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100 lines
3.7 KiB
100 lines
3.7 KiB
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ |
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/* Copyright (c) 2019 Facebook */ |
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#ifndef __RELO_CORE_H |
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#define __RELO_CORE_H |
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/* bpf_core_relo_kind encodes which aspect of captured field/type/enum value |
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* has to be adjusted by relocations. |
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*/ |
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enum bpf_core_relo_kind { |
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BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */ |
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BPF_FIELD_BYTE_SIZE = 1, /* field size in bytes */ |
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BPF_FIELD_EXISTS = 2, /* field existence in target kernel */ |
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BPF_FIELD_SIGNED = 3, /* field signedness (0 - unsigned, 1 - signed) */ |
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BPF_FIELD_LSHIFT_U64 = 4, /* bitfield-specific left bitshift */ |
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BPF_FIELD_RSHIFT_U64 = 5, /* bitfield-specific right bitshift */ |
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BPF_TYPE_ID_LOCAL = 6, /* type ID in local BPF object */ |
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BPF_TYPE_ID_TARGET = 7, /* type ID in target kernel */ |
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BPF_TYPE_EXISTS = 8, /* type existence in target kernel */ |
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BPF_TYPE_SIZE = 9, /* type size in bytes */ |
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BPF_ENUMVAL_EXISTS = 10, /* enum value existence in target kernel */ |
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BPF_ENUMVAL_VALUE = 11, /* enum value integer value */ |
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}; |
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/* The minimum bpf_core_relo checked by the loader |
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* |
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* CO-RE relocation captures the following data: |
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* - insn_off - instruction offset (in bytes) within a BPF program that needs |
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* its insn->imm field to be relocated with actual field info; |
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* - type_id - BTF type ID of the "root" (containing) entity of a relocatable |
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* type or field; |
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* - access_str_off - offset into corresponding .BTF string section. String |
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* interpretation depends on specific relocation kind: |
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* - for field-based relocations, string encodes an accessed field using |
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* a sequence of field and array indices, separated by colon (:). It's |
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* conceptually very close to LLVM's getelementptr ([0]) instruction's |
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* arguments for identifying offset to a field. |
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* - for type-based relocations, strings is expected to be just "0"; |
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* - for enum value-based relocations, string contains an index of enum |
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* value within its enum type; |
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* |
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* Example to provide a better feel. |
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* |
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* struct sample { |
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* int a; |
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* struct { |
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* int b[10]; |
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* }; |
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* }; |
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* |
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* struct sample *s = ...; |
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* int x = &s->a; // encoded as "0:0" (a is field #0) |
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* int y = &s->b[5]; // encoded as "0:1:0:5" (anon struct is field #1, |
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* // b is field #0 inside anon struct, accessing elem #5) |
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* int z = &s[10]->b; // encoded as "10:1" (ptr is used as an array) |
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* |
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* type_id for all relocs in this example will capture BTF type id of |
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* `struct sample`. |
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* |
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* Such relocation is emitted when using __builtin_preserve_access_index() |
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* Clang built-in, passing expression that captures field address, e.g.: |
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* |
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* bpf_probe_read(&dst, sizeof(dst), |
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* __builtin_preserve_access_index(&src->a.b.c)); |
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* |
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* In this case Clang will emit field relocation recording necessary data to |
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* be able to find offset of embedded `a.b.c` field within `src` struct. |
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* |
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* [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction |
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*/ |
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struct bpf_core_relo { |
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__u32 insn_off; |
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__u32 type_id; |
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__u32 access_str_off; |
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enum bpf_core_relo_kind kind; |
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}; |
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struct bpf_core_cand { |
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const struct btf *btf; |
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const struct btf_type *t; |
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const char *name; |
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__u32 id; |
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}; |
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/* dynamically sized list of type IDs and its associated struct btf */ |
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struct bpf_core_cand_list { |
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struct bpf_core_cand *cands; |
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int len; |
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}; |
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int bpf_core_apply_relo_insn(const char *prog_name, |
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struct bpf_insn *insn, int insn_idx, |
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const struct bpf_core_relo *relo, int relo_idx, |
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const struct btf *local_btf, |
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struct bpf_core_cand_list *cands); |
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int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id, |
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const struct btf *targ_btf, __u32 targ_id); |
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size_t bpf_core_essential_name_len(const char *name); |
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#endif
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