| // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) |
| /* Copyright (c) 2019 Facebook */ |
| |
| #ifdef __KERNEL__ |
| #include <linux/bpf.h> |
| #include <linux/btf.h> |
| #include <linux/string.h> |
| #include <linux/bpf_verifier.h> |
| #include "relo_core.h" |
| |
| static const char *btf_kind_str(const struct btf_type *t) |
| { |
| return btf_type_str(t); |
| } |
| |
| static bool is_ldimm64_insn(struct bpf_insn *insn) |
| { |
| return insn->code == (BPF_LD | BPF_IMM | BPF_DW); |
| } |
| |
| static const struct btf_type * |
| skip_mods_and_typedefs(const struct btf *btf, u32 id, u32 *res_id) |
| { |
| return btf_type_skip_modifiers(btf, id, res_id); |
| } |
| |
| static const char *btf__name_by_offset(const struct btf *btf, u32 offset) |
| { |
| return btf_name_by_offset(btf, offset); |
| } |
| |
| static s64 btf__resolve_size(const struct btf *btf, u32 type_id) |
| { |
| const struct btf_type *t; |
| int size; |
| |
| t = btf_type_by_id(btf, type_id); |
| t = btf_resolve_size(btf, t, &size); |
| if (IS_ERR(t)) |
| return PTR_ERR(t); |
| return size; |
| } |
| |
| enum libbpf_print_level { |
| LIBBPF_WARN, |
| LIBBPF_INFO, |
| LIBBPF_DEBUG, |
| }; |
| |
| #undef pr_warn |
| #undef pr_info |
| #undef pr_debug |
| #define pr_warn(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__) |
| #define pr_info(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__) |
| #define pr_debug(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__) |
| #define libbpf_print(level, fmt, ...) bpf_log((void *)prog_name, fmt, ##__VA_ARGS__) |
| #else |
| #include <stdio.h> |
| #include <string.h> |
| #include <errno.h> |
| #include <ctype.h> |
| #include <linux/err.h> |
| |
| #include "libbpf.h" |
| #include "bpf.h" |
| #include "btf.h" |
| #include "str_error.h" |
| #include "libbpf_internal.h" |
| #endif |
| |
| static bool is_flex_arr(const struct btf *btf, |
| const struct bpf_core_accessor *acc, |
| const struct btf_array *arr) |
| { |
| const struct btf_type *t; |
| |
| /* not a flexible array, if not inside a struct or has non-zero size */ |
| if (!acc->name || arr->nelems > 0) |
| return false; |
| |
| /* has to be the last member of enclosing struct */ |
| t = btf_type_by_id(btf, acc->type_id); |
| return acc->idx == btf_vlen(t) - 1; |
| } |
| |
| static const char *core_relo_kind_str(enum bpf_core_relo_kind kind) |
| { |
| switch (kind) { |
| case BPF_CORE_FIELD_BYTE_OFFSET: return "byte_off"; |
| case BPF_CORE_FIELD_BYTE_SIZE: return "byte_sz"; |
| case BPF_CORE_FIELD_EXISTS: return "field_exists"; |
| case BPF_CORE_FIELD_SIGNED: return "signed"; |
| case BPF_CORE_FIELD_LSHIFT_U64: return "lshift_u64"; |
| case BPF_CORE_FIELD_RSHIFT_U64: return "rshift_u64"; |
| case BPF_CORE_TYPE_ID_LOCAL: return "local_type_id"; |
| case BPF_CORE_TYPE_ID_TARGET: return "target_type_id"; |
| case BPF_CORE_TYPE_EXISTS: return "type_exists"; |
| case BPF_CORE_TYPE_SIZE: return "type_size"; |
| case BPF_CORE_ENUMVAL_EXISTS: return "enumval_exists"; |
| case BPF_CORE_ENUMVAL_VALUE: return "enumval_value"; |
| default: return "unknown"; |
| } |
| } |
| |
| static bool core_relo_is_field_based(enum bpf_core_relo_kind kind) |
| { |
| switch (kind) { |
| case BPF_CORE_FIELD_BYTE_OFFSET: |
| case BPF_CORE_FIELD_BYTE_SIZE: |
| case BPF_CORE_FIELD_EXISTS: |
| case BPF_CORE_FIELD_SIGNED: |
| case BPF_CORE_FIELD_LSHIFT_U64: |
| case BPF_CORE_FIELD_RSHIFT_U64: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| static bool core_relo_is_type_based(enum bpf_core_relo_kind kind) |
| { |
| switch (kind) { |
| case BPF_CORE_TYPE_ID_LOCAL: |
| case BPF_CORE_TYPE_ID_TARGET: |
| case BPF_CORE_TYPE_EXISTS: |
| case BPF_CORE_TYPE_SIZE: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind) |
| { |
| switch (kind) { |
| case BPF_CORE_ENUMVAL_EXISTS: |
| case BPF_CORE_ENUMVAL_VALUE: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| /* |
| * Turn bpf_core_relo into a low- and high-level spec representation, |
| * validating correctness along the way, as well as calculating resulting |
| * field bit offset, specified by accessor string. Low-level spec captures |
| * every single level of nestedness, including traversing anonymous |
| * struct/union members. High-level one only captures semantically meaningful |
| * "turning points": named fields and array indicies. |
| * E.g., for this case: |
| * |
| * struct sample { |
| * int __unimportant; |
| * struct { |
| * int __1; |
| * int __2; |
| * int a[7]; |
| * }; |
| * }; |
| * |
| * struct sample *s = ...; |
| * |
| * int x = &s->a[3]; // access string = '0:1:2:3' |
| * |
| * Low-level spec has 1:1 mapping with each element of access string (it's |
| * just a parsed access string representation): [0, 1, 2, 3]. |
| * |
| * High-level spec will capture only 3 points: |
| * - intial zero-index access by pointer (&s->... is the same as &s[0]...); |
| * - field 'a' access (corresponds to '2' in low-level spec); |
| * - array element #3 access (corresponds to '3' in low-level spec). |
| * |
| * Type-based relocations (TYPE_EXISTS/TYPE_SIZE, |
| * TYPE_ID_LOCAL/TYPE_ID_TARGET) don't capture any field information. Their |
| * spec and raw_spec are kept empty. |
| * |
| * Enum value-based relocations (ENUMVAL_EXISTS/ENUMVAL_VALUE) use access |
| * string to specify enumerator's value index that need to be relocated. |
| */ |
| static int bpf_core_parse_spec(const char *prog_name, const struct btf *btf, |
| __u32 type_id, |
| const char *spec_str, |
| enum bpf_core_relo_kind relo_kind, |
| struct bpf_core_spec *spec) |
| { |
| int access_idx, parsed_len, i; |
| struct bpf_core_accessor *acc; |
| const struct btf_type *t; |
| const char *name; |
| __u32 id; |
| __s64 sz; |
| |
| if (str_is_empty(spec_str) || *spec_str == ':') |
| return -EINVAL; |
| |
| memset(spec, 0, sizeof(*spec)); |
| spec->btf = btf; |
| spec->root_type_id = type_id; |
| spec->relo_kind = relo_kind; |
| |
| /* type-based relocations don't have a field access string */ |
| if (core_relo_is_type_based(relo_kind)) { |
| if (strcmp(spec_str, "0")) |
| return -EINVAL; |
| return 0; |
| } |
| |
| /* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */ |
| while (*spec_str) { |
| if (*spec_str == ':') |
| ++spec_str; |
| if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1) |
| return -EINVAL; |
| if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN) |
| return -E2BIG; |
| spec_str += parsed_len; |
| spec->raw_spec[spec->raw_len++] = access_idx; |
| } |
| |
| if (spec->raw_len == 0) |
| return -EINVAL; |
| |
| t = skip_mods_and_typedefs(btf, type_id, &id); |
| if (!t) |
| return -EINVAL; |
| |
| access_idx = spec->raw_spec[0]; |
| acc = &spec->spec[0]; |
| acc->type_id = id; |
| acc->idx = access_idx; |
| spec->len++; |
| |
| if (core_relo_is_enumval_based(relo_kind)) { |
| if (!btf_is_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t)) |
| return -EINVAL; |
| |
| /* record enumerator name in a first accessor */ |
| acc->name = btf__name_by_offset(btf, btf_enum(t)[access_idx].name_off); |
| 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, 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(local_type) != btf_kind(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_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; |
| |
| 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)) { |
| 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 struct btf_enum *e; |
| 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_enum(targ_type)) |
| return 0; |
| |
| local_essent_len = bpf_core_essential_name_len(local_acc->name); |
| |
| for (i = 0, e = btf_enum(targ_type); i < btf_vlen(targ_type); i++, e++) { |
| targ_name = btf__name_by_offset(targ_spec->btf, e->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, |
| __u32 *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: |
| /* enums will be assumed unsigned */ |
| *val = btf_is_enum(mt) || |
| (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, |
| __u32 *val) |
| { |
| __s64 sz; |
| |
| /* 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; |
| break; |
| case BPF_CORE_TYPE_EXISTS: |
| *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, |
| __u32 *val) |
| { |
| const struct btf_type *t; |
| const struct btf_enum *e; |
| |
| 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); |
| e = btf_enum(t) + spec->spec[0].idx; |
| *val = e->val; |
| break; |
| default: |
| return -EOPNOTSUPP; |
| } |
| |
| return 0; |
| } |
| |
| struct bpf_core_relo_res |
| { |
| /* expected value in the instruction, unless validate == false */ |
| __u32 orig_val; |
| /* new value that needs to be patched up to */ |
| __u32 new_val; |
| /* relocation unsuccessful, poison instruction, but don't fail load */ |
| bool poison; |
| /* some relocations can't be validated against orig_val */ |
| bool validate; |
| /* for field byte offset relocations or the forms: |
| * *(T *)(rX + <off>) = rY |
| * rX = *(T *)(rY + <off>), |
| * we remember original and resolved field size to adjust direct |
| * memory loads of pointers and integers; this is necessary for 32-bit |
| * host kernel architectures, but also allows to automatically |
| * relocate fields that were resized from, e.g., u32 to u64, etc. |
| */ |
| bool fail_memsz_adjust; |
| __u32 orig_sz; |
| __u32 orig_type_id; |
| __u32 new_sz; |
| __u32 new_type_id; |
| }; |
| |
| /* 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); |
| err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val); |
| } 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}. |
| */ |
| static 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) |
| { |
| __u32 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 %u -> %u\n", |
| prog_name, relo_idx, |
| insn_idx, insn->imm, orig_val, new_val); |
| return -EINVAL; |
| } |
| orig_val = insn->imm; |
| insn->imm = new_val; |
| pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %u -> %u\n", |
| prog_name, relo_idx, insn_idx, |
| orig_val, 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 %u -> %u\n", |
| prog_name, relo_idx, insn_idx, insn->off, orig_val, new_val); |
| return -EINVAL; |
| } |
| if (new_val > SHRT_MAX) { |
| pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %u\n", |
| prog_name, relo_idx, insn_idx, 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 %u -> %u\n", |
| prog_name, relo_idx, insn_idx, orig_val, 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 = 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 %u -> %u\n", |
| prog_name, relo_idx, |
| insn_idx, (unsigned long long)imm, |
| orig_val, new_val); |
| return -EINVAL; |
| } |
| |
| insn[0].imm = new_val; |
| insn[1].imm = 0; /* currently only 32-bit values are supported */ |
| pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %u\n", |
| prog_name, relo_idx, insn_idx, |
| (unsigned long long)imm, 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 |
| */ |
| static void bpf_core_dump_spec(const char *prog_name, int level, const struct bpf_core_spec *spec) |
| { |
| const struct btf_type *t; |
| const struct btf_enum *e; |
| const char *s; |
| __u32 type_id; |
| int i; |
| |
| 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); |
| |
| libbpf_print(level, "[%u] %s %s", type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s); |
| |
| if (core_relo_is_type_based(spec->relo_kind)) |
| return; |
| |
| if (core_relo_is_enumval_based(spec->relo_kind)) { |
| t = skip_mods_and_typedefs(spec->btf, type_id, NULL); |
| e = btf_enum(t) + spec->raw_spec[0]; |
| s = btf__name_by_offset(spec->btf, e->name_off); |
| |
| libbpf_print(level, "::%s = %u", s, e->val); |
| return; |
| } |
| |
| if (core_relo_is_field_based(spec->relo_kind)) { |
| for (i = 0; i < spec->len; i++) { |
| if (spec->spec[i].name) |
| libbpf_print(level, ".%s", spec->spec[i].name); |
| else if (i > 0 || spec->spec[i].idx > 0) |
| libbpf_print(level, "[%u]", spec->spec[i].idx); |
| } |
| |
| libbpf_print(level, " ("); |
| for (i = 0; i < spec->raw_len; i++) |
| libbpf_print(level, "%s%d", i == 0 ? "" : ":", spec->raw_spec[i]); |
| |
| if (spec->bit_offset % 8) |
| libbpf_print(level, " @ offset %u.%u)", |
| spec->bit_offset / 8, spec->bit_offset % 8); |
| else |
| libbpf_print(level, " @ offset %u)", spec->bit_offset / 8); |
| return; |
| } |
| } |
| |
| /* |
| * CO-RE relocate single instruction. |
| * |
| * 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 accomodate |
| * imprefection 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 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_apply_relo_insn(const char *prog_name, struct bpf_insn *insn, |
| int insn_idx, |
| 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_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, targ_res; |
| const struct btf_type *local_type; |
| const char *local_name; |
| __u32 local_id; |
| const char *spec_str; |
| 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; |
| |
| spec_str = btf__name_by_offset(local_btf, relo->access_str_off); |
| if (str_is_empty(spec_str)) |
| return -EINVAL; |
| |
| err = bpf_core_parse_spec(prog_name, local_btf, local_id, spec_str, |
| relo->kind, local_spec); |
| if (err) { |
| 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; |
| } |
| |
| pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name, |
| relo_idx, core_relo_kind_str(relo->kind), relo->kind); |
| bpf_core_dump_spec(prog_name, LIBBPF_DEBUG, local_spec); |
| libbpf_print(LIBBPF_DEBUG, "\n"); |
| |
| /* TYPE_ID_LOCAL relo is special and doesn't need candidate search */ |
| if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) { |
| targ_res.validate = true; |
| targ_res.poison = false; |
| targ_res.orig_val = local_spec->root_type_id; |
| targ_res.new_val = local_spec->root_type_id; |
| goto patch_insn; |
| } |
| |
| /* libbpf doesn't support candidate search for anonymous types */ |
| if (str_is_empty(spec_str)) { |
| 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) { |
| pr_warn("prog '%s': relo #%d: error matching candidate #%d ", |
| prog_name, relo_idx, i); |
| bpf_core_dump_spec(prog_name, LIBBPF_WARN, cand_spec); |
| libbpf_print(LIBBPF_WARN, ": %d\n", err); |
| return err; |
| } |
| |
| pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name, |
| relo_idx, err == 0 ? "non-matching" : "matching", i); |
| bpf_core_dump_spec(prog_name, LIBBPF_DEBUG, cand_spec); |
| libbpf_print(LIBBPF_DEBUG, "\n"); |
| |
| 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 %u != %s %u\n", |
| prog_name, relo_idx, |
| cand_res.poison ? "failure" : "success", cand_res.new_val, |
| targ_res.poison ? "failure" : "success", 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; |
| } |
| |
| patch_insn: |
| /* bpf_core_patch_insn() should know how to handle missing targ_spec */ |
| err = bpf_core_patch_insn(prog_name, insn, insn_idx, relo, relo_idx, &targ_res); |
| if (err) { |
| pr_warn("prog '%s': relo #%d: failed to patch insn #%u: %d\n", |
| prog_name, relo_idx, relo->insn_off / 8, err); |
| return -EINVAL; |
| } |
| |
| return 0; |
| } |