lld/MachO/Relocations.cpp

   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};