From: Alan Maguire <alan.maguire@oracle.com>
To: Mingpei CAO <caomingpei@gmail.com>, bpf@vger.kernel.org
Cc: alexei.starovoitov@gmail.com, andrii@kernel.org, eddyz87@gmail.com
Subject: Re: [PATCH bpf 2/2] selftests/bpf: Test array element comparison in BTF dedup
Date: Mon, 7 Sep 2026 16:45:10 +0100 [thread overview]
Message-ID: <f22d3b93-65b5-4b06-9af8-99d0e65eb33b@oracle.com> (raw)
In-Reply-To: <20260907131021.34343-3-caomingpei@gmail.com>
On 07/09/2026 14:10, Mingpei CAO wrote:
> Exercise recursive array comparison with different and identical
> element definitions. Check that distinct containers remain separate
> and identical types are deduplicated, including their references.
>
> The negative case fails before the fix and passes afterwards.
> The positive case passes both before and after the fix.
>
> Assisted-by: LLM
> Signed-off-by: Mingpei CAO <caomingpei@gmail.com>
this test would be better placed in prog_tests/btf.c I think where there
are a number of other BTF dedup tests; something like the following
is roughly equivalent to what you have:
diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index 67b9015cbd98..1c4a46e2a64d 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -7062,6 +7062,94 @@ static struct btf_dedup_test dedup_tests[] = {
BTF_STR_SEC("\0int\0long int"),
},
},
+{
+ .descr = "dedup: array element comparison",
+ .input = {
+ .raw_types = {
+ /* signed int */
+ BTF_TYPE_INT_ENC(NAME_NTH(1), BTF_INT_SIGNED, 0, 32, 4),
/* [1] */
+ /* unsigned int */
+ BTF_TYPE_INT_ENC(NAME_NTH(2), 0, 0, 32, 4),
/* [2] */
+ /* signed int[1] */
+ BTF_TYPE_ARRAY_ENC(1, 1, 1),
/* [3] */
+ /* duplicate signed int[1] */
+ BTF_TYPE_ARRAY_ENC(1, 1, 1), /* [4] */
+ /* unsigned int[1] */
+ BTF_TYPE_ARRAY_ENC(2, 2, 1), /* [5] */
+ /* struct s { signed int a[1]; signed int b[1]; } */
+ BTF_STRUCT_ENC(NAME_NTH(3), 2, 8), /* [6] */
+ BTF_MEMBER_ENC(NAME_NTH(4), 3, 0),
+ BTF_MEMBER_ENC(NAME_NTH(5), 3, 32),
+ /* struct s { signed int a[1]; unsigned int b[1]; } */
+ BTF_STRUCT_ENC(NAME_NTH(3), 2, 8), /* [7] */
+ BTF_MEMBER_ENC(NAME_NTH(4), 4, 0),
+ BTF_MEMBER_ENC(NAME_NTH(5), 5, 32),
+ BTF_END_RAW,
+ },
+ BTF_STR_SEC("\0int\0unsigned int\0s\0a\0b"),
+ },
+ .expect = {
+ .raw_types = {
+ BTF_TYPE_INT_ENC(NAME_NTH(1), BTF_INT_SIGNED, 0, 32, 4), /* [1] */
+ BTF_TYPE_INT_ENC(NAME_NTH(2), 0, 0, 32, 4), /* [2] */
+ BTF_TYPE_ARRAY_ENC(1, 1, 1), /* [3] */
+ BTF_TYPE_ARRAY_ENC(2, 2, 1), /* [4] */
+ BTF_STRUCT_ENC(NAME_NTH(3), 2, 8), /* [5] */
+ BTF_MEMBER_ENC(NAME_NTH(4), 3, 0),
+ BTF_MEMBER_ENC(NAME_NTH(5), 3, 32),
+ BTF_STRUCT_ENC(NAME_NTH(3), 2, 8), /* [6] */
+ BTF_MEMBER_ENC(NAME_NTH(4), 3, 0),
+ BTF_MEMBER_ENC(NAME_NTH(5), 4, 32),
+ BTF_END_RAW,
+ },
+ BTF_STR_SEC("\0int\0unsigned int\0s\0a\0b"),
+ },
+},
+{
+ .descr = "dedup: identical array element comparison",
+ .input = {
+ .raw_types = {
+ /* int */
+ BTF_TYPE_INT_ENC(NAME_NTH(1), BTF_INT_SIGNED, 0, 32, 4), /* [1] */
+ /* struct container { struct elem first[1]; struct elem second[1]; } */
+ BTF_STRUCT_ENC(NAME_NTH(2), 2, 8), /* [2] */
+ BTF_MEMBER_ENC(NAME_NTH(3), 3, 0),
+ BTF_MEMBER_ENC(NAME_NTH(4), 3, 32),
+ /* struct elem[1] */
+ BTF_TYPE_ARRAY_ENC(4, 1, 1), /* [3] */
+ /* struct elem { int x; } */
+ BTF_STRUCT_ENC(NAME_NTH(5), 1, 4), /* [4] */
+ BTF_MEMBER_ENC(NAME_NTH(6), 1, 0),
+ /* duplicate struct container */
+ BTF_STRUCT_ENC(NAME_NTH(2), 2, 8), /* [5] */
+ BTF_MEMBER_ENC(NAME_NTH(3), 6, 0),
+ BTF_MEMBER_ENC(NAME_NTH(4), 7, 32),
+ /* duplicate struct elem[1] */
+ BTF_TYPE_ARRAY_ENC(8, 1, 1), /* [6] */
+ BTF_TYPE_ARRAY_ENC(9, 1, 1), /* [7] */
+ /* duplicate struct elem */
+ BTF_STRUCT_ENC(NAME_NTH(5), 1, 4), /* [8] */
+ BTF_MEMBER_ENC(NAME_NTH(6), 1, 0),
+ BTF_STRUCT_ENC(NAME_NTH(5), 1, 4), /* [9] */
+ BTF_MEMBER_ENC(NAME_NTH(6), 1, 0),
+ BTF_END_RAW,
+ },
+ BTF_STR_SEC("\0int\0container\0first\0second\0elem\0x"),
+ },
+ .expect = {
+ .raw_types = {
+ BTF_TYPE_INT_ENC(NAME_NTH(1), BTF_INT_SIGNED, 0, 32, 4), /* [1] */
+ BTF_STRUCT_ENC(NAME_NTH(2), 2, 8), /* [2] */
+ BTF_MEMBER_ENC(NAME_NTH(3), 3, 0),
+ BTF_MEMBER_ENC(NAME_NTH(4), 3, 32),
+ BTF_TYPE_ARRAY_ENC(4, 1, 1), /* [3] */
+ BTF_STRUCT_ENC(NAME_NTH(5), 1, 4), /* [4] */
+ BTF_MEMBER_ENC(NAME_NTH(6), 1, 0),
+ BTF_END_RAW,
+ },
+ BTF_STR_SEC("\0int\0container\0first\0second\0elem\0x"),
+ },
+},
{
.descr = "dedup: struct example #1",
/*
> ---
> .../selftests/bpf/prog_tests/btf_dedup.c | 68 +++++++++++++++++++
> 1 file changed, 68 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/btf_dedup.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dedup.c b/tools/testing/selftests/bpf/prog_tests/btf_dedup.c
> new file mode 100644
> index 000000000000..3e889c0bed53
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/btf_dedup.c
> @@ -0,0 +1,68 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <bpf/btf.h>
> +#include "btf_helpers.h"
> +
> +static void test_array_element_types(bool identical)
> +{
> + struct btf *btf;
> +
> + btf = btf__new_empty();
> + if (!ASSERT_OK_PTR(btf, "btf_new"))
> + return;
> +
> + /*
> + * Comparing the first fields maps array [3] to [6]. The second
> + * fields reuse [3], requiring an identical-type check of [6]/[7].
> + * Place container [5] before its elements [8]/[9] so they still
> + * have distinct IDs when their definitions are compared.
> + */
> + if (!ASSERT_EQ(btf__add_int(btf, "int", 4, BTF_INT_SIGNED), 1, "int") ||
> + !ASSERT_EQ(btf__add_struct(btf, "container", 8), 2, "container1") ||
> + !ASSERT_OK(btf__add_field(btf, "first", 3, 0, 0), "first1") ||
> + !ASSERT_OK(btf__add_field(btf, "second", 3, 32, 0), "second1") ||
> + !ASSERT_EQ(btf__add_array(btf, 1, 4, 1), 3, "array1") ||
> + !ASSERT_EQ(btf__add_struct(btf, "elem", 4), 4, "elem1") ||
> + !ASSERT_OK(btf__add_field(btf, "x", 1, 0, 0), "elem1_field") ||
> + !ASSERT_EQ(btf__add_struct(btf, "container", 8), 5, "container2") ||
> + !ASSERT_OK(btf__add_field(btf, "first", 6, 0, 0), "first2") ||
> + !ASSERT_OK(btf__add_field(btf, "second", 7, 32, 0), "second2") ||
> + !ASSERT_EQ(btf__add_array(btf, 1, 8, 1), 6, "array2") ||
> + !ASSERT_EQ(btf__add_array(btf, 1, 9, 1), 7, "array3") ||
> + !ASSERT_EQ(btf__add_struct(btf, "elem", 4), 8, "elem2") ||
> + !ASSERT_OK(btf__add_field(btf, "x", 1, 0, 0), "elem2_field") ||
> + !ASSERT_EQ(btf__add_struct(btf, "elem", 4), 9, "elem3") ||
> + !ASSERT_OK(btf__add_field(btf, identical ? "x" : "y", 1, 0, 0), "elem3_field"))
> + goto out;
> +
> + if (!ASSERT_OK(btf__dedup(btf, NULL), "dedup"))
> + goto out;
> +
> + /* Identical elements leave only the first four expected types. */
> + btf_validate_raw(btf, identical ? 4 : 7, (const char *[]) {
> + "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
> + "[2] STRUCT 'container' size=8 vlen=2\n"
> + "\t'first' type_id=3 bits_offset=0\n"
> + "\t'second' type_id=3 bits_offset=32",
> + "[3] ARRAY '(anon)' type_id=4 index_type_id=1 nr_elems=1",
> + "[4] STRUCT 'elem' size=4 vlen=1\n"
> + "\t'x' type_id=1 bits_offset=0",
> + "[5] STRUCT 'container' size=8 vlen=2\n"
> + "\t'first' type_id=3 bits_offset=0\n"
> + "\t'second' type_id=6 bits_offset=32",
> + "[6] ARRAY '(anon)' type_id=7 index_type_id=1 nr_elems=1",
> + "[7] STRUCT 'elem' size=4 vlen=1\n"
> + "\t'y' type_id=1 bits_offset=0",
> + });
> +
> +out:
> + btf__free(btf);
> +}
> +
> +void test_btf_dedup(void)
> +{
> + if (test__start_subtest("array_different_element_types"))
> + test_array_element_types(false);
> + if (test__start_subtest("array_identical_element_types"))
> + test_array_element_types(true);
> +}
next prev parent reply other threads:[~2026-09-07 15:46 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-06 10:23 [BUG] libbpf: BTF dedup merges arrays with different element types Mingpei CAO
2026-09-06 21:27 ` Alexei Starovoitov
2026-09-07 13:10 ` [PATCH bpf 0/2] libbpf: Fix array comparison in BTF dedup Mingpei CAO
2026-09-07 13:10 ` [PATCH bpf 1/2] " Mingpei CAO
2026-09-07 13:10 ` [PATCH bpf 2/2] selftests/bpf: Test array element " Mingpei CAO
2026-09-07 15:45 ` Alan Maguire [this message]
2026-09-07 16:30 ` Mingpei CAO
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