lib/XRay/InstrumentationMap.cpp

   1 //===- InstrumentationMap.cpp - XRay Instrumentation Map ------------------===//
   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 // Implementation of the InstrumentationMap type for XRay sleds.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/XRay/InstrumentationMap.h"
  14 #include "llvm/ADT/DenseMap.h"
  15 #include "llvm/ADT/None.h"
  16 #include "llvm/ADT/STLExtras.h"
  17 #include "llvm/ADT/StringRef.h"
  18 #include "llvm/ADT/Triple.h"
  19 #include "llvm/ADT/Twine.h"
  20 #include "llvm/Object/Binary.h"
  21 #include "llvm/Object/ELFObjectFile.h"
  22 #include "llvm/Object/ObjectFile.h"
  23 #include "llvm/Support/DataExtractor.h"
  24 #include "llvm/Support/Error.h"
  25 #include "llvm/Support/FileSystem.h"
  26 #include "llvm/Support/YAMLTraits.h"
  27 #include <algorithm>
  28 #include <cstddef>
  29 #include <cstdint>
  30 #include <system_error>
  31 #include <vector>
  32
  33 using namespace llvm;
  34 using namespace xray;
  35
  36 Optional<int32_t> InstrumentationMap::getFunctionId(uint64_t Addr) const {
  37   auto I = FunctionIds.find(Addr);
  38   if (I != FunctionIds.end())
  39     return I->second;
  40   return None;
  41 }
  42
  43 Optional<uint64_t> InstrumentationMap::getFunctionAddr(int32_t FuncId) const {
  44   auto I = FunctionAddresses.find(FuncId);
  45   if (I != FunctionAddresses.end())
  46     return I->second;
  47   return None;
  48 }
  49
  50 using RelocMap = DenseMap<uint64_t, uint64_t>;
  51
  52 static Error
  53 loadObj(StringRef Filename, object::OwningBinary<object::ObjectFile> &ObjFile,
  54           InstrumentationMap::SledContainer &Sleds,
  55           InstrumentationMap::FunctionAddressMap &FunctionAddresses,
  56           InstrumentationMap::FunctionAddressReverseMap &FunctionIds) {
  57   InstrumentationMap Map;
  58
  59   // Find the section named "xray_instr_map".
  60   if ((!ObjFile.getBinary()->isELF() && !ObjFile.getBinary()->isMachO()) ||
  61       !(ObjFile.getBinary()->getArch() == Triple::x86_64 ||
  62         ObjFile.getBinary()->getArch() == Triple::ppc64le))
  63     return make_error<StringError>(
  64         "File format not supported (only does ELF and Mach-O little endian 64-bit).",
  65         std::make_error_code(std::errc::not_supported));
  66
  67   StringRef Contents = "";
  68   const auto &Sections = ObjFile.getBinary()->sections();
  69   auto I = llvm::find_if(Sections, [&](object::SectionRef Section) {
  70     StringRef Name = "";
  71     if (Section.getName(Name))
  72       return false;
  73     return Name == "xray_instr_map";
  74   });
  75
  76   if (I == Sections.end())
  77     return make_error<StringError>(
  78         "Failed to find XRay instrumentation map.",
  79         std::make_error_code(std::errc::executable_format_error));
  80
  81   if (Expected<StringRef> E = I->getContents())
  82     Contents = *E;
  83   else
  84     return E.takeError();
  85
  86   RelocMap Relocs;
  87   if (ObjFile.getBinary()->isELF()) {
  88     uint32_t RelativeRelocation = [](object::ObjectFile *ObjFile) {
  89       if (const auto *ELFObj = dyn_cast<object::ELF32LEObjectFile>(ObjFile))
  90         return ELFObj->getELFFile()->getRelativeRelocationType();
  91       else if (const auto *ELFObj = dyn_cast<object::ELF32BEObjectFile>(ObjFile))
  92         return ELFObj->getELFFile()->getRelativeRelocationType();
  93       else if (const auto *ELFObj = dyn_cast<object::ELF64LEObjectFile>(ObjFile))
  94         return ELFObj->getELFFile()->getRelativeRelocationType();
  95       else if (const auto *ELFObj = dyn_cast<object::ELF64BEObjectFile>(ObjFile))
  96         return ELFObj->getELFFile()->getRelativeRelocationType();
  97       else
  98         return static_cast<uint32_t>(0);
  99     }(ObjFile.getBinary());
 100
 101     for (const object::SectionRef &Section : Sections) {
 102       for (const object::RelocationRef &Reloc : Section.relocations()) {
 103         if (Reloc.getType() != RelativeRelocation)
 104           continue;
 105         if (auto AddendOrErr = object::ELFRelocationRef(Reloc).getAddend())
 106           Relocs.insert({Reloc.getOffset(), *AddendOrErr});
 107       }
 108     }
 109   }
 110
 111   // Copy the instrumentation map data into the Sleds data structure.
 112   auto C = Contents.bytes_begin();
 113   static constexpr size_t ELF64SledEntrySize = 32;
 114
 115   if ((C - Contents.bytes_end()) % ELF64SledEntrySize != 0)
 116     return make_error<StringError>(
 117         Twine("Instrumentation map entries not evenly divisible by size of "
 118               "an XRay sled entry in ELF64."),
 119         std::make_error_code(std::errc::executable_format_error));
 120
 121   auto RelocateOrElse = [&](uint64_t Offset, uint64_t Address) {
 122     if (!Address) {
 123       uint64_t A = I->getAddress() + C - Contents.bytes_begin() + Offset;
 124       RelocMap::const_iterator R = Relocs.find(A);
 125       if (R != Relocs.end())
 126         return R->second;
 127     }
 128     return Address;
 129   };
 130
 131   int32_t FuncId = 1;
 132   uint64_t CurFn = 0;
 133   for (; C != Contents.bytes_end(); C += ELF64SledEntrySize) {
 134     DataExtractor Extractor(
 135         StringRef(reinterpret_cast<const char *>(C), ELF64SledEntrySize), true,
 136         8);
 137     Sleds.push_back({});
 138     auto &Entry = Sleds.back();
 139     uint64_t OffsetPtr = 0;
 140     uint64_t AddrOff = OffsetPtr;
 141     Entry.Address = RelocateOrElse(AddrOff, Extractor.getU64(&OffsetPtr));
 142     uint64_t FuncOff = OffsetPtr;
 143     Entry.Function = RelocateOrElse(FuncOff, Extractor.getU64(&OffsetPtr));
 144     auto Kind = Extractor.getU8(&OffsetPtr);
 145     static constexpr SledEntry::FunctionKinds Kinds[] = {
 146         SledEntry::FunctionKinds::ENTRY, SledEntry::FunctionKinds::EXIT,
 147         SledEntry::FunctionKinds::TAIL,
 148         SledEntry::FunctionKinds::LOG_ARGS_ENTER,
 149         SledEntry::FunctionKinds::CUSTOM_EVENT};
 150     if (Kind >= sizeof(Kinds))
 151       return errorCodeToError(
 152           std::make_error_code(std::errc::executable_format_error));
 153     Entry.Kind = Kinds[Kind];
 154     Entry.AlwaysInstrument = Extractor.getU8(&OffsetPtr) != 0;
 155
 156     // We do replicate the function id generation scheme implemented in the
 157     // XRay runtime.
 158     // FIXME: Figure out how to keep this consistent with the XRay runtime.
 159     if (CurFn == 0) {
 160       CurFn = Entry.Function;
 161       FunctionAddresses[FuncId] = Entry.Function;
 162       FunctionIds[Entry.Function] = FuncId;
 163     }
 164     if (Entry.Function != CurFn) {
 165       ++FuncId;
 166       CurFn = Entry.Function;
 167       FunctionAddresses[FuncId] = Entry.Function;
 168       FunctionIds[Entry.Function] = FuncId;
 169     }
 170   }
 171   return Error::success();
 172 }
 173
 174 static Error
 175 loadYAML(sys::fs::file_t Fd, size_t FileSize, StringRef Filename,
 176          InstrumentationMap::SledContainer &Sleds,
 177          InstrumentationMap::FunctionAddressMap &FunctionAddresses,
 178          InstrumentationMap::FunctionAddressReverseMap &FunctionIds) {
 179   std::error_code EC;
 180   sys::fs::mapped_file_region MappedFile(
 181       Fd, sys::fs::mapped_file_region::mapmode::readonly, FileSize, 0, EC);
 182   sys::fs::closeFile(Fd);
 183   if (EC)
 184     return make_error<StringError>(
 185         Twine("Failed memory-mapping file '") + Filename + "'.", EC);
 186
 187   std::vector<YAMLXRaySledEntry> YAMLSleds;
 188   yaml::Input In(StringRef(MappedFile.data(), MappedFile.size()));
 189   In >> YAMLSleds;
 190   if (In.error())
 191     return make_error<StringError>(
 192         Twine("Failed loading YAML document from '") + Filename + "'.",
 193         In.error());
 194
 195   Sleds.reserve(YAMLSleds.size());
 196   for (const auto &Y : YAMLSleds) {
 197     FunctionAddresses[Y.FuncId] = Y.Function;
 198     FunctionIds[Y.Function] = Y.FuncId;
 199     Sleds.push_back(
 200         SledEntry{Y.Address, Y.Function, Y.Kind, Y.AlwaysInstrument});
 201   }
 202   return Error::success();
 203 }
 204
 205 // FIXME: Create error types that encapsulate a bit more information than what
 206 // StringError instances contain.
 207 Expected<InstrumentationMap>
 208 llvm::xray::loadInstrumentationMap(StringRef Filename) {
 209   // At this point we assume the file is an object file -- and if that doesn't
 210   // work, we treat it as YAML.
 211   // FIXME: Extend to support non-ELF and non-x86_64 binaries.
 212
 213   InstrumentationMap Map;
 214   auto ObjectFileOrError = object::ObjectFile::createObjectFile(Filename);
 215   if (!ObjectFileOrError) {
 216     auto E = ObjectFileOrError.takeError();
 217     // We try to load it as YAML if the ELF load didn't work.
 218     Expected<sys::fs::file_t> FdOrErr = sys::fs::openNativeFileForRead(Filename);
 219     if (!FdOrErr) {
 220       // Report the ELF load error if YAML failed.
 221       consumeError(FdOrErr.takeError());
 222       return std::move(E);
 223     }
 224
 225     uint64_t FileSize;
 226     if (sys::fs::file_size(Filename, FileSize))
 227       return std::move(E);
 228
 229     // If the file is empty, we return the original error.
 230     if (FileSize == 0)
 231       return std::move(E);
 232
 233     // From this point on the errors will be only for the YAML parts, so we
 234     // consume the errors at this point.
 235     consumeError(std::move(E));
 236     if (auto E = loadYAML(*FdOrErr, FileSize, Filename, Map.Sleds,
 237                           Map.FunctionAddresses, Map.FunctionIds))
 238       return std::move(E);
 239   } else if (auto E = loadObj(Filename, *ObjectFileOrError, Map.Sleds,
 240                                 Map.FunctionAddresses, Map.FunctionIds)) {
 241     return std::move(E);
 242   }
 243   return Map;
 244 }