1 //===- BTFParser.h ----------------------------------------------*- C++ -*-===// 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 // BTFParser reads .BTF and .BTF.ext ELF sections generated by LLVM 10 // BPF backend and provides introspection for the stored information. 11 // Currently the following information is accessible: 12 // - string table; 13 // - instruction offset to line information mapping; 14 // - types table; 15 // - CO-RE relocations table. 16 // 17 // See llvm/DebugInfo/BTF/BTF.h for some details about binary format 18 // and links to Linux Kernel documentation. 19 // 20 //===----------------------------------------------------------------------===// 21 22 #ifndef LLVM_DEBUGINFO_BTF_BTFPARSER_H 23 #define LLVM_DEBUGINFO_BTF_BTFPARSER_H 24 25 #include "llvm/ADT/DenseMap.h" 26 #include "llvm/DebugInfo/BTF/BTF.h" 27 #include "llvm/Object/ObjectFile.h" 28 #include "llvm/Support/DataExtractor.h" 29 30 namespace llvm { 31 using object::ObjectFile; 32 using object::SectionedAddress; 33 using object::SectionRef; 34 35 class BTFParser { 36 using BTFLinesVector = SmallVector<BTF::BPFLineInfo, 0>; 37 using BTFRelocVector = SmallVector<BTF::BPFFieldReloc, 0>; 38 39 // In BTF strings are stored as a continuous memory region with 40 // individual strings separated by 0 bytes. Strings are identified 41 // by an offset in such region. 42 // The `StringsTable` points to this region in the parsed ObjectFile. 43 StringRef StringsTable; 44 45 // A copy of types table from the object file but using native byte 46 // order. Should not be too big in practice, e.g. for ~250MiB vmlinux 47 // image it is ~4MiB. 48 OwningArrayRef<uint8_t> TypesBuffer; 49 50 // Maps ELF section number to instruction line number information. 51 // Each BTFLinesVector is sorted by `InsnOffset` to allow fast lookups. 52 DenseMap<uint64_t, BTFLinesVector> SectionLines; 53 54 // Maps ELF section number to CO-RE relocation information. 55 // Each BTFRelocVector is sorted by `InsnOffset` to allow fast lookups. 56 DenseMap<uint64_t, BTFRelocVector> SectionRelocs; 57 58 // Vector of pointers to all known types, index in this vector 59 // equals to logical type BTF id. 60 // Pointers point to memory owned by `TypesBuffer` 61 // (except pointer at index 0, which is statically allocated). 62 std::vector<const BTF::CommonType *> Types; 63 64 struct ParseContext; 65 Error parseBTF(ParseContext &Ctx, SectionRef BTF); 66 Error parseBTFExt(ParseContext &Ctx, SectionRef BTFExt); 67 Error parseLineInfo(ParseContext &Ctx, DataExtractor &Extractor, 68 uint64_t LineInfoStart, uint64_t LineInfoEnd); 69 Error parseRelocInfo(ParseContext &Ctx, DataExtractor &Extractor, 70 uint64_t RelocInfoStart, uint64_t RelocInfoEnd); 71 Error parseTypesInfo(ParseContext &Ctx, uint64_t TypesInfoStart, 72 StringRef RawData); 73 74 public: 75 // Looks-up a string in the .BTF section's string table. 76 // Offset is relative to string table start. 77 StringRef findString(uint32_t Offset) const; 78 79 // Search for line information for a specific address, 80 // address match is exact (contrary to DWARFContext). 81 // Return nullptr if no information found. 82 // If information is present, return a pointer to object 83 // owned by this class. 84 const BTF::BPFLineInfo *findLineInfo(SectionedAddress Address) const; 85 86 // Search for CO-RE relocation information for a specific address. 87 // Return nullptr if no information found. 88 // If information is present, return a pointer to object 89 // owned by this class. 90 const BTF::BPFFieldReloc *findFieldReloc(SectionedAddress Address) const; 91 92 // Return a human readable representation of the CO-RE relocation 93 // record, this is for display purpose only. 94 // See implementation for details. 95 void symbolize(const BTF::BPFFieldReloc *Reloc, 96 SmallVectorImpl<char> &Result) const; 97 98 // Lookup BTF type definition with a specific index. 99 // Return nullptr if no information found. 100 // If information is present, return a pointer to object 101 // owned by this class. 102 const BTF::CommonType *findType(uint32_t Id) const; 103 104 // Return total number of known BTF types. typesCount()105 size_t typesCount() const { return Types.size(); } 106 107 // Allow to selectively load BTF information. 108 struct ParseOptions { 109 bool LoadLines = false; 110 bool LoadTypes = false; 111 bool LoadRelocs = false; 112 }; 113 114 // Fills instance of BTFParser with information stored in .BTF and 115 // .BTF.ext sections of the `Obj`. If this instance was already 116 // filled, old data is discarded. 117 // 118 // If information cannot be parsed: 119 // - return an error describing the failure; 120 // - state of the BTFParser might be incomplete but is not invalid, 121 // queries might be run against it, but some (or all) information 122 // might be unavailable; 123 Error parse(const ObjectFile &Obj, const ParseOptions &Opts); parse(const ObjectFile & Obj)124 Error parse(const ObjectFile &Obj) { return parse(Obj, {true, true, true}); } 125 126 // Return true if `Obj` has .BTF and .BTF.ext sections. 127 static bool hasBTFSections(const ObjectFile &Obj); 128 }; 129 130 } // namespace llvm 131 132 #endif // LLVM_DEBUGINFO_BTF_BTFPARSER_H 133