Merge branch 'libbpf: BTF writer APIs'

Andrii Nakryiko says:

====================
This patch set introduces a new set of BTF APIs to libbpf that allow to
conveniently produce BTF types and strings. These APIs will allow libbpf to do
more intrusive modifications of program's BTF (by rewriting it, at least as of
right now), which is necessary for the upcoming libbpf static linking. But
they are complete and generic, so can be adopted by anyone who has a need to
produce BTF type information.

One such example outside of libbpf is pahole, which was actually converted to
these APIs (locally, pending landing of these changes in libbpf) completely
and shows reduction in amount of custom pahole code necessary and brings nice
savings in memory usage (about 370MB reduction at peak for my kernel
configuration) and even BTF deduplication times (one second reduction,
23.7s -> 22.7s). Memory savings are due to avoiding pahole's own copy of
"uncompressed" raw BTF data. Time reduction comes from faster string
search and deduplication by relying on hashmap instead of BST used by pahole's
own code. Consequently, these APIs are already tested on real-world
complicated kernel BTF, but there is also pretty extensive selftest doing
extra validations.

Selftests in patch #3 add a set of generic ASSERT_{EQ,STREQ,ERR,OK} macros
that are useful for writing shorter and less repretitive selftests. I decided
to keep them local to that selftest for now, but if they prove to be useful in
more contexts we should move them to test_progs.h. And few more (e.g.,
inequality tests) macros are probably necessary to have a more complete set.

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>

v2->v3:
  - resending original patches #7-9 as patches #1-3 due to merge conflict;

v1->v2:
  - fixed comments (John);
  - renamed btf__append_xxx() into btf__add_xxx() (Alexei);
  - added btf__find_str() in addition to btf__add_str();
  - btf__new_empty() now sets kernel FD to -1 initially.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/btf.h

@@ -49,6 +49,7 @@ LIBBPF_API int btf__fd(const struct btf *btf);
 LIBBPF_API void btf__set_fd(struct btf *btf, int fd);
 LIBBPF_API const void *btf__get_raw_data(const struct btf *btf, __u32 *size);
 LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
+LIBBPF_API const char *btf__str_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
 LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
 				    __u32 expected_key_size,
@@ -77,6 +78,44 @@ LIBBPF_API struct btf *libbpf_find_kernel_btf(void);
 LIBBPF_API int btf__find_str(struct btf *btf, const char *s);
 LIBBPF_API int btf__add_str(struct btf *btf, const char *s);
 
+LIBBPF_API int btf__add_int(struct btf *btf, const char *name, size_t byte_sz, int encoding);
+LIBBPF_API int btf__add_ptr(struct btf *btf, int ref_type_id);
+LIBBPF_API int btf__add_array(struct btf *btf,
+			      int index_type_id, int elem_type_id, __u32 nr_elems);
+/* struct/union construction APIs */
+LIBBPF_API int btf__add_struct(struct btf *btf, const char *name, __u32 sz);
+LIBBPF_API int btf__add_union(struct btf *btf, const char *name, __u32 sz);
+LIBBPF_API int btf__add_field(struct btf *btf, const char *name, int field_type_id,
+			      __u32 bit_offset, __u32 bit_size);
+
+/* enum construction APIs */
+LIBBPF_API int btf__add_enum(struct btf *btf, const char *name, __u32 bytes_sz);
+LIBBPF_API int btf__add_enum_value(struct btf *btf, const char *name, __s64 value);
+
+enum btf_fwd_kind {
+	BTF_FWD_STRUCT = 0,
+	BTF_FWD_UNION = 1,
+	BTF_FWD_ENUM = 2,
+};
+
+LIBBPF_API int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind);
+LIBBPF_API int btf__add_typedef(struct btf *btf, const char *name, int ref_type_id);
+LIBBPF_API int btf__add_volatile(struct btf *btf, int ref_type_id);
+LIBBPF_API int btf__add_const(struct btf *btf, int ref_type_id);
+LIBBPF_API int btf__add_restrict(struct btf *btf, int ref_type_id);
+
+/* func and func_proto construction APIs */
+LIBBPF_API int btf__add_func(struct btf *btf, const char *name,
+			     enum btf_func_linkage linkage, int proto_type_id);
+LIBBPF_API int btf__add_func_proto(struct btf *btf, int ret_type_id);
+LIBBPF_API int btf__add_func_param(struct btf *btf, const char *name, int type_id);
+
+/* var & datasec construction APIs */
+LIBBPF_API int btf__add_var(struct btf *btf, const char *name, int linkage, int type_id);
+LIBBPF_API int btf__add_datasec(struct btf *btf, const char *name, __u32 byte_sz);
+LIBBPF_API int btf__add_datasec_var_info(struct btf *btf, int var_type_id,
+					 __u32 offset, __u32 byte_sz);
+
 struct btf_dedup_opts {
 	unsigned int dedup_table_size;
 	bool dont_resolve_fwds;

tools/lib/bpf/libbpf.map

@@ -305,9 +305,29 @@ LIBBPF_0.2.0 {
 		bpf_prog_bind_map;
 		bpf_prog_test_run_opts;
 		bpf_program__section_name;
+		btf__add_array;
+		btf__add_const;
+		btf__add_enum;
+		btf__add_enum_value;
+		btf__add_datasec;
+		btf__add_datasec_var_info;
+		btf__add_field;
+		btf__add_func;
+		btf__add_func_param;
+		btf__add_func_proto;
+		btf__add_fwd;
+		btf__add_int;
+		btf__add_ptr;
+		btf__add_restrict;
 		btf__add_str;
+		btf__add_struct;
+		btf__add_typedef;
+		btf__add_union;
+		btf__add_var;
+		btf__add_volatile;
 		btf__find_str;
 		btf__new_empty;
+		btf__str_by_offset;
 		perf_buffer__buffer_cnt;
 		perf_buffer__buffer_fd;
 		perf_buffer__epoll_fd;

tools/testing/selftests/bpf/prog_tests/btf_write.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include <test_progs.h>
+#include <bpf/btf.h>
+
+#define ASSERT_EQ(actual, expected, name) ({				\
+	typeof(actual) ___act = (actual);				\
+	typeof(expected) ___exp = (expected);				\
+	bool ___ok = ___act == ___exp;					\
+	CHECK(!___ok, (name),						\
+	      "unexpected %s: actual %lld != expected %lld\n",		\
+	      (name), (long long)(___act), (long long)(___exp));	\
+	___ok;								\
+})
+
+#define ASSERT_STREQ(actual, expected, name) ({				\
+	const char *___act = actual;					\
+	const char *___exp = expected;					\
+	bool ___ok = strcmp(___act, ___exp) == 0;			\
+	CHECK(!___ok, (name),						\
+	      "unexpected %s: actual '%s' != expected '%s'\n",		\
+	      (name), ___act, ___exp);					\
+	___ok;								\
+})
+
+#define ASSERT_OK(res, name) ({						\
+	long long ___res = (res);					\
+	bool ___ok = ___res == 0;					\
+	CHECK(!___ok, (name), "unexpected error: %lld\n", ___res);	\
+	___ok;								\
+})
+
+#define ASSERT_ERR(res, name) ({					\
+	long long ___res = (res);					\
+	bool ___ok = ___res < 0;					\
+	CHECK(!___ok, (name), "unexpected success: %lld\n", ___res);	\
+	___ok;								\
+})
+
+static int duration = 0;
+
+void test_btf_write() {
+	const struct btf_var_secinfo *vi;
+	const struct btf_type *t;
+	const struct btf_member *m;
+	const struct btf_enum *v;
+	const struct btf_param *p;
+	struct btf *btf;
+	int id, err, str_off;
+
+	btf = btf__new_empty();
+	if (CHECK(IS_ERR(btf), "new_empty", "failed: %ld\n", PTR_ERR(btf)))
+		return;
+
+	str_off = btf__find_str(btf, "int");
+	ASSERT_EQ(str_off, -ENOENT, "int_str_missing_off");
+
+	str_off = btf__add_str(btf, "int");
+	ASSERT_EQ(str_off, 1, "int_str_off");
+
+	str_off = btf__find_str(btf, "int");
+	ASSERT_EQ(str_off, 1, "int_str_found_off");
+
+	/* BTF_KIND_INT */
+	id = btf__add_int(btf, "int", 4,  BTF_INT_SIGNED);
+	ASSERT_EQ(id, 1, "int_id");
+
+	t = btf__type_by_id(btf, 1);
+	/* should re-use previously added "int" string */
+	ASSERT_EQ(t->name_off, str_off, "int_name_off");
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "int", "int_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_INT, "int_kind");
+	ASSERT_EQ(t->size, 4, "int_sz");
+	ASSERT_EQ(btf_int_encoding(t), BTF_INT_SIGNED, "int_enc");
+	ASSERT_EQ(btf_int_bits(t), 32, "int_bits");
+
+	/* invalid int size */
+	id = btf__add_int(btf, "bad sz int", 7, 0);
+	ASSERT_ERR(id, "int_bad_sz");
+	/* invalid encoding */
+	id = btf__add_int(btf, "bad enc int", 4, 123);
+	ASSERT_ERR(id, "int_bad_enc");
+	/* NULL name */
+	id = btf__add_int(btf, NULL, 4, 0);
+	ASSERT_ERR(id, "int_bad_null_name");
+	/* empty name */
+	id = btf__add_int(btf, "", 4, 0);
+	ASSERT_ERR(id, "int_bad_empty_name");
+
+	/* PTR/CONST/VOLATILE/RESTRICT */
+	id = btf__add_ptr(btf, 1);
+	ASSERT_EQ(id, 2, "ptr_id");
+	t = btf__type_by_id(btf, 2);
+	ASSERT_EQ(btf_kind(t), BTF_KIND_PTR, "ptr_kind");
+	ASSERT_EQ(t->type, 1, "ptr_type");
+
+	id = btf__add_const(btf, 5); /* points forward to restrict */
+	ASSERT_EQ(id, 3, "const_id");
+	t = btf__type_by_id(btf, 3);
+	ASSERT_EQ(btf_kind(t), BTF_KIND_CONST, "const_kind");
+	ASSERT_EQ(t->type, 5, "const_type");
+
+	id = btf__add_volatile(btf, 3);
+	ASSERT_EQ(id, 4, "volatile_id");
+	t = btf__type_by_id(btf, 4);
+	ASSERT_EQ(btf_kind(t), BTF_KIND_VOLATILE, "volatile_kind");
+	ASSERT_EQ(t->type, 3, "volatile_type");
+
+	id = btf__add_restrict(btf, 4);
+	ASSERT_EQ(id, 5, "restrict_id");
+	t = btf__type_by_id(btf, 5);
+	ASSERT_EQ(btf_kind(t), BTF_KIND_RESTRICT, "restrict_kind");
+	ASSERT_EQ(t->type, 4, "restrict_type");
+
+	/* ARRAY */
+	id = btf__add_array(btf, 1, 2, 10); /* int *[10] */
+	ASSERT_EQ(id, 6, "array_id");
+	t = btf__type_by_id(btf, 6);
+	ASSERT_EQ(btf_kind(t), BTF_KIND_ARRAY, "array_kind");
+	ASSERT_EQ(btf_array(t)->index_type, 1, "array_index_type");
+	ASSERT_EQ(btf_array(t)->type, 2, "array_elem_type");
+	ASSERT_EQ(btf_array(t)->nelems, 10, "array_nelems");
+
+	/* STRUCT */
+	err = btf__add_field(btf, "field", 1, 0, 0);
+	ASSERT_ERR(err, "no_struct_field");
+	id = btf__add_struct(btf, "s1", 8);
+	ASSERT_EQ(id, 7, "struct_id");
+	err = btf__add_field(btf, "f1", 1, 0, 0);
+	ASSERT_OK(err, "f1_res");
+	err = btf__add_field(btf, "f2", 1, 32, 16);
+	ASSERT_OK(err, "f2_res");
+
+	t = btf__type_by_id(btf, 7);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "s1", "struct_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_STRUCT, "struct_kind");
+	ASSERT_EQ(btf_vlen(t), 2, "struct_vlen");
+	ASSERT_EQ(btf_kflag(t), true, "struct_kflag");
+	ASSERT_EQ(t->size, 8, "struct_sz");
+	m = btf_members(t) + 0;
+	ASSERT_STREQ(btf__str_by_offset(btf, m->name_off), "f1", "f1_name");
+	ASSERT_EQ(m->type, 1, "f1_type");
+	ASSERT_EQ(btf_member_bit_offset(t, 0), 0, "f1_bit_off");
+	ASSERT_EQ(btf_member_bitfield_size(t, 0), 0, "f1_bit_sz");
+	m = btf_members(t) + 1;
+	ASSERT_STREQ(btf__str_by_offset(btf, m->name_off), "f2", "f2_name");
+	ASSERT_EQ(m->type, 1, "f2_type");
+	ASSERT_EQ(btf_member_bit_offset(t, 1), 32, "f2_bit_off");
+	ASSERT_EQ(btf_member_bitfield_size(t, 1), 16, "f2_bit_sz");
+
+	/* UNION */
+	id = btf__add_union(btf, "u1", 8);
+	ASSERT_EQ(id, 8, "union_id");
+
+	/* invalid, non-zero offset */
+	err = btf__add_field(btf, "field", 1, 1, 0);
+	ASSERT_ERR(err, "no_struct_field");
+
+	err = btf__add_field(btf, "f1", 1, 0, 16);
+	ASSERT_OK(err, "f1_res");
+
+	t = btf__type_by_id(btf, 8);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "u1", "union_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_UNION, "union_kind");
+	ASSERT_EQ(btf_vlen(t), 1, "union_vlen");
+	ASSERT_EQ(btf_kflag(t), true, "union_kflag");
+	ASSERT_EQ(t->size, 8, "union_sz");
+	m = btf_members(t) + 0;
+	ASSERT_STREQ(btf__str_by_offset(btf, m->name_off), "f1", "f1_name");
+	ASSERT_EQ(m->type, 1, "f1_type");
+	ASSERT_EQ(btf_member_bit_offset(t, 0), 0, "f1_bit_off");
+	ASSERT_EQ(btf_member_bitfield_size(t, 0), 16, "f1_bit_sz");
+
+	/* ENUM */
+	id = btf__add_enum(btf, "e1", 4);
+	ASSERT_EQ(id, 9, "enum_id");
+	err = btf__add_enum_value(btf, "v1", 1);
+	ASSERT_OK(err, "v1_res");
+	err = btf__add_enum_value(btf, "v2", 2);
+	ASSERT_OK(err, "v2_res");
+
+	t = btf__type_by_id(btf, 9);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "e1", "enum_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_ENUM, "enum_kind");
+	ASSERT_EQ(btf_vlen(t), 2, "enum_vlen");
+	ASSERT_EQ(t->size, 4, "enum_sz");
+	v = btf_enum(t) + 0;
+	ASSERT_STREQ(btf__str_by_offset(btf, v->name_off), "v1", "v1_name");
+	ASSERT_EQ(v->val, 1, "v1_val");
+	v = btf_enum(t) + 1;
+	ASSERT_STREQ(btf__str_by_offset(btf, v->name_off), "v2", "v2_name");
+	ASSERT_EQ(v->val, 2, "v2_val");
+
+	/* FWDs */
+	id = btf__add_fwd(btf, "struct_fwd", BTF_FWD_STRUCT);
+	ASSERT_EQ(id, 10, "struct_fwd_id");
+	t = btf__type_by_id(btf, 10);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "struct_fwd", "fwd_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_FWD, "fwd_kind");
+	ASSERT_EQ(btf_kflag(t), 0, "fwd_kflag");
+
+	id = btf__add_fwd(btf, "union_fwd", BTF_FWD_UNION);
+	ASSERT_EQ(id, 11, "union_fwd_id");
+	t = btf__type_by_id(btf, 11);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "union_fwd", "fwd_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_FWD, "fwd_kind");
+	ASSERT_EQ(btf_kflag(t), 1, "fwd_kflag");
+
+	id = btf__add_fwd(btf, "enum_fwd", BTF_FWD_ENUM);
+	ASSERT_EQ(id, 12, "enum_fwd_id");
+	t = btf__type_by_id(btf, 12);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "enum_fwd", "fwd_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_ENUM, "enum_fwd_kind");
+	ASSERT_EQ(btf_vlen(t), 0, "enum_fwd_kind");
+	ASSERT_EQ(t->size, 4, "enum_fwd_sz");
+
+	/* TYPEDEF */
+	id = btf__add_typedef(btf, "typedef1", 1);
+	ASSERT_EQ(id, 13, "typedef_fwd_id");
+	t = btf__type_by_id(btf, 13);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "typedef1", "typedef_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_TYPEDEF, "typedef_kind");
+	ASSERT_EQ(t->type, 1, "typedef_type");
+
+	/* FUNC & FUNC_PROTO */
+	id = btf__add_func(btf, "func1", BTF_FUNC_GLOBAL, 15);
+	ASSERT_EQ(id, 14, "func_id");
+	t = btf__type_by_id(btf, 14);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "func1", "func_name");
+	ASSERT_EQ(t->type, 15, "func_type");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_FUNC, "func_kind");
+	ASSERT_EQ(btf_vlen(t), BTF_FUNC_GLOBAL, "func_vlen");
+
+	id = btf__add_func_proto(btf, 1);
+	ASSERT_EQ(id, 15, "func_proto_id");
+	err = btf__add_func_param(btf, "p1", 1);
+	ASSERT_OK(err, "p1_res");
+	err = btf__add_func_param(btf, "p2", 2);
+	ASSERT_OK(err, "p2_res");
+
+	t = btf__type_by_id(btf, 15);
+	ASSERT_EQ(btf_kind(t), BTF_KIND_FUNC_PROTO, "func_proto_kind");
+	ASSERT_EQ(btf_vlen(t), 2, "func_proto_vlen");
+	ASSERT_EQ(t->type, 1, "func_proto_ret_type");
+	p = btf_params(t) + 0;
+	ASSERT_STREQ(btf__str_by_offset(btf, p->name_off), "p1", "p1_name");
+	ASSERT_EQ(p->type, 1, "p1_type");
+	p = btf_params(t) + 1;
+	ASSERT_STREQ(btf__str_by_offset(btf, p->name_off), "p2", "p2_name");
+	ASSERT_EQ(p->type, 2, "p2_type");
+
+	/* VAR */
+	id = btf__add_var(btf, "var1", BTF_VAR_GLOBAL_ALLOCATED, 1);
+	ASSERT_EQ(id, 16, "var_id");
+	t = btf__type_by_id(btf, 16);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "var1", "var_name");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_VAR, "var_kind");
+	ASSERT_EQ(t->type, 1, "var_type");
+	ASSERT_EQ(btf_var(t)->linkage, BTF_VAR_GLOBAL_ALLOCATED, "var_type");
+
+	/* DATASECT */
+	id = btf__add_datasec(btf, "datasec1", 12);
+	ASSERT_EQ(id, 17, "datasec_id");
+	err = btf__add_datasec_var_info(btf, 1, 4, 8);
+	ASSERT_OK(err, "v1_res");
+
+	t = btf__type_by_id(btf, 17);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "datasec1", "datasec_name");
+	ASSERT_EQ(t->size, 12, "datasec_sz");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_DATASEC, "datasec_kind");
+	ASSERT_EQ(btf_vlen(t), 1, "datasec_vlen");
+	vi = btf_var_secinfos(t) + 0;
+	ASSERT_EQ(vi->type, 1, "v1_type");
+	ASSERT_EQ(vi->offset, 4, "v1_off");
+	ASSERT_EQ(vi->size, 8, "v1_sz");
+
+	btf__free(btf);
+}