include/btf.h

   1 /* Declarations and definitions relating to the BPF Type Format (BTF).
   2    Copyright (C) 2021-2024 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 /* Type ID 0 represents the void type.  */
  60 #define BTF_VOID_TYPEID 0
  61 /* Initial type ID for regular types.  */
  62 #define BTF_INIT_TYPEID 1
  63
  64 struct btf_type
  65 {
  66   uint32_t name_off;    /* Offset in string section of type name.  */
  67   uint32_t info;        /* Encoded kind, variant length, kind flag:
  68                            - bits  0-15: vlen
  69                            - bits 16-23: unused
  70                            - bits 24-28: kind
  71                            - bits 29-30: unused
  72                            - bit     31: kind_flag
  73                            See accessor macros below.  */
  74
  75   /* SIZE is used by INT, ENUM, STRUCT, UNION, DATASEC kinds.
  76      TYPE is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT, FUNC,
  77      FUNC_PROTO and VAR kinds.  */
  78   union
  79   {
  80     uint32_t size;      /* Size of the entire type, in bytes.  */
  81     uint32_t type;      /* A type_id referring to another type.  */
  82   };
  83 };
  84
  85 /* The following macros access the information encoded in btf_type.info.  */
  86 /* Type kind. See below.  */
  87 #define BTF_INFO_KIND(info)     (((info) >> 24) & 0x1f)
  88 /* Number of entries of variable length data following certain type kinds.
  89    For example, number of structure members, number of function parameters.  */
  90 #define BTF_INFO_VLEN(info)     ((info) & 0xffff)
  91 /* For BTF_KIND_FWD, 1 if forward to union, 0 if forward to struct.
  92    For BTF_KIND_STRUCT and BTF_KIND_UNION, 1 if the struct/union contains
  93    a bitfield.  */
  94 #define BTF_INFO_KFLAG(info)    ((info) >> 31)
  95
  96 /* Encoding for struct btf_type.info.  */
  97 #define BTF_TYPE_INFO(kind, kflag, vlen) \
  98   ((((kflag) ? 1 : 0 ) << 31) | ((kind & 0x1f) << 24) | ((vlen) & 0xffff))
  99
 100 #define BTF_KIND_UNKN           0       /* Unknown or invalid.  */
 101 #define BTF_KIND_INT            1       /* Integer.  */
 102 #define BTF_KIND_PTR            2       /* Pointer.  */
 103 #define BTF_KIND_ARRAY          3       /* Array.  */
 104 #define BTF_KIND_STRUCT         4       /* Struct.  */
 105 #define BTF_KIND_UNION          5       /* Union.  */
 106 #define BTF_KIND_ENUM           6       /* Enumeration.  */
 107 #define BTF_KIND_FWD            7       /* Forward.  */
 108 #define BTF_KIND_TYPEDEF        8       /* Typedef.  */
 109 #define BTF_KIND_VOLATILE       9       /* Referenced type is volatile.  */
 110 #define BTF_KIND_CONST          10      /* Referenced type is const.  */
 111 #define BTF_KIND_RESTRICT       11      /* Restrict.  */
 112 #define BTF_KIND_FUNC           12      /* Subprogram.  */
 113 #define BTF_KIND_FUNC_PROTO     13      /* Function Prototype.  */
 114 #define BTF_KIND_VAR            14      /* Variable.  */
 115 #define BTF_KIND_DATASEC        15      /* Section such as .bss or .data.  */
 116 #define BTF_KIND_FLOAT          16      /* Floating point.  */
 117 #define BTF_KIND_ENUM64         19      /* Enumeration up to 64 bits.  */
 118 #define BTF_KIND_MAX            BTF_KIND_ENUM64
 119 #define NR_BTF_KINDS            (BTF_KIND_MAX + 1)
 120
 121 /* For some BTF_KINDs, struct btf_type is immediately followed by
 122    additional data describing the type.  */
 123
 124 /* BTF_KIND_INT is followed by a 32-bit word, with the following
 125    bit arrangement.  */
 126 #define BTF_INT_ENCODING(VAL)   (((VAL) & 0x0f000000) >> 24)
 127 #define BTF_INT_OFFSET(VAL)     (((VAL) & 0x00ff0000) >> 16)
 128 #define BTF_INT_BITS(VAL)       ((VAL)  & 0x000000ff)
 129
 130 #define BTF_INT_DATA(encoding, offset, bits) \
 131   ((((encoding) & 0x0f) << 24) | (((offset) & 0xff) << 16) | ((bits) & 0xff))
 132
 133 /* BTF_INT_ENCODING holds the following attribute flags.  */
 134 #define BTF_INT_SIGNED  (1 << 0)
 135 #define BTF_INT_CHAR    (1 << 1)
 136 #define BTF_INT_BOOL    (1 << 2)
 137
 138 /* BTF_KIND_ENUM is followed by VLEN struct btf_enum entries,
 139    which describe the enumerators. */
 140 struct btf_enum
 141 {
 142   uint32_t name_off;    /* Offset in string section of enumerator name.  */
 143   int32_t  val;         /* Enumerator value.  */
 144 };
 145
 146 /* BTF_KF_ENUM_ holds the flags for kflags in BTF_KIND_ENUM{,64}.  */
 147 #define BTF_KF_ENUM_UNSIGNED    (0)
 148 #define BTF_KF_ENUM_SIGNED      (1 << 0)
 149
 150 /* BTF_KIND_ARRAY is followed by a single struct btf_array.  */
 151 struct btf_array
 152 {
 153   uint32_t type;        /* Type of array elements.  */
 154   uint32_t index_type;  /* Type of array index.  */
 155   uint32_t nelems;      /* Number of elements. 0 for unsized/variable length.  */
 156 };
 157
 158 /* BTF_KIND_STRUCT and BTF_KIND_UNION are followed by VLEN
 159    struct btf_member.  */
 160 struct btf_member
 161 {
 162   uint32_t name_off;    /* Offset in string section of member name.  */
 163   uint32_t type;        /* Type of member.  */
 164   uint32_t offset;      /* If the type info kind_flag is set, this contains
 165                            both the member bitfield size and bit offset,
 166                            according to the macros below. If kind_flag is not
 167                            set, offset contains only the bit offset (from the
 168                            beginning of the struct).  */
 169 };
 170
 171 /* If struct or union type info kind_flag is set, used to access member
 172    bitfield size from btf_member.offset.  */
 173 #define BTF_MEMBER_BITFIELD_SIZE (val)  ((val) >> 24)
 174 /* If struct or union type info kind_flag is set, used to access member
 175    bit offset from btf_member.offset.  */
 176 #define BTF_MEMBER_BIT_OFFSET (val)     ((val) & 0x00ffffff)
 177
 178 /* BTF_KIND_FUNC_PROTO is followed by VLEN struct btf_param entries, which
 179    describe the types of the function parameters.  */
 180 struct btf_param
 181 {
 182   uint32_t name_off;    /* Offset in string section of parameter name.  */
 183   uint32_t type;        /* Type of parameter.  */
 184 };
 185
 186 /* BTF_KIND_FUNC records encode linkage information in the VLEN bits
 187    of the type record.  These are the supported values.  */
 188 enum btf_func_linkage
 189 {
 190   BTF_FUNC_STATIC = 0,
 191   BTF_FUNC_GLOBAL = 1,
 192   BTF_FUNC_EXTERN = 2,
 193 };
 194
 195 /* BTF_KIND_VAR records encode linkage information in a single
 196    trailing struct btf_var.  These are the supported values.  */
 197 enum btf_var_linkage
 198 {
 199   BTF_VAR_STATIC = 0,
 200   BTF_VAR_GLOBAL_ALLOCATED = 1,
 201   BTF_VAR_GLOBAL_EXTERN = 2,
 202 };
 203
 204 /* BTF_KIND_VAR is followed by a single struct btf_var, which describes
 205    information about the variable.  */
 206 struct btf_var
 207 {
 208   uint32_t linkage;     /* 0=static, 1=global, 2=extern.  */
 209 };
 210
 211 /* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
 212    which describe all BTF_KIND_VAR or extern BTF_KIND_FUNC types contained
 213    in the section.  */
 214 struct btf_var_secinfo
 215 {
 216   uint32_t type;        /* Type of BTF_KIND_VAR or BTF_KIND_FUNC item.  */
 217   uint32_t offset;      /* In-section offset (in bytes) of item.  */
 218   uint32_t size;        /* Size (in bytes) of item.  */
 219 };
 220
 221 /* BTF_KIND_ENUM64 is followed by VLEN struct btf_enum64 entries,
 222    which describe the 64 bits enumerators.  */
 223 struct btf_enum64
 224 {
 225   uint32_t name_off;    /* Offset in string section of enumerator name.  */
 226   uint32_t val_lo32;    /* lower 32-bit value for a 64-bit value Enumerator */
 227   uint32_t val_hi32;    /* high 32-bit value for a 64-bit value Enumerator */
 228 };
 229
 230 #ifdef  __cplusplus
 231 }
 232 #endif
 233
 234 #endif /* _BTF_H_ */