lib/Target/BPF/BTF.h

   1 //===-- BTF.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 /// \file
  10 /// This file contains the layout of .BTF and .BTF.ext ELF sections.
  11 ///
  12 /// The binary layout for .BTF section:
  13 ///   struct Header
  14 ///   Type and Str subsections
  15 /// The Type subsection is a collection of types with type id starting with 1.
  16 /// The Str subsection is simply a collection of strings.
  17 ///
  18 /// The binary layout for .BTF.ext section:
  19 ///   struct ExtHeader
  20 ///   FuncInfo, LineInfo, OffsetReloc and ExternReloc subsections
  21 /// The FuncInfo subsection is defined as below:
  22 ///   BTFFuncInfo Size
  23 ///   struct SecFuncInfo for ELF section #1
  24 ///   A number of struct BPFFuncInfo for ELF section #1
  25 ///   struct SecFuncInfo for ELF section #2
  26 ///   A number of struct BPFFuncInfo for ELF section #2
  27 ///   ...
  28 /// The LineInfo subsection is defined as below:
  29 ///   BPFLineInfo Size
  30 ///   struct SecLineInfo for ELF section #1
  31 ///   A number of struct BPFLineInfo for ELF section #1
  32 ///   struct SecLineInfo for ELF section #2
  33 ///   A number of struct BPFLineInfo for ELF section #2
  34 ///   ...
  35 /// The OffsetReloc subsection is defined as below:
  36 ///   BPFOffsetReloc Size
  37 ///   struct SecOffsetReloc for ELF section #1
  38 ///   A number of struct BPFOffsetReloc for ELF section #1
  39 ///   struct SecOffsetReloc for ELF section #2
  40 ///   A number of struct BPFOffsetReloc for ELF section #2
  41 ///   ...
  42 /// The ExternReloc subsection is defined as below:
  43 ///   BPFExternReloc Size
  44 ///   struct SecExternReloc for ELF section #1
  45 ///   A number of struct BPFExternReloc for ELF section #1
  46 ///   struct SecExternReloc for ELF section #2
  47 ///   A number of struct BPFExternReloc for ELF section #2
  48 ///   ...
  49 ///
  50 /// The section formats are also defined at
  51 ///    https://github.com/torvalds/linux/blob/master/include/uapi/linux/btf.h
  52 ///
  53 //===----------------------------------------------------------------------===//
  54
  55 #ifndef LLVM_LIB_TARGET_BPF_BTF_H
  56 #define LLVM_LIB_TARGET_BPF_BTF_H
  57
  58 namespace llvm {
  59 namespace BTF {
  60
  61 enum : uint32_t { MAGIC = 0xeB9F, VERSION = 1 };
  62
  63 /// Sizes in bytes of various things in the BTF format.
  64 enum {
  65   HeaderSize = 24,
  66   ExtHeaderSize = 40,
  67   CommonTypeSize = 12,
  68   BTFArraySize = 12,
  69   BTFEnumSize = 8,
  70   BTFMemberSize = 12,
  71   BTFParamSize = 8,
  72   BTFDataSecVarSize = 12,
  73   SecFuncInfoSize = 8,
  74   SecLineInfoSize = 8,
  75   SecOffsetRelocSize = 8,
  76   SecExternRelocSize = 8,
  77   BPFFuncInfoSize = 8,
  78   BPFLineInfoSize = 16,
  79   BPFOffsetRelocSize = 12,
  80   BPFExternRelocSize = 8,
  81 };
  82
  83 /// The .BTF section header definition.
  84 struct Header {
  85   uint16_t Magic;  ///< Magic value
  86   uint8_t Version; ///< Version number
  87   uint8_t Flags;   ///< Extra flags
  88   uint32_t HdrLen; ///< Length of this header
  89
  90   /// All offsets are in bytes relative to the end of this header.
  91   uint32_t TypeOff; ///< Offset of type section
  92   uint32_t TypeLen; ///< Length of type section
  93   uint32_t StrOff;  ///< Offset of string section
  94   uint32_t StrLen;  ///< Length of string section
  95 };
  96
  97 enum : uint32_t {
  98   MAX_VLEN = 0xffff ///< Max # of struct/union/enum members or func args
  99 };
 100
 101 enum TypeKinds : uint8_t {
 102 #define HANDLE_BTF_KIND(ID, NAME) BTF_KIND_##NAME = ID,
 103 #include "BTF.def"
 104 };
 105
 106 /// The BTF common type definition. Different kinds may have
 107 /// additional information after this structure data.
 108 struct CommonType {
 109   /// Type name offset in the string table.
 110   uint32_t NameOff;
 111
 112   /// "Info" bits arrangement:
 113   /// Bits  0-15: vlen (e.g. # of struct's members)
 114   /// Bits 16-23: unused
 115   /// Bits 24-27: kind (e.g. int, ptr, array...etc)
 116   /// Bits 28-30: unused
 117   /// Bit     31: kind_flag, currently used by
 118   ///             struct, union and fwd
 119   uint32_t Info;
 120
 121   /// "Size" is used by INT, ENUM, STRUCT and UNION.
 122   /// "Size" tells the size of the type it is describing.
 123   ///
 124   /// "Type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
 125   /// FUNC, FUNC_PROTO and VAR.
 126   /// "Type" is a type_id referring to another type.
 127   union {
 128     uint32_t Size;
 129     uint32_t Type;
 130   };
 131 };
 132
 133 // For some specific BTF_KIND, "struct CommonType" is immediately
 134 // followed by extra data.
 135
 136 // BTF_KIND_INT is followed by a u32 and the following
 137 // is the 32 bits arrangement:
 138 // BTF_INT_ENCODING(VAL) : (((VAL) & 0x0f000000) >> 24)
 139 // BTF_INT_OFFSET(VAL) : (((VAL & 0x00ff0000)) >> 16)
 140 // BTF_INT_BITS(VAL) : ((VAL) & 0x000000ff)
 141
 142 /// Attributes stored in the INT_ENCODING.
 143 enum : uint8_t {
 144   INT_SIGNED = (1 << 0),
 145   INT_CHAR = (1 << 1),
 146   INT_BOOL = (1 << 2)
 147 };
 148
 149 /// BTF_KIND_ENUM is followed by multiple "struct BTFEnum".
 150 /// The exact number of btf_enum is stored in the vlen (of the
 151 /// info in "struct CommonType").
 152 struct BTFEnum {
 153   uint32_t NameOff; ///< Enum name offset in the string table
 154   int32_t Val;      ///< Enum member value
 155 };
 156
 157 /// BTF_KIND_ARRAY is followed by one "struct BTFArray".
 158 struct BTFArray {
 159   uint32_t ElemType;  ///< Element type
 160   uint32_t IndexType; ///< Index type
 161   uint32_t Nelems;    ///< Number of elements for this array
 162 };
 163
 164 /// BTF_KIND_STRUCT and BTF_KIND_UNION are followed
 165 /// by multiple "struct BTFMember".  The exact number
 166 /// of BTFMember is stored in the vlen (of the info in
 167 /// "struct CommonType").
 168 ///
 169 /// If the struct/union contains any bitfield member,
 170 /// the Offset below represents BitOffset (bits 0 - 23)
 171 /// and BitFieldSize(bits 24 - 31) with BitFieldSize = 0
 172 /// for non bitfield members. Otherwise, the Offset
 173 /// represents the BitOffset.
 174 struct BTFMember {
 175   uint32_t NameOff; ///< Member name offset in the string table
 176   uint32_t Type;    ///< Member type
 177   uint32_t Offset;  ///< BitOffset or BitFieldSize+BitOffset
 178 };
 179
 180 /// BTF_KIND_FUNC_PROTO are followed by multiple "struct BTFParam".
 181 /// The exist number of BTFParam is stored in the vlen (of the info
 182 /// in "struct CommonType").
 183 struct BTFParam {
 184   uint32_t NameOff;
 185   uint32_t Type;
 186 };
 187
 188 /// Variable scoping information.
 189 enum : uint8_t {
 190   VAR_STATIC = 0,           ///< Linkage: InternalLinkage
 191   VAR_GLOBAL_ALLOCATED = 1, ///< Linkage: ExternalLinkage
 192   VAR_GLOBAL_TENTATIVE = 2, ///< Linkage: CommonLinkage
 193   VAR_GLOBAL_EXTERNAL = 3,  ///< Linkage: ExternalLinkage
 194 };
 195
 196 /// BTF_KIND_DATASEC are followed by multiple "struct BTFDataSecVar".
 197 /// The exist number of BTFDataSec is stored in the vlen (of the info
 198 /// in "struct CommonType").
 199 struct BTFDataSec {
 200   uint32_t Type;   ///< A BTF_KIND_VAR type
 201   uint32_t Offset; ///< In-section offset
 202   uint32_t Size;   ///< Occupied memory size
 203 };
 204
 205 /// The .BTF.ext section header definition.
 206 struct ExtHeader {
 207   uint16_t Magic;
 208   uint8_t Version;
 209   uint8_t Flags;
 210   uint32_t HdrLen;
 211
 212   uint32_t FuncInfoOff;    ///< Offset of func info section
 213   uint32_t FuncInfoLen;    ///< Length of func info section
 214   uint32_t LineInfoOff;    ///< Offset of line info section
 215   uint32_t LineInfoLen;    ///< Length of line info section
 216   uint32_t OffsetRelocOff; ///< Offset of offset reloc section
 217   uint32_t OffsetRelocLen; ///< Length of offset reloc section
 218   uint32_t ExternRelocOff; ///< Offset of extern reloc section
 219   uint32_t ExternRelocLen; ///< Length of extern reloc section
 220 };
 221
 222 /// Specifying one function info.
 223 struct BPFFuncInfo {
 224   uint32_t InsnOffset; ///< Byte offset in the section
 225   uint32_t TypeId;     ///< Type id referring to .BTF type section
 226 };
 227
 228 /// Specifying function info's in one section.
 229 struct SecFuncInfo {
 230   uint32_t SecNameOff;  ///< Section name index in the .BTF string table
 231   uint32_t NumFuncInfo; ///< Number of func info's in this section
 232 };
 233
 234 /// Specifying one line info.
 235 struct BPFLineInfo {
 236   uint32_t InsnOffset;  ///< Byte offset in this section
 237   uint32_t FileNameOff; ///< File name index in the .BTF string table
 238   uint32_t LineOff;     ///< Line index in the .BTF string table
 239   uint32_t LineCol;     ///< Line num: line_col >> 10,
 240                         ///  col num: line_col & 0x3ff
 241 };
 242
 243 /// Specifying line info's in one section.
 244 struct SecLineInfo {
 245   uint32_t SecNameOff;  ///< Section name index in the .BTF string table
 246   uint32_t NumLineInfo; ///< Number of line info's in this section
 247 };
 248
 249 /// Specifying one offset relocation.
 250 struct BPFOffsetReloc {
 251   uint32_t InsnOffset;    ///< Byte offset in this section
 252   uint32_t TypeID;        ///< TypeID for the relocation
 253   uint32_t OffsetNameOff; ///< The string to traverse types
 254 };
 255
 256 /// Specifying offset relocation's in one section.
 257 struct SecOffsetReloc {
 258   uint32_t SecNameOff;     ///< Section name index in the .BTF string table
 259   uint32_t NumOffsetReloc; ///< Number of offset reloc's in this section
 260 };
 261
 262 /// Specifying one offset relocation.
 263 struct BPFExternReloc {
 264   uint32_t InsnOffset;    ///< Byte offset in this section
 265   uint32_t ExternNameOff; ///< The string for external variable
 266 };
 267
 268 /// Specifying extern relocation's in one section.
 269 struct SecExternReloc {
 270   uint32_t SecNameOff;     ///< Section name index in the .BTF string table
 271   uint32_t NumExternReloc; ///< Number of extern reloc's in this section
 272 };
 273
 274 } // End namespace BTF.
 275 } // End namespace llvm.
 276
 277 #endif