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selftests/bpf: Add test for btf__add_btf() with split BTF sources

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Add a test that verifies btf__add_btf() correctly handles merging
multiple split BTF objects that share the same base BTF. The test
creates two sibling split BTFs on a common base, merges them into
a combined split BTF, and validates that base type references are
preserved while split type references are properly remapped.

Assisted-by: Claude:claude-opus-4-6

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/bpf/64a8c947bff1ae89efa9ba8c099466477762490f.1772657690.git.josef@toxicpanda.com
This commit is contained in:
Josef Bacik 2026-03-04 15:56:52 -05:00 committed by Andrii Nakryiko
parent d8d5c01511
commit fefeeec612
1 changed files with 111 additions and 0 deletions
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111
tools/testing/selftests/bpf/prog_tests/btf_write.c
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@ -497,10 +497,121 @@ static void test_btf_add_btf()
btf__free(btf2);
}
static void test_btf_add_btf_split()
{
struct btf *base = NULL, *split1 = NULL, *split2 = NULL;
struct btf *combined = NULL;
int id, err;
/* Create a base BTF with an INT and a PTR to it */
base = btf__new_empty();
if (!ASSERT_OK_PTR(base, "base"))
return;
id = btf__add_int(base, "int", 4, BTF_INT_SIGNED);
ASSERT_EQ(id, 1, "base_int_id");
id = btf__add_ptr(base, 1);
ASSERT_EQ(id, 2, "base_ptr_id");
/* base has 2 types, type IDs 1..2 */
ASSERT_EQ(btf__type_cnt(base), 3, "base_type_cnt");
/* Create split1 on base: a STRUCT referencing base's int (ID 1) */
split1 = btf__new_empty_split(base);
if (!ASSERT_OK_PTR(split1, "split1"))
goto cleanup;
id = btf__add_struct(split1, "s1", 4);
/* split types start at base_type_cnt = 3 */
ASSERT_EQ(id, 3, "split1_struct_id");
btf__add_field(split1, "x", 1, 0, 0); /* refers to base int */
id = btf__add_ptr(split1, 3);
ASSERT_EQ(id, 4, "split1_ptr_id"); /* ptr to the struct (split self-ref) */
/* Add a typedef "int_alias" -> base int in split1, which will be
* duplicated in split2 to test that btf__dedup() merges them.
*/
id = btf__add_typedef(split1, "int_alias", 1);
ASSERT_EQ(id, 5, "split1_typedef_id");
/* Create split2 on base: a TYPEDEF referencing base's ptr (ID 2) */
split2 = btf__new_empty_split(base);
if (!ASSERT_OK_PTR(split2, "split2"))
goto cleanup;
id = btf__add_typedef(split2, "int_ptr", 2); /* refers to base ptr */
ASSERT_EQ(id, 3, "split2_typedef_id");
id = btf__add_struct(split2, "s2", 8);
ASSERT_EQ(id, 4, "split2_struct_id");
btf__add_field(split2, "p", 3, 0, 0); /* refers to split2's own typedef */
/* Same "int_alias" typedef as split1 - should be deduped away */
id = btf__add_typedef(split2, "int_alias", 1);
ASSERT_EQ(id, 5, "split2_dup_typedef_id");
/* Create combined split BTF on same base and merge both */
combined = btf__new_empty_split(base);
if (!ASSERT_OK_PTR(combined, "combined"))
goto cleanup;
/* Merge split1: its types (3,4,5) should land at IDs 3,4,5 */
id = btf__add_btf(combined, split1);
if (!ASSERT_GE(id, 0, "add_split1"))
goto cleanup;
ASSERT_EQ(id, 3, "split1_first_id");
/* Merge split2: its types (3,4,5) should be remapped to 6,7,8 */
id = btf__add_btf(combined, split2);
if (!ASSERT_GE(id, 0, "add_split2"))
goto cleanup;
ASSERT_EQ(id, 6, "split2_first_id");
/* Before dedup: base (2) + split1 (3) + split2 (3) = 8 types + void */
ASSERT_EQ(btf__type_cnt(combined), 9, "pre_dedup_type_cnt");
VALIDATE_RAW_BTF(
combined,
/* base types (IDs 1-2) */
"[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
"[2] PTR '(anon)' type_id=1",
/* split1 types (IDs 3-5): base refs unchanged */
"[3] STRUCT 's1' size=4 vlen=1\n"
"\t'x' type_id=1 bits_offset=0", /* refers to base int=1 */
"[4] PTR '(anon)' type_id=3", /* refers to split1's struct=3 */
"[5] TYPEDEF 'int_alias' type_id=1", /* refers to base int=1 */
/* split2 types (IDs 6-8): remapped from 3,4,5 to 6,7,8 */
"[6] TYPEDEF 'int_ptr' type_id=2", /* base ptr=2, unchanged */
"[7] STRUCT 's2' size=8 vlen=1\n"
"\t'p' type_id=6 bits_offset=0", /* split2 typedef: 3->6 */
"[8] TYPEDEF 'int_alias' type_id=1"); /* dup of [5] */
/* Dedup to mirror the bpftool merge flow; should remove the
* duplicate "int_alias" typedef.
*/
err = btf__dedup(combined, NULL);
if (!ASSERT_OK(err, "dedup"))
goto cleanup;
/* After dedup: one int_alias removed, so 7 types + void */
ASSERT_EQ(btf__type_cnt(combined), 8, "dedup_type_cnt");
cleanup:
btf__free(combined);
btf__free(split2);
btf__free(split1);
btf__free(base);
}
void test_btf_write()
{
if (test__start_subtest("btf_add"))
test_btf_add();
if (test__start_subtest("btf_add_btf"))
test_btf_add_btf();
if (test__start_subtest("btf_add_btf_split"))
test_btf_add_btf_split();
}