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1690 lines
51 KiB
1690 lines
51 KiB
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) |
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/* Copyright (c) 2019 Facebook */ |
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|
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#ifdef __KERNEL__ |
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#include <linux/bpf.h> |
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#include <linux/btf.h> |
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#include <linux/string.h> |
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#include <linux/bpf_verifier.h> |
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#include "relo_core.h" |
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|
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static const char *btf_kind_str(const struct btf_type *t) |
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{ |
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return btf_type_str(t); |
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} |
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|
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static bool is_ldimm64_insn(struct bpf_insn *insn) |
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{ |
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return insn->code == (BPF_LD | BPF_IMM | BPF_DW); |
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} |
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|
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static const struct btf_type * |
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skip_mods_and_typedefs(const struct btf *btf, u32 id, u32 *res_id) |
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{ |
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return btf_type_skip_modifiers(btf, id, res_id); |
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} |
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|
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static const char *btf__name_by_offset(const struct btf *btf, u32 offset) |
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{ |
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return btf_name_by_offset(btf, offset); |
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} |
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|
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static s64 btf__resolve_size(const struct btf *btf, u32 type_id) |
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{ |
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const struct btf_type *t; |
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int size; |
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|
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t = btf_type_by_id(btf, type_id); |
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t = btf_resolve_size(btf, t, &size); |
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if (IS_ERR(t)) |
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return PTR_ERR(t); |
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return size; |
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} |
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|
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enum libbpf_print_level { |
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LIBBPF_WARN, |
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LIBBPF_INFO, |
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LIBBPF_DEBUG, |
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}; |
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|
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#undef pr_warn |
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#undef pr_info |
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#undef pr_debug |
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#define pr_warn(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__) |
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#define pr_info(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__) |
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#define pr_debug(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__) |
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#define libbpf_print(level, fmt, ...) bpf_log((void *)prog_name, fmt, ##__VA_ARGS__) |
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#else |
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#include <stdio.h> |
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#include <string.h> |
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#include <errno.h> |
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#include <ctype.h> |
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#include <linux/err.h> |
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|
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#include "libbpf.h" |
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#include "bpf.h" |
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#include "btf.h" |
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#include "str_error.h" |
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#include "libbpf_internal.h" |
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#endif |
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|
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static bool is_flex_arr(const struct btf *btf, |
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const struct bpf_core_accessor *acc, |
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const struct btf_array *arr) |
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{ |
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const struct btf_type *t; |
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|
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/* not a flexible array, if not inside a struct or has non-zero size */ |
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if (!acc->name || arr->nelems > 0) |
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return false; |
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|
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/* has to be the last member of enclosing struct */ |
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t = btf_type_by_id(btf, acc->type_id); |
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return acc->idx == btf_vlen(t) - 1; |
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} |
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|
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static const char *core_relo_kind_str(enum bpf_core_relo_kind kind) |
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{ |
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switch (kind) { |
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case BPF_CORE_FIELD_BYTE_OFFSET: return "byte_off"; |
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case BPF_CORE_FIELD_BYTE_SIZE: return "byte_sz"; |
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case BPF_CORE_FIELD_EXISTS: return "field_exists"; |
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case BPF_CORE_FIELD_SIGNED: return "signed"; |
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case BPF_CORE_FIELD_LSHIFT_U64: return "lshift_u64"; |
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case BPF_CORE_FIELD_RSHIFT_U64: return "rshift_u64"; |
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case BPF_CORE_TYPE_ID_LOCAL: return "local_type_id"; |
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case BPF_CORE_TYPE_ID_TARGET: return "target_type_id"; |
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case BPF_CORE_TYPE_EXISTS: return "type_exists"; |
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case BPF_CORE_TYPE_MATCHES: return "type_matches"; |
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case BPF_CORE_TYPE_SIZE: return "type_size"; |
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case BPF_CORE_ENUMVAL_EXISTS: return "enumval_exists"; |
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case BPF_CORE_ENUMVAL_VALUE: return "enumval_value"; |
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default: return "unknown"; |
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} |
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} |
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|
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static bool core_relo_is_field_based(enum bpf_core_relo_kind kind) |
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{ |
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switch (kind) { |
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case BPF_CORE_FIELD_BYTE_OFFSET: |
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case BPF_CORE_FIELD_BYTE_SIZE: |
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case BPF_CORE_FIELD_EXISTS: |
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case BPF_CORE_FIELD_SIGNED: |
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case BPF_CORE_FIELD_LSHIFT_U64: |
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case BPF_CORE_FIELD_RSHIFT_U64: |
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return true; |
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default: |
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return false; |
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} |
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} |
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|
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static bool core_relo_is_type_based(enum bpf_core_relo_kind kind) |
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{ |
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switch (kind) { |
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case BPF_CORE_TYPE_ID_LOCAL: |
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case BPF_CORE_TYPE_ID_TARGET: |
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case BPF_CORE_TYPE_EXISTS: |
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case BPF_CORE_TYPE_MATCHES: |
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case BPF_CORE_TYPE_SIZE: |
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return true; |
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default: |
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return false; |
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} |
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} |
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|
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static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind) |
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{ |
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switch (kind) { |
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case BPF_CORE_ENUMVAL_EXISTS: |
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case BPF_CORE_ENUMVAL_VALUE: |
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return true; |
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default: |
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return false; |
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} |
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} |
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|
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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, int level) |
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{ |
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const struct btf_type *local_type, *targ_type; |
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int depth = 32; /* max recursion depth */ |
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|
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/* caller made sure that names match (ignoring flavor suffix) */ |
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local_type = btf_type_by_id(local_btf, local_id); |
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targ_type = btf_type_by_id(targ_btf, targ_id); |
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if (!btf_kind_core_compat(local_type, targ_type)) |
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return 0; |
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|
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recur: |
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depth--; |
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if (depth < 0) |
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return -EINVAL; |
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|
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local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id); |
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targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id); |
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if (!local_type || !targ_type) |
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return -EINVAL; |
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|
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if (!btf_kind_core_compat(local_type, targ_type)) |
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return 0; |
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|
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switch (btf_kind(local_type)) { |
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case BTF_KIND_UNKN: |
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case BTF_KIND_STRUCT: |
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case BTF_KIND_UNION: |
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case BTF_KIND_ENUM: |
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case BTF_KIND_FWD: |
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case BTF_KIND_ENUM64: |
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return 1; |
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case BTF_KIND_INT: |
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/* just reject deprecated bitfield-like integers; all other |
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* integers are by default compatible between each other |
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*/ |
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return btf_int_offset(local_type) == 0 && btf_int_offset(targ_type) == 0; |
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case BTF_KIND_PTR: |
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local_id = local_type->type; |
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targ_id = targ_type->type; |
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goto recur; |
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case BTF_KIND_ARRAY: |
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local_id = btf_array(local_type)->type; |
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targ_id = btf_array(targ_type)->type; |
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goto recur; |
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case BTF_KIND_FUNC_PROTO: { |
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struct btf_param *local_p = btf_params(local_type); |
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struct btf_param *targ_p = btf_params(targ_type); |
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__u16 local_vlen = btf_vlen(local_type); |
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__u16 targ_vlen = btf_vlen(targ_type); |
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int i, err; |
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|
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if (local_vlen != targ_vlen) |
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return 0; |
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|
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for (i = 0; i < local_vlen; i++, local_p++, targ_p++) { |
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if (level <= 0) |
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return -EINVAL; |
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|
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skip_mods_and_typedefs(local_btf, local_p->type, &local_id); |
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skip_mods_and_typedefs(targ_btf, targ_p->type, &targ_id); |
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err = __bpf_core_types_are_compat(local_btf, local_id, targ_btf, targ_id, |
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level - 1); |
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if (err <= 0) |
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return err; |
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} |
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|
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/* tail recurse for return type check */ |
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skip_mods_and_typedefs(local_btf, local_type->type, &local_id); |
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skip_mods_and_typedefs(targ_btf, targ_type->type, &targ_id); |
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goto recur; |
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} |
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default: |
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pr_warn("unexpected kind %s relocated, local [%d], target [%d]\n", |
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btf_kind_str(local_type), local_id, targ_id); |
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return 0; |
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} |
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} |
|
|
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/* |
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* Turn bpf_core_relo into a low- and high-level spec representation, |
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* validating correctness along the way, as well as calculating resulting |
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* field bit offset, specified by accessor string. Low-level spec captures |
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* every single level of nestedness, including traversing anonymous |
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* struct/union members. High-level one only captures semantically meaningful |
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* "turning points": named fields and array indicies. |
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* E.g., for this case: |
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* |
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* struct sample { |
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* int __unimportant; |
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* struct { |
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* int __1; |
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* int __2; |
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* int a[7]; |
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* }; |
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* }; |
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* |
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* struct sample *s = ...; |
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* |
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* int x = &s->a[3]; // access string = '0:1:2:3' |
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* |
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* Low-level spec has 1:1 mapping with each element of access string (it's |
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* just a parsed access string representation): [0, 1, 2, 3]. |
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* |
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* High-level spec will capture only 3 points: |
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* - initial zero-index access by pointer (&s->... is the same as &s[0]...); |
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* - field 'a' access (corresponds to '2' in low-level spec); |
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* - array element #3 access (corresponds to '3' in low-level spec). |
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* |
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* Type-based relocations (TYPE_EXISTS/TYPE_MATCHES/TYPE_SIZE, |
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* TYPE_ID_LOCAL/TYPE_ID_TARGET) don't capture any field information. Their |
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* spec and raw_spec are kept empty. |
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* |
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* Enum value-based relocations (ENUMVAL_EXISTS/ENUMVAL_VALUE) use access |
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* string to specify enumerator's value index that need to be relocated. |
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*/ |
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int bpf_core_parse_spec(const char *prog_name, const struct btf *btf, |
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const struct bpf_core_relo *relo, |
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struct bpf_core_spec *spec) |
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{ |
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int access_idx, parsed_len, i; |
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struct bpf_core_accessor *acc; |
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const struct btf_type *t; |
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const char *name, *spec_str; |
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__u32 id, name_off; |
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__s64 sz; |
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spec_str = btf__name_by_offset(btf, relo->access_str_off); |
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if (str_is_empty(spec_str) || *spec_str == ':') |
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return -EINVAL; |
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|
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memset(spec, 0, sizeof(*spec)); |
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spec->btf = btf; |
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spec->root_type_id = relo->type_id; |
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spec->relo_kind = relo->kind; |
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|
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/* type-based relocations don't have a field access string */ |
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if (core_relo_is_type_based(relo->kind)) { |
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if (strcmp(spec_str, "0")) |
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return -EINVAL; |
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return 0; |
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} |
|
|
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/* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */ |
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while (*spec_str) { |
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if (*spec_str == ':') |
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++spec_str; |
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if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1) |
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return -EINVAL; |
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if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN) |
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return -E2BIG; |
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spec_str += parsed_len; |
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spec->raw_spec[spec->raw_len++] = access_idx; |
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} |
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|
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if (spec->raw_len == 0) |
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return -EINVAL; |
|
|
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t = skip_mods_and_typedefs(btf, relo->type_id, &id); |
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if (!t) |
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return -EINVAL; |
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|
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access_idx = spec->raw_spec[0]; |
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acc = &spec->spec[0]; |
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acc->type_id = id; |
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acc->idx = access_idx; |
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spec->len++; |
|
|
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if (core_relo_is_enumval_based(relo->kind)) { |
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if (!btf_is_any_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t)) |
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return -EINVAL; |
|
|
|
/* record enumerator name in a first accessor */ |
|
name_off = btf_is_enum(t) ? btf_enum(t)[access_idx].name_off |
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: btf_enum64(t)[access_idx].name_off; |
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acc->name = btf__name_by_offset(btf, name_off); |
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return 0; |
|
} |
|
|
|
if (!core_relo_is_field_based(relo->kind)) |
|
return -EINVAL; |
|
|
|
sz = btf__resolve_size(btf, id); |
|
if (sz < 0) |
|
return sz; |
|
spec->bit_offset = access_idx * sz * 8; |
|
|
|
for (i = 1; i < spec->raw_len; i++) { |
|
t = skip_mods_and_typedefs(btf, id, &id); |
|
if (!t) |
|
return -EINVAL; |
|
|
|
access_idx = spec->raw_spec[i]; |
|
acc = &spec->spec[spec->len]; |
|
|
|
if (btf_is_composite(t)) { |
|
const struct btf_member *m; |
|
__u32 bit_offset; |
|
|
|
if (access_idx >= btf_vlen(t)) |
|
return -EINVAL; |
|
|
|
bit_offset = btf_member_bit_offset(t, access_idx); |
|
spec->bit_offset += bit_offset; |
|
|
|
m = btf_members(t) + access_idx; |
|
if (m->name_off) { |
|
name = btf__name_by_offset(btf, m->name_off); |
|
if (str_is_empty(name)) |
|
return -EINVAL; |
|
|
|
acc->type_id = id; |
|
acc->idx = access_idx; |
|
acc->name = name; |
|
spec->len++; |
|
} |
|
|
|
id = m->type; |
|
} else if (btf_is_array(t)) { |
|
const struct btf_array *a = btf_array(t); |
|
bool flex; |
|
|
|
t = skip_mods_and_typedefs(btf, a->type, &id); |
|
if (!t) |
|
return -EINVAL; |
|
|
|
flex = is_flex_arr(btf, acc - 1, a); |
|
if (!flex && access_idx >= a->nelems) |
|
return -EINVAL; |
|
|
|
spec->spec[spec->len].type_id = id; |
|
spec->spec[spec->len].idx = access_idx; |
|
spec->len++; |
|
|
|
sz = btf__resolve_size(btf, id); |
|
if (sz < 0) |
|
return sz; |
|
spec->bit_offset += access_idx * sz * 8; |
|
} else { |
|
pr_warn("prog '%s': relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n", |
|
prog_name, relo->type_id, spec_str, i, id, btf_kind_str(t)); |
|
return -EINVAL; |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* Check two types for compatibility for the purpose of field access |
|
* relocation. const/volatile/restrict and typedefs are skipped to ensure we |
|
* are relocating semantically compatible entities: |
|
* - any two STRUCTs/UNIONs are compatible and can be mixed; |
|
* - any two FWDs are compatible, if their names match (modulo flavor suffix); |
|
* - any two PTRs are always compatible; |
|
* - for ENUMs, names should be the same (ignoring flavor suffix) or at |
|
* least one of enums should be anonymous; |
|
* - for ENUMs, check sizes, names are ignored; |
|
* - for INT, size and signedness are ignored; |
|
* - any two FLOATs are always compatible; |
|
* - for ARRAY, dimensionality is ignored, element types are checked for |
|
* compatibility recursively; |
|
* - everything else shouldn't be ever a target of relocation. |
|
* These rules are not set in stone and probably will be adjusted as we get |
|
* more experience with using BPF CO-RE relocations. |
|
*/ |
|
static int bpf_core_fields_are_compat(const struct btf *local_btf, |
|
__u32 local_id, |
|
const struct btf *targ_btf, |
|
__u32 targ_id) |
|
{ |
|
const struct btf_type *local_type, *targ_type; |
|
|
|
recur: |
|
local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id); |
|
targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id); |
|
if (!local_type || !targ_type) |
|
return -EINVAL; |
|
|
|
if (btf_is_composite(local_type) && btf_is_composite(targ_type)) |
|
return 1; |
|
if (!btf_kind_core_compat(local_type, targ_type)) |
|
return 0; |
|
|
|
switch (btf_kind(local_type)) { |
|
case BTF_KIND_PTR: |
|
case BTF_KIND_FLOAT: |
|
return 1; |
|
case BTF_KIND_FWD: |
|
case BTF_KIND_ENUM64: |
|
case BTF_KIND_ENUM: { |
|
const char *local_name, *targ_name; |
|
size_t local_len, targ_len; |
|
|
|
local_name = btf__name_by_offset(local_btf, |
|
local_type->name_off); |
|
targ_name = btf__name_by_offset(targ_btf, targ_type->name_off); |
|
local_len = bpf_core_essential_name_len(local_name); |
|
targ_len = bpf_core_essential_name_len(targ_name); |
|
/* one of them is anonymous or both w/ same flavor-less names */ |
|
return local_len == 0 || targ_len == 0 || |
|
(local_len == targ_len && |
|
strncmp(local_name, targ_name, local_len) == 0); |
|
} |
|
case BTF_KIND_INT: |
|
/* just reject deprecated bitfield-like integers; all other |
|
* integers are by default compatible between each other |
|
*/ |
|
return btf_int_offset(local_type) == 0 && |
|
btf_int_offset(targ_type) == 0; |
|
case BTF_KIND_ARRAY: |
|
local_id = btf_array(local_type)->type; |
|
targ_id = btf_array(targ_type)->type; |
|
goto recur; |
|
default: |
|
return 0; |
|
} |
|
} |
|
|
|
/* |
|
* Given single high-level named field accessor in local type, find |
|
* corresponding high-level accessor for a target type. Along the way, |
|
* maintain low-level spec for target as well. Also keep updating target |
|
* bit offset. |
|
* |
|
* Searching is performed through recursive exhaustive enumeration of all |
|
* fields of a struct/union. If there are any anonymous (embedded) |
|
* structs/unions, they are recursively searched as well. If field with |
|
* desired name is found, check compatibility between local and target types, |
|
* before returning result. |
|
* |
|
* 1 is returned, if field is found. |
|
* 0 is returned if no compatible field is found. |
|
* <0 is returned on error. |
|
*/ |
|
static int bpf_core_match_member(const struct btf *local_btf, |
|
const struct bpf_core_accessor *local_acc, |
|
const struct btf *targ_btf, |
|
__u32 targ_id, |
|
struct bpf_core_spec *spec, |
|
__u32 *next_targ_id) |
|
{ |
|
const struct btf_type *local_type, *targ_type; |
|
const struct btf_member *local_member, *m; |
|
const char *local_name, *targ_name; |
|
__u32 local_id; |
|
int i, n, found; |
|
|
|
targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id); |
|
if (!targ_type) |
|
return -EINVAL; |
|
if (!btf_is_composite(targ_type)) |
|
return 0; |
|
|
|
local_id = local_acc->type_id; |
|
local_type = btf_type_by_id(local_btf, local_id); |
|
local_member = btf_members(local_type) + local_acc->idx; |
|
local_name = btf__name_by_offset(local_btf, local_member->name_off); |
|
|
|
n = btf_vlen(targ_type); |
|
m = btf_members(targ_type); |
|
for (i = 0; i < n; i++, m++) { |
|
__u32 bit_offset; |
|
|
|
bit_offset = btf_member_bit_offset(targ_type, i); |
|
|
|
/* too deep struct/union/array nesting */ |
|
if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN) |
|
return -E2BIG; |
|
|
|
/* speculate this member will be the good one */ |
|
spec->bit_offset += bit_offset; |
|
spec->raw_spec[spec->raw_len++] = i; |
|
|
|
targ_name = btf__name_by_offset(targ_btf, m->name_off); |
|
if (str_is_empty(targ_name)) { |
|
/* embedded struct/union, we need to go deeper */ |
|
found = bpf_core_match_member(local_btf, local_acc, |
|
targ_btf, m->type, |
|
spec, next_targ_id); |
|
if (found) /* either found or error */ |
|
return found; |
|
} else if (strcmp(local_name, targ_name) == 0) { |
|
/* matching named field */ |
|
struct bpf_core_accessor *targ_acc; |
|
|
|
targ_acc = &spec->spec[spec->len++]; |
|
targ_acc->type_id = targ_id; |
|
targ_acc->idx = i; |
|
targ_acc->name = targ_name; |
|
|
|
*next_targ_id = m->type; |
|
found = bpf_core_fields_are_compat(local_btf, |
|
local_member->type, |
|
targ_btf, m->type); |
|
if (!found) |
|
spec->len--; /* pop accessor */ |
|
return found; |
|
} |
|
/* member turned out not to be what we looked for */ |
|
spec->bit_offset -= bit_offset; |
|
spec->raw_len--; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* Try to match local spec to a target type and, if successful, produce full |
|
* target spec (high-level, low-level + bit offset). |
|
*/ |
|
static int bpf_core_spec_match(struct bpf_core_spec *local_spec, |
|
const struct btf *targ_btf, __u32 targ_id, |
|
struct bpf_core_spec *targ_spec) |
|
{ |
|
const struct btf_type *targ_type; |
|
const struct bpf_core_accessor *local_acc; |
|
struct bpf_core_accessor *targ_acc; |
|
int i, sz, matched; |
|
__u32 name_off; |
|
|
|
memset(targ_spec, 0, sizeof(*targ_spec)); |
|
targ_spec->btf = targ_btf; |
|
targ_spec->root_type_id = targ_id; |
|
targ_spec->relo_kind = local_spec->relo_kind; |
|
|
|
if (core_relo_is_type_based(local_spec->relo_kind)) { |
|
if (local_spec->relo_kind == BPF_CORE_TYPE_MATCHES) |
|
return bpf_core_types_match(local_spec->btf, |
|
local_spec->root_type_id, |
|
targ_btf, targ_id); |
|
else |
|
return bpf_core_types_are_compat(local_spec->btf, |
|
local_spec->root_type_id, |
|
targ_btf, targ_id); |
|
} |
|
|
|
local_acc = &local_spec->spec[0]; |
|
targ_acc = &targ_spec->spec[0]; |
|
|
|
if (core_relo_is_enumval_based(local_spec->relo_kind)) { |
|
size_t local_essent_len, targ_essent_len; |
|
const char *targ_name; |
|
|
|
/* has to resolve to an enum */ |
|
targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id, &targ_id); |
|
if (!btf_is_any_enum(targ_type)) |
|
return 0; |
|
|
|
local_essent_len = bpf_core_essential_name_len(local_acc->name); |
|
|
|
for (i = 0; i < btf_vlen(targ_type); i++) { |
|
if (btf_is_enum(targ_type)) |
|
name_off = btf_enum(targ_type)[i].name_off; |
|
else |
|
name_off = btf_enum64(targ_type)[i].name_off; |
|
|
|
targ_name = btf__name_by_offset(targ_spec->btf, name_off); |
|
targ_essent_len = bpf_core_essential_name_len(targ_name); |
|
if (targ_essent_len != local_essent_len) |
|
continue; |
|
if (strncmp(local_acc->name, targ_name, local_essent_len) == 0) { |
|
targ_acc->type_id = targ_id; |
|
targ_acc->idx = i; |
|
targ_acc->name = targ_name; |
|
targ_spec->len++; |
|
targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx; |
|
targ_spec->raw_len++; |
|
return 1; |
|
} |
|
} |
|
return 0; |
|
} |
|
|
|
if (!core_relo_is_field_based(local_spec->relo_kind)) |
|
return -EINVAL; |
|
|
|
for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) { |
|
targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id, |
|
&targ_id); |
|
if (!targ_type) |
|
return -EINVAL; |
|
|
|
if (local_acc->name) { |
|
matched = bpf_core_match_member(local_spec->btf, |
|
local_acc, |
|
targ_btf, targ_id, |
|
targ_spec, &targ_id); |
|
if (matched <= 0) |
|
return matched; |
|
} else { |
|
/* for i=0, targ_id is already treated as array element |
|
* type (because it's the original struct), for others |
|
* we should find array element type first |
|
*/ |
|
if (i > 0) { |
|
const struct btf_array *a; |
|
bool flex; |
|
|
|
if (!btf_is_array(targ_type)) |
|
return 0; |
|
|
|
a = btf_array(targ_type); |
|
flex = is_flex_arr(targ_btf, targ_acc - 1, a); |
|
if (!flex && local_acc->idx >= a->nelems) |
|
return 0; |
|
if (!skip_mods_and_typedefs(targ_btf, a->type, |
|
&targ_id)) |
|
return -EINVAL; |
|
} |
|
|
|
/* too deep struct/union/array nesting */ |
|
if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN) |
|
return -E2BIG; |
|
|
|
targ_acc->type_id = targ_id; |
|
targ_acc->idx = local_acc->idx; |
|
targ_acc->name = NULL; |
|
targ_spec->len++; |
|
targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx; |
|
targ_spec->raw_len++; |
|
|
|
sz = btf__resolve_size(targ_btf, targ_id); |
|
if (sz < 0) |
|
return sz; |
|
targ_spec->bit_offset += local_acc->idx * sz * 8; |
|
} |
|
} |
|
|
|
return 1; |
|
} |
|
|
|
static int bpf_core_calc_field_relo(const char *prog_name, |
|
const struct bpf_core_relo *relo, |
|
const struct bpf_core_spec *spec, |
|
__u64 *val, __u32 *field_sz, __u32 *type_id, |
|
bool *validate) |
|
{ |
|
const struct bpf_core_accessor *acc; |
|
const struct btf_type *t; |
|
__u32 byte_off, byte_sz, bit_off, bit_sz, field_type_id; |
|
const struct btf_member *m; |
|
const struct btf_type *mt; |
|
bool bitfield; |
|
__s64 sz; |
|
|
|
*field_sz = 0; |
|
|
|
if (relo->kind == BPF_CORE_FIELD_EXISTS) { |
|
*val = spec ? 1 : 0; |
|
return 0; |
|
} |
|
|
|
if (!spec) |
|
return -EUCLEAN; /* request instruction poisoning */ |
|
|
|
acc = &spec->spec[spec->len - 1]; |
|
t = btf_type_by_id(spec->btf, acc->type_id); |
|
|
|
/* a[n] accessor needs special handling */ |
|
if (!acc->name) { |
|
if (relo->kind == BPF_CORE_FIELD_BYTE_OFFSET) { |
|
*val = spec->bit_offset / 8; |
|
/* remember field size for load/store mem size */ |
|
sz = btf__resolve_size(spec->btf, acc->type_id); |
|
if (sz < 0) |
|
return -EINVAL; |
|
*field_sz = sz; |
|
*type_id = acc->type_id; |
|
} else if (relo->kind == BPF_CORE_FIELD_BYTE_SIZE) { |
|
sz = btf__resolve_size(spec->btf, acc->type_id); |
|
if (sz < 0) |
|
return -EINVAL; |
|
*val = sz; |
|
} else { |
|
pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access\n", |
|
prog_name, relo->kind, relo->insn_off / 8); |
|
return -EINVAL; |
|
} |
|
if (validate) |
|
*validate = true; |
|
return 0; |
|
} |
|
|
|
m = btf_members(t) + acc->idx; |
|
mt = skip_mods_and_typedefs(spec->btf, m->type, &field_type_id); |
|
bit_off = spec->bit_offset; |
|
bit_sz = btf_member_bitfield_size(t, acc->idx); |
|
|
|
bitfield = bit_sz > 0; |
|
if (bitfield) { |
|
byte_sz = mt->size; |
|
byte_off = bit_off / 8 / byte_sz * byte_sz; |
|
/* figure out smallest int size necessary for bitfield load */ |
|
while (bit_off + bit_sz - byte_off * 8 > byte_sz * 8) { |
|
if (byte_sz >= 8) { |
|
/* bitfield can't be read with 64-bit read */ |
|
pr_warn("prog '%s': relo %d at insn #%d can't be satisfied for bitfield\n", |
|
prog_name, relo->kind, relo->insn_off / 8); |
|
return -E2BIG; |
|
} |
|
byte_sz *= 2; |
|
byte_off = bit_off / 8 / byte_sz * byte_sz; |
|
} |
|
} else { |
|
sz = btf__resolve_size(spec->btf, field_type_id); |
|
if (sz < 0) |
|
return -EINVAL; |
|
byte_sz = sz; |
|
byte_off = spec->bit_offset / 8; |
|
bit_sz = byte_sz * 8; |
|
} |
|
|
|
/* for bitfields, all the relocatable aspects are ambiguous and we |
|
* might disagree with compiler, so turn off validation of expected |
|
* value, except for signedness |
|
*/ |
|
if (validate) |
|
*validate = !bitfield; |
|
|
|
switch (relo->kind) { |
|
case BPF_CORE_FIELD_BYTE_OFFSET: |
|
*val = byte_off; |
|
if (!bitfield) { |
|
*field_sz = byte_sz; |
|
*type_id = field_type_id; |
|
} |
|
break; |
|
case BPF_CORE_FIELD_BYTE_SIZE: |
|
*val = byte_sz; |
|
break; |
|
case BPF_CORE_FIELD_SIGNED: |
|
*val = (btf_is_any_enum(mt) && BTF_INFO_KFLAG(mt->info)) || |
|
(btf_int_encoding(mt) & BTF_INT_SIGNED); |
|
if (validate) |
|
*validate = true; /* signedness is never ambiguous */ |
|
break; |
|
case BPF_CORE_FIELD_LSHIFT_U64: |
|
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ |
|
*val = 64 - (bit_off + bit_sz - byte_off * 8); |
|
#else |
|
*val = (8 - byte_sz) * 8 + (bit_off - byte_off * 8); |
|
#endif |
|
break; |
|
case BPF_CORE_FIELD_RSHIFT_U64: |
|
*val = 64 - bit_sz; |
|
if (validate) |
|
*validate = true; /* right shift is never ambiguous */ |
|
break; |
|
case BPF_CORE_FIELD_EXISTS: |
|
default: |
|
return -EOPNOTSUPP; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo, |
|
const struct bpf_core_spec *spec, |
|
__u64 *val, bool *validate) |
|
{ |
|
__s64 sz; |
|
|
|
/* by default, always check expected value in bpf_insn */ |
|
if (validate) |
|
*validate = true; |
|
|
|
/* type-based relos return zero when target type is not found */ |
|
if (!spec) { |
|
*val = 0; |
|
return 0; |
|
} |
|
|
|
switch (relo->kind) { |
|
case BPF_CORE_TYPE_ID_TARGET: |
|
*val = spec->root_type_id; |
|
/* type ID, embedded in bpf_insn, might change during linking, |
|
* so enforcing it is pointless |
|
*/ |
|
if (validate) |
|
*validate = false; |
|
break; |
|
case BPF_CORE_TYPE_EXISTS: |
|
case BPF_CORE_TYPE_MATCHES: |
|
*val = 1; |
|
break; |
|
case BPF_CORE_TYPE_SIZE: |
|
sz = btf__resolve_size(spec->btf, spec->root_type_id); |
|
if (sz < 0) |
|
return -EINVAL; |
|
*val = sz; |
|
break; |
|
case BPF_CORE_TYPE_ID_LOCAL: |
|
/* BPF_CORE_TYPE_ID_LOCAL is handled specially and shouldn't get here */ |
|
default: |
|
return -EOPNOTSUPP; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int bpf_core_calc_enumval_relo(const struct bpf_core_relo *relo, |
|
const struct bpf_core_spec *spec, |
|
__u64 *val) |
|
{ |
|
const struct btf_type *t; |
|
|
|
switch (relo->kind) { |
|
case BPF_CORE_ENUMVAL_EXISTS: |
|
*val = spec ? 1 : 0; |
|
break; |
|
case BPF_CORE_ENUMVAL_VALUE: |
|
if (!spec) |
|
return -EUCLEAN; /* request instruction poisoning */ |
|
t = btf_type_by_id(spec->btf, spec->spec[0].type_id); |
|
if (btf_is_enum(t)) |
|
*val = btf_enum(t)[spec->spec[0].idx].val; |
|
else |
|
*val = btf_enum64_value(btf_enum64(t) + spec->spec[0].idx); |
|
break; |
|
default: |
|
return -EOPNOTSUPP; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* Calculate original and target relocation values, given local and target |
|
* specs and relocation kind. These values are calculated for each candidate. |
|
* If there are multiple candidates, resulting values should all be consistent |
|
* with each other. Otherwise, libbpf will refuse to proceed due to ambiguity. |
|
* If instruction has to be poisoned, *poison will be set to true. |
|
*/ |
|
static int bpf_core_calc_relo(const char *prog_name, |
|
const struct bpf_core_relo *relo, |
|
int relo_idx, |
|
const struct bpf_core_spec *local_spec, |
|
const struct bpf_core_spec *targ_spec, |
|
struct bpf_core_relo_res *res) |
|
{ |
|
int err = -EOPNOTSUPP; |
|
|
|
res->orig_val = 0; |
|
res->new_val = 0; |
|
res->poison = false; |
|
res->validate = true; |
|
res->fail_memsz_adjust = false; |
|
res->orig_sz = res->new_sz = 0; |
|
res->orig_type_id = res->new_type_id = 0; |
|
|
|
if (core_relo_is_field_based(relo->kind)) { |
|
err = bpf_core_calc_field_relo(prog_name, relo, local_spec, |
|
&res->orig_val, &res->orig_sz, |
|
&res->orig_type_id, &res->validate); |
|
err = err ?: bpf_core_calc_field_relo(prog_name, relo, targ_spec, |
|
&res->new_val, &res->new_sz, |
|
&res->new_type_id, NULL); |
|
if (err) |
|
goto done; |
|
/* Validate if it's safe to adjust load/store memory size. |
|
* Adjustments are performed only if original and new memory |
|
* sizes differ. |
|
*/ |
|
res->fail_memsz_adjust = false; |
|
if (res->orig_sz != res->new_sz) { |
|
const struct btf_type *orig_t, *new_t; |
|
|
|
orig_t = btf_type_by_id(local_spec->btf, res->orig_type_id); |
|
new_t = btf_type_by_id(targ_spec->btf, res->new_type_id); |
|
|
|
/* There are two use cases in which it's safe to |
|
* adjust load/store's mem size: |
|
* - reading a 32-bit kernel pointer, while on BPF |
|
* size pointers are always 64-bit; in this case |
|
* it's safe to "downsize" instruction size due to |
|
* pointer being treated as unsigned integer with |
|
* zero-extended upper 32-bits; |
|
* - reading unsigned integers, again due to |
|
* zero-extension is preserving the value correctly. |
|
* |
|
* In all other cases it's incorrect to attempt to |
|
* load/store field because read value will be |
|
* incorrect, so we poison relocated instruction. |
|
*/ |
|
if (btf_is_ptr(orig_t) && btf_is_ptr(new_t)) |
|
goto done; |
|
if (btf_is_int(orig_t) && btf_is_int(new_t) && |
|
btf_int_encoding(orig_t) != BTF_INT_SIGNED && |
|
btf_int_encoding(new_t) != BTF_INT_SIGNED) |
|
goto done; |
|
|
|
/* mark as invalid mem size adjustment, but this will |
|
* only be checked for LDX/STX/ST insns |
|
*/ |
|
res->fail_memsz_adjust = true; |
|
} |
|
} else if (core_relo_is_type_based(relo->kind)) { |
|
err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val, &res->validate); |
|
err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val, NULL); |
|
} else if (core_relo_is_enumval_based(relo->kind)) { |
|
err = bpf_core_calc_enumval_relo(relo, local_spec, &res->orig_val); |
|
err = err ?: bpf_core_calc_enumval_relo(relo, targ_spec, &res->new_val); |
|
} |
|
|
|
done: |
|
if (err == -EUCLEAN) { |
|
/* EUCLEAN is used to signal instruction poisoning request */ |
|
res->poison = true; |
|
err = 0; |
|
} else if (err == -EOPNOTSUPP) { |
|
/* EOPNOTSUPP means unknown/unsupported relocation */ |
|
pr_warn("prog '%s': relo #%d: unrecognized CO-RE relocation %s (%d) at insn #%d\n", |
|
prog_name, relo_idx, core_relo_kind_str(relo->kind), |
|
relo->kind, relo->insn_off / 8); |
|
} |
|
|
|
return err; |
|
} |
|
|
|
/* |
|
* Turn instruction for which CO_RE relocation failed into invalid one with |
|
* distinct signature. |
|
*/ |
|
static void bpf_core_poison_insn(const char *prog_name, int relo_idx, |
|
int insn_idx, struct bpf_insn *insn) |
|
{ |
|
pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n", |
|
prog_name, relo_idx, insn_idx); |
|
insn->code = BPF_JMP | BPF_CALL; |
|
insn->dst_reg = 0; |
|
insn->src_reg = 0; |
|
insn->off = 0; |
|
/* if this instruction is reachable (not a dead code), |
|
* verifier will complain with the following message: |
|
* invalid func unknown#195896080 |
|
*/ |
|
insn->imm = 195896080; /* => 0xbad2310 => "bad relo" */ |
|
} |
|
|
|
static int insn_bpf_size_to_bytes(struct bpf_insn *insn) |
|
{ |
|
switch (BPF_SIZE(insn->code)) { |
|
case BPF_DW: return 8; |
|
case BPF_W: return 4; |
|
case BPF_H: return 2; |
|
case BPF_B: return 1; |
|
default: return -1; |
|
} |
|
} |
|
|
|
static int insn_bytes_to_bpf_size(__u32 sz) |
|
{ |
|
switch (sz) { |
|
case 8: return BPF_DW; |
|
case 4: return BPF_W; |
|
case 2: return BPF_H; |
|
case 1: return BPF_B; |
|
default: return -1; |
|
} |
|
} |
|
|
|
/* |
|
* Patch relocatable BPF instruction. |
|
* |
|
* Patched value is determined by relocation kind and target specification. |
|
* For existence relocations target spec will be NULL if field/type is not found. |
|
* Expected insn->imm value is determined using relocation kind and local |
|
* spec, and is checked before patching instruction. If actual insn->imm value |
|
* is wrong, bail out with error. |
|
* |
|
* Currently supported classes of BPF instruction are: |
|
* 1. rX = <imm> (assignment with immediate operand); |
|
* 2. rX += <imm> (arithmetic operations with immediate operand); |
|
* 3. rX = <imm64> (load with 64-bit immediate value); |
|
* 4. rX = *(T *)(rY + <off>), where T is one of {u8, u16, u32, u64}; |
|
* 5. *(T *)(rX + <off>) = rY, where T is one of {u8, u16, u32, u64}; |
|
* 6. *(T *)(rX + <off>) = <imm>, where T is one of {u8, u16, u32, u64}. |
|
*/ |
|
int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn, |
|
int insn_idx, const struct bpf_core_relo *relo, |
|
int relo_idx, const struct bpf_core_relo_res *res) |
|
{ |
|
__u64 orig_val, new_val; |
|
__u8 class; |
|
|
|
class = BPF_CLASS(insn->code); |
|
|
|
if (res->poison) { |
|
poison: |
|
/* poison second part of ldimm64 to avoid confusing error from |
|
* verifier about "unknown opcode 00" |
|
*/ |
|
if (is_ldimm64_insn(insn)) |
|
bpf_core_poison_insn(prog_name, relo_idx, insn_idx + 1, insn + 1); |
|
bpf_core_poison_insn(prog_name, relo_idx, insn_idx, insn); |
|
return 0; |
|
} |
|
|
|
orig_val = res->orig_val; |
|
new_val = res->new_val; |
|
|
|
switch (class) { |
|
case BPF_ALU: |
|
case BPF_ALU64: |
|
if (BPF_SRC(insn->code) != BPF_K) |
|
return -EINVAL; |
|
if (res->validate && insn->imm != orig_val) { |
|
pr_warn("prog '%s': relo #%d: unexpected insn #%d (ALU/ALU64) value: got %u, exp %llu -> %llu\n", |
|
prog_name, relo_idx, |
|
insn_idx, insn->imm, (unsigned long long)orig_val, |
|
(unsigned long long)new_val); |
|
return -EINVAL; |
|
} |
|
orig_val = insn->imm; |
|
insn->imm = new_val; |
|
pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %llu -> %llu\n", |
|
prog_name, relo_idx, insn_idx, |
|
(unsigned long long)orig_val, (unsigned long long)new_val); |
|
break; |
|
case BPF_LDX: |
|
case BPF_ST: |
|
case BPF_STX: |
|
if (res->validate && insn->off != orig_val) { |
|
pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDX/ST/STX) value: got %u, exp %llu -> %llu\n", |
|
prog_name, relo_idx, insn_idx, insn->off, (unsigned long long)orig_val, |
|
(unsigned long long)new_val); |
|
return -EINVAL; |
|
} |
|
if (new_val > SHRT_MAX) { |
|
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %llu\n", |
|
prog_name, relo_idx, insn_idx, (unsigned long long)new_val); |
|
return -ERANGE; |
|
} |
|
if (res->fail_memsz_adjust) { |
|
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) accesses field incorrectly. " |
|
"Make sure you are accessing pointers, unsigned integers, or fields of matching type and size.\n", |
|
prog_name, relo_idx, insn_idx); |
|
goto poison; |
|
} |
|
|
|
orig_val = insn->off; |
|
insn->off = new_val; |
|
pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) off %llu -> %llu\n", |
|
prog_name, relo_idx, insn_idx, (unsigned long long)orig_val, |
|
(unsigned long long)new_val); |
|
|
|
if (res->new_sz != res->orig_sz) { |
|
int insn_bytes_sz, insn_bpf_sz; |
|
|
|
insn_bytes_sz = insn_bpf_size_to_bytes(insn); |
|
if (insn_bytes_sz != res->orig_sz) { |
|
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) unexpected mem size: got %d, exp %u\n", |
|
prog_name, relo_idx, insn_idx, insn_bytes_sz, res->orig_sz); |
|
return -EINVAL; |
|
} |
|
|
|
insn_bpf_sz = insn_bytes_to_bpf_size(res->new_sz); |
|
if (insn_bpf_sz < 0) { |
|
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) invalid new mem size: %u\n", |
|
prog_name, relo_idx, insn_idx, res->new_sz); |
|
return -EINVAL; |
|
} |
|
|
|
insn->code = BPF_MODE(insn->code) | insn_bpf_sz | BPF_CLASS(insn->code); |
|
pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) mem_sz %u -> %u\n", |
|
prog_name, relo_idx, insn_idx, res->orig_sz, res->new_sz); |
|
} |
|
break; |
|
case BPF_LD: { |
|
__u64 imm; |
|
|
|
if (!is_ldimm64_insn(insn) || |
|
insn[0].src_reg != 0 || insn[0].off != 0 || |
|
insn[1].code != 0 || insn[1].dst_reg != 0 || |
|
insn[1].src_reg != 0 || insn[1].off != 0) { |
|
pr_warn("prog '%s': relo #%d: insn #%d (LDIMM64) has unexpected form\n", |
|
prog_name, relo_idx, insn_idx); |
|
return -EINVAL; |
|
} |
|
|
|
imm = (__u32)insn[0].imm | ((__u64)insn[1].imm << 32); |
|
if (res->validate && imm != orig_val) { |
|
pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %llu -> %llu\n", |
|
prog_name, relo_idx, |
|
insn_idx, (unsigned long long)imm, |
|
(unsigned long long)orig_val, (unsigned long long)new_val); |
|
return -EINVAL; |
|
} |
|
|
|
insn[0].imm = new_val; |
|
insn[1].imm = new_val >> 32; |
|
pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %llu\n", |
|
prog_name, relo_idx, insn_idx, |
|
(unsigned long long)imm, (unsigned long long)new_val); |
|
break; |
|
} |
|
default: |
|
pr_warn("prog '%s': relo #%d: trying to relocate unrecognized insn #%d, code:0x%x, src:0x%x, dst:0x%x, off:0x%x, imm:0x%x\n", |
|
prog_name, relo_idx, insn_idx, insn->code, |
|
insn->src_reg, insn->dst_reg, insn->off, insn->imm); |
|
return -EINVAL; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* Output spec definition in the format: |
|
* [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>, |
|
* where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b |
|
*/ |
|
int bpf_core_format_spec(char *buf, size_t buf_sz, const struct bpf_core_spec *spec) |
|
{ |
|
const struct btf_type *t; |
|
const char *s; |
|
__u32 type_id; |
|
int i, len = 0; |
|
|
|
#define append_buf(fmt, args...) \ |
|
({ \ |
|
int r; \ |
|
r = snprintf(buf, buf_sz, fmt, ##args); \ |
|
len += r; \ |
|
if (r >= buf_sz) \ |
|
r = buf_sz; \ |
|
buf += r; \ |
|
buf_sz -= r; \ |
|
}) |
|
|
|
type_id = spec->root_type_id; |
|
t = btf_type_by_id(spec->btf, type_id); |
|
s = btf__name_by_offset(spec->btf, t->name_off); |
|
|
|
append_buf("<%s> [%u] %s %s", |
|
core_relo_kind_str(spec->relo_kind), |
|
type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s); |
|
|
|
if (core_relo_is_type_based(spec->relo_kind)) |
|
return len; |
|
|
|
if (core_relo_is_enumval_based(spec->relo_kind)) { |
|
t = skip_mods_and_typedefs(spec->btf, type_id, NULL); |
|
if (btf_is_enum(t)) { |
|
const struct btf_enum *e; |
|
const char *fmt_str; |
|
|
|
e = btf_enum(t) + spec->raw_spec[0]; |
|
s = btf__name_by_offset(spec->btf, e->name_off); |
|
fmt_str = BTF_INFO_KFLAG(t->info) ? "::%s = %d" : "::%s = %u"; |
|
append_buf(fmt_str, s, e->val); |
|
} else { |
|
const struct btf_enum64 *e; |
|
const char *fmt_str; |
|
|
|
e = btf_enum64(t) + spec->raw_spec[0]; |
|
s = btf__name_by_offset(spec->btf, e->name_off); |
|
fmt_str = BTF_INFO_KFLAG(t->info) ? "::%s = %lld" : "::%s = %llu"; |
|
append_buf(fmt_str, s, (unsigned long long)btf_enum64_value(e)); |
|
} |
|
return len; |
|
} |
|
|
|
if (core_relo_is_field_based(spec->relo_kind)) { |
|
for (i = 0; i < spec->len; i++) { |
|
if (spec->spec[i].name) |
|
append_buf(".%s", spec->spec[i].name); |
|
else if (i > 0 || spec->spec[i].idx > 0) |
|
append_buf("[%u]", spec->spec[i].idx); |
|
} |
|
|
|
append_buf(" ("); |
|
for (i = 0; i < spec->raw_len; i++) |
|
append_buf("%s%d", i == 0 ? "" : ":", spec->raw_spec[i]); |
|
|
|
if (spec->bit_offset % 8) |
|
append_buf(" @ offset %u.%u)", spec->bit_offset / 8, spec->bit_offset % 8); |
|
else |
|
append_buf(" @ offset %u)", spec->bit_offset / 8); |
|
return len; |
|
} |
|
|
|
return len; |
|
#undef append_buf |
|
} |
|
|
|
/* |
|
* Calculate CO-RE relocation target result. |
|
* |
|
* The outline and important points of the algorithm: |
|
* 1. For given local type, find corresponding candidate target types. |
|
* Candidate type is a type with the same "essential" name, ignoring |
|
* everything after last triple underscore (___). E.g., `sample`, |
|
* `sample___flavor_one`, `sample___flavor_another_one`, are all candidates |
|
* for each other. Names with triple underscore are referred to as |
|
* "flavors" and are useful, among other things, to allow to |
|
* specify/support incompatible variations of the same kernel struct, which |
|
* might differ between different kernel versions and/or build |
|
* configurations. |
|
* |
|
* N.B. Struct "flavors" could be generated by bpftool's BTF-to-C |
|
* converter, when deduplicated BTF of a kernel still contains more than |
|
* one different types with the same name. In that case, ___2, ___3, etc |
|
* are appended starting from second name conflict. But start flavors are |
|
* also useful to be defined "locally", in BPF program, to extract same |
|
* data from incompatible changes between different kernel |
|
* versions/configurations. For instance, to handle field renames between |
|
* kernel versions, one can use two flavors of the struct name with the |
|
* same common name and use conditional relocations to extract that field, |
|
* depending on target kernel version. |
|
* 2. For each candidate type, try to match local specification to this |
|
* candidate target type. Matching involves finding corresponding |
|
* high-level spec accessors, meaning that all named fields should match, |
|
* as well as all array accesses should be within the actual bounds. Also, |
|
* types should be compatible (see bpf_core_fields_are_compat for details). |
|
* 3. It is supported and expected that there might be multiple flavors |
|
* matching the spec. As long as all the specs resolve to the same set of |
|
* offsets across all candidates, there is no error. If there is any |
|
* ambiguity, CO-RE relocation will fail. This is necessary to accommodate |
|
* imperfection of BTF deduplication, which can cause slight duplication of |
|
* the same BTF type, if some directly or indirectly referenced (by |
|
* pointer) type gets resolved to different actual types in different |
|
* object files. If such a situation occurs, deduplicated BTF will end up |
|
* with two (or more) structurally identical types, which differ only in |
|
* types they refer to through pointer. This should be OK in most cases and |
|
* is not an error. |
|
* 4. Candidate types search is performed by linearly scanning through all |
|
* types in target BTF. It is anticipated that this is overall more |
|
* efficient memory-wise and not significantly worse (if not better) |
|
* CPU-wise compared to prebuilding a map from all local type names to |
|
* a list of candidate type names. It's also sped up by caching resolved |
|
* list of matching candidates per each local "root" type ID, that has at |
|
* least one bpf_core_relo associated with it. This list is shared |
|
* between multiple relocations for the same type ID and is updated as some |
|
* of the candidates are pruned due to structural incompatibility. |
|
*/ |
|
int bpf_core_calc_relo_insn(const char *prog_name, |
|
const struct bpf_core_relo *relo, |
|
int relo_idx, |
|
const struct btf *local_btf, |
|
struct bpf_core_cand_list *cands, |
|
struct bpf_core_spec *specs_scratch, |
|
struct bpf_core_relo_res *targ_res) |
|
{ |
|
struct bpf_core_spec *local_spec = &specs_scratch[0]; |
|
struct bpf_core_spec *cand_spec = &specs_scratch[1]; |
|
struct bpf_core_spec *targ_spec = &specs_scratch[2]; |
|
struct bpf_core_relo_res cand_res; |
|
const struct btf_type *local_type; |
|
const char *local_name; |
|
__u32 local_id; |
|
char spec_buf[256]; |
|
int i, j, err; |
|
|
|
local_id = relo->type_id; |
|
local_type = btf_type_by_id(local_btf, local_id); |
|
local_name = btf__name_by_offset(local_btf, local_type->name_off); |
|
if (!local_name) |
|
return -EINVAL; |
|
|
|
err = bpf_core_parse_spec(prog_name, local_btf, relo, local_spec); |
|
if (err) { |
|
const char *spec_str; |
|
|
|
spec_str = btf__name_by_offset(local_btf, relo->access_str_off); |
|
pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n", |
|
prog_name, relo_idx, local_id, btf_kind_str(local_type), |
|
str_is_empty(local_name) ? "<anon>" : local_name, |
|
spec_str ?: "<?>", err); |
|
return -EINVAL; |
|
} |
|
|
|
bpf_core_format_spec(spec_buf, sizeof(spec_buf), local_spec); |
|
pr_debug("prog '%s': relo #%d: %s\n", prog_name, relo_idx, spec_buf); |
|
|
|
/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */ |
|
if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) { |
|
/* bpf_insn's imm value could get out of sync during linking */ |
|
memset(targ_res, 0, sizeof(*targ_res)); |
|
targ_res->validate = false; |
|
targ_res->poison = false; |
|
targ_res->orig_val = local_spec->root_type_id; |
|
targ_res->new_val = local_spec->root_type_id; |
|
return 0; |
|
} |
|
|
|
/* libbpf doesn't support candidate search for anonymous types */ |
|
if (str_is_empty(local_name)) { |
|
pr_warn("prog '%s': relo #%d: <%s> (%d) relocation doesn't support anonymous types\n", |
|
prog_name, relo_idx, core_relo_kind_str(relo->kind), relo->kind); |
|
return -EOPNOTSUPP; |
|
} |
|
|
|
for (i = 0, j = 0; i < cands->len; i++) { |
|
err = bpf_core_spec_match(local_spec, cands->cands[i].btf, |
|
cands->cands[i].id, cand_spec); |
|
if (err < 0) { |
|
bpf_core_format_spec(spec_buf, sizeof(spec_buf), cand_spec); |
|
pr_warn("prog '%s': relo #%d: error matching candidate #%d %s: %d\n ", |
|
prog_name, relo_idx, i, spec_buf, err); |
|
return err; |
|
} |
|
|
|
bpf_core_format_spec(spec_buf, sizeof(spec_buf), cand_spec); |
|
pr_debug("prog '%s': relo #%d: %s candidate #%d %s\n", prog_name, |
|
relo_idx, err == 0 ? "non-matching" : "matching", i, spec_buf); |
|
|
|
if (err == 0) |
|
continue; |
|
|
|
err = bpf_core_calc_relo(prog_name, relo, relo_idx, local_spec, cand_spec, &cand_res); |
|
if (err) |
|
return err; |
|
|
|
if (j == 0) { |
|
*targ_res = cand_res; |
|
*targ_spec = *cand_spec; |
|
} else if (cand_spec->bit_offset != targ_spec->bit_offset) { |
|
/* if there are many field relo candidates, they |
|
* should all resolve to the same bit offset |
|
*/ |
|
pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n", |
|
prog_name, relo_idx, cand_spec->bit_offset, |
|
targ_spec->bit_offset); |
|
return -EINVAL; |
|
} else if (cand_res.poison != targ_res->poison || |
|
cand_res.new_val != targ_res->new_val) { |
|
/* all candidates should result in the same relocation |
|
* decision and value, otherwise it's dangerous to |
|
* proceed due to ambiguity |
|
*/ |
|
pr_warn("prog '%s': relo #%d: relocation decision ambiguity: %s %llu != %s %llu\n", |
|
prog_name, relo_idx, |
|
cand_res.poison ? "failure" : "success", |
|
(unsigned long long)cand_res.new_val, |
|
targ_res->poison ? "failure" : "success", |
|
(unsigned long long)targ_res->new_val); |
|
return -EINVAL; |
|
} |
|
|
|
cands->cands[j++] = cands->cands[i]; |
|
} |
|
|
|
/* |
|
* For BPF_CORE_FIELD_EXISTS relo or when used BPF program has field |
|
* existence checks or kernel version/config checks, it's expected |
|
* that we might not find any candidates. In this case, if field |
|
* wasn't found in any candidate, the list of candidates shouldn't |
|
* change at all, we'll just handle relocating appropriately, |
|
* depending on relo's kind. |
|
*/ |
|
if (j > 0) |
|
cands->len = j; |
|
|
|
/* |
|
* If no candidates were found, it might be both a programmer error, |
|
* as well as expected case, depending whether instruction w/ |
|
* relocation is guarded in some way that makes it unreachable (dead |
|
* code) if relocation can't be resolved. This is handled in |
|
* bpf_core_patch_insn() uniformly by replacing that instruction with |
|
* BPF helper call insn (using invalid helper ID). If that instruction |
|
* is indeed unreachable, then it will be ignored and eliminated by |
|
* verifier. If it was an error, then verifier will complain and point |
|
* to a specific instruction number in its log. |
|
*/ |
|
if (j == 0) { |
|
pr_debug("prog '%s': relo #%d: no matching targets found\n", |
|
prog_name, relo_idx); |
|
|
|
/* calculate single target relo result explicitly */ |
|
err = bpf_core_calc_relo(prog_name, relo, relo_idx, local_spec, NULL, targ_res); |
|
if (err) |
|
return err; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static bool bpf_core_names_match(const struct btf *local_btf, size_t local_name_off, |
|
const struct btf *targ_btf, size_t targ_name_off) |
|
{ |
|
const char *local_n, *targ_n; |
|
size_t local_len, targ_len; |
|
|
|
local_n = btf__name_by_offset(local_btf, local_name_off); |
|
targ_n = btf__name_by_offset(targ_btf, targ_name_off); |
|
|
|
if (str_is_empty(targ_n)) |
|
return str_is_empty(local_n); |
|
|
|
targ_len = bpf_core_essential_name_len(targ_n); |
|
local_len = bpf_core_essential_name_len(local_n); |
|
|
|
return targ_len == local_len && strncmp(local_n, targ_n, local_len) == 0; |
|
} |
|
|
|
static int bpf_core_enums_match(const struct btf *local_btf, const struct btf_type *local_t, |
|
const struct btf *targ_btf, const struct btf_type *targ_t) |
|
{ |
|
__u16 local_vlen = btf_vlen(local_t); |
|
__u16 targ_vlen = btf_vlen(targ_t); |
|
int i, j; |
|
|
|
if (local_t->size != targ_t->size) |
|
return 0; |
|
|
|
if (local_vlen > targ_vlen) |
|
return 0; |
|
|
|
/* iterate over the local enum's variants and make sure each has |
|
* a symbolic name correspondent in the target |
|
*/ |
|
for (i = 0; i < local_vlen; i++) { |
|
bool matched = false; |
|
__u32 local_n_off, targ_n_off; |
|
|
|
local_n_off = btf_is_enum(local_t) ? btf_enum(local_t)[i].name_off : |
|
btf_enum64(local_t)[i].name_off; |
|
|
|
for (j = 0; j < targ_vlen; j++) { |
|
targ_n_off = btf_is_enum(targ_t) ? btf_enum(targ_t)[j].name_off : |
|
btf_enum64(targ_t)[j].name_off; |
|
|
|
if (bpf_core_names_match(local_btf, local_n_off, targ_btf, targ_n_off)) { |
|
matched = true; |
|
break; |
|
} |
|
} |
|
|
|
if (!matched) |
|
return 0; |
|
} |
|
return 1; |
|
} |
|
|
|
static int bpf_core_composites_match(const struct btf *local_btf, const struct btf_type *local_t, |
|
const struct btf *targ_btf, const struct btf_type *targ_t, |
|
bool behind_ptr, int level) |
|
{ |
|
const struct btf_member *local_m = btf_members(local_t); |
|
__u16 local_vlen = btf_vlen(local_t); |
|
__u16 targ_vlen = btf_vlen(targ_t); |
|
int i, j, err; |
|
|
|
if (local_vlen > targ_vlen) |
|
return 0; |
|
|
|
/* check that all local members have a match in the target */ |
|
for (i = 0; i < local_vlen; i++, local_m++) { |
|
const struct btf_member *targ_m = btf_members(targ_t); |
|
bool matched = false; |
|
|
|
for (j = 0; j < targ_vlen; j++, targ_m++) { |
|
if (!bpf_core_names_match(local_btf, local_m->name_off, |
|
targ_btf, targ_m->name_off)) |
|
continue; |
|
|
|
err = __bpf_core_types_match(local_btf, local_m->type, targ_btf, |
|
targ_m->type, behind_ptr, level - 1); |
|
if (err < 0) |
|
return err; |
|
if (err > 0) { |
|
matched = true; |
|
break; |
|
} |
|
} |
|
|
|
if (!matched) |
|
return 0; |
|
} |
|
return 1; |
|
} |
|
|
|
/* Check that two types "match". This function assumes that root types were |
|
* already checked for name match. |
|
* |
|
* The matching relation is defined as follows: |
|
* - modifiers and typedefs are stripped (and, hence, effectively ignored) |
|
* - generally speaking types need to be of same kind (struct vs. struct, union |
|
* vs. union, etc.) |
|
* - exceptions are struct/union behind a pointer which could also match a |
|
* forward declaration of a struct or union, respectively, and enum vs. |
|
* enum64 (see below) |
|
* Then, depending on type: |
|
* - integers: |
|
* - match if size and signedness match |
|
* - arrays & pointers: |
|
* - target types are recursively matched |
|
* - structs & unions: |
|
* - local members need to exist in target with the same name |
|
* - for each member we recursively check match unless it is already behind a |
|
* pointer, in which case we only check matching names and compatible kind |
|
* - enums: |
|
* - local variants have to have a match in target by symbolic name (but not |
|
* numeric value) |
|
* - size has to match (but enum may match enum64 and vice versa) |
|
* - function pointers: |
|
* - number and position of arguments in local type has to match target |
|
* - for each argument and the return value we recursively check match |
|
*/ |
|
int __bpf_core_types_match(const struct btf *local_btf, __u32 local_id, const struct btf *targ_btf, |
|
__u32 targ_id, bool behind_ptr, int level) |
|
{ |
|
const struct btf_type *local_t, *targ_t; |
|
int depth = 32; /* max recursion depth */ |
|
__u16 local_k, targ_k; |
|
|
|
if (level <= 0) |
|
return -EINVAL; |
|
|
|
local_t = btf_type_by_id(local_btf, local_id); |
|
targ_t = btf_type_by_id(targ_btf, targ_id); |
|
|
|
recur: |
|
depth--; |
|
if (depth < 0) |
|
return -EINVAL; |
|
|
|
local_t = skip_mods_and_typedefs(local_btf, local_id, &local_id); |
|
targ_t = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id); |
|
if (!local_t || !targ_t) |
|
return -EINVAL; |
|
|
|
/* While the name check happens after typedefs are skipped, root-level |
|
* typedefs would still be name-matched as that's the contract with |
|
* callers. |
|
*/ |
|
if (!bpf_core_names_match(local_btf, local_t->name_off, targ_btf, targ_t->name_off)) |
|
return 0; |
|
|
|
local_k = btf_kind(local_t); |
|
targ_k = btf_kind(targ_t); |
|
|
|
switch (local_k) { |
|
case BTF_KIND_UNKN: |
|
return local_k == targ_k; |
|
case BTF_KIND_FWD: { |
|
bool local_f = BTF_INFO_KFLAG(local_t->info); |
|
|
|
if (behind_ptr) { |
|
if (local_k == targ_k) |
|
return local_f == BTF_INFO_KFLAG(targ_t->info); |
|
|
|
/* for forward declarations kflag dictates whether the |
|
* target is a struct (0) or union (1) |
|
*/ |
|
return (targ_k == BTF_KIND_STRUCT && !local_f) || |
|
(targ_k == BTF_KIND_UNION && local_f); |
|
} else { |
|
if (local_k != targ_k) |
|
return 0; |
|
|
|
/* match if the forward declaration is for the same kind */ |
|
return local_f == BTF_INFO_KFLAG(targ_t->info); |
|
} |
|
} |
|
case BTF_KIND_ENUM: |
|
case BTF_KIND_ENUM64: |
|
if (!btf_is_any_enum(targ_t)) |
|
return 0; |
|
|
|
return bpf_core_enums_match(local_btf, local_t, targ_btf, targ_t); |
|
case BTF_KIND_STRUCT: |
|
case BTF_KIND_UNION: |
|
if (behind_ptr) { |
|
bool targ_f = BTF_INFO_KFLAG(targ_t->info); |
|
|
|
if (local_k == targ_k) |
|
return 1; |
|
|
|
if (targ_k != BTF_KIND_FWD) |
|
return 0; |
|
|
|
return (local_k == BTF_KIND_UNION) == targ_f; |
|
} else { |
|
if (local_k != targ_k) |
|
return 0; |
|
|
|
return bpf_core_composites_match(local_btf, local_t, targ_btf, targ_t, |
|
behind_ptr, level); |
|
} |
|
case BTF_KIND_INT: { |
|
__u8 local_sgn; |
|
__u8 targ_sgn; |
|
|
|
if (local_k != targ_k) |
|
return 0; |
|
|
|
local_sgn = btf_int_encoding(local_t) & BTF_INT_SIGNED; |
|
targ_sgn = btf_int_encoding(targ_t) & BTF_INT_SIGNED; |
|
|
|
return local_t->size == targ_t->size && local_sgn == targ_sgn; |
|
} |
|
case BTF_KIND_PTR: |
|
if (local_k != targ_k) |
|
return 0; |
|
|
|
behind_ptr = true; |
|
|
|
local_id = local_t->type; |
|
targ_id = targ_t->type; |
|
goto recur; |
|
case BTF_KIND_ARRAY: { |
|
const struct btf_array *local_array = btf_array(local_t); |
|
const struct btf_array *targ_array = btf_array(targ_t); |
|
|
|
if (local_k != targ_k) |
|
return 0; |
|
|
|
if (local_array->nelems != targ_array->nelems) |
|
return 0; |
|
|
|
local_id = local_array->type; |
|
targ_id = targ_array->type; |
|
goto recur; |
|
} |
|
case BTF_KIND_FUNC_PROTO: { |
|
struct btf_param *local_p = btf_params(local_t); |
|
struct btf_param *targ_p = btf_params(targ_t); |
|
__u16 local_vlen = btf_vlen(local_t); |
|
__u16 targ_vlen = btf_vlen(targ_t); |
|
int i, err; |
|
|
|
if (local_k != targ_k) |
|
return 0; |
|
|
|
if (local_vlen != targ_vlen) |
|
return 0; |
|
|
|
for (i = 0; i < local_vlen; i++, local_p++, targ_p++) { |
|
err = __bpf_core_types_match(local_btf, local_p->type, targ_btf, |
|
targ_p->type, behind_ptr, level - 1); |
|
if (err <= 0) |
|
return err; |
|
} |
|
|
|
/* tail recurse for return type check */ |
|
local_id = local_t->type; |
|
targ_id = targ_t->type; |
|
goto recur; |
|
} |
|
default: |
|
pr_warn("unexpected kind %s relocated, local [%d], target [%d]\n", |
|
btf_kind_str(local_t), local_id, targ_id); |
|
return 0; |
|
} |
|
}
|
|
|