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, FieldReloc 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 FieldReloc subsection is defined as below:
36/// BPFFieldReloc Size
37/// struct SecFieldReloc for ELF section #1
38/// A number of struct BPFFieldReloc for ELF section #1
39/// struct SecFieldReloc for ELF section #2
40/// A number of struct BPFFieldReloc for ELF section #2
41/// ...
42///
43/// The section formats are also defined at
44/// https://github.com/torvalds/linux/blob/master/include/uapi/linux/btf.h
45///
46//===----------------------------------------------------------------------===//
47
48#ifndef LLVM_LIB_TARGET_BPF_BTF_H
49#define LLVM_LIB_TARGET_BPF_BTF_H
50
51#include "llvm/ADT/ArrayRef.h"
52#include "llvm/Support/TrailingObjects.h"
53
54namespace llvm {
55namespace BTF {
56
57enum : uint32_t { MAGIC = 0xeB9F, VERSION = 1 };
58
59/// Sizes in bytes of various things in the BTF format.
60enum {
61 HeaderSize = 24,
62 ExtHeaderSize = 32,
63 CommonTypeSize = 12,
64 BTFArraySize = 12,
65 BTFEnumSize = 8,
66 BTFEnum64Size = 12,
67 BTFMemberSize = 12,
68 BTFParamSize = 8,
69 BTFDataSecVarSize = 12,
70 SecFuncInfoSize = 8,
71 SecLineInfoSize = 8,
72 SecFieldRelocSize = 8,
73 BPFFuncInfoSize = 8,
74 BPFLineInfoSize = 16,
75 BPFFieldRelocSize = 16,
76};
77
78/// The .BTF section header definition.
79struct Header {
80 uint16_t Magic; ///< Magic value
81 uint8_t Version; ///< Version number
82 uint8_t Flags; ///< Extra flags
83 uint32_t HdrLen; ///< Length of this header
84
85 /// All offsets are in bytes relative to the end of this header.
86 uint32_t TypeOff; ///< Offset of type section
87 uint32_t TypeLen; ///< Length of type section
88 uint32_t StrOff; ///< Offset of string section
89 uint32_t StrLen; ///< Length of string section
90};
91
92enum : uint32_t {
93 MAX_VLEN = 0xffff ///< Max # of struct/union/enum members or func args
94};
95
96enum TypeKinds : uint8_t {
97#define HANDLE_BTF_KIND(ID, NAME) BTF_KIND_##NAME = ID,
98#include "BTF.def"
99};
100
101// Constants for CommonType::Info field.
102constexpr uint32_t FWD_UNION_FLAG = 1u << 31;
103constexpr uint32_t ENUM_SIGNED_FLAG = 1u << 31;
104
105/// The BTF common type definition. Different kinds may have
106/// additional information after this structure data.
107struct CommonType {
108 /// Type name offset in the string table.
109 uint32_t NameOff;
110
111 /// "Info" bits arrangement:
112 /// Bits 0-15: vlen (e.g. # of struct's members)
113 /// Bits 16-23: unused
114 /// Bits 24-28: kind (e.g. int, ptr, array...etc)
115 /// Bits 29-30: unused
116 /// Bit 31: kind_flag, currently used by
117 /// struct, union and fwd
118 uint32_t Info;
119
120 /// "Size" is used by INT, ENUM, STRUCT and UNION.
121 /// "Size" tells the size of the type it is describing.
122 ///
123 /// "Type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
124 /// FUNC, FUNC_PROTO, VAR, DECL_TAG and TYPE_TAG.
125 /// "Type" is a type_id referring to another type.
126 union {
127 uint32_t Size;
128 uint32_t Type;
129 };
130
131 uint32_t getKind() const { return Info >> 24 & 0x1f; }
132 uint32_t getVlen() const { return Info & 0xffff; }
133};
134
135// For some specific BTF_KIND, "struct CommonType" is immediately
136// followed by extra data.
137
138// BTF_KIND_INT is followed by a u32 and the following
139// is the 32 bits arrangement:
140// BTF_INT_ENCODING(VAL) : (((VAL) & 0x0f000000) >> 24)
141// BTF_INT_OFFSET(VAL) : (((VAL & 0x00ff0000)) >> 16)
142// BTF_INT_BITS(VAL) : ((VAL) & 0x000000ff)
143
144/// Attributes stored in the INT_ENCODING.
145enum : uint8_t {
146 INT_SIGNED = (1 << 0),
147 INT_CHAR = (1 << 1),
148 INT_BOOL = (1 << 2)
149};
150
151/// BTF_KIND_ENUM is followed by multiple "struct BTFEnum".
152/// The exact number of btf_enum is stored in the vlen (of the
153/// info in "struct CommonType").
154struct BTFEnum {
155 uint32_t NameOff; ///< Enum name offset in the string table
156 int32_t Val; ///< Enum member value
157};
158
159/// BTF_KIND_ENUM64 is followed by multiple "struct BTFEnum64".
160/// The exact number of BTFEnum64 is stored in the vlen (of the
161/// info in "struct CommonType").
162struct BTFEnum64 {
163 uint32_t NameOff; ///< Enum name offset in the string table
164 uint32_t Val_Lo32; ///< Enum member lo32 value
165 uint32_t Val_Hi32; ///< Enum member hi32 value
166};
167
168/// BTF_KIND_ARRAY is followed by one "struct BTFArray".
169struct BTFArray {
170 uint32_t ElemType; ///< Element type
171 uint32_t IndexType; ///< Index type
172 uint32_t Nelems; ///< Number of elements for this array
173};
174
175/// BTF_KIND_STRUCT and BTF_KIND_UNION are followed
176/// by multiple "struct BTFMember". The exact number
177/// of BTFMember is stored in the vlen (of the info in
178/// "struct CommonType").
179///
180/// If the struct/union contains any bitfield member,
181/// the Offset below represents BitOffset (bits 0 - 23)
182/// and BitFieldSize(bits 24 - 31) with BitFieldSize = 0
183/// for non bitfield members. Otherwise, the Offset
184/// represents the BitOffset.
185struct BTFMember {
186 uint32_t NameOff; ///< Member name offset in the string table
187 uint32_t Type; ///< Member type
188 uint32_t Offset; ///< BitOffset or BitFieldSize+BitOffset
189};
190
191/// BTF_KIND_FUNC_PROTO are followed by multiple "struct BTFParam".
192/// The exist number of BTFParam is stored in the vlen (of the info
193/// in "struct CommonType").
194struct BTFParam {
195 uint32_t NameOff;
196 uint32_t Type;
197};
198
199/// BTF_KIND_FUNC can be global, static or extern.
200enum : uint8_t {
201 FUNC_STATIC = 0,
202 FUNC_GLOBAL = 1,
203 FUNC_EXTERN = 2,
204};
205
206/// Variable scoping information.
207enum : uint8_t {
208 VAR_STATIC = 0, ///< Linkage: InternalLinkage
209 VAR_GLOBAL_ALLOCATED = 1, ///< Linkage: ExternalLinkage
210 VAR_GLOBAL_EXTERNAL = 2, ///< Linkage: ExternalLinkage
211};
212
213/// BTF_KIND_DATASEC are followed by multiple "struct BTFDataSecVar".
214/// The exist number of BTFDataSec is stored in the vlen (of the info
215/// in "struct CommonType").
216struct BTFDataSec {
217 uint32_t Type; ///< A BTF_KIND_VAR type
218 uint32_t Offset; ///< In-section offset
219 uint32_t Size; ///< Occupied memory size
220};
221
222/// The .BTF.ext section header definition.
223struct ExtHeader {
224 uint16_t Magic;
225 uint8_t Version;
226 uint8_t Flags;
227 uint32_t HdrLen;
228
229 uint32_t FuncInfoOff; ///< Offset of func info section
230 uint32_t FuncInfoLen; ///< Length of func info section
231 uint32_t LineInfoOff; ///< Offset of line info section
232 uint32_t LineInfoLen; ///< Length of line info section
233 uint32_t FieldRelocOff; ///< Offset of offset reloc section
234 uint32_t FieldRelocLen; ///< Length of offset reloc section
235};
236
237/// Specifying one function info.
238struct BPFFuncInfo {
239 uint32_t InsnOffset; ///< Byte offset in the section
240 uint32_t TypeId; ///< Type id referring to .BTF type section
241};
242
243/// Specifying function info's in one section.
244struct SecFuncInfo {
245 uint32_t SecNameOff; ///< Section name index in the .BTF string table
246 uint32_t NumFuncInfo; ///< Number of func info's in this section
247};
248
249/// Specifying one line info.
250struct BPFLineInfo {
251 uint32_t InsnOffset; ///< Byte offset in this section
252 uint32_t FileNameOff; ///< File name index in the .BTF string table
253 uint32_t LineOff; ///< Line index in the .BTF string table
254 uint32_t LineCol; ///< Line num: line_col >> 10,
255 /// col num: line_col & 0x3ff
256 uint32_t getLine() const { return LineCol >> 10; }
257 uint32_t getCol() const { return LineCol & 0x3ff; }
258};
259
260/// Specifying line info's in one section.
261struct SecLineInfo {
262 uint32_t SecNameOff; ///< Section name index in the .BTF string table
263 uint32_t NumLineInfo; ///< Number of line info's in this section
264};
265
266/// Specifying one offset relocation.
267struct BPFFieldReloc {
268 uint32_t InsnOffset; ///< Byte offset in this section
269 uint32_t TypeID; ///< TypeID for the relocation
270 uint32_t OffsetNameOff; ///< The string to traverse types
271 uint32_t RelocKind; ///< What to patch the instruction
272};
273
274/// Specifying offset relocation's in one section.
275struct SecFieldReloc {
276 uint32_t SecNameOff; ///< Section name index in the .BTF string table
277 uint32_t NumFieldReloc; ///< Number of offset reloc's in this section
278};
279
280/// CO-RE relocation kind codes used in .BTF.ext section.
281enum PatchableRelocKind : uint32_t {
282 FIELD_BYTE_OFFSET = 0,
283 FIELD_BYTE_SIZE,
284 FIELD_EXISTENCE,
285 FIELD_SIGNEDNESS,
286 FIELD_LSHIFT_U64,
287 FIELD_RSHIFT_U64,
288 BTF_TYPE_ID_LOCAL,
289 BTF_TYPE_ID_REMOTE,
290 TYPE_EXISTENCE,
291 TYPE_SIZE,
292 ENUM_VALUE_EXISTENCE,
293 ENUM_VALUE,
294 TYPE_MATCH,
295 MAX_FIELD_RELOC_KIND,
296};
297
298// Define a number of sub-types for CommonType, each with:
299// - An accessor for a relevant "tail" information (data fields that
300// follow the CommonType record in binary format).
301// - A classof() definition based on CommonType::getKind() value to
302// allow use with dyn_cast<>() function.
303
304// For CommonType sub-types that are followed by a single entry of
305// some type in the binary format.
306#define BTF_DEFINE_TAIL(Type, Accessor) \
307 const Type &Accessor() const { return *getTrailingObjects<Type>(); }
308
309// For CommonType sub-types that are followed by CommonType::getVlen()
310// number of entries of some type in the binary format.
311#define BTF_DEFINE_TAIL_ARR(Type, Accessor) \
312 ArrayRef<Type> Accessor() const { \
313 return ArrayRef<Type>(getTrailingObjects<Type>(), getVlen()); \
314 }
315
316struct ArrayType final : CommonType,
317 private TrailingObjects<ArrayType, BTFArray> {
318 friend TrailingObjects;
319 BTF_DEFINE_TAIL(BTFArray, getArray)
320
321 static bool classof(const CommonType *V) {
322 return V->getKind() == BTF_KIND_ARRAY;
323 }
324};
325
326struct StructType final : CommonType,
327 private TrailingObjects<StructType, BTFMember> {
328 friend TrailingObjects;
329 BTF_DEFINE_TAIL_ARR(BTFMember, members)
330
331 static bool classof(const CommonType *V) {
332 return V->getKind() == BTF_KIND_STRUCT || V->getKind() == BTF_KIND_UNION;
333 }
334};
335
336struct EnumType final : CommonType, private TrailingObjects<EnumType, BTFEnum> {
337 friend TrailingObjects;
338 BTF_DEFINE_TAIL_ARR(BTFEnum, values)
339
340 static bool classof(const CommonType *V) {
341 return V->getKind() == BTF_KIND_ENUM;
342 }
343};
344
345struct Enum64Type final : CommonType,
346 private TrailingObjects<Enum64Type, BTFEnum64> {
347 friend TrailingObjects;
348 BTF_DEFINE_TAIL_ARR(BTFEnum64, values)
349
350 static bool classof(const CommonType *V) {
351 return V->getKind() == BTF_KIND_ENUM64;
352 }
353};
354
355#undef BTF_DEFINE_TAIL
356#undef BTF_DEFINE_TAIL_ARR
357
358} // End namespace BTF.
359} // End namespace llvm.
360
361#endif
362