checkInt(loc, val, 21, rel);
checkAlignment(loc, val, 2, rel);
uint32_t insn = read32le(loc) & 0xFFF;
uint32_t imm20 = extractBits(val, 20, 20) << 31;
uint32_t imm10_1 = extractBits(val, 10, 1) << 21;
uint32_t imm11 = extractBits(val, 11, 11) << 20;
uint32_t imm19_12 = extractBits(val, 19, 12) << 12;
insn |= imm20 | imm10_1 | imm11 | imm19_12;
write32le(loc, insn);
return;
}
case R_RISCV_BRANCH: {
checkInt(loc, val, 13, rel);
checkAlignment(loc, val, 2, rel);
uint32_t insn = read32le(loc) & 0x1FFF07F;
uint32_t imm12 = extractBits(val, 12, 12) << 31;
uint32_t imm10_5 = extractBits(val, 10, 5) << 25;
uint32_t imm4_1 = extractBits(val, 4, 1) << 8;
uint32_t imm11 = extractBits(val, 11, 11) << 7;
insn |= imm12 | imm10_5 | imm4_1 | imm11;
write32le(loc, insn);
return;
}
// auipc + jalr pair
case R_RISCV_CALL:
case R_RISCV_CALL_PLT: {
int64_t hi = SignExtend64(val + 0x800, bits) >> 12;
checkInt(loc, hi, 20, rel);
if (isInt<20>(hi)) {
relocateNoSym(loc, R_RISCV_PCREL_HI20, val);
relocateNoSym(loc + 4, R_RISCV_PCREL_LO12_I, val);
}
return;
}
case R_RISCV_GOT_HI20:
case R_RISCV_PCREL_HI20:
case R_RISCV_TLSDESC_HI20:
case R_RISCV_TLS_GD_HI20:
case R_RISCV_TLS_GOT_HI20:
case R_RISCV_TPREL_HI20:
case R_RISCV_HI20: {
uint64_t hi = val + 0x800;
checkInt(loc, SignExtend64(hi, bits) >> 12, 20, rel);
write32le(loc, (read32le(loc) & 0xFFF) | (hi & 0xFFFFF000));
return;
}
case R_RISCV_PCREL_LO12_I:
case R_RISCV_TLSDESC_LOAD_LO12:
case R_RISCV_TLSDESC_ADD_LO12:
case R_RISCV_TPREL_LO12_I:
case R_RISCV_LO12_I: {
uint64_t hi = (val + 0x800) >> 12;
uint64_t lo = val - (hi << 12);
write32le(loc, setLO12_I(read32le(loc), lo & 0xfff));
return;
}
case R_RISCV_PCREL_LO12_S:
case R_RISCV_TPREL_LO12_S:
case R_RISCV_LO12_S: {
uint64_t hi = (val + 0x800) >> 12;
uint64_t lo = val - (hi << 12);
write32le(loc, setLO12_S(read32le(loc), lo));
return;
}
case INTERNAL_R_RISCV_GPREL_I:
case INTERNAL_R_RISCV_GPREL_S: {
Defined *gp = ElfSym::riscvGlobalPointer;
int64_t displace = SignExtend64(val - gp->getVA(), bits);
checkInt(loc, displace, 12, rel);
uint32_t insn = (read32le(loc) & ~(31 << 15)) | (X_GP << 15);
if (rel.type == INTERNAL_R_RISCV_GPREL_I)
insn = setLO12_I(insn, displace);
else
insn = setLO12_S(insn, displace);
write32le(loc, insn);
return;
}
case R_RISCV_ADD8:
*loc += val;
return;
case R_RISCV_ADD16:
write16le(loc, read16le(loc) + val);
return;
case R_RISCV_ADD32:
write32le(loc, read32le(loc) + val);
return;
case R_RISCV_ADD64:
write64le(loc, read64le(loc) + val);
return;
case R_RISCV_SUB6:
*loc = (*loc & 0xc0) | (((*loc & 0x3f) - val) & 0x3f);
return;
case R_RISCV_SUB8:
*loc -= val;
return;
case R_RISCV_SUB16:
write16le(loc, read16le(loc) - val);
return;
case R_RISCV_SUB32:
write32le(loc, read32le(loc) - val);
return;
case R_RISCV_SUB64:
write64le(loc, read64le(loc) - val);
return;
case R_RISCV_SET6:
*loc = (*loc & 0xc0) | (val & 0x3f);
return;
case R_RISCV_SET8:
*loc = val;
return;
case R_RISCV_SET16:
write16le(loc, val);
return;
case R_RISCV_SET32:
case R_RISCV_32_PCREL:
case R_RISCV_PLT32:
case R_RISCV_GOT32_PCREL:
checkInt(loc, val, 32, rel);
write32le(loc, val);
return;
case R_RISCV_TLS_DTPREL32:
write32le(loc, val - dtpOffset);
break;
case R_RISCV_TLS_DTPREL64:
write64le(loc, val - dtpOffset);
break;
case R_RISCV_RELAX:
return;
case R_RISCV_TLSDESC:
// The addend is stored in the second word.
if (config->is64)
write64le(loc + 8, val);
else
write32le(loc + 4, val);
break;
default:
llvm_unreachable("unknown relocation");
}
}
static bool relaxable(ArrayRef<Relocation> relocs, size_t i) {
return i + 1 != relocs.size() && relocs[i + 1].type == R_RISCV_RELAX;
}
static void tlsdescToIe(uint8_t *loc, const Relocation &rel, uint64_t val) {
switch (rel.type) {
case R_RISCV_TLSDESC_HI20:
case R_RISCV_TLSDESC_LOAD_LO12:
write32le(loc, 0x00000013); // nop
break;
case R_RISCV_TLSDESC_ADD_LO12:
write32le(loc, utype(AUIPC, X_A0, hi20(val))); // auipc a0,<hi20>
break;
case R_RISCV_TLSDESC_CALL:
if (config->is64)
write32le(loc, itype(LD, X_A0, X_A0, lo12(val))); // ld a0,<lo12>(a0)
else
write32le(loc, itype(LW, X_A0, X_A0, lo12(val))); // lw a0,<lo12>(a0)
break;
default:
llvm_unreachable("unsupported relocation for TLSDESC to IE");
}
}
static void tlsdescToLe(uint8_t *loc, const Relocation &rel, uint64_t val) {
switch (rel.type) {
case R_RISCV_TLSDESC_HI20:
case R_RISCV_TLSDESC_LOAD_LO12:
write32le(loc, 0x00000013); // nop
return;
case R_RISCV_TLSDESC_ADD_LO12:
if (isInt<12>(val))
write32le(loc, 0x00000013); // nop
else
write32le(loc, utype(LUI, X_A0, hi20(val))); // lui a0,<hi20>
return;
case R_RISCV_TLSDESC_CALL:
if (isInt<12>(val))
write32le(loc, itype(ADDI, X_A0, 0, val)); // addi a0,zero,<lo12>
else
write32le(loc, itype(ADDI, X_A0, X_A0, lo12(val))); // addi a0,a0,<lo12>
return;
default:
llvm_unreachable("unsupported relocation for TLSDESC to LE");
}
}
void RISCV::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const {
uint64_t secAddr = sec.getOutputSection()->addr;
if (auto *s = dyn_cast<InputSection>(&sec))
secAddr += s->outSecOff;
else if (auto *ehIn = dyn_cast<EhInputSection>(&sec))
secAddr += ehIn->getParent()->outSecOff;
uint64_t tlsdescVal = 0;
bool tlsdescRelax = false, isToLe = false;
const ArrayRef<Relocation> relocs = sec.relocs();
for (size_t i = 0, size = relocs.size(); i != size; ++i) {
const Relocation &rel = relocs[i];
uint8_t *loc = buf + rel.offset;
uint64_t val =
sec.getRelocTargetVA(sec.file, rel.type, rel.addend,
secAddr + rel.offset, *rel.sym, rel.expr);
switch (rel.expr) {
case R_RELAX_HINT:
continue;
case R_TLSDESC_PC:
// For R_RISCV_TLSDESC_HI20, store &got(sym)-PC to be used by the
// following two instructions L[DW] and ADDI.
if (rel.type == R_RISCV_TLSDESC_HI20)
tlsdescVal = val;
else
val = tlsdescVal;
break;
case R_RELAX_TLS_GD_TO_IE:
// Only R_RISCV_TLSDESC_HI20 reaches here. tlsdescVal will be finalized
// after we see R_RISCV_TLSDESC_ADD_LO12 in the R_RELAX_TLS_GD_TO_LE case.
// The net effect is that tlsdescVal will be smaller than `val` to take
// into account of NOP instructions (in the absence of R_RISCV_RELAX)
// before AUIPC.
tlsdescVal = val + rel.offset;
isToLe = false;
tlsdescRelax = relaxable(relocs, i);
if (!tlsdescRelax)
tlsdescToIe(loc, rel, val);
continue;
case R_RELAX_TLS_GD_TO_LE:
// See the comment in handleTlsRelocation. For TLSDESC=>IE,
// R_RISCV_TLSDESC_{LOAD_LO12,ADD_LO12,CALL} also reach here. If isToIe is
// true, this is actually TLSDESC=>IE optimization.
if (rel.type == R_RISCV_TLSDESC_HI20) {
tlsdescVal = val;
isToLe = true;
tlsdescRelax = relaxable(relocs, i);
} else {
if (!isToLe && rel.type == R_RISCV_TLSDESC_ADD_LO12)
tlsdescVal -= rel.offset;
val = tlsdescVal;
}
// When NOP conversion is eligible and relaxation applies, don't write a
// NOP in case an unrelated instruction follows the current instruction.
if (tlsdescRelax &&
(rel.type == R_RISCV_TLSDESC_HI20 ||
rel.type == R_RISCV_TLSDESC_LOAD_LO12 ||
(rel.type == R_RISCV_TLSDESC_ADD_LO12 && isToLe && !hi20(val))))
continue;
if (isToLe)
tlsdescToLe(loc, rel, val);
else
tlsdescToIe(loc, rel, val);
continue;
case R_RISCV_LEB128:
if (i + 1 < size) {
const Relocation &rel1 = relocs[i + 1];
if (rel.type == R_RISCV_SET_ULEB128 &&
rel1.type == R_RISCV_SUB_ULEB128 && rel.offset == rel1.offset) {
auto val = rel.sym->getVA(rel.addend) - rel1.sym->getVA(rel1.addend);
if (overwriteULEB128(loc, val) >= 0x80)
errorOrWarn(sec.getLocation(rel.offset) + ": ULEB128 value " +
Twine(val) + " exceeds available space; references '" +
lld::toString(*rel.sym) + "'");
++i;
continue;
}
}
errorOrWarn(sec.getLocation(rel.offset) +
": R_RISCV_SET_ULEB128 not paired with R_RISCV_SUB_SET128");
return;
default:
break;
}
relocate(loc, rel, val);
}
}
void elf::initSymbolAnchors() {
SmallVector<InputSection *, 0> storage;
for (OutputSection *osec : outputSections) {
if (!(osec->flags & SHF_EXECINSTR))
continue;
for (InputSection *sec : getInputSections(*osec, storage)) {
sec->relaxAux = make<RelaxAux>();
if (sec->relocs().size()) {
sec->relaxAux->relocDeltas =
std::make_unique<uint32_t[]>(sec->relocs().size());
sec->relaxAux->relocTypes =
std::make_unique<RelType[]>(sec->relocs().size());
}
}
}
// Store anchors (st_value and st_value+st_size) for symbols relative to text
// sections.
//
// For a defined symbol foo, we may have `d->file != file` with --wrap=foo.
// We should process foo, as the defining object file's symbol table may not
// contain foo after redirectSymbols changed the foo entry to __wrap_foo. To
// avoid adding a Defined that is undefined in one object file, use
// `!d->scriptDefined` to exclude symbols that are definitely not wrapped.
//
// `relaxAux->anchors` may contain duplicate symbols, but that is fine.
for (InputFile *file : ctx.objectFiles)
for (Symbol *sym : file->getSymbols()) {
auto *d = dyn_cast<Defined>(sym);
if (!d || (d->file != file && !d->scriptDefined))
continue;
if (auto *sec = dyn_cast_or_null<InputSection>(d->section))
if (sec->flags & SHF_EXECINSTR && sec->relaxAux) {
// If sec is discarded, relaxAux will be nullptr.
sec->relaxAux->anchors.push_back({d->value, d, false});
sec->relaxAux->anchors.push_back({d->value + d->size, d, true});
}
}
// Sort anchors by offset so that we can find the closest relocation
// efficiently. For a zero size symbol, ensure that its start anchor precedes
// its end anchor. For two symbols with anchors at the same offset, their
// order does not matter.
for (OutputSection *osec : outputSections) {
if (!(osec->flags & SHF_EXECINSTR))
continue;
for (InputSection *sec : getInputSections(*osec, storage)) {
llvm::sort(sec->relaxAux->anchors, [](auto &a, auto &b) {
return std::make_pair(a.offset, a.end) <
std::make_pair(b.offset, b.end);
});
}
}
}
// Relax R_RISCV_CALL/R_RISCV_CALL_PLT auipc+jalr to c.j, c.jal, or jal.
static void relaxCall(const InputSection &sec, size_t i, uint64_t loc,
Relocation &r, uint32_t &remove) {
const bool rvc = getEFlags(sec.file) & EF_RISCV_RVC;
const Symbol &sym = *r.sym;
const uint64_t insnPair = read64le(sec.content().data() + r.offset);
const uint32_t rd = extractBits(insnPair, 32 + 11, 32 + 7);
const uint64_t dest =
(r.expr == R_PLT_PC ? sym.getPltVA() : sym.getVA()) + r.addend;
const int64_t displace = dest - loc;
if (rvc && isInt<12>(displace) && rd == 0) {
sec.relaxAux->relocTypes[i] = R_RISCV_RVC_JUMP;
sec.relaxAux->writes.push_back(0xa001); // c.j
remove = 6;
} else if (rvc && isInt<12>(displace) && rd == X_RA &&
!config->is64) { // RV32C only
sec.relaxAux->relocTypes[i] = R_RISCV_RVC_JUMP;
sec.relaxAux->writes.push_back(0x2001); // c.jal
remove = 6;
} else if (isInt<21>(displace)) {
sec.relaxAux->relocTypes[i] = R_RISCV_JAL;
sec.relaxAux->writes.push_back(0x6f | rd << 7); // jal
remove = 4;
}
}
// Relax local-exec TLS when hi20 is zero.
static void relaxTlsLe(const InputSection &sec, size_t i, uint64_t loc,
Relocation &r, uint32_t &remove) {
uint64_t val = r.sym->getVA(r.addend);
if (hi20(val) != 0)
return;
uint32_t insn = read32le(sec.content().data() + r.offset);
switch (r.type) {
case R_RISCV_TPREL_HI20:
case R_RISCV_TPREL_ADD:
// Remove lui rd, %tprel_hi(x) and add rd, rd, tp, %tprel_add(x).
sec.relaxAux->relocTypes[i] = R_RISCV_RELAX;
remove = 4;
break;
case R_RISCV_TPREL_LO12_I:
// addi rd, rd, %tprel_lo(x) => addi rd, tp, st_value(x)
sec.relaxAux->relocTypes[i] = R_RISCV_32;
insn = (insn & ~(31 << 15)) | (X_TP << 15);
sec.relaxAux->writes.push_back(setLO12_I(insn, val));
break;
case R_RISCV_TPREL_LO12_S:
// sw rs, %tprel_lo(x)(rd) => sw rs, st_value(x)(rd)
sec.relaxAux->relocTypes[i] = R_RISCV_32;
insn = (insn & ~(31 << 15)) | (X_TP << 15);
sec.relaxAux->writes.push_back(setLO12_S(insn, val));
break;
}
}
static void relaxHi20Lo12(const InputSection &sec, size_t i, uint64_t loc,
Relocation &r, uint32_t &remove) {
const Defined *gp = ElfSym::riscvGlobalPointer;
if (!gp)
return;
if (!isInt<12>(r.sym->getVA(r.addend) - gp->getVA()))
return;
switch (r.type) {
case R_RISCV_HI20:
// Remove lui rd, %hi20(x).
sec.relaxAux->relocTypes[i] = R_RISCV_RELAX;
remove = 4;
break;
case R_RISCV_LO12_I:
sec.relaxAux->relocTypes[i] = INTERNAL_R_RISCV_GPREL_I;
break;
case R_RISCV_LO12_S:
sec.relaxAux->relocTypes[i] = INTERNAL_R_RISCV_GPREL_S;
break;
}
}
static bool relax(InputSection &sec) {
const uint64_t secAddr = sec.getVA();
const MutableArrayRef<Relocation> relocs = sec.relocs();
auto &aux = *sec.relaxAux;
bool changed = false;
ArrayRef<SymbolAnchor> sa = ArrayRef(aux.anchors);
uint64_t delta = 0;
bool tlsdescRelax = false, toLeShortForm = false;
std::fill_n(aux.relocTypes.get(), relocs.size(), R_RISCV_NONE);
aux.writes.clear();
for (auto [i, r] : llvm::enumerate(relocs)) {
const uint64_t loc = secAddr + r.offset - delta;
uint32_t &cur = aux.relocDeltas[i], remove = 0;
switch (r.type) {
case R_RISCV_ALIGN: {
const uint64_t nextLoc = loc + r.addend;
const uint64_t align = PowerOf2Ceil(r.addend + 2);
// All bytes beyond the alignment boundary should be removed.
remove = nextLoc - ((loc + align - 1) & -align);
// If we can't satisfy this alignment, we've found a bad input.
if (LLVM_UNLIKELY(static_cast<int32_t>(remove) < 0)) {
errorOrWarn(getErrorLocation((const uint8_t*)loc) +
"insufficient padding bytes for " + lld::toString(r.type) +
": " + Twine(r.addend) + " bytes available "
"for requested alignment of " + Twine(align) + " bytes");
remove = 0;
}
break;
}
case R_RISCV_CALL:
case R_RISCV_CALL_PLT:
if (relaxable(relocs, i))
relaxCall(sec, i, loc, r, remove);
break;
case R_RISCV_TPREL_HI20:
case R_RISCV_TPREL_ADD:
case R_RISCV_TPREL_LO12_I:
case R_RISCV_TPREL_LO12_S:
if (relaxable(relocs, i))
relaxTlsLe(sec, i, loc, r, remove);
break;
case R_RISCV_HI20:
case R_RISCV_LO12_I:
case R_RISCV_LO12_S:
if (relaxable(relocs, i))
relaxHi20Lo12(sec, i, loc, r, remove);
break;
case R_RISCV_TLSDESC_HI20:
// For TLSDESC=>LE, we can use the short form if hi20 is zero.
tlsdescRelax = relaxable(relocs, i);
toLeShortForm = tlsdescRelax && r.expr == R_RELAX_TLS_GD_TO_LE &&
!hi20(r.sym->getVA(r.addend));
[[fallthrough]];
case R_RISCV_TLSDESC_LOAD_LO12:
// For TLSDESC=>LE/IE, AUIPC and L[DW] are removed if relaxable.
if (tlsdescRelax && r.expr != R_TLSDESC_PC)
remove = 4;
break;
case R_RISCV_TLSDESC_ADD_LO12:
if (toLeShortForm)
remove = 4;
break;
}
// For all anchors whose offsets are <= r.offset, they are preceded by
// the previous relocation whose `relocDeltas` value equals `delta`.
// Decrease their st_value and update their st_size.
for (; sa.size() && sa[0].offset <= r.offset; sa = sa.slice(1)) {
if (sa[0].end)
sa[0].d->size = sa[0].offset - delta - sa[0].d->value;
else
sa[0].d->value = sa[0].offset - delta;
}
delta += remove;
if (delta != cur) {
cur = delta;
changed = true;
}
}
for (const SymbolAnchor &a : sa) {
if (a.end)
a.d->size = a.offset - delta - a.d->value;
else
a.d->value = a.offset - delta;
}
// Inform assignAddresses that the size has changed.
if (!isUInt<32>(delta))
fatal("section size decrease is too large: " + Twine(delta));
sec.bytesDropped = delta;
return changed;
}
// When relaxing just R_RISCV_ALIGN, relocDeltas is usually changed only once in
// the absence of a linker script. For call and load/store R_RISCV_RELAX, code
// shrinkage may reduce displacement and make more relocations eligible for
// relaxation. Code shrinkage may increase displacement to a call/load/store
// target at a higher fixed address, invalidating an earlier relaxation. Any
// change in section sizes can have cascading effect and require another
// relaxation pass.
bool RISCV::relaxOnce(int pass) const {
llvm::TimeTraceScope timeScope("RISC-V relaxOnce");
if (config->relocatable)
return false;
if (pass == 0)
initSymbolAnchors();
SmallVector<InputSection *, 0> storage;
bool changed = false;
for (OutputSection *osec : outputSections) {
if (!(osec->flags & SHF_EXECINSTR))
continue;
for (InputSection *sec : getInputSections(*osec, storage))
changed |= relax(*sec);
}
return changed;
}
void RISCV::finalizeRelax(int passes) const {
llvm::TimeTraceScope timeScope("Finalize RISC-V relaxation");
log("relaxation passes: " + Twine(passes));
SmallVector<InputSection *, 0> storage;
for (OutputSection *osec : outputSections) {
if (!(osec->flags & SHF_EXECINSTR))
continue;
for (InputSection *sec : getInputSections(*osec, storage)) {
RelaxAux &aux = *sec->relaxAux;
if (!aux.relocDeltas)
continue;
MutableArrayRef<Relocation> rels = sec->relocs();
ArrayRef<uint8_t> old = sec->content();
size_t newSize = old.size() - aux.relocDeltas[rels.size() - 1];
size_t writesIdx = 0;
uint8_t *p = context().bAlloc.Allocate<uint8_t>(newSize);
uint64_t offset = 0;
int64_t delta = 0;
sec->content_ = p;
sec->size = newSize;
sec->bytesDropped = 0;
// Update section content: remove NOPs for R_RISCV_ALIGN and rewrite
// instructions for relaxed relocations.
for (size_t i = 0, e = rels.size(); i != e; ++i) {
uint32_t remove = aux.relocDeltas[i] - delta;
delta = aux.relocDeltas[i];
if (remove == 0 && aux.relocTypes[i] == R_RISCV_NONE)
continue;
// Copy from last location to the current relocated location.
const Relocation &r = rels[i];
uint64_t size = r.offset - offset;
memcpy(p, old.data() + offset, size);
p += size;
// For R_RISCV_ALIGN, we will place `offset` in a location (among NOPs)
// to satisfy the alignment requirement. If both `remove` and r.addend
// are multiples of 4, it is as if we have skipped some NOPs. Otherwise
// we are in the middle of a 4-byte NOP, and we need to rewrite the NOP
// sequence.
int64_t skip = 0;
if (r.type == R_RISCV_ALIGN) {
if (remove % 4 || r.addend % 4) {
skip = r.addend - remove;
int64_t j = 0;
for (; j + 4 <= skip; j += 4)
write32le(p + j, 0x00000013); // nop
if (j != skip) {
assert(j + 2 == skip);
write16le(p + j, 0x0001); // c.nop
}
}
} else if (RelType newType = aux.relocTypes[i]) {
switch (newType) {
case INTERNAL_R_RISCV_GPREL_I:
case INTERNAL_R_RISCV_GPREL_S:
break;
case R_RISCV_RELAX:
// Used by relaxTlsLe to indicate the relocation is ignored.
break;
case R_RISCV_RVC_JUMP:
skip = 2;
write16le(p, aux.writes[writesIdx++]);
break;
case R_RISCV_JAL:
skip = 4;
write32le(p, aux.writes[writesIdx++]);
break;
case R_RISCV_32:
// Used by relaxTlsLe to write a uint32_t then suppress the handling
// in relocateAlloc.
skip = 4;
write32le(p, aux.writes[writesIdx++]);
aux.relocTypes[i] = R_RISCV_NONE;
break;
default:
llvm_unreachable("unsupported type");
}
}
p += skip;
offset = r.offset + skip + remove;
}
memcpy(p, old.data() + offset, old.size() - offset);
// Subtract the previous relocDeltas value from the relocation offset.
// For a pair of R_RISCV_CALL/R_RISCV_RELAX with the same offset, decrease
// their r_offset by the same delta.
delta = 0;
for (size_t i = 0, e = rels.size(); i != e;) {
uint64_t cur = rels[i].offset;
do {
rels[i].offset -= delta;
if (aux.relocTypes[i] != R_RISCV_NONE)
rels[i].type = aux.relocTypes[i];
} while (++i != e && rels[i].offset == cur);
delta = aux.relocDeltas[i - 1];
}
}
}
}
namespace {
// Representation of the merged .riscv.attributes input sections. The psABI
// specifies merge policy for attributes. E.g. if we link an object without an
// extension with an object with the extension, the output Tag_RISCV_arch shall
// contain the extension. Some tools like objdump parse .riscv.attributes and
// disabling some instructions if the first Tag_RISCV_arch does not contain an
// extension.
class RISCVAttributesSection final : public SyntheticSection {
public:
RISCVAttributesSection()
: SyntheticSection(0, SHT_RISCV_ATTRIBUTES, 1, ".riscv.attributes") {}
size_t getSize() const override { return size; }
void writeTo(uint8_t *buf) override;
static constexpr StringRef vendor = "riscv";
DenseMap<unsigned, unsigned> intAttr;
DenseMap<unsigned, StringRef> strAttr;
size_t size = 0;
};
} // namespace
static void mergeArch(RISCVISAInfo::OrderedExtensionMap &mergedExts,
unsigned &mergedXlen, const InputSectionBase *sec,
StringRef s) {
auto maybeInfo = RISCVISAInfo::parseNormalizedArchString(s);
if (!maybeInfo) {
errorOrWarn(toString(sec) + ": " + s + ": " +
llvm::toString(maybeInfo.takeError()));
return;
}
// Merge extensions.
RISCVISAInfo &info = **maybeInfo;
if (mergedExts.empty()) {
mergedExts = info.getExtensions();
mergedXlen = info.getXLen();
} else {
for (const auto &ext : info.getExtensions()) {
if (auto it = mergedExts.find(ext.first); it != mergedExts.end()) {
if (std::tie(it->second.Major, it->second.Minor) >=
std::tie(ext.second.Major, ext.second.Minor))
continue;
}
mergedExts[ext.first] = ext.second;
}
}
}
static RISCVAttributesSection *
mergeAttributesSection(const SmallVector<InputSectionBase *, 0> &sections) {
RISCVISAInfo::OrderedExtensionMap exts;
const InputSectionBase *firstStackAlign = nullptr;
unsigned firstStackAlignValue = 0, xlen = 0;
bool hasArch = false;
in.riscvAttributes = std::make_unique<RISCVAttributesSection>();
auto &merged = static_cast<RISCVAttributesSection &>(*in.riscvAttributes);
// Collect all tags values from attributes section.
const auto &attributesTags = RISCVAttrs::getRISCVAttributeTags();
for (const InputSectionBase *sec : sections) {
RISCVAttributeParser parser;
if (Error e = parser.parse(sec->content(), llvm::endianness::little))
warn(toString(sec) + ": " + llvm::toString(std::move(e)));
for (const auto &tag : attributesTags) {
switch (RISCVAttrs::AttrType(tag.attr)) {
// Integer attributes.
case RISCVAttrs::STACK_ALIGN:
if (auto i = parser.getAttributeValue(tag.attr)) {
auto r = merged.intAttr.try_emplace(tag.attr, *i);
if (r.second) {
firstStackAlign = sec;
firstStackAlignValue = *i;
} else if (r.first->second != *i) {
errorOrWarn(toString(sec) + " has stack_align=" + Twine(*i) +
" but " + toString(firstStackAlign) +
" has stack_align=" + Twine(firstStackAlignValue));
}
}
continue;
case RISCVAttrs::UNALIGNED_ACCESS:
if (auto i = parser.getAttributeValue(tag.attr))
merged.intAttr[tag.attr] |= *i;
continue;
// String attributes.
case RISCVAttrs::ARCH:
if (auto s = parser.getAttributeString(tag.attr)) {
hasArch = true;
mergeArch(exts, xlen, sec, *s);
}
continue;
// Attributes which use the default handling.
case RISCVAttrs::PRIV_SPEC:
case RISCVAttrs::PRIV_SPEC_MINOR:
case RISCVAttrs::PRIV_SPEC_REVISION:
break;
}
// Fallback for deprecated priv_spec* and other unknown attributes: retain
// the attribute if all input sections agree on the value. GNU ld uses 0
// and empty strings as default values which are not dumped to the output.
// TODO Adjust after resolution to
// https://github.com/riscv-non-isa/riscv-elf-psabi-doc/issues/352
if (tag.attr % 2 == 0) {
if (auto i = parser.getAttributeValue(tag.attr)) {
auto r = merged.intAttr.try_emplace(tag.attr, *i);
if (!r.second && r.first->second != *i)
r.first->second = 0;
}
} else if (auto s = parser.getAttributeString(tag.attr)) {
auto r = merged.strAttr.try_emplace(tag.attr, *s);
if (!r.second && r.first->second != *s)
r.first->second = {};
}
}
}
if (hasArch) {
if (auto result = RISCVISAInfo::postProcessAndChecking(
std::make_unique<RISCVISAInfo>(xlen, exts))) {
merged.strAttr.try_emplace(RISCVAttrs::ARCH,
saver().save((*result)->toString()));
} else {
errorOrWarn(llvm::toString(result.takeError()));
}
}
// The total size of headers: format-version [ <section-length> "vendor-name"
// [ <file-tag> <size>.
size_t size = 5 + merged.vendor.size() + 1 + 5;
for (auto &attr : merged.intAttr)
if (attr.second != 0)
size += getULEB128Size(attr.first) + getULEB128Size(attr.second);
for (auto &attr : merged.strAttr)
if (!attr.second.empty())
size += getULEB128Size(attr.first) + attr.second.size() + 1;
merged.size = size;
return &merged;
}
void RISCVAttributesSection::writeTo(uint8_t *buf) {
const size_t size = getSize();
uint8_t *const end = buf + size;
*buf = ELFAttrs::Format_Version;
write32(buf + 1, size - 1);
buf += 5;
memcpy(buf, vendor.data(), vendor.size());
buf += vendor.size() + 1;
*buf = ELFAttrs::File;
write32(buf + 1, end - buf);
buf += 5;
for (auto &attr : intAttr) {
if (attr.second == 0)
continue;
buf += encodeULEB128(attr.first, buf);
buf += encodeULEB128(attr.second, buf);
}
for (auto &attr : strAttr) {
if (attr.second.empty())
continue;
buf += encodeULEB128(attr.first, buf);
memcpy(buf, attr.second.data(), attr.second.size());
buf += attr.second.size() + 1;
}
}
void elf::mergeRISCVAttributesSections() {
// Find the first input SHT_RISCV_ATTRIBUTES; return if not found.
size_t place =
llvm::find_if(ctx.inputSections,
[](auto *s) { return s->type == SHT_RISCV_ATTRIBUTES; }) -
ctx.inputSections.begin();
if (place == ctx.inputSections.size())
return;
// Extract all SHT_RISCV_ATTRIBUTES sections into `sections`.
SmallVector<InputSectionBase *, 0> sections;
llvm::erase_if(ctx.inputSections, [&](InputSectionBase *s) {
if (s->type != SHT_RISCV_ATTRIBUTES)
return false;
sections.push_back(s);
return true;
});
// Add the merged section.
ctx.inputSections.insert(ctx.inputSections.begin() + place,
mergeAttributesSection(sections));
}
TargetInfo *elf::getRISCVTargetInfo() {
static RISCV target;
return &target;
}