-static bool is_ldimm64_insn(struct bpf_insn *insn)

-{

- return insn->code == (BPF_LD | BPF_IMM | BPF_DW);

-}

-

-#define BPF_CORE_SPEC_MAX_LEN 64

-

-/* represents BPF CO-RE field or array element accessor */

-struct bpf_core_accessor {

- __u32 type_id; /* struct/union type or array element type */

- __u32 idx; /* field index or array index */

- const char *name; /* field name or NULL for array accessor */

-};

-

-struct bpf_core_spec {

- const struct btf *btf;

- /* high-level spec: named fields and array indices only */

- struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];

- /* original unresolved (no skip_mods_or_typedefs) root type ID */

- __u32 root_type_id;

- /* CO-RE relocation kind */

- enum bpf_core_relo_kind relo_kind;

- /* high-level spec length */

- int len;

- /* raw, low-level spec: 1-to-1 with accessor spec string */

- int raw_spec[BPF_CORE_SPEC_MAX_LEN];

- /* raw spec length */

- int raw_len;

- /* field bit offset represented by spec */

- __u32 bit_offset;

-};

-

-static bool str_is_empty(const char *s)

-{

- return !s || !s[0];

-}

-

-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_FIELD_BYTE_OFFSET: return "byte_off";

- case BPF_FIELD_BYTE_SIZE: return "byte_sz";

- case BPF_FIELD_EXISTS: return "field_exists";

- case BPF_FIELD_SIGNED: return "signed";

- case BPF_FIELD_LSHIFT_U64: return "lshift_u64";

- case BPF_FIELD_RSHIFT_U64: return "rshift_u64";

- case BPF_TYPE_ID_LOCAL: return "local_type_id";

- case BPF_TYPE_ID_TARGET: return "target_type_id";

- case BPF_TYPE_EXISTS: return "type_exists";

- case BPF_TYPE_SIZE: return "type_size";

- case BPF_ENUMVAL_EXISTS: return "enumval_exists";

- case BPF_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_FIELD_BYTE_OFFSET:

- case BPF_FIELD_BYTE_SIZE:

- case BPF_FIELD_EXISTS:

- case BPF_FIELD_SIGNED:

- case BPF_FIELD_LSHIFT_U64:

- case BPF_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_TYPE_ID_LOCAL:

- case BPF_TYPE_ID_TARGET:

- case BPF_TYPE_EXISTS:

- case BPF_TYPE_SIZE:

- return true;

- default:

- return false;

- }

-}

-

-static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind)

-{

- switch (kind) {

- case BPF_ENUMVAL_EXISTS:

- case BPF_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 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("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n",

- type_id, spec_str, i, id, btf_kind_str(t));

- return -EINVAL;

- }

- }

-

- return 0;

-}

-

-static size_t bpf_core_essential_name_len(const char *name)

-/* 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:

- pr_warn("unexpected kind %d relocated, local [%d], target [%d]\n",

- btf_kind(local_type), local_id, targ_id);

- 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;

-}

-

-static int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,

- const struct btf *targ_btf, __u32 targ_id)

-/*

- * 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_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_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_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_FIELD_BYTE_OFFSET:

- *val = byte_off;

- if (!bitfield) {

- *field_sz = byte_sz;

- *type_id = field_type_id;

- }

- break;

- case BPF_FIELD_BYTE_SIZE:

- *val = byte_sz;

- break;

- case BPF_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_FIELD_LSHIFT_U64:

-#if __BYTE_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_FIELD_RSHIFT_U64:

- *val = 64 - bit_sz;

- if (validate)

- *validate = true; /* right shift is never ambiguous */

- break;

- case BPF_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_TYPE_ID_TARGET:

- *val = spec->root_type_id;

- break;

- case BPF_TYPE_EXISTS:

- *val = 1;

- break;

- case BPF_TYPE_SIZE:

- sz = btf__resolve_size(spec->btf, spec->root_type_id);

- if (sz < 0)

- return -EINVAL;

- *val = sz;

- break;

- case BPF_TYPE_ID_LOCAL:

- /* BPF_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_ENUMVAL_EXISTS:

- *val = spec ? 1 : 0;

- break;

- case BPF_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(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.

- */

-static 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 local_spec, cand_spec, targ_spec = {};

- 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);

- if (!local_type)

- return -EINVAL;

-

- 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(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(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_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(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(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_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 #%zu: %d\n",

- prog_name, relo_idx, relo->insn_off / BPF_INSN_SZ, err);

- return -EINVAL;

- }

-

- return 0;

-}

-