cregit-Linux how code gets into the kernel

Release 4.18 include/uapi/linux/btf.h

/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/* Copyright (c) 2018 Facebook */
#ifndef _UAPI__LINUX_BTF_H__

#define _UAPI__LINUX_BTF_H__

#include <linux/types.h>


#define BTF_MAGIC	0xeB9F

#define BTF_VERSION	1


struct btf_header {
	
__u16	magic;
	
__u8	version;
	
__u8	flags;
	
__u32	hdr_len;

	/* All offsets are in bytes relative to the end of this header */
	
__u32	type_off;	/* offset of type section       */
	
__u32	type_len;	/* length of type section       */
	
__u32	str_off;	/* offset of string section     */
	
__u32	str_len;	/* length of string section     */
};

/* Max # of type identifier */

#define BTF_MAX_TYPE	0x0000ffff
/* Max offset into the string section */

#define BTF_MAX_NAME_OFFSET	0x0000ffff
/* Max # of struct/union/enum members or func args */

#define BTF_MAX_VLEN	0xffff


struct btf_type {
	
__u32 name_off;
	/* "info" bits arrangement
         * bits  0-15: vlen (e.g. # of struct's members)
         * bits 16-23: unused
         * bits 24-27: kind (e.g. int, ptr, array...etc)
         * bits 28-31: unused
         */
	
__u32 info;
	/* "size" is used by INT, ENUM, STRUCT and UNION.
         * "size" tells the size of the type it is describing.
         *
         * "type" is used by PTR, TYPEDEF, VOLATILE, CONST and RESTRICT.
         * "type" is a type_id referring to another type.
         */
	
union {
		
__u32 size;
		
__u32 type;
	};
};


#define BTF_INFO_KIND(info)	(((info) >> 24) & 0x0f)

#define BTF_INFO_VLEN(info)	((info) & 0xffff)


#define BTF_KIND_UNKN		0	
/* Unknown      */

#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	
/* Volatile     */

#define BTF_KIND_CONST		10	
/* Const        */

#define BTF_KIND_RESTRICT	11	
/* Restrict     */

#define BTF_KIND_MAX		11

#define NR_BTF_KINDS		12

/* For some specific BTF_KIND, "struct btf_type" is immediately
 * followed by extra data.
 */

/* BTF_KIND_INT is followed by a u32 and the following
 * is the 32 bits arrangement:
 */

#define BTF_INT_ENCODING(VAL)	(((VAL) & 0x0f000000) >> 24)

#define BTF_INT_OFFSET(VAL)	(((VAL  & 0x00ff0000)) >> 16)

#define BTF_INT_BITS(VAL)	((VAL)  & 0x000000ff)

/* Attributes stored in the BTF_INT_ENCODING */

#define BTF_INT_SIGNED	(1 << 0)

#define BTF_INT_CHAR	(1 << 1)

#define BTF_INT_BOOL	(1 << 2)

/* BTF_KIND_ENUM is followed by multiple "struct btf_enum".
 * The exact number of btf_enum is stored in the vlen (of the
 * info in "struct btf_type").
 */

struct btf_enum {
	
__u32	name_off;
	
__s32	val;
};

/* BTF_KIND_ARRAY is followed by one "struct btf_array" */

struct btf_array {
	
__u32	type;
	
__u32	index_type;
	
__u32	nelems;
};

/* BTF_KIND_STRUCT and BTF_KIND_UNION are followed
 * by multiple "struct btf_member".  The exact number
 * of btf_member is stored in the vlen (of the info in
 * "struct btf_type").
 */

struct btf_member {
	
__u32	name_off;
	
__u32	type;
	
__u32	offset;	/* offset in bits */
};

#endif /* _UAPI__LINUX_BTF_H__ */

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