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1//===------------------------------------------------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLD_ELF_RELOCSCAN_H10#define LLD_ELF_RELOCSCAN_H11 12#include "Config.h"13#include "InputFiles.h"14#include "InputSection.h"15#include "Relocations.h"16#include "SyntheticSections.h"17#include "Target.h"18 19using namespace llvm;20using namespace llvm::ELF;21using namespace llvm::object;22 23namespace lld::elf {24 25// Build a bitmask with one bit set for each 64 subset of RelExpr.26inline constexpr uint64_t buildMask() { return 0; }27 28template <typename... Tails>29inline constexpr uint64_t buildMask(int head, Tails... tails) {30 return (0 <= head && head < 64 ? uint64_t(1) << head : 0) |31 buildMask(tails...);32}33 34// Return true if `Expr` is one of `Exprs`.35// There are more than 64 but less than 128 RelExprs, so we divide the set of36// exprs into [0, 64) and [64, 128) and represent each range as a constant37// 64-bit mask. Then we decide which mask to test depending on the value of38// expr and use a simple shift and bitwise-and to test for membership.39template <RelExpr... Exprs> bool oneof(RelExpr expr) {40 assert(0 <= expr && (int)expr < 128 &&41 "RelExpr is too large for 128-bit mask!");42 43 if (expr >= 64)44 return (uint64_t(1) << (expr - 64)) & buildMask((Exprs - 64)...);45 return (uint64_t(1) << expr) & buildMask(Exprs...);46}47 48// This class encapsulates states needed to scan relocations for one49// InputSectionBase.50class RelocScan {51public:52 Ctx &ctx;53 InputSectionBase *sec;54 55 RelocScan(Ctx &ctx, InputSectionBase *sec = nullptr) : ctx(ctx), sec(sec) {}56 template <class ELFT, class RelTy>57 void scan(typename Relocs<RelTy>::const_iterator &i, RelType type,58 int64_t addend);59 void scanEhSection(EhInputSection &s);60 61 template <class ELFT, class RelTy>62 int64_t getAddend(const RelTy &r, RelType type);63 bool maybeReportUndefined(Undefined &sym, uint64_t offset);64 bool checkTlsLe(uint64_t offset, Symbol &sym, RelType type);65 bool isStaticLinkTimeConstant(RelExpr e, RelType type, const Symbol &sym,66 uint64_t relOff) const;67 void process(RelExpr expr, RelType type, uint64_t offset, Symbol &sym,68 int64_t addend) const;69 unsigned handleTlsRelocation(RelExpr expr, RelType type, uint64_t offset,70 Symbol &sym, int64_t addend);71};72 73template <class ELFT, class RelTy>74int64_t RelocScan::getAddend(const RelTy &r, RelType type) {75 return RelTy::HasAddend ? elf::getAddend<ELFT>(r)76 : ctx.target->getImplicitAddend(77 sec->content().data() + r.r_offset, type);78}79 80template <class ELFT, class RelTy>81void RelocScan::scan(typename Relocs<RelTy>::const_iterator &it, RelType type,82 int64_t addend) {83 const RelTy &rel = *it;84 uint32_t symIdx = rel.getSymbol(false);85 Symbol &sym = sec->getFile<ELFT>()->getSymbol(symIdx);86 uint64_t offset = rel.r_offset;87 RelExpr expr =88 ctx.target->getRelExpr(type, sym, sec->content().data() + offset);89 90 // Ignore R_*_NONE and other marker relocations.91 if (expr == R_NONE)92 return;93 94 // Error if the target symbol is undefined. Symbol index 0 may be used by95 // marker relocations, e.g. R_*_NONE and R_ARM_V4BX. Don't error on them.96 if (sym.isUndefined() && symIdx != 0 &&97 maybeReportUndefined(cast<Undefined>(sym), offset))98 return;99 100 // Ensure GOT or GOTPLT is created for relocations that reference their base101 // addresses without directly creating entries.102 if (oneof<R_GOTPLTONLY_PC, R_GOTPLTREL, R_GOTPLT, R_PLT_GOTPLT,103 R_TLSDESC_GOTPLT, R_TLSGD_GOTPLT>(expr)) {104 ctx.in.gotPlt->hasGotPltOffRel.store(true, std::memory_order_relaxed);105 } else if (oneof<R_GOTONLY_PC, R_GOTREL, RE_PPC32_PLTREL>(expr)) {106 ctx.in.got->hasGotOffRel.store(true, std::memory_order_relaxed);107 }108 109 // Process TLS relocations, including TLS optimizations. Note that110 // R_TPREL and R_TPREL_NEG relocations are resolved in processAux.111 //112 // Some RISCV TLSDESC relocations reference a local NOTYPE symbol,113 // but we need to process them in handleTlsRelocation.114 if (sym.isTls() || oneof<R_TLSDESC_PC, R_TLSDESC_CALL>(expr)) {115 if (unsigned processed =116 handleTlsRelocation(expr, type, offset, sym, addend)) {117 it += processed - 1;118 return;119 }120 }121 122 process(expr, type, offset, sym, addend);123}124} // namespace lld::elf125 126#endif127