1 //===- InputSection.cpp ---------------------------------------------------===//
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-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "InputSection.h"
10 #include "InputFiles.h"
11 #include "OutputSegment.h"
12 #include "Symbols.h"
13 #include "SyntheticSections.h"
14 #include "Target.h"
15 #include "Writer.h"
16 #include "lld/Common/Memory.h"
17 #include "llvm/Support/Endian.h"
18 
19 using namespace llvm;
20 using namespace llvm::MachO;
21 using namespace llvm::support;
22 using namespace lld;
23 using namespace lld::macho;
24 
25 std::vector<InputSection *> macho::inputSections;
26 
27 uint64_t InputSection::getFileOffset() const {
28   return parent->fileOff + outSecFileOff;
29 }
30 
31 uint64_t InputSection::getFileSize() const {
32   return isZeroFill(flags) ? 0 : getSize();
33 }
34 
35 uint64_t InputSection::getVA() const { return parent->addr + outSecOff; }
36 
37 static uint64_t resolveSymbolVA(const Symbol *sym, uint8_t type) {
38   const RelocAttrs &relocAttrs = target->getRelocAttrs(type);
39   if (relocAttrs.hasAttr(RelocAttrBits::BRANCH))
40     return sym->resolveBranchVA();
41   else if (relocAttrs.hasAttr(RelocAttrBits::GOT))
42     return sym->resolveGotVA();
43   else if (relocAttrs.hasAttr(RelocAttrBits::TLV))
44     return sym->resolveTlvVA();
45   return sym->getVA();
46 }
47 
48 void InputSection::writeTo(uint8_t *buf) {
49   assert(!shouldOmitFromOutput());
50 
51   if (getFileSize() == 0)
52     return;
53 
54   memcpy(buf, data.data(), data.size());
55 
56   for (size_t i = 0; i < relocs.size(); i++) {
57     const Reloc &r = relocs[i];
58     uint8_t *loc = buf + r.offset;
59     uint64_t referentVA = 0;
60     if (target->hasAttr(r.type, RelocAttrBits::SUBTRAHEND)) {
61       const Symbol *fromSym = r.referent.get<Symbol *>();
62       const Reloc &minuend = relocs[++i];
63       uint64_t minuendVA;
64       if (const Symbol *toSym = minuend.referent.dyn_cast<Symbol *>())
65         minuendVA = toSym->getVA();
66       else {
67         auto *referentIsec = minuend.referent.get<InputSection *>();
68         assert(!referentIsec->shouldOmitFromOutput());
69         minuendVA = referentIsec->getVA();
70       }
71       referentVA = minuendVA - fromSym->getVA() + minuend.addend;
72     } else if (auto *referentSym = r.referent.dyn_cast<Symbol *>()) {
73       if (target->hasAttr(r.type, RelocAttrBits::LOAD) &&
74           !referentSym->isInGot())
75         target->relaxGotLoad(loc, r.type);
76       referentVA = resolveSymbolVA(referentSym, r.type);
77 
78       if (isThreadLocalVariables(flags)) {
79         // References from thread-local variable sections are treated as offsets
80         // relative to the start of the thread-local data memory area, which
81         // is initialized via copying all the TLV data sections (which are all
82         // contiguous).
83         if (isa<Defined>(referentSym))
84           referentVA -= firstTLVDataSection->addr;
85       }
86     } else if (auto *referentIsec = r.referent.dyn_cast<InputSection *>()) {
87       assert(!referentIsec->shouldOmitFromOutput());
88       referentVA = referentIsec->getVA();
89     }
90     target->relocateOne(loc, r, referentVA + r.addend, getVA() + r.offset);
91   }
92 }
93 
94 bool macho::isCodeSection(const InputSection *isec) {
95   uint32_t type = isec->flags & SECTION_TYPE;
96   if (type != S_REGULAR && type != S_COALESCED)
97     return false;
98 
99   uint32_t attr = isec->flags & SECTION_ATTRIBUTES_USR;
100   if (attr == S_ATTR_PURE_INSTRUCTIONS)
101     return true;
102 
103   if (isec->segname == segment_names::text)
104     return StringSwitch<bool>(isec->name)
105         .Cases(section_names::textCoalNt, section_names::staticInit, true)
106         .Default(false);
107 
108   return false;
109 }
110 
111 std::string lld::toString(const InputSection *isec) {
112   return (toString(isec->file) + ":(" + isec->name + ")").str();
113 }
114