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     Expected<StringRef> NameOrErr = Section.getName();
  71     if (NameOrErr)
  72       return *NameOrErr == "xray_instr_map";
  73     consumeError(NameOrErr.takeError());
  74     return false;
  75   });
  76
  77   if (I == Sections.end())
  78     return make_error<StringError>(
  79         "Failed to find XRay instrumentation map.",
  80         std::make_error_code(std::errc::executable_format_error));
  81
  82   if (Expected<StringRef> E = I->getContents())
  83     Contents = *E;
  84   else
  85     return E.takeError();
  86
  87   RelocMap Relocs;
  88   if (ObjFile.getBinary()->isELF()) {
  89     uint32_t RelativeRelocation = [](object::ObjectFile *ObjFile) {
  90       if (const auto *ELFObj = dyn_cast<object::ELF32LEObjectFile>(ObjFile))
  91         return ELFObj->getELFFile()->getRelativeRelocationType();
  92       else if (const auto *ELFObj = dyn_cast<object::ELF32BEObjectFile>(ObjFile))
  93         return ELFObj->getELFFile()->getRelativeRelocationType();
  94       else if (const auto *ELFObj = dyn_cast<object::ELF64LEObjectFile>(ObjFile))
  95         return ELFObj->getELFFile()->getRelativeRelocationType();
  96       else if (const auto *ELFObj = dyn_cast<object::ELF64BEObjectFile>(ObjFile))
  97         return ELFObj->getELFFile()->getRelativeRelocationType();
  98       else
  99         return static_cast<uint32_t>(0);
 100     }(ObjFile.getBinary());
 101
 102     for (const object::SectionRef &Section : Sections) {
 103       for (const object::RelocationRef &Reloc : Section.relocations()) {
 104         if (Reloc.getType() != RelativeRelocation)
 105           continue;
 106         if (auto AddendOrErr = object::ELFRelocationRef(Reloc).getAddend())
 107           Relocs.insert({Reloc.getOffset(), *AddendOrErr});
 108       }
 109     }
 110   }
 111
 112   // Copy the instrumentation map data into the Sleds data structure.
 113   auto C = Contents.bytes_begin();
 114   static constexpr size_t ELF64SledEntrySize = 32;
 115
 116   if ((C - Contents.bytes_end()) % ELF64SledEntrySize != 0)
 117     return make_error<StringError>(
 118         Twine("Instrumentation map entries not evenly divisible by size of "
 119               "an XRay sled entry in ELF64."),
 120         std::make_error_code(std::errc::executable_format_error));
 121
 122   auto RelocateOrElse = [&](uint64_t Offset, uint64_t Address) {
 123     if (!Address) {
 124       uint64_t A = I->getAddress() + C - Contents.bytes_begin() + Offset;
 125       RelocMap::const_iterator R = Relocs.find(A);
 126       if (R != Relocs.end())
 127         return R->second;
 128     }
 129     return Address;
 130   };
 131
 132   int32_t FuncId = 1;
 133   uint64_t CurFn = 0;
 134   for (; C != Contents.bytes_end(); C += ELF64SledEntrySize) {
 135     DataExtractor Extractor(
 136         StringRef(reinterpret_cast<const char *>(C), ELF64SledEntrySize), true,
 137         8);
 138     Sleds.push_back({});
 139     auto &Entry = Sleds.back();
 140     uint64_t OffsetPtr = 0;
 141     uint64_t AddrOff = OffsetPtr;
 142     Entry.Address = RelocateOrElse(AddrOff, Extractor.getU64(&OffsetPtr));
 143     uint64_t FuncOff = OffsetPtr;
 144     Entry.Function = RelocateOrElse(FuncOff, Extractor.getU64(&OffsetPtr));
 145     auto Kind = Extractor.getU8(&OffsetPtr);
 146     static constexpr SledEntry::FunctionKinds Kinds[] = {
 147         SledEntry::FunctionKinds::ENTRY, SledEntry::FunctionKinds::EXIT,
 148         SledEntry::FunctionKinds::TAIL,
 149         SledEntry::FunctionKinds::LOG_ARGS_ENTER,
 150         SledEntry::FunctionKinds::CUSTOM_EVENT};
 151     if (Kind >= sizeof(Kinds))
 152       return errorCodeToError(
 153           std::make_error_code(std::errc::executable_format_error));
 154     Entry.Kind = Kinds[Kind];
 155     Entry.AlwaysInstrument = Extractor.getU8(&OffsetPtr) != 0;
 156
 157     // We do replicate the function id generation scheme implemented in the
 158     // XRay runtime.
 159     // FIXME: Figure out how to keep this consistent with the XRay runtime.
 160     if (CurFn == 0) {
 161       CurFn = Entry.Function;
 162       FunctionAddresses[FuncId] = Entry.Function;
 163       FunctionIds[Entry.Function] = FuncId;
 164     }
 165     if (Entry.Function != CurFn) {
 166       ++FuncId;
 167       CurFn = Entry.Function;
 168       FunctionAddresses[FuncId] = Entry.Function;
 169       FunctionIds[Entry.Function] = FuncId;
 170     }
 171   }
 172   return Error::success();
 173 }
 174
 175 static Error
 176 loadYAML(sys::fs::file_t Fd, size_t FileSize, StringRef Filename,
 177          InstrumentationMap::SledContainer &Sleds,
 178          InstrumentationMap::FunctionAddressMap &FunctionAddresses,
 179          InstrumentationMap::FunctionAddressReverseMap &FunctionIds) {
 180   std::error_code EC;
 181   sys::fs::mapped_file_region MappedFile(
 182       Fd, sys::fs::mapped_file_region::mapmode::readonly, FileSize, 0, EC);
 183   sys::fs::closeFile(Fd);
 184   if (EC)
 185     return make_error<StringError>(
 186         Twine("Failed memory-mapping file '") + Filename + "'.", EC);
 187
 188   std::vector<YAMLXRaySledEntry> YAMLSleds;
 189   yaml::Input In(StringRef(MappedFile.data(), MappedFile.size()));
 190   In >> YAMLSleds;
 191   if (In.error())
 192     return make_error<StringError>(
 193         Twine("Failed loading YAML document from '") + Filename + "'.",
 194         In.error());
 195
 196   Sleds.reserve(YAMLSleds.size());
 197   for (const auto &Y : YAMLSleds) {
 198     FunctionAddresses[Y.FuncId] = Y.Function;
 199     FunctionIds[Y.Function] = Y.FuncId;
 200     Sleds.push_back(
 201         SledEntry{Y.Address, Y.Function, Y.Kind, Y.AlwaysInstrument});
 202   }
 203   return Error::success();
 204 }
 205
 206 // FIXME: Create error types that encapsulate a bit more information than what
 207 // StringError instances contain.
 208 Expected<InstrumentationMap>
 209 llvm::xray::loadInstrumentationMap(StringRef Filename) {
 210   // At this point we assume the file is an object file -- and if that doesn't
 211   // work, we treat it as YAML.
 212   // FIXME: Extend to support non-ELF and non-x86_64 binaries.
 213
 214   InstrumentationMap Map;
 215   auto ObjectFileOrError = object::ObjectFile::createObjectFile(Filename);
 216   if (!ObjectFileOrError) {
 217     auto E = ObjectFileOrError.takeError();
 218     // We try to load it as YAML if the ELF load didn't work.
 219     Expected<sys::fs::file_t> FdOrErr = sys::fs::openNativeFileForRead(Filename);
 220     if (!FdOrErr) {
 221       // Report the ELF load error if YAML failed.
 222       consumeError(FdOrErr.takeError());
 223       return std::move(E);
 224     }
 225
 226     uint64_t FileSize;
 227     if (sys::fs::file_size(Filename, FileSize))
 228       return std::move(E);
 229
 230     // If the file is empty, we return the original error.
 231     if (FileSize == 0)
 232       return std::move(E);
 233
 234     // From this point on the errors will be only for the YAML parts, so we
 235     // consume the errors at this point.
 236     consumeError(std::move(E));
 237     if (auto E = loadYAML(*FdOrErr, FileSize, Filename, Map.Sleds,
 238                           Map.FunctionAddresses, Map.FunctionIds))
 239       return std::move(E);
 240   } else if (auto E = loadObj(Filename, *ObjectFileOrError, Map.Sleds,
 241                                 Map.FunctionAddresses, Map.FunctionIds)) {
 242     return std::move(E);
 243   }
 244   return Map;
 245 }