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