@@ -107,7 +107,7 @@ ifeq ($(feature-reallocarray), 0)
endif
# Append required CFLAGS
-override CFLAGS += $(EXTRA_WARNINGS)
+override CFLAGS += $(EXTRA_WARNINGS) -Wno-switch-enum
override CFLAGS += -Werror -Wall
override CFLAGS += -fPIC
override CFLAGS += $(INCLUDES)
@@ -19,6 +19,18 @@ enum bpf_field_info_kind {
BPF_FIELD_RSHIFT_U64 = 5,
};
+/* second argument to __builtin_btf_type_id() built-in */
+enum bpf_type_id_kind {
+ BPF_TYPE_ID_LOCAL = 0, /* BTF type ID in local program */
+ BPF_TYPE_ID_TARGET = 1, /* BTF type ID in target kernel */
+};
+
+/* second argument to __builtin_preserve_type_info() built-in */
+enum bpf_type_info_kind {
+ BPF_TYPE_EXISTS = 0, /* type existence in target kernel */
+ BPF_TYPE_SIZE = 1, /* type size in target kernel */
+};
+
#define __CORE_RELO(src, field, info) \
__builtin_preserve_field_info((src)->field, BPF_FIELD_##info)
@@ -92,12 +104,50 @@ enum bpf_field_info_kind {
__builtin_preserve_field_info(field, BPF_FIELD_EXISTS)
/*
- * Convenience macro to get byte size of a field. Works for integers,
+ * Convenience macro to get the byte size of a field. Works for integers,
* struct/unions, pointers, arrays, and enums.
*/
#define bpf_core_field_size(field) \
__builtin_preserve_field_info(field, BPF_FIELD_BYTE_SIZE)
+/*
+ * Convenience macro to get BTF type ID of a specified type, using a local BTF
+ * information. Return 32-bit unsigned integer with type ID from program's own
+ * BTF. Always succeeds.
+ */
+#define bpf_core_type_id_local(type) \
+ __builtin_btf_type_id(*(typeof(type) *)0, BPF_TYPE_ID_LOCAL)
+
+/*
+ * Convenience macro to get BTF type ID of a target kernel's type that matches
+ * specified local type.
+ * Returns:
+ * - valid 32-bit unsigned type ID in kernel BTF;
+ * - 0, if no matching type was found in a target kernel BTF.
+ */
+#define bpf_core_type_id_kernel(type) \
+ __builtin_btf_type_id(*(typeof(type) *)0, BPF_TYPE_ID_TARGET)
+
+/*
+ * Convenience macro to check that provided named type
+ * (struct/union/enum/typedef) exists in a target kernel.
+ * Returns:
+ * 1, if such type is present in target kernel's BTF;
+ * 0, if no matching type is found.
+ */
+#define bpf_core_type_exists(type) \
+ __builtin_preserve_type_info(*(typeof(type) *)0, BPF_TYPE_EXISTS)
+
+/*
+ * Convenience macro to get the byte size of a provided named type
+ * (struct/union/enum/typedef) in a target kernel.
+ * Returns:
+ * >= 0 size (in bytes), if type is present in target kernel's BTF;
+ * 0, if no matching type is found.
+ */
+#define bpf_core_type_size(type) \
+ __builtin_preserve_type_info(*(typeof(type) *)0, BPF_TYPE_SIZE)
+
/*
* bpf_core_read() abstracts away bpf_probe_read() call and captures offset
* relocation for source address using __builtin_preserve_access_index()
@@ -4072,6 +4072,10 @@ static const char *core_relo_kind_str(enum bpf_core_relo_kind kind)
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";
default: return "unknown";
}
}
@@ -4091,6 +4095,19 @@ static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
}
}
+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;
+ }
+}
+
/*
* Turn bpf_core_relo into a low- and high-level spec representation,
* validating correctness along the way, as well as calculating resulting
@@ -4121,6 +4138,9 @@ static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
* - 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.
*/
static int bpf_core_parse_spec(const struct btf *btf,
__u32 type_id,
@@ -4143,6 +4163,13 @@ static int bpf_core_parse_spec(const struct 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 == ':')
@@ -4278,7 +4305,7 @@ static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
const struct btf *targ_btf)
{
size_t local_essent_len, targ_essent_len;
- const char *local_name, *targ_name, *targ_kind;
+ const char *local_name, *targ_name;
const struct btf_type *t, *local_t;
struct ids_vec *cand_ids;
__u32 *new_ids;
@@ -4300,13 +4327,11 @@ static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
n = btf__get_nr_types(targ_btf);
for (i = 1; i <= n; i++) {
t = btf__type_by_id(targ_btf, i);
- targ_name = btf__name_by_offset(targ_btf, t->name_off);
- if (str_is_empty(targ_name))
+ if (btf_kind(t) != btf_kind(local_t))
continue;
- targ_kind = btf_kind_str(t);
- t = skip_mods_and_typedefs(targ_btf, i, NULL);
- if (!btf_is_composite(t) && !btf_is_array(t))
+ targ_name = btf__name_by_offset(targ_btf, t->name_off);
+ if (str_is_empty(targ_name))
continue;
targ_essent_len = bpf_core_essential_name_len(targ_name);
@@ -4316,7 +4341,7 @@ static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
if (strncmp(local_name, targ_name, local_essent_len) == 0) {
pr_debug("CO-RE relocating [%d] %s %s: found target candidate [%d] %s %s\n",
local_type_id, btf_kind_str(local_t),
- local_name, i, targ_kind, targ_name);
+ local_name, i, btf_kind_str(t), targ_name);
new_ids = reallocarray(cand_ids->data,
cand_ids->len + 1,
sizeof(*cand_ids->data));
@@ -4334,8 +4359,9 @@ static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
return ERR_PTR(err);
}
-/* Check two types for compatibility, skipping const/volatile/restrict and
- * typedefs, to ensure we are relocating compatible entities:
+/* 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;
@@ -4490,6 +4516,100 @@ static int bpf_core_match_member(const struct btf *local_btf,
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
+ * checked for name match. Beyond that initial root-level name check, names
+ * are completely ignored. Compatibility rules are as follows:
+ * - any two STRUCTs/UNIONs/FWDs/ENUMs/INTs are considered compatible, but
+ * kind should match for local and target types (i.e., STRUCT is not
+ * compatible with UNION);
+ * - for ENUMs, the size is ignored;
+ * - for INT, size and signedness are ignored;
+ * - for ARRAY, dimensionality is ignored, element types are checked for
+ * compatibility recursively;
+ * - CONST/VOLATILE/RESTRICT modifiers are ignored;
+ * - TYPEDEFs/PTRs are compatible if types they pointing to are compatible;
+ * - FUNC_PROTOs are compatible if they have compatible signature: same
+ * number of input args and compatible return and argument types.
+ * 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)
+{
+ const struct btf_type *local_type, *targ_type;
+ int depth = 32; /* max recursion depth */
+
+ /* caller made sure that names match (ignoring flavor suffix) */
+ local_type = btf__type_by_id(local_btf, local_id);
+ targ_type = btf__type_by_id(local_btf, local_id);
+ if (btf_kind(local_type) != btf_kind(targ_type))
+ return 0;
+
+recur:
+ depth--;
+ if (depth < 0)
+ return -EINVAL;
+
+ 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_kind(local_type) != btf_kind(targ_type))
+ return 0;
+
+ switch (btf_kind(local_type)) {
+ case BTF_KIND_UNKN:
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ case BTF_KIND_ENUM:
+ case BTF_KIND_FWD:
+ return 1;
+ 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_PTR:
+ local_id = local_type->type;
+ targ_id = targ_type->type;
+ goto recur;
+ case BTF_KIND_ARRAY:
+ local_id = btf_array(local_type)->type;
+ targ_id = btf_array(targ_type)->type;
+ goto recur;
+ case BTF_KIND_FUNC_PROTO: {
+ struct btf_param *local_p = btf_params(local_type);
+ struct btf_param *targ_p = btf_params(targ_type);
+ __u16 local_vlen = btf_vlen(local_type);
+ __u16 targ_vlen = btf_vlen(targ_type);
+ int i, err;
+
+ if (local_vlen != targ_vlen)
+ return 0;
+
+ for (i = 0; i < local_vlen; i++, local_p++, targ_p++) {
+ skip_mods_and_typedefs(local_btf, local_p->type, &local_id);
+ skip_mods_and_typedefs(targ_btf, targ_p->type, &targ_id);
+ err = bpf_core_types_are_compat(local_btf, local_id, targ_btf, targ_id);
+ if (err <= 0)
+ return err;
+ }
+
+ /* tail recurse for return type check */
+ skip_mods_and_typedefs(local_btf, local_type->type, &local_id);
+ skip_mods_and_typedefs(targ_btf, targ_type->type, &targ_id);
+ goto recur;
+ }
+ default:
+ pr_warn("unexpected kind %s relocated, local [%d], target [%d]\n",
+ btf_kind_str(local_type), local_id, targ_id);
+ return 0;
+ }
+}
+
/*
* Try to match local spec to a target type and, if successful, produce full
* target spec (high-level, low-level + bit offset).
@@ -4508,6 +4628,12 @@ static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
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];
@@ -4681,6 +4807,40 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
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;
+}
+
struct bpf_core_relo_res
{
/* expected value in the instruction, unless validate == false */
@@ -4716,6 +4876,9 @@ static int bpf_core_calc_relo(const struct bpf_program *prog,
if (core_relo_is_field_based(relo->kind)) {
err = bpf_core_calc_field_relo(prog, relo, local_spec, &res->orig_val, &res->validate);
err = err ?: bpf_core_calc_field_relo(prog, relo, targ_spec, &res->new_val, NULL);
+ } 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);
}
if (err == -EUCLEAN) {
@@ -4855,6 +5018,9 @@ static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
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_field_based(spec->relo_kind)) {
for (i = 0; i < spec->len; i++) {
if (spec->spec[i].name)
@@ -4872,6 +5038,7 @@ static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
spec->bit_offset / 8, spec->bit_offset % 8);
else
libbpf_print(level, " @ offset %u)", spec->bit_offset / 8);
+ return;
}
}
@@ -4940,12 +5107,12 @@ static void *u32_as_hash_key(__u32 x)
* 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_reloc_field(struct bpf_program *prog,
- const struct bpf_core_relo *relo,
- int relo_idx,
- const struct btf *local_btf,
- const struct btf *targ_btf,
- struct hashmap *cand_cache)
+static int bpf_core_apply_relo(struct bpf_program *prog,
+ const struct bpf_core_relo *relo,
+ int relo_idx,
+ const struct btf *local_btf,
+ const struct btf *targ_btf,
+ struct hashmap *cand_cache)
{
const char *prog_name = bpf_program__title(prog, false);
struct bpf_core_spec local_spec, cand_spec, targ_spec;
@@ -4964,7 +5131,7 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
return -EINVAL;
local_name = btf__name_by_offset(local_btf, local_type->name_off);
- if (str_is_empty(local_name))
+ if (!local_name)
return -EINVAL;
spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
@@ -4975,7 +5142,8 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
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),
- local_name, spec_str, err);
+ str_is_empty(local_name) ? "<anon>" : local_name,
+ spec_str, err);
return -EINVAL;
}
@@ -4984,12 +5152,28 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
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;
+ }
+
if (!hashmap__find(cand_cache, type_key, (void **)&cand_ids)) {
cand_ids = bpf_core_find_cands(local_btf, local_id, targ_btf);
if (IS_ERR(cand_ids)) {
pr_warn("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld",
- prog_name, relo_idx, local_id, btf_kind_str(local_type), local_name,
- PTR_ERR(cand_ids));
+ prog_name, relo_idx, local_id, btf_kind_str(local_type),
+ local_name, PTR_ERR(cand_ids));
return PTR_ERR(cand_ids);
}
err = hashmap__set(cand_cache, type_key, cand_ids, NULL, NULL);
@@ -5045,7 +5229,7 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
return -EINVAL;
}
- cand_ids->data[j++] = cand_spec.spec[0].type_id;
+ cand_ids->data[j++] = cand_spec.root_type_id;
}
/*
@@ -5064,7 +5248,7 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
* 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_reloc_insn() uniformly by replacing that instruction with
+ * 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
@@ -5080,6 +5264,7 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
return err;
}
+patch_insn:
/* bpf_core_patch_insn() should know how to handle missing targ_spec */
err = bpf_core_patch_insn(prog, relo, relo_idx, &targ_res);
if (err) {
@@ -5147,8 +5332,8 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
sec_name, sec->num_info);
for_each_btf_ext_rec(seg, sec, i, rec) {
- err = bpf_core_reloc_field(prog, rec, i, obj->btf,
- targ_btf, cand_cache);
+ err = bpf_core_apply_relo(prog, rec, i, obj->btf,
+ targ_btf, cand_cache);
if (err) {
pr_warn("prog '%s': relo #%d: failed to relocate: %d\n",
sec_name, i, err);
@@ -218,6 +218,10 @@ enum bpf_core_relo_kind {
BPF_FIELD_SIGNED = 3, /* field signedness (0 - unsigned, 1 - signed) */
BPF_FIELD_LSHIFT_U64 = 4, /* bitfield-specific left bitshift */
BPF_FIELD_RSHIFT_U64 = 5, /* bitfield-specific right bitshift */
+ BPF_TYPE_ID_LOCAL = 6, /* type ID in local BPF object */
+ BPF_TYPE_ID_TARGET = 7, /* type ID in target kernel */
+ BPF_TYPE_EXISTS = 8, /* type existence in target kernel */
+ BPF_TYPE_SIZE = 9, /* type size in bytes */
};
/* The minimum bpf_core_relo checked by the loader
Implement support for TYPE_EXISTS/TYPE_SIZE/TYPE_ID_LOCAL/TYPE_ID_REMOTE relocations. These are examples of type-based relocations, as opposed to field-based relocations supported already. The difference is that they are calculating relocation values based on the type itself, not a field within a struct/union. Type-based relos have slightly different semantics when matching local types to kernel target types, see comments in bpf_core_types_are_compat() for details. Their behavior on failure to find target type in kernel BTF also differs. Instead of "poisoning" relocatable instruction and failing load subsequently in kernel, they return 0 (which is rarely a valid return result, so user BPF code can use that to detect success/failure of the relocation and deal with it without extra "guarding" relocations). Also, it's always possible to check existence of the type in target kernel with TYPE_EXISTS relocation, similarly to a field-based FIELD_EXISTS. TYPE_ID_LOCAL relocation is a bit special in that it always succeeds (barring any libbpf/Clang bugs) and resolved to BTF ID using **local** BTF info of BPF program itself. Tests in subsequent patches demonstrate the usage and semantics of new relocations. Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- tools/lib/bpf/Makefile | 2 +- tools/lib/bpf/bpf_core_read.h | 52 ++++++- tools/lib/bpf/libbpf.c | 231 ++++++++++++++++++++++++++++---- tools/lib/bpf/libbpf_internal.h | 4 + 4 files changed, 264 insertions(+), 25 deletions(-)