From 58e185a0dc359a6c1c9eff348d7badfc9f722159 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Thu, 13 Jun 2024 10:50:06 +0100 Subject: [PATCH 1/6] libbpf: Add btf__distill_base() creating split BTF with distilled base BTF To support more robust split BTF, adding supplemental context for the base BTF type ids that split BTF refers to is required. Without such references, a simple shuffling of base BTF type ids (without any other significant change) invalidates the split BTF. Here the attempt is made to store additional context to make split BTF more robust. This context comes in the form of distilled base BTF providing minimal information (name and - in some cases - size) for base INTs, FLOATs, STRUCTs, UNIONs, ENUMs and ENUM64s along with modified split BTF that points at that base and contains any additional types needed (such as TYPEDEF, PTR and anonymous STRUCT/UNION declarations). This information constitutes the minimal BTF representation needed to disambiguate or remove split BTF references to base BTF. The rules are as follows: - INT, FLOAT, FWD are recorded in full. - if a named base BTF STRUCT or UNION is referred to from split BTF, it will be encoded as a zero-member sized STRUCT/UNION (preserving size for later relocation checks). Only base BTF STRUCT/UNIONs that are either embedded in split BTF STRUCT/UNIONs or that have multiple STRUCT/UNION instances of the same name will _need_ size checks at relocation time, but as it is possible a different set of types will be duplicates in the later to-be-resolved base BTF, we preserve size information for all named STRUCT/UNIONs. - if an ENUM[64] is named, a ENUM forward representation (an ENUM with no values) of the same size is used. - in all other cases, the type is added to the new split BTF. Avoiding struct/union/enum/enum64 expansion is important to keep the distilled base BTF representation to a minimum size. When successful, new representations of the distilled base BTF and new split BTF that refers to it are returned. Both need to be freed by the caller. So to take a simple example, with split BTF with a type referring to "struct sk_buff", we will generate distilled base BTF with a 0-member STRUCT sk_buff of the appropriate size, and the split BTF will refer to it instead. Tools like pahole can utilize such split BTF to populate the .BTF section (split BTF) and an additional .BTF.base section. Then when the split BTF is loaded, the distilled base BTF can be used to relocate split BTF to reference the current (and possibly changed) base BTF. So for example if "struct sk_buff" was id 502 when the split BTF was originally generated, we can use the distilled base BTF to see that id 502 refers to a "struct sk_buff" and replace instances of id 502 with the current (relocated) base BTF sk_buff type id. Distilled base BTF is small; when building a kernel with all modules using distilled base BTF as a test, overall module size grew by only 5.3Mb total across ~2700 modules. Signed-off-by: Alan Maguire Signed-off-by: Andrii Nakryiko Acked-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/20240613095014.357981-2-alan.maguire@oracle.com --- tools/lib/bpf/btf.c | 319 ++++++++++++++++++++++++++++++++++++++- tools/lib/bpf/btf.h | 21 +++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 335 insertions(+), 6 deletions(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 775ca55a541c..407ed92b4134 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -1770,9 +1770,8 @@ static int btf_rewrite_str(struct btf_pipe *p, __u32 *str_off) return 0; } -int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_type *src_type) +static int btf_add_type(struct btf_pipe *p, const struct btf_type *src_type) { - struct btf_pipe p = { .src = src_btf, .dst = btf }; struct btf_field_iter it; struct btf_type *t; __u32 *str_off; @@ -1783,10 +1782,10 @@ int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_t return libbpf_err(sz); /* deconstruct BTF, if necessary, and invalidate raw_data */ - if (btf_ensure_modifiable(btf)) + if (btf_ensure_modifiable(p->dst)) return libbpf_err(-ENOMEM); - t = btf_add_type_mem(btf, sz); + t = btf_add_type_mem(p->dst, sz); if (!t) return libbpf_err(-ENOMEM); @@ -1797,12 +1796,19 @@ int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_t return libbpf_err(err); while ((str_off = btf_field_iter_next(&it))) { - err = btf_rewrite_str(&p, str_off); + err = btf_rewrite_str(p, str_off); if (err) return libbpf_err(err); } - return btf_commit_type(btf, sz); + return btf_commit_type(p->dst, sz); +} + +int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_type *src_type) +{ + struct btf_pipe p = { .src = src_btf, .dst = btf }; + + return btf_add_type(&p, src_type); } static size_t btf_dedup_identity_hash_fn(long key, void *ctx); @@ -5276,3 +5282,304 @@ int btf_ext_visit_str_offs(struct btf_ext *btf_ext, str_off_visit_fn visit, void return 0; } + +struct btf_distill { + struct btf_pipe pipe; + int *id_map; + unsigned int split_start_id; + unsigned int split_start_str; + int diff_id; +}; + +static int btf_add_distilled_type_ids(struct btf_distill *dist, __u32 i) +{ + struct btf_type *split_t = btf_type_by_id(dist->pipe.src, i); + struct btf_field_iter it; + __u32 *id; + int err; + + err = btf_field_iter_init(&it, split_t, BTF_FIELD_ITER_IDS); + if (err) + return err; + while ((id = btf_field_iter_next(&it))) { + struct btf_type *base_t; + + if (!*id) + continue; + /* split BTF id, not needed */ + if (*id >= dist->split_start_id) + continue; + /* already added ? */ + if (dist->id_map[*id] > 0) + continue; + + /* only a subset of base BTF types should be referenced from + * split BTF; ensure nothing unexpected is referenced. + */ + base_t = btf_type_by_id(dist->pipe.src, *id); + switch (btf_kind(base_t)) { + case BTF_KIND_INT: + case BTF_KIND_FLOAT: + case BTF_KIND_FWD: + case BTF_KIND_ARRAY: + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + case BTF_KIND_TYPEDEF: + case BTF_KIND_ENUM: + case BTF_KIND_ENUM64: + case BTF_KIND_PTR: + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + case BTF_KIND_VOLATILE: + case BTF_KIND_FUNC_PROTO: + case BTF_KIND_TYPE_TAG: + dist->id_map[*id] = *id; + break; + default: + pr_warn("unexpected reference to base type[%u] of kind [%u] when creating distilled base BTF.\n", + *id, btf_kind(base_t)); + return -EINVAL; + } + /* If a base type is used, ensure types it refers to are + * marked as used also; so for example if we find a PTR to INT + * we need both the PTR and INT. + * + * The only exception is named struct/unions, since distilled + * base BTF composite types have no members. + */ + if (btf_is_composite(base_t) && base_t->name_off) + continue; + err = btf_add_distilled_type_ids(dist, *id); + if (err) + return err; + } + return 0; +} + +static int btf_add_distilled_types(struct btf_distill *dist) +{ + bool adding_to_base = dist->pipe.dst->start_id == 1; + int id = btf__type_cnt(dist->pipe.dst); + struct btf_type *t; + int i, err = 0; + + + /* Add types for each of the required references to either distilled + * base or split BTF, depending on type characteristics. + */ + for (i = 1; i < dist->split_start_id; i++) { + const char *name; + int kind; + + if (!dist->id_map[i]) + continue; + t = btf_type_by_id(dist->pipe.src, i); + kind = btf_kind(t); + name = btf__name_by_offset(dist->pipe.src, t->name_off); + + switch (kind) { + case BTF_KIND_INT: + case BTF_KIND_FLOAT: + case BTF_KIND_FWD: + /* Named int, float, fwd are added to base. */ + if (!adding_to_base) + continue; + err = btf_add_type(&dist->pipe, t); + break; + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + /* Named struct/union are added to base as 0-vlen + * struct/union of same size. Anonymous struct/unions + * are added to split BTF as-is. + */ + if (adding_to_base) { + if (!t->name_off) + continue; + err = btf_add_composite(dist->pipe.dst, kind, name, t->size); + } else { + if (t->name_off) + continue; + err = btf_add_type(&dist->pipe, t); + } + break; + case BTF_KIND_ENUM: + case BTF_KIND_ENUM64: + /* Named enum[64]s are added to base as a sized + * enum; relocation will match with appropriately-named + * and sized enum or enum64. + * + * Anonymous enums are added to split BTF as-is. + */ + if (adding_to_base) { + if (!t->name_off) + continue; + err = btf__add_enum(dist->pipe.dst, name, t->size); + } else { + if (t->name_off) + continue; + err = btf_add_type(&dist->pipe, t); + } + break; + case BTF_KIND_ARRAY: + case BTF_KIND_TYPEDEF: + case BTF_KIND_PTR: + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + case BTF_KIND_VOLATILE: + case BTF_KIND_FUNC_PROTO: + case BTF_KIND_TYPE_TAG: + /* All other types are added to split BTF. */ + if (adding_to_base) + continue; + err = btf_add_type(&dist->pipe, t); + break; + default: + pr_warn("unexpected kind when adding base type '%s'[%u] of kind [%u] to distilled base BTF.\n", + name, i, kind); + return -EINVAL; + + } + if (err < 0) + break; + dist->id_map[i] = id++; + } + return err; +} + +/* Split BTF ids without a mapping will be shifted downwards since distilled + * base BTF is smaller than the original base BTF. For those that have a + * mapping (either to base or updated split BTF), update the id based on + * that mapping. + */ +static int btf_update_distilled_type_ids(struct btf_distill *dist, __u32 i) +{ + struct btf_type *t = btf_type_by_id(dist->pipe.dst, i); + struct btf_field_iter it; + __u32 *id; + int err; + + err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_IDS); + if (err) + return err; + while ((id = btf_field_iter_next(&it))) { + if (dist->id_map[*id]) + *id = dist->id_map[*id]; + else if (*id >= dist->split_start_id) + *id -= dist->diff_id; + } + return 0; +} + +/* Create updated split BTF with distilled base BTF; distilled base BTF + * consists of BTF information required to clarify the types that split + * BTF refers to, omitting unneeded details. Specifically it will contain + * base types and memberless definitions of named structs, unions and enumerated + * types. Associated reference types like pointers, arrays and anonymous + * structs, unions and enumerated types will be added to split BTF. + * Size is recorded for named struct/unions to help guide matching to the + * target base BTF during later relocation. + * + * The only case where structs, unions or enumerated types are fully represented + * is when they are anonymous; in such cases, the anonymous type is added to + * split BTF in full. + * + * We return newly-created split BTF where the split BTF refers to a newly-created + * distilled base BTF. Both must be freed separately by the caller. + */ +int btf__distill_base(const struct btf *src_btf, struct btf **new_base_btf, + struct btf **new_split_btf) +{ + struct btf *new_base = NULL, *new_split = NULL; + const struct btf *old_base; + unsigned int n = btf__type_cnt(src_btf); + struct btf_distill dist = {}; + struct btf_type *t; + int i, err = 0; + + /* src BTF must be split BTF. */ + old_base = btf__base_btf(src_btf); + if (!new_base_btf || !new_split_btf || !old_base) + return libbpf_err(-EINVAL); + + new_base = btf__new_empty(); + if (!new_base) + return libbpf_err(-ENOMEM); + dist.id_map = calloc(n, sizeof(*dist.id_map)); + if (!dist.id_map) { + err = -ENOMEM; + goto done; + } + dist.pipe.src = src_btf; + dist.pipe.dst = new_base; + dist.pipe.str_off_map = hashmap__new(btf_dedup_identity_hash_fn, btf_dedup_equal_fn, NULL); + if (IS_ERR(dist.pipe.str_off_map)) { + err = -ENOMEM; + goto done; + } + dist.split_start_id = btf__type_cnt(old_base); + dist.split_start_str = old_base->hdr->str_len; + + /* Pass over src split BTF; generate the list of base BTF type ids it + * references; these will constitute our distilled BTF set to be + * distributed over base and split BTF as appropriate. + */ + for (i = src_btf->start_id; i < n; i++) { + err = btf_add_distilled_type_ids(&dist, i); + if (err < 0) + goto done; + } + /* Next add types for each of the required references to base BTF and split BTF + * in turn. + */ + err = btf_add_distilled_types(&dist); + if (err < 0) + goto done; + + /* Create new split BTF with distilled base BTF as its base; the final + * state is split BTF with distilled base BTF that represents enough + * about its base references to allow it to be relocated with the base + * BTF available. + */ + new_split = btf__new_empty_split(new_base); + if (!new_split_btf) { + err = -errno; + goto done; + } + dist.pipe.dst = new_split; + /* First add all split types */ + for (i = src_btf->start_id; i < n; i++) { + t = btf_type_by_id(src_btf, i); + err = btf_add_type(&dist.pipe, t); + if (err < 0) + goto done; + } + /* Now add distilled types to split BTF that are not added to base. */ + err = btf_add_distilled_types(&dist); + if (err < 0) + goto done; + + /* All split BTF ids will be shifted downwards since there are less base + * BTF ids in distilled base BTF. + */ + dist.diff_id = dist.split_start_id - btf__type_cnt(new_base); + + n = btf__type_cnt(new_split); + /* Now update base/split BTF ids. */ + for (i = 1; i < n; i++) { + err = btf_update_distilled_type_ids(&dist, i); + if (err < 0) + break; + } +done: + free(dist.id_map); + hashmap__free(dist.pipe.str_off_map); + if (err) { + btf__free(new_split); + btf__free(new_base); + return libbpf_err(err); + } + *new_base_btf = new_base; + *new_split_btf = new_split; + + return 0; +} diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index 8e6880d91c84..cb08ee9a5a10 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -107,6 +107,27 @@ LIBBPF_API struct btf *btf__new_empty(void); */ LIBBPF_API struct btf *btf__new_empty_split(struct btf *base_btf); +/** + * @brief **btf__distill_base()** creates new versions of the split BTF + * *src_btf* and its base BTF. The new base BTF will only contain the types + * needed to improve robustness of the split BTF to small changes in base BTF. + * When that split BTF is loaded against a (possibly changed) base, this + * distilled base BTF will help update references to that (possibly changed) + * base BTF. + * + * Both the new split and its associated new base BTF must be freed by + * the caller. + * + * If successful, 0 is returned and **new_base_btf** and **new_split_btf** + * will point at new base/split BTF. Both the new split and its associated + * new base BTF must be freed by the caller. + * + * A negative value is returned on error and the thread-local `errno` variable + * is set to the error code as well. + */ +LIBBPF_API int btf__distill_base(const struct btf *src_btf, struct btf **new_base_btf, + struct btf **new_split_btf); + LIBBPF_API struct btf *btf__parse(const char *path, struct btf_ext **btf_ext); LIBBPF_API struct btf *btf__parse_split(const char *path, struct btf *base_btf); LIBBPF_API struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 40595233dc7f..175d1536e070 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -419,6 +419,7 @@ LIBBPF_1.4.0 { LIBBPF_1.5.0 { global: + btf__distill_base; bpf_map__autoattach; bpf_map__set_autoattach; bpf_program__attach_sockmap; From eb20e727c4343ad591cff2bef243590c77f62cf1 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Thu, 13 Jun 2024 10:50:07 +0100 Subject: [PATCH 2/6] selftests/bpf: Test distilled base, split BTF generation Test generation of split+distilled base BTF, ensuring that - named base BTF STRUCTs and UNIONs are represented as 0-vlen sized STRUCT/UNIONs - named ENUM[64]s are represented as 0-vlen named ENUM[64]s - anonymous struct/unions are represented in full in split BTF - anonymous enums are represented in full in split BTF - types unreferenced from split BTF are not present in distilled base BTF Also test that with vmlinux BTF and split BTF based upon it, we only represent needed base types referenced from split BTF in distilled base. Signed-off-by: Alan Maguire Signed-off-by: Andrii Nakryiko Acked-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/20240613095014.357981-3-alan.maguire@oracle.com --- .../selftests/bpf/prog_tests/btf_distill.c | 274 ++++++++++++++++++ 1 file changed, 274 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/btf_distill.c diff --git a/tools/testing/selftests/bpf/prog_tests/btf_distill.c b/tools/testing/selftests/bpf/prog_tests/btf_distill.c new file mode 100644 index 000000000000..5c3a38747962 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/btf_distill.c @@ -0,0 +1,274 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024, Oracle and/or its affiliates. */ + +#include +#include +#include "btf_helpers.h" + +/* Fabricate base, split BTF with references to base types needed; then create + * split BTF with distilled base BTF and ensure expectations are met: + * - only referenced base types from split BTF are present + * - struct/union/enum are represented as empty unless anonymous, when they + * are represented in full in split BTF + */ +static void test_distilled_base(void) +{ + struct btf *btf1 = NULL, *btf2 = NULL, *btf3 = NULL, *btf4 = NULL; + + btf1 = btf__new_empty(); + if (!ASSERT_OK_PTR(btf1, "empty_main_btf")) + return; + + btf__add_int(btf1, "int", 4, BTF_INT_SIGNED); /* [1] int */ + btf__add_ptr(btf1, 1); /* [2] ptr to int */ + btf__add_struct(btf1, "s1", 8); /* [3] struct s1 { */ + btf__add_field(btf1, "f1", 2, 0, 0); /* int *f1; */ + /* } */ + btf__add_struct(btf1, "", 12); /* [4] struct { */ + btf__add_field(btf1, "f1", 1, 0, 0); /* int f1; */ + btf__add_field(btf1, "f2", 3, 32, 0); /* struct s1 f2; */ + /* } */ + btf__add_int(btf1, "unsigned int", 4, 0); /* [5] unsigned int */ + btf__add_union(btf1, "u1", 12); /* [6] union u1 { */ + btf__add_field(btf1, "f1", 1, 0, 0); /* int f1; */ + btf__add_field(btf1, "f2", 2, 0, 0); /* int *f2; */ + /* } */ + btf__add_union(btf1, "", 4); /* [7] union { */ + btf__add_field(btf1, "f1", 1, 0, 0); /* int f1; */ + /* } */ + btf__add_enum(btf1, "e1", 4); /* [8] enum e1 { */ + btf__add_enum_value(btf1, "v1", 1); /* v1 = 1; */ + /* } */ + btf__add_enum(btf1, "", 4); /* [9] enum { */ + btf__add_enum_value(btf1, "av1", 2); /* av1 = 2; */ + /* } */ + btf__add_enum64(btf1, "e641", 8, true); /* [10] enum64 { */ + btf__add_enum64_value(btf1, "v1", 1024); /* v1 = 1024; */ + /* } */ + btf__add_enum64(btf1, "", 8, true); /* [11] enum64 { */ + btf__add_enum64_value(btf1, "v1", 1025); /* v1 = 1025; */ + /* } */ + btf__add_struct(btf1, "unneeded", 4); /* [12] struct unneeded { */ + btf__add_field(btf1, "f1", 1, 0, 0); /* int f1; */ + /* } */ + btf__add_struct(btf1, "embedded", 4); /* [13] struct embedded { */ + btf__add_field(btf1, "f1", 1, 0, 0); /* int f1; */ + /* } */ + btf__add_func_proto(btf1, 1); /* [14] int (*)(int *p1); */ + btf__add_func_param(btf1, "p1", 1); + + btf__add_array(btf1, 1, 1, 3); /* [15] int [3]; */ + + btf__add_struct(btf1, "from_proto", 4); /* [16] struct from_proto { */ + btf__add_field(btf1, "f1", 1, 0, 0); /* int f1; */ + /* } */ + btf__add_union(btf1, "u1", 4); /* [17] union u1 { */ + btf__add_field(btf1, "f1", 1, 0, 0); /* int f1; */ + /* } */ + VALIDATE_RAW_BTF( + btf1, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] PTR '(anon)' type_id=1", + "[3] STRUCT 's1' size=8 vlen=1\n" + "\t'f1' type_id=2 bits_offset=0", + "[4] STRUCT '(anon)' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=3 bits_offset=32", + "[5] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)", + "[6] UNION 'u1' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=2 bits_offset=0", + "[7] UNION '(anon)' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[8] ENUM 'e1' encoding=UNSIGNED size=4 vlen=1\n" + "\t'v1' val=1", + "[9] ENUM '(anon)' encoding=UNSIGNED size=4 vlen=1\n" + "\t'av1' val=2", + "[10] ENUM64 'e641' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1024", + "[11] ENUM64 '(anon)' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1025", + "[12] STRUCT 'unneeded' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[13] STRUCT 'embedded' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[14] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=1", + "[15] ARRAY '(anon)' type_id=1 index_type_id=1 nr_elems=3", + "[16] STRUCT 'from_proto' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[17] UNION 'u1' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0"); + + btf2 = btf__new_empty_split(btf1); + if (!ASSERT_OK_PTR(btf2, "empty_split_btf")) + goto cleanup; + + btf__add_ptr(btf2, 3); /* [18] ptr to struct s1 */ + /* add ptr to struct anon */ + btf__add_ptr(btf2, 4); /* [19] ptr to struct (anon) */ + btf__add_const(btf2, 6); /* [20] const union u1 */ + btf__add_restrict(btf2, 7); /* [21] restrict union (anon) */ + btf__add_volatile(btf2, 8); /* [22] volatile enum e1 */ + btf__add_typedef(btf2, "et", 9); /* [23] typedef enum (anon) */ + btf__add_const(btf2, 10); /* [24] const enum64 e641 */ + btf__add_ptr(btf2, 11); /* [25] restrict enum64 (anon) */ + btf__add_struct(btf2, "with_embedded", 4); /* [26] struct with_embedded { */ + btf__add_field(btf2, "f1", 13, 0, 0); /* struct embedded f1; */ + /* } */ + btf__add_func(btf2, "fn", BTF_FUNC_STATIC, 14); /* [27] int fn(int p1); */ + btf__add_typedef(btf2, "arraytype", 15); /* [28] typedef int[3] foo; */ + btf__add_func_proto(btf2, 1); /* [29] int (*)(struct from proto p1); */ + btf__add_func_param(btf2, "p1", 16); + + VALIDATE_RAW_BTF( + btf2, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] PTR '(anon)' type_id=1", + "[3] STRUCT 's1' size=8 vlen=1\n" + "\t'f1' type_id=2 bits_offset=0", + "[4] STRUCT '(anon)' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=3 bits_offset=32", + "[5] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)", + "[6] UNION 'u1' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=2 bits_offset=0", + "[7] UNION '(anon)' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[8] ENUM 'e1' encoding=UNSIGNED size=4 vlen=1\n" + "\t'v1' val=1", + "[9] ENUM '(anon)' encoding=UNSIGNED size=4 vlen=1\n" + "\t'av1' val=2", + "[10] ENUM64 'e641' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1024", + "[11] ENUM64 '(anon)' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1025", + "[12] STRUCT 'unneeded' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[13] STRUCT 'embedded' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[14] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=1", + "[15] ARRAY '(anon)' type_id=1 index_type_id=1 nr_elems=3", + "[16] STRUCT 'from_proto' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[17] UNION 'u1' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[18] PTR '(anon)' type_id=3", + "[19] PTR '(anon)' type_id=4", + "[20] CONST '(anon)' type_id=6", + "[21] RESTRICT '(anon)' type_id=7", + "[22] VOLATILE '(anon)' type_id=8", + "[23] TYPEDEF 'et' type_id=9", + "[24] CONST '(anon)' type_id=10", + "[25] PTR '(anon)' type_id=11", + "[26] STRUCT 'with_embedded' size=4 vlen=1\n" + "\t'f1' type_id=13 bits_offset=0", + "[27] FUNC 'fn' type_id=14 linkage=static", + "[28] TYPEDEF 'arraytype' type_id=15", + "[29] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=16"); + + if (!ASSERT_EQ(0, btf__distill_base(btf2, &btf3, &btf4), + "distilled_base") || + !ASSERT_OK_PTR(btf3, "distilled_base") || + !ASSERT_OK_PTR(btf4, "distilled_split") || + !ASSERT_EQ(8, btf__type_cnt(btf3), "distilled_base_type_cnt")) + goto cleanup; + + VALIDATE_RAW_BTF( + btf4, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] STRUCT 's1' size=8 vlen=0", + "[3] UNION 'u1' size=12 vlen=0", + "[4] ENUM 'e1' encoding=UNSIGNED size=4 vlen=0", + "[5] ENUM 'e641' encoding=UNSIGNED size=8 vlen=0", + "[6] STRUCT 'embedded' size=4 vlen=0", + "[7] STRUCT 'from_proto' size=4 vlen=0", + /* split BTF; these types should match split BTF above from 17-28, with + * updated type id references + */ + "[8] PTR '(anon)' type_id=2", + "[9] PTR '(anon)' type_id=20", + "[10] CONST '(anon)' type_id=3", + "[11] RESTRICT '(anon)' type_id=21", + "[12] VOLATILE '(anon)' type_id=4", + "[13] TYPEDEF 'et' type_id=22", + "[14] CONST '(anon)' type_id=5", + "[15] PTR '(anon)' type_id=23", + "[16] STRUCT 'with_embedded' size=4 vlen=1\n" + "\t'f1' type_id=6 bits_offset=0", + "[17] FUNC 'fn' type_id=24 linkage=static", + "[18] TYPEDEF 'arraytype' type_id=25", + "[19] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=7", + /* split BTF types added from original base BTF below */ + "[20] STRUCT '(anon)' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=2 bits_offset=32", + "[21] UNION '(anon)' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[22] ENUM '(anon)' encoding=UNSIGNED size=4 vlen=1\n" + "\t'av1' val=2", + "[23] ENUM64 '(anon)' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1025", + "[24] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=1", + "[25] ARRAY '(anon)' type_id=1 index_type_id=1 nr_elems=3"); + +cleanup: + btf__free(btf4); + btf__free(btf3); + btf__free(btf2); + btf__free(btf1); +} + +/* create split reference BTF from vmlinux + split BTF with a few type references; + * ensure the resultant split reference BTF is as expected, containing only types + * needed to disambiguate references from split BTF. + */ +static void test_distilled_base_vmlinux(void) +{ + struct btf *split_btf = NULL, *vmlinux_btf = btf__load_vmlinux_btf(); + struct btf *split_dist = NULL, *base_dist = NULL; + __s32 int_id, myint_id; + + if (!ASSERT_OK_PTR(vmlinux_btf, "load_vmlinux")) + return; + int_id = btf__find_by_name_kind(vmlinux_btf, "int", BTF_KIND_INT); + if (!ASSERT_GT(int_id, 0, "find_int")) + goto cleanup; + split_btf = btf__new_empty_split(vmlinux_btf); + if (!ASSERT_OK_PTR(split_btf, "new_split")) + goto cleanup; + myint_id = btf__add_typedef(split_btf, "myint", int_id); + btf__add_ptr(split_btf, myint_id); + + if (!ASSERT_EQ(btf__distill_base(split_btf, &base_dist, &split_dist), 0, + "distill_vmlinux_base")) + goto cleanup; + + if (!ASSERT_OK_PTR(split_dist, "split_distilled") || + !ASSERT_OK_PTR(base_dist, "base_dist")) + goto cleanup; + VALIDATE_RAW_BTF( + split_dist, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] TYPEDEF 'myint' type_id=1", + "[3] PTR '(anon)' type_id=2"); + +cleanup: + btf__free(split_dist); + btf__free(base_dist); + btf__free(split_btf); + btf__free(vmlinux_btf); +} + +void test_btf_distill(void) +{ + if (test__start_subtest("distilled_base")) + test_distilled_base(); + if (test__start_subtest("distilled_base_vmlinux")) + test_distilled_base_vmlinux(); +} From 19e00c897d5031bed969dd79af28e899e038009f Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Thu, 13 Jun 2024 10:50:08 +0100 Subject: [PATCH 3/6] libbpf: Split BTF relocation Map distilled base BTF type ids referenced in split BTF and their references to the base BTF passed in, and if the mapping succeeds, reparent the split BTF to the base BTF. Relocation is done by first verifying that distilled base BTF only consists of named INT, FLOAT, ENUM, FWD, STRUCT and UNION kinds; then we sort these to speed lookups. Once sorted, the base BTF is iterated, and for each relevant kind we check for an equivalent in distilled base BTF. When found, the mapping from distilled -> base BTF id and string offset is recorded. In establishing mappings, we need to ensure we check STRUCT/UNION size when the STRUCT/UNION is embedded in a split BTF STRUCT/UNION, and when duplicate names exist for the same STRUCT/UNION. Otherwise size is ignored in matching STRUCT/UNIONs. Once all mappings are established, we can update type ids and string offsets in split BTF and reparent it to the new base. Signed-off-by: Alan Maguire Signed-off-by: Andrii Nakryiko Acked-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/20240613095014.357981-4-alan.maguire@oracle.com --- tools/lib/bpf/Build | 2 +- tools/lib/bpf/btf.c | 17 ++ tools/lib/bpf/btf.h | 14 + tools/lib/bpf/btf_relocate.c | 506 ++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_internal.h | 3 + 6 files changed, 542 insertions(+), 1 deletion(-) create mode 100644 tools/lib/bpf/btf_relocate.c diff --git a/tools/lib/bpf/Build b/tools/lib/bpf/Build index b6619199a706..336da6844d42 100644 --- a/tools/lib/bpf/Build +++ b/tools/lib/bpf/Build @@ -1,4 +1,4 @@ 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 hashmap.o \ btf_dump.o ringbuf.o strset.o linker.o gen_loader.o relo_core.o \ - usdt.o zip.o elf.o features.o + usdt.o zip.o elf.o features.o btf_relocate.o diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 407ed92b4134..5e20354fbcfa 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -5583,3 +5583,20 @@ done: return 0; } + +const struct btf_header *btf_header(const struct btf *btf) +{ + return btf->hdr; +} + +void btf_set_base_btf(struct btf *btf, const struct btf *base_btf) +{ + btf->base_btf = (struct btf *)base_btf; + btf->start_id = btf__type_cnt(base_btf); + btf->start_str_off = base_btf->hdr->str_len; +} + +int btf__relocate(struct btf *btf, const struct btf *base_btf) +{ + return libbpf_err(btf_relocate(btf, base_btf, NULL)); +} diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index cb08ee9a5a10..8a93120b7385 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -252,6 +252,20 @@ struct btf_dedup_opts { LIBBPF_API int btf__dedup(struct btf *btf, const struct btf_dedup_opts *opts); +/** + * @brief **btf__relocate()** will check the split BTF *btf* for references + * to base BTF kinds, and verify those references are compatible with + * *base_btf*; if they are, *btf* is adjusted such that is re-parented to + * *base_btf* and type ids and strings are adjusted to accommodate this. + * + * If successful, 0 is returned and **btf** now has **base_btf** as its + * base. + * + * A negative value is returned on error and the thread-local `errno` variable + * is set to the error code as well. + */ +LIBBPF_API int btf__relocate(struct btf *btf, const struct btf *base_btf); + struct btf_dump; struct btf_dump_opts { diff --git a/tools/lib/bpf/btf_relocate.c b/tools/lib/bpf/btf_relocate.c new file mode 100644 index 000000000000..eabb8755f662 --- /dev/null +++ b/tools/lib/bpf/btf_relocate.c @@ -0,0 +1,506 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024, Oracle and/or its affiliates. */ + +#ifndef _GNU_SOURCE +#define _GNU_SOURCE +#endif + +#include "btf.h" +#include "bpf.h" +#include "libbpf.h" +#include "libbpf_internal.h" + +struct btf; + +struct btf_relocate { + struct btf *btf; + const struct btf *base_btf; + const struct btf *dist_base_btf; + unsigned int nr_base_types; + unsigned int nr_split_types; + unsigned int nr_dist_base_types; + int dist_str_len; + int base_str_len; + __u32 *id_map; + __u32 *str_map; +}; + +/* Set temporarily in relocation id_map if distilled base struct/union is + * embedded in a split BTF struct/union; in such a case, size information must + * match between distilled base BTF and base BTF representation of type. + */ +#define BTF_IS_EMBEDDED ((__u32)-1) + +/* triple used in sorting/searching distilled base BTF. */ +struct btf_name_info { + const char *name; + /* set when search requires a size match */ + int needs_size:1, + size:31; + __u32 id; +}; + +static int btf_relocate_rewrite_type_id(struct btf_relocate *r, __u32 i) +{ + struct btf_type *t = btf_type_by_id(r->btf, i); + struct btf_field_iter it; + __u32 *id; + int err; + + err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_IDS); + if (err) + return err; + + while ((id = btf_field_iter_next(&it))) + *id = r->id_map[*id]; + return 0; +} + +/* Simple string comparison used for sorting within BTF, since all distilled + * types are named. If strings match, and size is non-zero for both elements + * fall back to using size for ordering. + */ +static int cmp_btf_name_size(const void *n1, const void *n2) +{ + const struct btf_name_info *ni1 = n1; + const struct btf_name_info *ni2 = n2; + int name_diff = strcmp(ni1->name, ni2->name); + + if (!name_diff && ni1->needs_size && ni2->needs_size) + return ni2->size - ni1->size; + return name_diff; +} + +/* Binary search with a small twist; find leftmost element that matches + * so that we can then iterate through all exact matches. So for example + * searching { "a", "bb", "bb", "c" } we would always match on the + * leftmost "bb". + */ +static struct btf_name_info *search_btf_name_size(struct btf_name_info *key, + struct btf_name_info *vals, + int nelems) +{ + struct btf_name_info *ret = NULL; + int high = nelems - 1; + int low = 0; + + while (low <= high) { + int mid = (low + high)/2; + struct btf_name_info *val = &vals[mid]; + int diff = cmp_btf_name_size(key, val); + + if (diff == 0) + ret = val; + /* even if found, keep searching for leftmost match */ + if (diff <= 0) + high = mid - 1; + else + low = mid + 1; + } + return ret; +} + +/* If a member of a split BTF struct/union refers to a base BTF + * struct/union, mark that struct/union id temporarily in the id_map + * with BTF_IS_EMBEDDED. Members can be const/restrict/volatile/typedef + * reference types, but if a pointer is encountered, the type is no longer + * considered embedded. + */ +static int btf_mark_embedded_composite_type_ids(struct btf_relocate *r, __u32 i) +{ + struct btf_type *t = btf_type_by_id(r->btf, i); + struct btf_field_iter it; + __u32 *id; + int err; + + if (!btf_is_composite(t)) + return 0; + + err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_IDS); + if (err) + return err; + + while ((id = btf_field_iter_next(&it))) { + __u32 next_id = *id; + + while (next_id) { + t = btf_type_by_id(r->btf, next_id); + switch (btf_kind(t)) { + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + case BTF_KIND_VOLATILE: + case BTF_KIND_TYPEDEF: + case BTF_KIND_TYPE_TAG: + next_id = t->type; + break; + case BTF_KIND_ARRAY: { + struct btf_array *a = btf_array(t); + + next_id = a->type; + break; + } + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + if (next_id < r->nr_dist_base_types) + r->id_map[next_id] = BTF_IS_EMBEDDED; + next_id = 0; + break; + default: + next_id = 0; + break; + } + } + } + + return 0; +} + +/* Build a map from distilled base BTF ids to base BTF ids. To do so, iterate + * through base BTF looking up distilled type (using binary search) equivalents. + */ +static int btf_relocate_map_distilled_base(struct btf_relocate *r) +{ + struct btf_name_info *dist_base_info_sorted, *dist_base_info_sorted_end; + struct btf_type *base_t, *dist_t; + __u8 *base_name_cnt = NULL; + int err = 0; + __u32 id; + + /* generate a sort index array of name/type ids sorted by name for + * distilled base BTF to speed name-based lookups. + */ + dist_base_info_sorted = calloc(r->nr_dist_base_types, sizeof(*dist_base_info_sorted)); + if (!dist_base_info_sorted) { + err = -ENOMEM; + goto done; + } + dist_base_info_sorted_end = dist_base_info_sorted + r->nr_dist_base_types; + for (id = 0; id < r->nr_dist_base_types; id++) { + dist_t = btf_type_by_id(r->dist_base_btf, id); + dist_base_info_sorted[id].name = btf__name_by_offset(r->dist_base_btf, + dist_t->name_off); + dist_base_info_sorted[id].id = id; + dist_base_info_sorted[id].size = dist_t->size; + dist_base_info_sorted[id].needs_size = true; + } + qsort(dist_base_info_sorted, r->nr_dist_base_types, sizeof(*dist_base_info_sorted), + cmp_btf_name_size); + + /* Mark distilled base struct/union members of split BTF structs/unions + * in id_map with BTF_IS_EMBEDDED; this signals that these types + * need to match both name and size, otherwise embeddding the base + * struct/union in the split type is invalid. + */ + for (id = r->nr_dist_base_types; id < r->nr_split_types; id++) { + err = btf_mark_embedded_composite_type_ids(r, id); + if (err) + goto done; + } + + /* Collect name counts for composite types in base BTF. If multiple + * instances of a struct/union of the same name exist, we need to use + * size to determine which to map to since name alone is ambiguous. + */ + base_name_cnt = calloc(r->base_str_len, sizeof(*base_name_cnt)); + if (!base_name_cnt) { + err = -ENOMEM; + goto done; + } + for (id = 1; id < r->nr_base_types; id++) { + base_t = btf_type_by_id(r->base_btf, id); + if (!btf_is_composite(base_t) || !base_t->name_off) + continue; + if (base_name_cnt[base_t->name_off] < 255) + base_name_cnt[base_t->name_off]++; + } + + /* Now search base BTF for matching distilled base BTF types. */ + for (id = 1; id < r->nr_base_types; id++) { + struct btf_name_info *dist_name_info, *dist_name_info_next = NULL; + struct btf_name_info base_name_info = {}; + int dist_kind, base_kind; + + base_t = btf_type_by_id(r->base_btf, id); + /* distilled base consists of named types only. */ + if (!base_t->name_off) + continue; + base_kind = btf_kind(base_t); + base_name_info.id = id; + base_name_info.name = btf__name_by_offset(r->base_btf, base_t->name_off); + switch (base_kind) { + case BTF_KIND_INT: + case BTF_KIND_FLOAT: + case BTF_KIND_ENUM: + case BTF_KIND_ENUM64: + /* These types should match both name and size */ + base_name_info.needs_size = true; + base_name_info.size = base_t->size; + break; + case BTF_KIND_FWD: + /* No size considerations for fwds. */ + break; + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + /* Size only needs to be used for struct/union if there + * are multiple types in base BTF with the same name. + * If there are multiple _distilled_ types with the same + * name (a very unlikely scenario), that doesn't matter + * unless corresponding _base_ types to match them are + * missing. + */ + base_name_info.needs_size = base_name_cnt[base_t->name_off] > 1; + base_name_info.size = base_t->size; + break; + default: + continue; + } + /* iterate over all matching distilled base types */ + for (dist_name_info = search_btf_name_size(&base_name_info, dist_base_info_sorted, + r->nr_dist_base_types); + dist_name_info != NULL; dist_name_info = dist_name_info_next) { + /* Are there more distilled matches to process after + * this one? + */ + dist_name_info_next = dist_name_info + 1; + if (dist_name_info_next >= dist_base_info_sorted_end || + cmp_btf_name_size(&base_name_info, dist_name_info_next)) + dist_name_info_next = NULL; + + if (!dist_name_info->id || dist_name_info->id > r->nr_dist_base_types) { + pr_warn("base BTF id [%d] maps to invalid distilled base BTF id [%d]\n", + id, dist_name_info->id); + err = -EINVAL; + goto done; + } + dist_t = btf_type_by_id(r->dist_base_btf, dist_name_info->id); + dist_kind = btf_kind(dist_t); + + /* Validate that the found distilled type is compatible. + * Do not error out on mismatch as another match may + * occur for an identically-named type. + */ + switch (dist_kind) { + case BTF_KIND_FWD: + switch (base_kind) { + case BTF_KIND_FWD: + if (btf_kflag(dist_t) != btf_kflag(base_t)) + continue; + break; + case BTF_KIND_STRUCT: + if (btf_kflag(base_t)) + continue; + break; + case BTF_KIND_UNION: + if (!btf_kflag(base_t)) + continue; + break; + default: + continue; + } + break; + case BTF_KIND_INT: + if (dist_kind != base_kind || + btf_int_encoding(base_t) != btf_int_encoding(dist_t)) + continue; + break; + case BTF_KIND_FLOAT: + if (dist_kind != base_kind) + continue; + break; + case BTF_KIND_ENUM: + /* ENUM and ENUM64 are encoded as sized ENUM in + * distilled base BTF. + */ + if (base_kind != dist_kind && base_kind != BTF_KIND_ENUM64) + continue; + break; + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + /* size verification is required for embedded + * struct/unions. + */ + if (r->id_map[dist_name_info->id] == BTF_IS_EMBEDDED && + base_t->size != dist_t->size) + continue; + break; + default: + continue; + } + if (r->id_map[dist_name_info->id] && + r->id_map[dist_name_info->id] != BTF_IS_EMBEDDED) { + /* we already have a match; this tells us that + * multiple base types of the same name + * have the same size, since for cases where + * multiple types have the same name we match + * on name and size. In this case, we have + * no way of determining which to relocate + * to in base BTF, so error out. + */ + pr_warn("distilled base BTF type '%s' [%u], size %u has multiple candidates of the same size (ids [%u, %u]) in base BTF\n", + base_name_info.name, dist_name_info->id, + base_t->size, id, r->id_map[dist_name_info->id]); + err = -EINVAL; + goto done; + } + /* map id and name */ + r->id_map[dist_name_info->id] = id; + r->str_map[dist_t->name_off] = base_t->name_off; + } + } + /* ensure all distilled BTF ids now have a mapping... */ + for (id = 1; id < r->nr_dist_base_types; id++) { + const char *name; + + if (r->id_map[id] && r->id_map[id] != BTF_IS_EMBEDDED) + continue; + dist_t = btf_type_by_id(r->dist_base_btf, id); + name = btf__name_by_offset(r->dist_base_btf, dist_t->name_off); + pr_warn("distilled base BTF type '%s' [%d] is not mapped to base BTF id\n", + name, id); + err = -EINVAL; + break; + } +done: + free(base_name_cnt); + free(dist_base_info_sorted); + return err; +} + +/* distilled base should only have named int/float/enum/fwd/struct/union types. */ +static int btf_relocate_validate_distilled_base(struct btf_relocate *r) +{ + unsigned int i; + + for (i = 1; i < r->nr_dist_base_types; i++) { + struct btf_type *t = btf_type_by_id(r->dist_base_btf, i); + int kind = btf_kind(t); + + switch (kind) { + case BTF_KIND_INT: + case BTF_KIND_FLOAT: + case BTF_KIND_ENUM: + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + case BTF_KIND_FWD: + if (t->name_off) + break; + pr_warn("type [%d], kind [%d] is invalid for distilled base BTF; it is anonymous\n", + i, kind); + return -EINVAL; + default: + pr_warn("type [%d] in distilled based BTF has unexpected kind [%d]\n", + i, kind); + return -EINVAL; + } + } + return 0; +} + +static int btf_relocate_rewrite_strs(struct btf_relocate *r, __u32 i) +{ + struct btf_type *t = btf_type_by_id(r->btf, i); + struct btf_field_iter it; + __u32 *str_off; + int off, err; + + err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_STRS); + if (err) + return err; + + while ((str_off = btf_field_iter_next(&it))) { + if (!*str_off) + continue; + if (*str_off >= r->dist_str_len) { + *str_off += r->base_str_len - r->dist_str_len; + } else { + off = r->str_map[*str_off]; + if (!off) { + pr_warn("string '%s' [offset %u] is not mapped to base BTF", + btf__str_by_offset(r->btf, off), *str_off); + return -ENOENT; + } + *str_off = off; + } + } + return 0; +} + +/* If successful, output of relocation is updated BTF with base BTF pointing + * at base_btf, and type ids, strings adjusted accordingly. + */ +int btf_relocate(struct btf *btf, const struct btf *base_btf, __u32 **id_map) +{ + unsigned int nr_types = btf__type_cnt(btf); + const struct btf_header *dist_base_hdr; + const struct btf_header *base_hdr; + struct btf_relocate r = {}; + int err = 0; + __u32 id, i; + + r.dist_base_btf = btf__base_btf(btf); + if (!base_btf || r.dist_base_btf == base_btf) + return -EINVAL; + + r.nr_dist_base_types = btf__type_cnt(r.dist_base_btf); + r.nr_base_types = btf__type_cnt(base_btf); + r.nr_split_types = nr_types - r.nr_dist_base_types; + r.btf = btf; + r.base_btf = base_btf; + + r.id_map = calloc(nr_types, sizeof(*r.id_map)); + r.str_map = calloc(btf_header(r.dist_base_btf)->str_len, sizeof(*r.str_map)); + dist_base_hdr = btf_header(r.dist_base_btf); + base_hdr = btf_header(r.base_btf); + r.dist_str_len = dist_base_hdr->str_len; + r.base_str_len = base_hdr->str_len; + if (!r.id_map || !r.str_map) { + err = -ENOMEM; + goto err_out; + } + + err = btf_relocate_validate_distilled_base(&r); + if (err) + goto err_out; + + /* Split BTF ids need to be adjusted as base and distilled base + * have different numbers of types, changing the start id of split + * BTF. + */ + for (id = r.nr_dist_base_types; id < nr_types; id++) + r.id_map[id] = id + r.nr_base_types - r.nr_dist_base_types; + + /* Build a map from distilled base ids to actual base BTF ids; it is used + * to update split BTF id references. Also build a str_map mapping from + * distilled base BTF names to base BTF names. + */ + err = btf_relocate_map_distilled_base(&r); + if (err) + goto err_out; + + /* Next, rewrite type ids in split BTF, replacing split ids with updated + * ids based on number of types in base BTF, and base ids with + * relocated ids from base_btf. + */ + for (i = 0, id = r.nr_dist_base_types; i < r.nr_split_types; i++, id++) { + err = btf_relocate_rewrite_type_id(&r, id); + if (err) + goto err_out; + } + /* String offsets now need to be updated using the str_map. */ + for (i = 0; i < r.nr_split_types; i++) { + err = btf_relocate_rewrite_strs(&r, i + r.nr_dist_base_types); + if (err) + goto err_out; + } + /* Finally reset base BTF to be base_btf */ + btf_set_base_btf(btf, base_btf); + + if (id_map) { + *id_map = r.id_map; + r.id_map = NULL; + } +err_out: + free(r.id_map); + free(r.str_map); + return err; +} diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 175d1536e070..8f0d9ea3b1b4 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -420,6 +420,7 @@ LIBBPF_1.4.0 { LIBBPF_1.5.0 { global: btf__distill_base; + btf__relocate; bpf_map__autoattach; bpf_map__set_autoattach; bpf_program__attach_sockmap; diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index e2f06609c624..408df59e0771 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -234,6 +234,9 @@ struct btf_type; struct btf_type *btf_type_by_id(const struct btf *btf, __u32 type_id); const char *btf_kind_str(const struct btf_type *t); const struct btf_type *skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id); +const struct btf_header *btf_header(const struct btf *btf); +void btf_set_base_btf(struct btf *btf, const struct btf *base_btf); +int btf_relocate(struct btf *btf, const struct btf *base_btf, __u32 **id_map); static inline enum btf_func_linkage btf_func_linkage(const struct btf_type *t) { From affdeb50616b190c3236cc2bf116e1b931a43be2 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Thu, 13 Jun 2024 10:50:09 +0100 Subject: [PATCH 4/6] selftests/bpf: Extend distilled BTF tests to cover BTF relocation Ensure relocated BTF looks as expected; in this case identical to original split BTF, with a few duplicate anonymous types added to split BTF by the relocation process. Also add relocation tests for edge cases like missing type in base BTF and multiple types of the same name. Signed-off-by: Alan Maguire Signed-off-by: Andrii Nakryiko Acked-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/20240613095014.357981-5-alan.maguire@oracle.com --- .../selftests/bpf/prog_tests/btf_distill.c | 278 ++++++++++++++++++ 1 file changed, 278 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/btf_distill.c b/tools/testing/selftests/bpf/prog_tests/btf_distill.c index 5c3a38747962..bfbe795823a2 100644 --- a/tools/testing/selftests/bpf/prog_tests/btf_distill.c +++ b/tools/testing/selftests/bpf/prog_tests/btf_distill.c @@ -217,6 +217,73 @@ static void test_distilled_base(void) "\t'p1' type_id=1", "[25] ARRAY '(anon)' type_id=1 index_type_id=1 nr_elems=3"); + if (!ASSERT_EQ(btf__relocate(btf4, btf1), 0, "relocate_split")) + goto cleanup; + + VALIDATE_RAW_BTF( + btf4, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] PTR '(anon)' type_id=1", + "[3] STRUCT 's1' size=8 vlen=1\n" + "\t'f1' type_id=2 bits_offset=0", + "[4] STRUCT '(anon)' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=3 bits_offset=32", + "[5] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)", + "[6] UNION 'u1' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=2 bits_offset=0", + "[7] UNION '(anon)' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[8] ENUM 'e1' encoding=UNSIGNED size=4 vlen=1\n" + "\t'v1' val=1", + "[9] ENUM '(anon)' encoding=UNSIGNED size=4 vlen=1\n" + "\t'av1' val=2", + "[10] ENUM64 'e641' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1024", + "[11] ENUM64 '(anon)' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1025", + "[12] STRUCT 'unneeded' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[13] STRUCT 'embedded' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[14] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=1", + "[15] ARRAY '(anon)' type_id=1 index_type_id=1 nr_elems=3", + "[16] STRUCT 'from_proto' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[17] UNION 'u1' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[18] PTR '(anon)' type_id=3", + "[19] PTR '(anon)' type_id=30", + "[20] CONST '(anon)' type_id=6", + "[21] RESTRICT '(anon)' type_id=31", + "[22] VOLATILE '(anon)' type_id=8", + "[23] TYPEDEF 'et' type_id=32", + "[24] CONST '(anon)' type_id=10", + "[25] PTR '(anon)' type_id=33", + "[26] STRUCT 'with_embedded' size=4 vlen=1\n" + "\t'f1' type_id=13 bits_offset=0", + "[27] FUNC 'fn' type_id=34 linkage=static", + "[28] TYPEDEF 'arraytype' type_id=35", + "[29] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=16", + /* below here are (duplicate) anon base types added by distill + * process to split BTF. + */ + "[30] STRUCT '(anon)' size=12 vlen=2\n" + "\t'f1' type_id=1 bits_offset=0\n" + "\t'f2' type_id=3 bits_offset=32", + "[31] UNION '(anon)' size=4 vlen=1\n" + "\t'f1' type_id=1 bits_offset=0", + "[32] ENUM '(anon)' encoding=UNSIGNED size=4 vlen=1\n" + "\t'av1' val=2", + "[33] ENUM64 '(anon)' encoding=SIGNED size=8 vlen=1\n" + "\t'v1' val=1025", + "[34] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n" + "\t'p1' type_id=1", + "[35] ARRAY '(anon)' type_id=1 index_type_id=1 nr_elems=3"); + cleanup: btf__free(btf4); btf__free(btf3); @@ -224,6 +291,209 @@ cleanup: btf__free(btf1); } +/* ensure we can cope with multiple types with the same name in + * distilled base BTF. In this case because sizes are different, + * we can still disambiguate them. + */ +static void test_distilled_base_multi(void) +{ + struct btf *btf1 = NULL, *btf2 = NULL, *btf3 = NULL, *btf4 = NULL; + + btf1 = btf__new_empty(); + if (!ASSERT_OK_PTR(btf1, "empty_main_btf")) + return; + btf__add_int(btf1, "int", 4, BTF_INT_SIGNED); /* [1] int */ + btf__add_int(btf1, "int", 8, BTF_INT_SIGNED); /* [2] int */ + VALIDATE_RAW_BTF( + btf1, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=8 bits_offset=0 nr_bits=64 encoding=SIGNED"); + btf2 = btf__new_empty_split(btf1); + if (!ASSERT_OK_PTR(btf2, "empty_split_btf")) + goto cleanup; + btf__add_ptr(btf2, 1); + btf__add_const(btf2, 2); + VALIDATE_RAW_BTF( + btf2, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=8 bits_offset=0 nr_bits=64 encoding=SIGNED", + "[3] PTR '(anon)' type_id=1", + "[4] CONST '(anon)' type_id=2"); + if (!ASSERT_EQ(0, btf__distill_base(btf2, &btf3, &btf4), + "distilled_base") || + !ASSERT_OK_PTR(btf3, "distilled_base") || + !ASSERT_OK_PTR(btf4, "distilled_split") || + !ASSERT_EQ(3, btf__type_cnt(btf3), "distilled_base_type_cnt")) + goto cleanup; + VALIDATE_RAW_BTF( + btf3, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=8 bits_offset=0 nr_bits=64 encoding=SIGNED"); + if (!ASSERT_EQ(btf__relocate(btf4, btf1), 0, "relocate_split")) + goto cleanup; + + VALIDATE_RAW_BTF( + btf4, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=8 bits_offset=0 nr_bits=64 encoding=SIGNED", + "[3] PTR '(anon)' type_id=1", + "[4] CONST '(anon)' type_id=2"); + +cleanup: + btf__free(btf4); + btf__free(btf3); + btf__free(btf2); + btf__free(btf1); +} + +/* If a needed type is not present in the base BTF we wish to relocate + * with, btf__relocate() should error our. + */ +static void test_distilled_base_missing_err(void) +{ + struct btf *btf1 = NULL, *btf2 = NULL, *btf3 = NULL, *btf4 = NULL, *btf5 = NULL; + + btf1 = btf__new_empty(); + if (!ASSERT_OK_PTR(btf1, "empty_main_btf")) + return; + btf__add_int(btf1, "int", 4, BTF_INT_SIGNED); /* [1] int */ + btf__add_int(btf1, "int", 8, BTF_INT_SIGNED); /* [2] int */ + VALIDATE_RAW_BTF( + btf1, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=8 bits_offset=0 nr_bits=64 encoding=SIGNED"); + btf2 = btf__new_empty_split(btf1); + if (!ASSERT_OK_PTR(btf2, "empty_split_btf")) + goto cleanup; + btf__add_ptr(btf2, 1); + btf__add_const(btf2, 2); + VALIDATE_RAW_BTF( + btf2, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=8 bits_offset=0 nr_bits=64 encoding=SIGNED", + "[3] PTR '(anon)' type_id=1", + "[4] CONST '(anon)' type_id=2"); + if (!ASSERT_EQ(0, btf__distill_base(btf2, &btf3, &btf4), + "distilled_base") || + !ASSERT_OK_PTR(btf3, "distilled_base") || + !ASSERT_OK_PTR(btf4, "distilled_split") || + !ASSERT_EQ(3, btf__type_cnt(btf3), "distilled_base_type_cnt")) + goto cleanup; + VALIDATE_RAW_BTF( + btf3, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=8 bits_offset=0 nr_bits=64 encoding=SIGNED"); + btf5 = btf__new_empty(); + if (!ASSERT_OK_PTR(btf5, "empty_reloc_btf")) + return; + btf__add_int(btf5, "int", 4, BTF_INT_SIGNED); /* [1] int */ + VALIDATE_RAW_BTF( + btf5, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED"); + ASSERT_EQ(btf__relocate(btf4, btf5), -EINVAL, "relocate_split"); + +cleanup: + btf__free(btf5); + btf__free(btf4); + btf__free(btf3); + btf__free(btf2); + btf__free(btf1); +} + +/* With 2 types of same size in distilled base BTF, relocation should + * fail as we have no means to choose between them. + */ +static void test_distilled_base_multi_err(void) +{ + struct btf *btf1 = NULL, *btf2 = NULL, *btf3 = NULL, *btf4 = NULL; + + btf1 = btf__new_empty(); + if (!ASSERT_OK_PTR(btf1, "empty_main_btf")) + return; + btf__add_int(btf1, "int", 4, BTF_INT_SIGNED); /* [1] int */ + btf__add_int(btf1, "int", 4, BTF_INT_SIGNED); /* [2] int */ + VALIDATE_RAW_BTF( + btf1, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED"); + btf2 = btf__new_empty_split(btf1); + if (!ASSERT_OK_PTR(btf2, "empty_split_btf")) + goto cleanup; + btf__add_ptr(btf2, 1); + btf__add_const(btf2, 2); + VALIDATE_RAW_BTF( + btf2, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[3] PTR '(anon)' type_id=1", + "[4] CONST '(anon)' type_id=2"); + if (!ASSERT_EQ(0, btf__distill_base(btf2, &btf3, &btf4), + "distilled_base") || + !ASSERT_OK_PTR(btf3, "distilled_base") || + !ASSERT_OK_PTR(btf4, "distilled_split") || + !ASSERT_EQ(3, btf__type_cnt(btf3), "distilled_base_type_cnt")) + goto cleanup; + VALIDATE_RAW_BTF( + btf3, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED"); + ASSERT_EQ(btf__relocate(btf4, btf1), -EINVAL, "relocate_split"); +cleanup: + btf__free(btf4); + btf__free(btf3); + btf__free(btf2); + btf__free(btf1); +} + +/* With 2 types of same size in base BTF, relocation should + * fail as we have no means to choose between them. + */ +static void test_distilled_base_multi_err2(void) +{ + struct btf *btf1 = NULL, *btf2 = NULL, *btf3 = NULL, *btf4 = NULL, *btf5 = NULL; + + btf1 = btf__new_empty(); + if (!ASSERT_OK_PTR(btf1, "empty_main_btf")) + return; + btf__add_int(btf1, "int", 4, BTF_INT_SIGNED); /* [1] int */ + VALIDATE_RAW_BTF( + btf1, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED"); + btf2 = btf__new_empty_split(btf1); + if (!ASSERT_OK_PTR(btf2, "empty_split_btf")) + goto cleanup; + btf__add_ptr(btf2, 1); + VALIDATE_RAW_BTF( + btf2, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] PTR '(anon)' type_id=1"); + if (!ASSERT_EQ(0, btf__distill_base(btf2, &btf3, &btf4), + "distilled_base") || + !ASSERT_OK_PTR(btf3, "distilled_base") || + !ASSERT_OK_PTR(btf4, "distilled_split") || + !ASSERT_EQ(2, btf__type_cnt(btf3), "distilled_base_type_cnt")) + goto cleanup; + VALIDATE_RAW_BTF( + btf3, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED"); + btf5 = btf__new_empty(); + if (!ASSERT_OK_PTR(btf5, "empty_reloc_btf")) + return; + btf__add_int(btf5, "int", 4, BTF_INT_SIGNED); /* [1] int */ + btf__add_int(btf5, "int", 4, BTF_INT_SIGNED); /* [2] int */ + VALIDATE_RAW_BTF( + btf5, + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED", + "[2] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED"); + ASSERT_EQ(btf__relocate(btf4, btf5), -EINVAL, "relocate_split"); +cleanup: + btf__free(btf5); + btf__free(btf4); + btf__free(btf3); + btf__free(btf2); + btf__free(btf1); +} + /* create split reference BTF from vmlinux + split BTF with a few type references; * ensure the resultant split reference BTF is as expected, containing only types * needed to disambiguate references from split BTF. @@ -269,6 +539,14 @@ void test_btf_distill(void) { if (test__start_subtest("distilled_base")) test_distilled_base(); + if (test__start_subtest("distilled_base_multi")) + test_distilled_base_multi(); + if (test__start_subtest("distilled_base_missing_err")) + test_distilled_base_missing_err(); + if (test__start_subtest("distilled_base_multi_err")) + test_distilled_base_multi_err(); + if (test__start_subtest("distilled_base_multi_err2")) + test_distilled_base_multi_err2(); if (test__start_subtest("distilled_base_vmlinux")) test_distilled_base_vmlinux(); } From c86f180ffc993975fed5907a869fc9b1555d0cfb Mon Sep 17 00:00:00 2001 From: Eduard Zingerman Date: Thu, 13 Jun 2024 10:50:10 +0100 Subject: [PATCH 5/6] libbpf: Make btf_parse_elf process .BTF.base transparently Update btf_parse_elf() to check if .BTF.base section is present. The logic is as follows: if .BTF.base section exists: distilled_base := btf_new(.BTF.base) if distilled_base: btf := btf_new(.BTF, .base_btf=distilled_base) if base_btf: btf_relocate(btf, base_btf) else: btf := btf_new(.BTF) return btf In other words: - if .BTF.base section exists, load BTF from it and use it as a base for .BTF load; - if base_btf is specified and .BTF.base section exist, relocate newly loaded .BTF against base_btf. Signed-off-by: Eduard Zingerman Signed-off-by: Alan Maguire Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20240613095014.357981-6-alan.maguire@oracle.com --- tools/lib/bpf/btf.c | 186 ++++++++++++++++++++++++++++---------------- tools/lib/bpf/btf.h | 1 + 2 files changed, 122 insertions(+), 65 deletions(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 5e20354fbcfa..ef1b2f573c1b 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -116,6 +116,9 @@ struct btf { /* whether strings are already deduplicated */ bool strs_deduped; + /* whether base_btf should be freed in btf_free for this instance */ + bool owns_base; + /* BTF object FD, if loaded into kernel */ int fd; @@ -969,6 +972,8 @@ void btf__free(struct btf *btf) free(btf->raw_data); free(btf->raw_data_swapped); free(btf->type_offs); + if (btf->owns_base) + btf__free(btf->base_btf); free(btf); } @@ -1084,16 +1089,86 @@ struct btf *btf__new_split(const void *data, __u32 size, struct btf *base_btf) return libbpf_ptr(btf_new(data, size, base_btf)); } +struct btf_elf_secs { + Elf_Data *btf_data; + Elf_Data *btf_ext_data; + Elf_Data *btf_base_data; +}; + +static int btf_find_elf_sections(Elf *elf, const char *path, struct btf_elf_secs *secs) +{ + Elf_Scn *scn = NULL; + Elf_Data *data; + GElf_Ehdr ehdr; + size_t shstrndx; + int idx = 0; + + if (!gelf_getehdr(elf, &ehdr)) { + pr_warn("failed to get EHDR from %s\n", path); + goto err; + } + + if (elf_getshdrstrndx(elf, &shstrndx)) { + pr_warn("failed to get section names section index for %s\n", + path); + goto err; + } + + if (!elf_rawdata(elf_getscn(elf, shstrndx), NULL)) { + pr_warn("failed to get e_shstrndx from %s\n", path); + goto err; + } + + while ((scn = elf_nextscn(elf, scn)) != NULL) { + Elf_Data **field; + GElf_Shdr sh; + char *name; + + idx++; + if (gelf_getshdr(scn, &sh) != &sh) { + pr_warn("failed to get section(%d) header from %s\n", + idx, path); + goto err; + } + name = elf_strptr(elf, shstrndx, sh.sh_name); + if (!name) { + pr_warn("failed to get section(%d) name from %s\n", + idx, path); + goto err; + } + + if (strcmp(name, BTF_ELF_SEC) == 0) + field = &secs->btf_data; + else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) + field = &secs->btf_ext_data; + else if (strcmp(name, BTF_BASE_ELF_SEC) == 0) + field = &secs->btf_base_data; + else + continue; + + data = elf_getdata(scn, 0); + if (!data) { + pr_warn("failed to get section(%d, %s) data from %s\n", + idx, name, path); + goto err; + } + *field = data; + } + + return 0; + +err: + return -LIBBPF_ERRNO__FORMAT; +} + static struct btf *btf_parse_elf(const char *path, struct btf *base_btf, struct btf_ext **btf_ext) { - Elf_Data *btf_data = NULL, *btf_ext_data = NULL; - int err = 0, fd = -1, idx = 0; + struct btf_elf_secs secs = {}; + struct btf *dist_base_btf = NULL; struct btf *btf = NULL; - Elf_Scn *scn = NULL; + int err = 0, fd = -1; Elf *elf = NULL; - GElf_Ehdr ehdr; - size_t shstrndx; if (elf_version(EV_CURRENT) == EV_NONE) { pr_warn("failed to init libelf for %s\n", path); @@ -1107,73 +1182,48 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf, return ERR_PTR(err); } - err = -LIBBPF_ERRNO__FORMAT; - elf = elf_begin(fd, ELF_C_READ, NULL); if (!elf) { pr_warn("failed to open %s as ELF file\n", path); goto done; } - if (!gelf_getehdr(elf, &ehdr)) { - pr_warn("failed to get EHDR from %s\n", path); + + err = btf_find_elf_sections(elf, path, &secs); + if (err) goto done; - } - if (elf_getshdrstrndx(elf, &shstrndx)) { - pr_warn("failed to get section names section index for %s\n", - path); - goto done; - } - - if (!elf_rawdata(elf_getscn(elf, shstrndx), NULL)) { - pr_warn("failed to get e_shstrndx from %s\n", path); - goto done; - } - - while ((scn = elf_nextscn(elf, scn)) != NULL) { - GElf_Shdr sh; - char *name; - - idx++; - if (gelf_getshdr(scn, &sh) != &sh) { - pr_warn("failed to get section(%d) header from %s\n", - idx, path); - goto done; - } - name = elf_strptr(elf, shstrndx, sh.sh_name); - if (!name) { - pr_warn("failed to get section(%d) name from %s\n", - idx, path); - goto done; - } - if (strcmp(name, BTF_ELF_SEC) == 0) { - btf_data = elf_getdata(scn, 0); - if (!btf_data) { - pr_warn("failed to get section(%d, %s) data from %s\n", - idx, name, path); - goto done; - } - continue; - } else if (btf_ext && strcmp(name, BTF_EXT_ELF_SEC) == 0) { - btf_ext_data = elf_getdata(scn, 0); - if (!btf_ext_data) { - pr_warn("failed to get section(%d, %s) data from %s\n", - idx, name, path); - goto done; - } - continue; - } - } - - if (!btf_data) { + if (!secs.btf_data) { pr_warn("failed to find '%s' ELF section in %s\n", BTF_ELF_SEC, path); err = -ENODATA; goto done; } - btf = btf_new(btf_data->d_buf, btf_data->d_size, base_btf); - err = libbpf_get_error(btf); - if (err) + + if (secs.btf_base_data) { + dist_base_btf = btf_new(secs.btf_base_data->d_buf, secs.btf_base_data->d_size, + NULL); + if (IS_ERR(dist_base_btf)) { + err = PTR_ERR(dist_base_btf); + dist_base_btf = NULL; + goto done; + } + } + + btf = btf_new(secs.btf_data->d_buf, secs.btf_data->d_size, + dist_base_btf ?: base_btf); + if (IS_ERR(btf)) { + err = PTR_ERR(btf); goto done; + } + if (dist_base_btf && base_btf) { + err = btf__relocate(btf, base_btf); + if (err) + goto done; + btf__free(dist_base_btf); + dist_base_btf = NULL; + } + + if (dist_base_btf) + btf->owns_base = true; switch (gelf_getclass(elf)) { case ELFCLASS32: @@ -1187,11 +1237,12 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf, break; } - if (btf_ext && btf_ext_data) { - *btf_ext = btf_ext__new(btf_ext_data->d_buf, btf_ext_data->d_size); - err = libbpf_get_error(*btf_ext); - if (err) + if (btf_ext && secs.btf_ext_data) { + *btf_ext = btf_ext__new(secs.btf_ext_data->d_buf, secs.btf_ext_data->d_size); + if (IS_ERR(*btf_ext)) { + err = PTR_ERR(*btf_ext); goto done; + } } else if (btf_ext) { *btf_ext = NULL; } @@ -1205,6 +1256,7 @@ done: if (btf_ext) btf_ext__free(*btf_ext); + btf__free(dist_base_btf); btf__free(btf); return ERR_PTR(err); @@ -5598,5 +5650,9 @@ void btf_set_base_btf(struct btf *btf, const struct btf *base_btf) int btf__relocate(struct btf *btf, const struct btf *base_btf) { - return libbpf_err(btf_relocate(btf, base_btf, NULL)); + int err = btf_relocate(btf, base_btf, NULL); + + if (!err) + btf->owns_base = false; + return libbpf_err(err); } diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index 8a93120b7385..b68d216837a9 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -18,6 +18,7 @@ extern "C" { #define BTF_ELF_SEC ".BTF" #define BTF_EXT_ELF_SEC ".BTF.ext" +#define BTF_BASE_ELF_SEC ".BTF.base" #define MAPS_ELF_SEC ".maps" struct btf; From 6ba77385f386053cea2a1cad33717de74a26db4e Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Thu, 13 Jun 2024 10:50:11 +0100 Subject: [PATCH 6/6] resolve_btfids: Handle presence of .BTF.base section Now that btf_parse_elf() handles .BTF.base section presence, we need to ensure that resolve_btfids uses .BTF.base when present rather than the vmlinux base BTF passed in via the -B option. Detect .BTF.base section presence and unset the base BTF path to ensure that BTF ELF parsing will do the right thing. Signed-off-by: Alan Maguire Signed-off-by: Andrii Nakryiko Reviewed-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/20240613095014.357981-7-alan.maguire@oracle.com --- tools/bpf/resolve_btfids/main.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c index af393c7dee1f..936ef95c3d32 100644 --- a/tools/bpf/resolve_btfids/main.c +++ b/tools/bpf/resolve_btfids/main.c @@ -409,6 +409,14 @@ static int elf_collect(struct object *obj) obj->efile.idlist = data; obj->efile.idlist_shndx = idx; obj->efile.idlist_addr = sh.sh_addr; + } else if (!strcmp(name, BTF_BASE_ELF_SEC)) { + /* If a .BTF.base section is found, do not resolve + * BTF ids relative to vmlinux; resolve relative + * to the .BTF.base section instead. btf__parse_split() + * will take care of this once the base BTF it is + * passed is NULL. + */ + obj->base_btf_path = NULL; } if (compressed_section_fix(elf, scn, &sh))