f80442a4cd
There are currently unused section descriptions in the btf_header. Those sections are here to support future BTF use cases. For example, the func section (func_off) is to support function signature (e.g. the BPF prog function signature). Instead of spelling out all potential sections up-front in the btf_header. This patch makes changes to btf_header such that extending it (e.g. adding a section) is possible later. The unused ones can be removed for now and they can be added back later. This patch: 1. adds a hdr_len to the btf_header. It will allow adding sections (and other info like parent_label and parent_name) later. The check is similar to the existing bpf_attr. If a user passes in a longer hdr_len, the kernel ensures the extra tailing bytes are 0. 2. allows the section order in the BTF object to be different from its sec_off order in btf_header. 3. each sec_off is followed by a sec_len. It must not have gap or overlapping among sections. The string section is ensured to be at the end due to the 4 bytes alignment requirement of the type section. The above changes will allow enough flexibility to add new sections (and other info) to the btf_header later. This patch also removes an unnecessary !err check at the end of btf_parse(). Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
124 lines
3.4 KiB
C
124 lines
3.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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/* Copyright (c) 2018 Facebook */
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#ifndef _UAPI__LINUX_BTF_H__
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#define _UAPI__LINUX_BTF_H__
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#include <linux/types.h>
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#define BTF_MAGIC 0xeB9F
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#define BTF_VERSION 1
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struct btf_header {
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__u16 magic;
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__u8 version;
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__u8 flags;
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__u32 hdr_len;
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/* All offsets are in bytes relative to the end of this header */
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__u32 type_off; /* offset of type section */
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__u32 type_len; /* length of type section */
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__u32 str_off; /* offset of string section */
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__u32 str_len; /* length of string section */
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};
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/* Max # of type identifier */
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#define BTF_MAX_TYPE 0x7fffffff
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/* Max offset into the string section */
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#define BTF_MAX_NAME_OFFSET 0x7fffffff
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/* Max # of struct/union/enum members or func args */
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#define BTF_MAX_VLEN 0xffff
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/* The type id is referring to a parent BTF */
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#define BTF_TYPE_PARENT(id) (((id) >> 31) & 0x1)
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#define BTF_TYPE_ID(id) ((id) & BTF_MAX_TYPE)
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/* String is in the ELF string section */
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#define BTF_STR_TBL_ELF_ID(ref) (((ref) >> 31) & 0x1)
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#define BTF_STR_OFFSET(ref) ((ref) & BTF_MAX_NAME_OFFSET)
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struct btf_type {
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__u32 name_off;
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/* "info" bits arrangement
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* bits 0-15: vlen (e.g. # of struct's members)
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* bits 16-23: unused
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* bits 24-28: kind (e.g. int, ptr, array...etc)
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* bits 29-30: unused
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* bits 31: root
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*/
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__u32 info;
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/* "size" is used by INT, ENUM, STRUCT and UNION.
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* "size" tells the size of the type it is describing.
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*
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* "type" is used by PTR, TYPEDEF, VOLATILE, CONST and RESTRICT.
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* "type" is a type_id referring to another type.
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*/
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union {
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__u32 size;
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__u32 type;
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};
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};
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#define BTF_INFO_KIND(info) (((info) >> 24) & 0x1f)
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#define BTF_INFO_ISROOT(info) (!!(((info) >> 24) & 0x80))
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#define BTF_INFO_VLEN(info) ((info) & 0xffff)
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#define BTF_KIND_UNKN 0 /* Unknown */
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#define BTF_KIND_INT 1 /* Integer */
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#define BTF_KIND_PTR 2 /* Pointer */
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#define BTF_KIND_ARRAY 3 /* Array */
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#define BTF_KIND_STRUCT 4 /* Struct */
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#define BTF_KIND_UNION 5 /* Union */
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#define BTF_KIND_ENUM 6 /* Enumeration */
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#define BTF_KIND_FWD 7 /* Forward */
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#define BTF_KIND_TYPEDEF 8 /* Typedef */
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#define BTF_KIND_VOLATILE 9 /* Volatile */
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#define BTF_KIND_CONST 10 /* Const */
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#define BTF_KIND_RESTRICT 11 /* Restrict */
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#define BTF_KIND_MAX 11
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#define NR_BTF_KINDS 12
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/* For some specific BTF_KIND, "struct btf_type" is immediately
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* followed by extra data.
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*/
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/* BTF_KIND_INT is followed by a u32 and the following
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* is the 32 bits arrangement:
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*/
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#define BTF_INT_ENCODING(VAL) (((VAL) & 0xff000000) >> 24)
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#define BTF_INT_OFFSET(VAL) (((VAL & 0x00ff0000)) >> 16)
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#define BTF_INT_BITS(VAL) ((VAL) & 0x0000ffff)
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/* Attributes stored in the BTF_INT_ENCODING */
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#define BTF_INT_SIGNED 0x1
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#define BTF_INT_CHAR 0x2
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#define BTF_INT_BOOL 0x4
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#define BTF_INT_VARARGS 0x8
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/* BTF_KIND_ENUM is followed by multiple "struct btf_enum".
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* The exact number of btf_enum is stored in the vlen (of the
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* info in "struct btf_type").
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*/
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struct btf_enum {
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__u32 name_off;
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__s32 val;
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};
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/* BTF_KIND_ARRAY is followed by one "struct btf_array" */
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struct btf_array {
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__u32 type;
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__u32 index_type;
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__u32 nelems;
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};
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/* BTF_KIND_STRUCT and BTF_KIND_UNION are followed
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* by multiple "struct btf_member". The exact number
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* of btf_member is stored in the vlen (of the info in
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* "struct btf_type").
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*/
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struct btf_member {
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__u32 name_off;
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__u32 type;
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__u32 offset; /* offset in bits */
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};
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#endif /* _UAPI__LINUX_BTF_H__ */
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