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/* Declarations and definitions relating to the BPF Type Format (BTF).
Copyright (C) 2021-2024 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
License for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
/* This file is derived from the BTF specification described in the
Linux kernel source tree (linux/Documentation/bpf/btf.rst). */
#ifndef _BTF_H_
#define _BTF_H_
#include <stdint.h>
#ifdef __cplusplus
extern "C"
{
#endif
/* BTF magic number to identify header, endianness. */
#define BTF_MAGIC 0xeb9f
/* Data format version number. */
#define BTF_VERSION 1
struct btf_header
{
uint16_t magic; /* Magic number (BTF_MAGIC). */
uint8_t version; /* Data format version (BTF_VERSION). */
uint8_t flags; /* Flags. Currently unused. */
uint32_t hdr_len; /* Length of this header (sizeof (struct btf_header)). */
/* Following offsets are relative to the end of this header. */
uint32_t type_off; /* Offset of type section, in bytes. */
uint32_t type_len; /* Length of type section, in bytes. */
uint32_t str_off; /* Offset of string section, in bytes. */
uint32_t str_len; /* Length of string section, in bytes. */
};
/* Maximum type identifier. */
#define BTF_MAX_TYPE 0x000fffff
/* Maximum offset into the string section. */
#define BTF_MAX_NAME_OFFSET 0x00ffffff
/* Maximum number of struct, union, enum members or func args. */
#define BTF_MAX_VLEN 0xffff
/* Type ID 0 represents the void type. */
#define BTF_VOID_TYPEID 0
/* Initial type ID for regular types. */
#define BTF_INIT_TYPEID 1
struct btf_type
{
uint32_t name_off; /* Offset in string section of type name. */
uint32_t info; /* Encoded kind, variant length, kind flag:
- bits 0-15: vlen
- bits 16-23: unused
- bits 24-28: kind
- bits 29-30: unused
- bit 31: kind_flag
See accessor macros below. */
/* SIZE is used by INT, ENUM, STRUCT, UNION, DATASEC kinds.
TYPE is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT, FUNC,
FUNC_PROTO and VAR kinds. */
union
{
uint32_t size; /* Size of the entire type, in bytes. */
uint32_t type; /* A type_id referring to another type. */
};
};
/* The folloing macros access the information encoded in btf_type.info. */
/* Type kind. See below. */
#define BTF_INFO_KIND(info) (((info) >> 24) & 0x1f)
/* Number of entries of variable length data following certain type kinds.
For example, number of structure members, number of function parameters. */
#define BTF_INFO_VLEN(info) ((info) & 0xffff)
/* For BTF_KIND_FWD, 1 if forward to union, 0 if forward to struct.
For BTF_KIND_STRUCT and BTF_KIND_UNION, 1 if the struct/union contains
a bitfield. */
#define BTF_INFO_KFLAG(info) ((info) >> 31)
/* Encoding for struct btf_type.info. */
#define BTF_TYPE_INFO(kind, kflag, vlen) \
((((kflag) ? 1 : 0 ) << 31) | ((kind) << 24) | ((vlen) & 0xffff))
#define BTF_KIND_UNKN 0 /* Unknown or invalid. */
#define BTF_KIND_INT 1 /* Integer. */
#define BTF_KIND_PTR 2 /* Pointer. */
#define BTF_KIND_ARRAY 3 /* Array. */
#define BTF_KIND_STRUCT 4 /* Struct. */
#define BTF_KIND_UNION 5 /* Union. */
#define BTF_KIND_ENUM 6 /* Enumeration. */
#define BTF_KIND_FWD 7 /* Forward. */
#define BTF_KIND_TYPEDEF 8 /* Typedef. */
#define BTF_KIND_VOLATILE 9 /* Referenced type is volatile. */
#define BTF_KIND_CONST 10 /* Referenced type is const. */
#define BTF_KIND_RESTRICT 11 /* Restrict. */
#define BTF_KIND_FUNC 12 /* Subprogram. */
#define BTF_KIND_FUNC_PROTO 13 /* Function Prototype. */
#define BTF_KIND_VAR 14 /* Variable. */
#define BTF_KIND_DATASEC 15 /* Section such as .bss or .data. */
#define BTF_KIND_FLOAT 16 /* Floating point. */
#define BTF_KIND_ENUM64 19 /* Enumeration up to 64 bits. */
#define BTF_KIND_MAX BTF_KIND_ENUM64
#define NR_BTF_KINDS (BTF_KIND_MAX + 1)
/* For some BTF_KINDs, struct btf_type is immediately followed by
additional data describing the type. */
/* BTF_KIND_INT is followed by a 32-bit word, with the following
bit arrangement. */
#define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24)
#define BTF_INT_OFFSET(VAL) (((VAL) & 0x00ff0000) >> 16)
#define BTF_INT_BITS(VAL) ((VAL) & 0x000000ff)
#define BTF_INT_DATA(encoding, offset, bits) \
((((encoding) & 0x0f) << 24) | (((offset) & 0xff) << 16) | ((bits) & 0xff))
/* BTF_INT_ENCODING holds the following attribute flags. */
#define BTF_INT_SIGNED (1 << 0)
#define BTF_INT_CHAR (1 << 1)
#define BTF_INT_BOOL (1 << 2)
/* BTF_KIND_ENUM is followed by VLEN struct btf_enum entries,
which describe the enumerators. */
struct btf_enum
{
uint32_t name_off; /* Offset in string section of enumerator name. */
int32_t val; /* Enumerator value. */
};
/* BTF_KF_ENUM_ holds the flags for kflags in BTF_KIND_ENUM{,64}. */
#define BTF_KF_ENUM_UNSIGNED (0)
#define BTF_KF_ENUM_SIGNED (1 << 0)
/* BTF_KIND_ARRAY is followed by a single struct btf_array. */
struct btf_array
{
uint32_t type; /* Type of array elements. */
uint32_t index_type; /* Type of array index. */
uint32_t nelems; /* Number of elements. 0 for unsized/variable length. */
};
/* BTF_KIND_STRUCT and BTF_KIND_UNION are followed by VLEN
struct btf_member. */
struct btf_member
{
uint32_t name_off; /* Offset in string section of member name. */
uint32_t type; /* Type of member. */
uint32_t offset; /* If the type info kind_flag is set, this contains
both the member bitfield size and bit offset,
according to the macros below. If kind_flag is not
set, offset contains only the bit offset (from the
beginning of the struct). */
};
/* If struct or union type info kind_flag is set, used to access member
bitfield size from btf_member.offset. */
#define BTF_MEMBER_BITFIELD_SIZE (val) ((val) >> 24)
/* If struct or union type info kind_flag is set, used to access member
bit offset from btf_member.offset. */
#define BTF_MEMBER_BIT_OFFSET (val) ((val) & 0x00ffffff)
/* BTF_KIND_FUNC_PROTO is followed by VLEN struct btf_param entries, which
describe the types of the function parameters. */
struct btf_param
{
uint32_t name_off; /* Offset in string section of parameter name. */
uint32_t type; /* Type of parameter. */
};
/* BTF_KIND_FUNC records encode linkage information in the VLEN bits
of the type record. These are the supported values. */
enum btf_func_linkage
{
BTF_FUNC_STATIC = 0,
BTF_FUNC_GLOBAL = 1,
BTF_FUNC_EXTERN = 2,
};
/* BTF_KIND_VAR records encode linkage information in a single
trailing struct btf_var. These are the supported values. */
enum btf_var_linkage
{
BTF_VAR_STATIC = 0,
BTF_VAR_GLOBAL_ALLOCATED = 1,
BTF_VAR_GLOBAL_EXTERN = 2,
};
/* BTF_KIND_VAR is followed by a single struct btf_var, which describes
information about the variable. */
struct btf_var
{
uint32_t linkage; /* 0=static, 1=global, 2=extern. */
};
/* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
which describe all BTF_KIND_VAR or extern BTF_KIND_FUNC types contained
in the section. */
struct btf_var_secinfo
{
uint32_t type; /* Type of BTF_KIND_VAR or BTF_KIND_FUNC item. */
uint32_t offset; /* In-section offset (in bytes) of item. */
uint32_t size; /* Size (in bytes) of item. */
};
/* BTF_KIND_ENUM64 is followed by VLEN struct btf_enum64 entries,
which describe the 64 bits enumerators. */
struct btf_enum64
{
uint32_t name_off; /* Offset in string section of enumerator name. */
uint32_t val_lo32; /* lower 32-bit value for a 64-bit value Enumerator */
uint32_t val_hi32; /* high 32-bit value for a 64-bit value Enumerator */
};
#ifdef __cplusplus
}
#endif
#endif /* _BTF_H_ */