1 /* Declarations and definitions relating to the BPF Type Format (BTF).
2 Copyright (C) 2021-2023 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
14 License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20 /* This file is derived from the BTF specification described in the
21 Linux kernel source tree (linux/Documentation/bpf/btf.rst). */
22
23 #ifndef _BTF_H_
24 #define _BTF_H_
25
26 #include <stdint.h>
27
28 #ifdef __cplusplus
29 extern "C"
30 {
31 #endif
32
33 /* BTF magic number to identify header, endianness. */
34 #define BTF_MAGIC 0xeb9f
35 /* Data format version number. */
36 #define BTF_VERSION 1
37
38 struct btf_header
39 {
40 uint16_t magic; /* Magic number (BTF_MAGIC). */
41 uint8_t version; /* Data format version (BTF_VERSION). */
42 uint8_t flags; /* Flags. Currently unused. */
43 uint32_t hdr_len; /* Length of this header (sizeof (struct btf_header)). */
44
45 /* Following offsets are relative to the end of this header. */
46 uint32_t type_off; /* Offset of type section, in bytes. */
47 uint32_t type_len; /* Length of type section, in bytes. */
48 uint32_t str_off; /* Offset of string section, in bytes. */
49 uint32_t str_len; /* Length of string section, in bytes. */
50 };
51
52 /* Maximum type identifier. */
53 #define BTF_MAX_TYPE 0x000fffff
54 /* Maximum offset into the string section. */
55 #define BTF_MAX_NAME_OFFSET 0x00ffffff
56 /* Maximum number of struct, union, enum members or func args. */
57 #define BTF_MAX_VLEN 0xffff
58
59 struct btf_type
60 {
61 uint32_t name_off; /* Offset in string section of type name. */
62 uint32_t info; /* Encoded kind, variant length, kind flag:
63 - bits 0-15: vlen
64 - bits 16-23: unused
65 - bits 24-28: kind
66 - bits 29-30: unused
67 - bit 31: kind_flag
68 See accessor macros below. */
69
70 /* SIZE is used by INT, ENUM, STRUCT, UNION, DATASEC kinds.
71 TYPE is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT, FUNC,
72 FUNC_PROTO and VAR kinds. */
73 union
74 {
75 uint32_t size; /* Size of the entire type, in bytes. */
76 uint32_t type; /* A type_id referring to another type. */
77 };
78 };
79
80 /* The folloing macros access the information encoded in btf_type.info. */
81 /* Type kind. See below. */
82 #define BTF_INFO_KIND(info) (((info) >> 24) & 0x1f)
83 /* Number of entries of variable length data following certain type kinds.
84 For example, number of structure members, number of function parameters. */
85 #define BTF_INFO_VLEN(info) ((info) & 0xffff)
86 /* For BTF_KIND_FWD, 1 if forward to union, 0 if forward to struct.
87 For BTF_KIND_STRUCT and BTF_KIND_UNION, 1 if the struct/union contains
88 a bitfield. */
89 #define BTF_INFO_KFLAG(info) ((info) >> 31)
90
91 /* Encoding for struct btf_type.info. */
92 #define BTF_TYPE_INFO(kind, kflag, vlen) \
93 ((((kflag) ? 1 : 0 ) << 31) | ((kind) << 24) | ((vlen) & 0xffff))
94
95 #define BTF_KIND_UNKN 0 /* Unknown or invalid. */
96 #define BTF_KIND_INT 1 /* Integer. */
97 #define BTF_KIND_PTR 2 /* Pointer. */
98 #define BTF_KIND_ARRAY 3 /* Array. */
99 #define BTF_KIND_STRUCT 4 /* Struct. */
100 #define BTF_KIND_UNION 5 /* Union. */
101 #define BTF_KIND_ENUM 6 /* Enumeration. */
102 #define BTF_KIND_FWD 7 /* Forward. */
103 #define BTF_KIND_TYPEDEF 8 /* Typedef. */
104 #define BTF_KIND_VOLATILE 9 /* Referenced type is volatile. */
105 #define BTF_KIND_CONST 10 /* Referenced type is const. */
106 #define BTF_KIND_RESTRICT 11 /* Restrict. */
107 #define BTF_KIND_FUNC 12 /* Subprogram. */
108 #define BTF_KIND_FUNC_PROTO 13 /* Function Prototype. */
109 #define BTF_KIND_VAR 14 /* Variable. */
110 #define BTF_KIND_DATASEC 15 /* Section such as .bss or .data. */
111 #define BTF_KIND_FLOAT 16 /* Floating point. */
112 #define BTF_KIND_ENUM64 19 /* Enumeration up to 64 bits. */
113 #define BTF_KIND_MAX BTF_KIND_ENUM64
114 #define NR_BTF_KINDS (BTF_KIND_MAX + 1)
115
116 /* For some BTF_KINDs, struct btf_type is immediately followed by
117 additional data describing the type. */
118
119 /* BTF_KIND_INT is followed by a 32-bit word, with the following
120 bit arrangement. */
121 #define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24)
122 #define BTF_INT_OFFSET(VAL) (((VAL) & 0x00ff0000) >> 16)
123 #define BTF_INT_BITS(VAL) ((VAL) & 0x000000ff)
124
125 #define BTF_INT_DATA(encoding, offset, bits) \
126 ((((encoding) & 0x0f) << 24) | (((offset) & 0xff) << 16) | ((bits) & 0xff))
127
128 /* BTF_INT_ENCODING holds the following attribute flags. */
129 #define BTF_INT_SIGNED (1 << 0)
130 #define BTF_INT_CHAR (1 << 1)
131 #define BTF_INT_BOOL (1 << 2)
132
133 /* BTF_KIND_ENUM is followed by VLEN struct btf_enum entries,
134 which describe the enumerators. */
135 struct btf_enum
136 {
137 uint32_t name_off; /* Offset in string section of enumerator name. */
138 int32_t val; /* Enumerator value. */
139 };
140
141 /* BTF_KF_ENUM_ holds the flags for kflags in BTF_KIND_ENUM{,64}. */
142 #define BTF_KF_ENUM_UNSIGNED (0)
143 #define BTF_KF_ENUM_SIGNED (1 << 0)
144
145 /* BTF_KIND_ARRAY is followed by a single struct btf_array. */
146 struct btf_array
147 {
148 uint32_t type; /* Type of array elements. */
149 uint32_t index_type; /* Type of array index. */
150 uint32_t nelems; /* Number of elements. 0 for unsized/variable length. */
151 };
152
153 /* BTF_KIND_STRUCT and BTF_KIND_UNION are followed by VLEN
154 struct btf_member. */
155 struct btf_member
156 {
157 uint32_t name_off; /* Offset in string section of member name. */
158 uint32_t type; /* Type of member. */
159 uint32_t offset; /* If the type info kind_flag is set, this contains
160 both the member bitfield size and bit offset,
161 according to the macros below. If kind_flag is not
162 set, offset contains only the bit offset (from the
163 beginning of the struct). */
164 };
165
166 /* If struct or union type info kind_flag is set, used to access member
167 bitfield size from btf_member.offset. */
168 #define BTF_MEMBER_BITFIELD_SIZE (val) ((val) >> 24)
169 /* If struct or union type info kind_flag is set, used to access member
170 bit offset from btf_member.offset. */
171 #define BTF_MEMBER_BIT_OFFSET (val) ((val) & 0x00ffffff)
172
173 /* BTF_KIND_FUNC_PROTO is followed by VLEN struct btf_param entries, which
174 describe the types of the function parameters. */
175 struct btf_param
176 {
177 uint32_t name_off; /* Offset in string section of parameter name. */
178 uint32_t type; /* Type of parameter. */
179 };
180
181 /* BTF_KIND_FUNC records encode linkage information in the VLEN bits
182 of the type record. These are the supported values. */
183 enum btf_func_linkage
184 {
185 BTF_FUNC_STATIC = 0,
186 BTF_FUNC_GLOBAL = 1,
187 BTF_FUNC_EXTERN = 2,
188 };
189
190 /* BTF_KIND_VAR records encode linkage information in a single
191 trailing struct btf_var. These are the supported values. */
192 enum btf_var_linkage
193 {
194 BTF_VAR_STATIC = 0,
195 BTF_VAR_GLOBAL_ALLOCATED = 1,
196 BTF_VAR_GLOBAL_EXTERN = 2,
197 };
198
199 /* BTF_KIND_VAR is followed by a single struct btf_var, which describes
200 information about the variable. */
201 struct btf_var
202 {
203 uint32_t linkage; /* 0=static, 1=global, 2=extern. */
204 };
205
206 /* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
207 which describe all BTF_KIND_VAR or extern BTF_KIND_FUNC types contained
208 in the section. */
209 struct btf_var_secinfo
210 {
211 uint32_t type; /* Type of BTF_KIND_VAR or BTF_KIND_FUNC item. */
212 uint32_t offset; /* In-section offset (in bytes) of item. */
213 uint32_t size; /* Size (in bytes) of item. */
214 };
215
216 /* BTF_KIND_ENUM64 is followed by VLEN struct btf_enum64 entries,
217 which describe the 64 bits enumerators. */
218 struct btf_enum64
219 {
220 uint32_t name_off; /* Offset in string section of enumerator name. */
221 uint32_t val_lo32; /* lower 32-bit value for a 64-bit value Enumerator */
222 uint32_t val_hi32; /* high 32-bit value for a 64-bit value Enumerator */
223 };
224
225 #ifdef __cplusplus
226 }
227 #endif
228
229 #endif /* _BTF_H_ */