| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20210721000822.40958-5-alexei.starovoitov@gmail.com>
Date: Tue, 20 Jul 2021 17:08:22 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: davem@...emloft.net
Cc: daniel@...earbox.net, andrii@...nel.org, netdev@...r.kernel.org,
bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH bpf-next 4/4] libbpf: Split CO-RE logic into relo_core.c.
From: Alexei Starovoitov <ast@...nel.org>
Move CO-RE logic into separate file.
The internal interface between libbpf and CO-RE is through
bpf_core_apply_relo_insn() function and few structs defined in relo_core.h.
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
tools/lib/bpf/Build | 2 +-
tools/lib/bpf/libbpf.c | 1297 +-----------------------------
tools/lib/bpf/libbpf_internal.h | 10 +
tools/lib/bpf/relo_core.c | 1326 +++++++++++++++++++++++++++++++
tools/lib/bpf/relo_core.h | 10 +
5 files changed, 1350 insertions(+), 1295 deletions(-)
create mode 100644 tools/lib/bpf/relo_core.c
diff --git a/tools/lib/bpf/Build b/tools/lib/bpf/Build
index 430f6874fa41..94f0a146bb7b 100644
--- a/tools/lib/bpf/Build
+++ b/tools/lib/bpf/Build
@@ -1,3 +1,3 @@
libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o \
netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o hashmap.o \
- btf_dump.o ringbuf.o strset.o linker.o gen_loader.o
+ btf_dump.o ringbuf.o strset.o linker.o gen_loader.o relo_core.o
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7ae5992a79e2..c8c7419b3efd 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -595,11 +595,6 @@ static bool insn_is_subprog_call(const struct bpf_insn *insn)
insn->off == 0;
}
-static bool is_ldimm64_insn(struct bpf_insn *insn)
-{
- return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
-}
-
static bool is_call_insn(const struct bpf_insn *insn)
{
return insn->code == (BPF_JMP | BPF_CALL);
@@ -4725,279 +4720,6 @@ bpf_object__create_maps(struct bpf_object *obj)
return err;
}
-#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 bool bpf_core_is_flavor_sep(const char *s)
{
/* check X___Y name pattern, where X and Y are not underscores */
@@ -5010,7 +4732,7 @@ static bool bpf_core_is_flavor_sep(const char *s)
* before last triple underscore. Struct name part after last triple
* underscore is ignored by BPF CO-RE relocation during relocation matching.
*/
-static size_t bpf_core_essential_name_len(const char *name)
+size_t bpf_core_essential_name_len(const char *name)
{
size_t n = strlen(name);
int i;
@@ -5229,165 +4951,6 @@ bpf_core_find_cands(struct bpf_object *obj, const struct btf *local_btf, __u32 l
return ERR_PTR(err);
}
-/* 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;
-}
-
/* Check local and target types for compatibility. This check is used for
* type-based CO-RE relocations and follow slightly different rules than
* field-based relocations. This function assumes that root types were already
@@ -5407,8 +4970,8 @@ static int bpf_core_match_member(const struct btf *local_btf,
* 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_types_are_compat(const struct btf *local_btf, __u32 local_id,
- const struct btf *targ_btf, __u32 targ_id)
+int bpf_core_types_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;
int depth = 32; /* max recursion depth */
@@ -5482,658 +5045,6 @@ static int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_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;
- }
-}
-
static size_t bpf_core_hash_fn(const void *key, void *ctx)
{
return (size_t)key;
@@ -6149,208 +5060,6 @@ static void *u32_as_hash_key(__u32 x)
return (void *)(uintptr_t)x;
}
-/*
- * 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;
-}
-
static int bpf_core_apply_relo(struct bpf_program *prog,
const struct bpf_core_relo *relo,
int relo_idx,
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 3178d5685dce..f7b691d5f9eb 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -425,4 +425,14 @@ static inline void *libbpf_ptr(void *ret)
return ret;
}
+static inline bool str_is_empty(const char *s)
+{
+ return !s || !s[0];
+}
+
+static inline bool is_ldimm64_insn(struct bpf_insn *insn)
+{
+ return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
+}
+
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */
diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
new file mode 100644
index 000000000000..8fd5440dc17b
--- /dev/null
+++ b/tools/lib/bpf/relo_core.c
@@ -0,0 +1,1326 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <libgen.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <string.h>
+#include <unistd.h>
+#include <endian.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <ctype.h>
+#include <asm/unistd.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/filter.h>
+#include <linux/list.h>
+#include <linux/limits.h>
+#include <linux/perf_event.h>
+#include <linux/ring_buffer.h>
+#include <linux/version.h>
+#include <sys/epoll.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/vfs.h>
+#include <sys/utsname.h>
+#include <sys/resource.h>
+#include <libelf.h>
+#include <gelf.h>
+#include <zlib.h>
+
+#include "libbpf.h"
+#include "bpf.h"
+#include "btf.h"
+#include "str_error.h"
+#include "libbpf_internal.h"
+
+#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 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;
+}
+
+/* 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;
+}
+
+/*
+ * 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.
+ */
+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 #%u: %d\n",
+ prog_name, relo_idx, relo->insn_off / 8, err);
+ return -EINVAL;
+ }
+
+ return 0;
+}
diff --git a/tools/lib/bpf/relo_core.h b/tools/lib/bpf/relo_core.h
index 62633e73c297..40534650d807 100644
--- a/tools/lib/bpf/relo_core.h
+++ b/tools/lib/bpf/relo_core.h
@@ -89,4 +89,14 @@ struct bpf_core_cand_list {
int len;
};
+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);
+int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
+ const struct btf *targ_btf, __u32 targ_id);
+
+size_t bpf_core_essential_name_len(const char *name);
#endif
--
2.30.2
Powered by blists - more mailing lists