[PATCH v3 bpf-next 02/11] selftests/bpf: test distilled base, split BTF generation

[Alan Maguire <alan.maguire@oracle.com>]

Test generation of split+distilled base BTF, ensuring that

- base BTF STRUCTs which are embedded in split BTF structs are
  represented as 0-member sized structs, allowing size checking
- FWDs are used in place of full named struct/union declarations
- FWDs are used in place of full named enum declarations
- 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 <alan.maguire@oracle.com>
---
 .../selftests/bpf/prog_tests/btf_distill.c    | 272 ++++++++++++++++++
 1 file changed, 272 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..400df8740943
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/btf_distill.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024, Oracle and/or its affiliates. */
+
+#include <test_progs.h>
+#include <bpf/btf.h>
+#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 FWDs unless anonymous, when they
+ *    are represented in full, or if embedded in a split BTF struct, in which
+ *    case they are represented by a STRUCT with specified size and vlen=0.
+ */
+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; */
+							/* } */
+	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");
+
+	btf2 = btf__new_empty_split(btf1);
+	if (!ASSERT_OK_PTR(btf2, "empty_split_btf"))
+		goto cleanup;
+
+	btf__add_ptr(btf2, 3);				/* [17] ptr to struct s1 */
+	/* add ptr to struct anon */
+	btf__add_ptr(btf2, 4);				/* [18] ptr to struct (anon) */
+	btf__add_const(btf2, 6);			/* [19] const union u1 */
+	btf__add_restrict(btf2, 7);			/* [20] restrict union (anon) */
+	btf__add_volatile(btf2, 8);			/* [21] volatile enum e1 */
+	btf__add_typedef(btf2, "et", 9);		/* [22] typedef enum (anon) */
+	btf__add_const(btf2, 10);			/* [23] const enum64 e641 */
+	btf__add_ptr(btf2, 11);				/* [24] restrict enum64 (anon) */
+	btf__add_struct(btf2, "with_embedded", 4);	/* [25] struct with_embedded { */
+	btf__add_field(btf2, "f1", 13, 0, 0);		/*	struct embedded f1; */
+							/* } */
+	btf__add_func(btf2, "fn", BTF_FUNC_STATIC, 14);	/* [26] int fn(int p1); */
+	btf__add_typedef(btf2, "arraytype", 15);	/* [27] typedef int[3] foo; */
+	btf__add_func_proto(btf2, 1);			/* [28] 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] PTR '(anon)' type_id=3",
+		"[18] PTR '(anon)' type_id=4",
+		"[19] CONST '(anon)' type_id=6",
+		"[20] RESTRICT '(anon)' type_id=7",
+		"[21] VOLATILE '(anon)' type_id=8",
+		"[22] TYPEDEF 'et' type_id=9",
+		"[23] CONST '(anon)' type_id=10",
+		"[24] PTR '(anon)' type_id=11",
+		"[25] STRUCT 'with_embedded' size=4 vlen=1\n"
+		"\t'f1' type_id=13 bits_offset=0",
+		"[26] FUNC 'fn' type_id=14 linkage=static",
+		"[27] TYPEDEF 'arraytype' type_id=15",
+		"[28] 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] FWD 's1' fwd_kind=struct",
+		"[3] FWD 'u1' fwd_kind=union",
+		"[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] FWD 'from_proto' fwd_kind=struct",
+		/* 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, sk_buff_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;
+	sk_buff_id = btf__find_by_name_kind(vmlinux_btf, "sk_buff", BTF_KIND_STRUCT);
+	if (!ASSERT_GT(sk_buff_id, 0, "find_sk_buff_id"))
+		goto cleanup;
+	split_btf = btf__new_empty_split(vmlinux_btf);
+	if (!ASSERT_OK_PTR(split_btf, "new_split"))
+		goto cleanup;
+	btf__add_typedef(split_btf, "myint", int_id);
+	btf__add_ptr(split_btf, sk_buff_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] FWD 'sk_buff' fwd_kind=struct",
+		"[3] TYPEDEF 'myint' type_id=1",
+		"[4] 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();
+}
-- 
2.31.1