1 //===- Relocations.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 "Relocations.h"
10 #include "ConcatOutputSection.h"
11 #include "Symbols.h"
12 #include "SyntheticSections.h"
13 #include "Target.h"
14 
15 #include "lld/Common/ErrorHandler.h"
16 
17 using namespace llvm;
18 using namespace lld;
19 using namespace lld::macho;
20 
21 static_assert(sizeof(void *) != 8 || sizeof(Reloc) == 24,
22               "Try to minimize Reloc's size; we create many instances");
23 
24 InputSection *Reloc::getReferentInputSection() const {
25   if (const auto *sym = referent.dyn_cast<Symbol *>()) {
26     if (const auto *d = dyn_cast<Defined>(sym))
27       return d->isec;
28     return nullptr;
29   } else {
30     return referent.get<InputSection *>();
31   }
32 }
33 
34 bool macho::validateSymbolRelocation(const Symbol *sym,
35                                      const InputSection *isec, const Reloc &r) {
36   const RelocAttrs &relocAttrs = target->getRelocAttrs(r.type);
37   bool valid = true;
38   auto message = [&](const Twine &diagnostic) {
39     valid = false;
40     return (isec->getLocation(r.offset) + ": " + relocAttrs.name +
41             " relocation " + diagnostic)
42         .str();
43   };
44 
45   if (relocAttrs.hasAttr(RelocAttrBits::TLV) != sym->isTlv())
46     error(message(Twine("requires that symbol ") + sym->getName() + " " +
47                   (sym->isTlv() ? "not " : "") + "be thread-local"));
48 
49   return valid;
50 }
51 
52 // Given an offset in the output buffer, figure out which ConcatInputSection (if
53 // any) maps to it. At the same time, update the offset such that it is relative
54 // to the InputSection rather than to the output buffer.
55 //
56 // Obtaining the InputSection allows us to have better error diagnostics.
57 // However, many of our relocation-handling methods do not take the InputSection
58 // as a parameter. Since we are already passing the buffer offsets to our Target
59 // methods, this function allows us to emit better errors without threading an
60 // additional InputSection argument through the call stack.
61 //
62 // This is implemented as a slow linear search through OutputSegments,
63 // OutputSections, and finally the InputSections themselves. However, this
64 // function should be called only on error paths, so some overhead is fine.
65 InputSection *macho::offsetToInputSection(uint64_t *off) {
66   for (OutputSegment *seg : outputSegments) {
67     if (*off < seg->fileOff || *off >= seg->fileOff + seg->fileSize)
68       continue;
69 
70     const std::vector<OutputSection *> &sections = seg->getSections();
71     size_t osecIdx = 0;
72     for (; osecIdx < sections.size(); ++osecIdx)
73       if (*off < sections[osecIdx]->fileOff)
74         break;
75     assert(osecIdx > 0);
76     // We should be only calling this function on offsets that belong to
77     // ConcatOutputSections.
78     auto *osec = cast<ConcatOutputSection>(sections[osecIdx - 1]);
79     *off -= osec->fileOff;
80 
81     size_t isecIdx = 0;
82     for (; isecIdx < osec->inputs.size(); ++isecIdx) {
83       const ConcatInputSection *isec = osec->inputs[isecIdx];
84       if (*off < isec->outSecOff)
85         break;
86     }
87     assert(isecIdx > 0);
88     ConcatInputSection *isec = osec->inputs[isecIdx - 1];
89     *off -= isec->outSecOff;
90     return isec;
91   }
92   return nullptr;
93 }
94 
95 void macho::reportRangeError(void *loc, const Reloc &r, const Twine &v,
96                              uint8_t bits, int64_t min, uint64_t max) {
97   std::string hint;
98   uint64_t off = reinterpret_cast<const uint8_t *>(loc) - in.bufferStart;
99   const InputSection *isec = offsetToInputSection(&off);
100   std::string locStr = isec ? isec->getLocation(off) : "(invalid location)";
101   if (auto *sym = r.referent.dyn_cast<Symbol *>())
102     hint = "; references " + toString(*sym);
103   error(locStr + ": relocation " + target->getRelocAttrs(r.type).name +
104         " is out of range: " + v + " is not in [" + Twine(min) + ", " +
105         Twine(max) + "]" + hint);
106 }
107 
108 void macho::reportRangeError(void *loc, SymbolDiagnostic d, const Twine &v,
109                              uint8_t bits, int64_t min, uint64_t max) {
110   // FIXME: should we use `loc` somehow to provide a better error message?
111   std::string hint;
112   if (d.symbol)
113     hint = "; references " + toString(*d.symbol);
114   error(d.reason + " is out of range: " + v + " is not in [" + Twine(min) +
115         ", " + Twine(max) + "]" + hint);
116 }
117 
118 const RelocAttrs macho::invalidRelocAttrs{"INVALID", RelocAttrBits::_0};
119