selftests/bpf: Add test cases for btf__permute functionality

This patch introduces test cases for the btf__permute function to ensure
it works correctly with both base BTF and split BTF scenarios.

The test suite includes:
- test_permute_base: Validates permutation on base BTF
- test_permute_split: Tests permutation on split BTF

Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20260109130003.3313716-3-dolinux.peng@gmail.com

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_permute.c b/tools/testing/selftests/bpf/prog_tests/btf_permute.c
new file mode 100644 (file)
index 0000000..04ade5a
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/btf_permute.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Xiaomi */
+
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include "btf_helpers.h"
+
+static void permute_base_check(struct btf *btf)
+{
+       VALIDATE_RAW_BTF(
+               btf,
+               "[1] STRUCT 's2' size=4 vlen=1\n"
+               "\t'm' type_id=4 bits_offset=0",
+               "[2] FUNC 'f' type_id=6 linkage=static",
+               "[3] PTR '(anon)' type_id=4",
+               "[4] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
+               "[5] STRUCT 's1' size=4 vlen=1\n"
+               "\t'm' type_id=4 bits_offset=0",
+               "[6] FUNC_PROTO '(anon)' ret_type_id=4 vlen=1\n"
+               "\t'p' type_id=3");
+}
+
+/* Ensure btf__permute works as expected in the base-BTF scenario */
+static void test_permute_base(void)
+{
+       struct btf *btf;
+       __u32 permute_ids[7];
+       int err;
+
+       btf = btf__new_empty();
+       if (!ASSERT_OK_PTR(btf, "empty_main_btf"))
+               return;
+
+       btf__add_int(btf, "int", 4, BTF_INT_SIGNED);    /* [1] int */
+       btf__add_ptr(btf, 1);                           /* [2] ptr to int */
+       btf__add_struct(btf, "s1", 4);                  /* [3] struct s1 { */
+       btf__add_field(btf, "m", 1, 0, 0);              /*       int m; */
+                                                       /* } */
+       btf__add_struct(btf, "s2", 4);                  /* [4] struct s2 { */
+       btf__add_field(btf, "m", 1, 0, 0);              /*       int m; */
+                                                       /* } */
+       btf__add_func_proto(btf, 1);                    /* [5] int (*)(int *p); */
+       btf__add_func_param(btf, "p", 2);
+       btf__add_func(btf, "f", BTF_FUNC_STATIC, 5);    /* [6] int f(int *p); */
+
+       VALIDATE_RAW_BTF(
+               btf,
+               "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
+               "[2] PTR '(anon)' type_id=1",
+               "[3] STRUCT 's1' size=4 vlen=1\n"
+               "\t'm' type_id=1 bits_offset=0",
+               "[4] STRUCT 's2' size=4 vlen=1\n"
+               "\t'm' type_id=1 bits_offset=0",
+               "[5] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n"
+               "\t'p' type_id=2",
+               "[6] FUNC 'f' type_id=5 linkage=static");
+
+       permute_ids[0] = 0; /* [0] -> [0] */
+       permute_ids[1] = 4; /* [1] -> [4] */
+       permute_ids[2] = 3; /* [2] -> [3] */
+       permute_ids[3] = 5; /* [3] -> [5] */
+       permute_ids[4] = 1; /* [4] -> [1] */
+       permute_ids[5] = 6; /* [5] -> [6] */
+       permute_ids[6] = 2; /* [6] -> [2] */
+       err = btf__permute(btf, permute_ids, ARRAY_SIZE(permute_ids), NULL);
+       if (!ASSERT_OK(err, "btf__permute_base"))
+               goto done;
+       permute_base_check(btf);
+
+       /* ids[0] must be 0 for base BTF */
+       permute_ids[0] = 4; /* [0] -> [0] */
+       permute_ids[1] = 0; /* [1] -> [4] */
+       permute_ids[2] = 3; /* [2] -> [3] */
+       permute_ids[3] = 5; /* [3] -> [5] */
+       permute_ids[4] = 1; /* [4] -> [1] */
+       permute_ids[5] = 6; /* [5] -> [6] */
+       permute_ids[6] = 2; /* [6] -> [2] */
+       err = btf__permute(btf, permute_ids, ARRAY_SIZE(permute_ids), NULL);
+       if (!ASSERT_ERR(err, "btf__permute_base"))
+               goto done;
+       /* BTF is not modified */
+       permute_base_check(btf);
+
+       /* id_map_cnt is invalid */
+       permute_ids[0] = 0; /* [0] -> [0] */
+       permute_ids[1] = 4; /* [1] -> [4] */
+       permute_ids[2] = 3; /* [2] -> [3] */
+       permute_ids[3] = 5; /* [3] -> [5] */
+       permute_ids[4] = 1; /* [4] -> [1] */
+       permute_ids[5] = 6; /* [5] -> [6] */
+       permute_ids[6] = 2; /* [6] -> [2] */
+       err = btf__permute(btf, permute_ids, ARRAY_SIZE(permute_ids) - 1, NULL);
+       if (!ASSERT_ERR(err, "btf__permute_base"))
+               goto done;
+       /* BTF is not modified */
+       permute_base_check(btf);
+
+       /* Multiple types can not be mapped to the same ID */
+       permute_ids[0] = 0;
+       permute_ids[1] = 4;
+       permute_ids[2] = 4;
+       permute_ids[3] = 5;
+       permute_ids[4] = 1;
+       permute_ids[5] = 6;
+       permute_ids[6] = 2;
+       err = btf__permute(btf, permute_ids, ARRAY_SIZE(permute_ids), NULL);
+       if (!ASSERT_ERR(err, "btf__permute_base"))
+               goto done;
+       /* BTF is not modified */
+       permute_base_check(btf);
+
+       /* Type ID must be valid */
+       permute_ids[0] = 0;
+       permute_ids[1] = 4;
+       permute_ids[2] = 3;
+       permute_ids[3] = 5;
+       permute_ids[4] = 1;
+       permute_ids[5] = 7;
+       permute_ids[6] = 2;
+       err = btf__permute(btf, permute_ids, ARRAY_SIZE(permute_ids), NULL);
+       if (!ASSERT_ERR(err, "btf__permute_base"))
+               goto done;
+       /* BTF is not modified */
+       permute_base_check(btf);
+
+done:
+       btf__free(btf);
+}
+
+static void permute_split_check(struct btf *btf)
+{
+       VALIDATE_RAW_BTF(
+               btf,
+               "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
+               "[2] PTR '(anon)' type_id=1",
+               "[3] STRUCT 's2' size=4 vlen=1\n"
+               "\t'm' type_id=1 bits_offset=0",
+               "[4] FUNC 'f' type_id=5 linkage=static",
+               "[5] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n"
+               "\t'p' type_id=2",
+               "[6] STRUCT 's1' size=4 vlen=1\n"
+               "\t'm' type_id=1 bits_offset=0");
+}
+
+/* Ensure btf__permute works as expected in the split-BTF scenario */
+static void test_permute_split(void)
+{
+       struct btf *split_btf = NULL, *base_btf = NULL;
+       __u32 permute_ids[4];
+       int err, start_id;
+
+       base_btf = btf__new_empty();
+       if (!ASSERT_OK_PTR(base_btf, "empty_main_btf"))
+               return;
+
+       btf__add_int(base_btf, "int", 4, BTF_INT_SIGNED);       /* [1] int */
+       btf__add_ptr(base_btf, 1);                              /* [2] ptr to int */
+       VALIDATE_RAW_BTF(
+               base_btf,
+               "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
+               "[2] PTR '(anon)' type_id=1");
+       split_btf = btf__new_empty_split(base_btf);
+       if (!ASSERT_OK_PTR(split_btf, "empty_split_btf"))
+               goto cleanup;
+       btf__add_struct(split_btf, "s1", 4);                    /* [3] struct s1 { */
+       btf__add_field(split_btf, "m", 1, 0, 0);                /*   int m; */
+                                                               /* } */
+       btf__add_struct(split_btf, "s2", 4);                    /* [4] struct s2 { */
+       btf__add_field(split_btf, "m", 1, 0, 0);                /*   int m; */
+                                                               /* } */
+       btf__add_func_proto(split_btf, 1);                      /* [5] int (*)(int p); */
+       btf__add_func_param(split_btf, "p", 2);
+       btf__add_func(split_btf, "f", BTF_FUNC_STATIC, 5);      /* [6] int f(int *p); */
+
+       VALIDATE_RAW_BTF(
+               split_btf,
+               "[1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
+               "[2] PTR '(anon)' type_id=1",
+               "[3] STRUCT 's1' size=4 vlen=1\n"
+               "\t'm' type_id=1 bits_offset=0",
+               "[4] STRUCT 's2' size=4 vlen=1\n"
+               "\t'm' type_id=1 bits_offset=0",
+               "[5] FUNC_PROTO '(anon)' ret_type_id=1 vlen=1\n"
+               "\t'p' type_id=2",
+               "[6] FUNC 'f' type_id=5 linkage=static");
+
+       start_id = btf__type_cnt(base_btf);
+       permute_ids[3 - start_id] = 6; /* [3] -> [6] */
+       permute_ids[4 - start_id] = 3; /* [4] -> [3] */
+       permute_ids[5 - start_id] = 5; /* [5] -> [5] */
+       permute_ids[6 - start_id] = 4; /* [6] -> [4] */
+       err = btf__permute(split_btf, permute_ids, ARRAY_SIZE(permute_ids), NULL);
+       if (!ASSERT_OK(err, "btf__permute_split"))
+               goto cleanup;
+       permute_split_check(split_btf);
+
+       /*
+        * For split BTF, id_map_cnt must equal to the number of types
+        * added on top of base BTF
+        */
+       permute_ids[3 - start_id] = 4;
+       permute_ids[4 - start_id] = 3;
+       permute_ids[5 - start_id] = 5;
+       permute_ids[6 - start_id] = 6;
+       err = btf__permute(split_btf, permute_ids, ARRAY_SIZE(permute_ids) - 1, NULL);
+       if (!ASSERT_ERR(err, "btf__permute_split"))
+               goto cleanup;
+       /* BTF is not modified */
+       permute_split_check(split_btf);
+
+       /* Multiple types can not be mapped to the same ID */
+       permute_ids[3 - start_id] = 4;
+       permute_ids[4 - start_id] = 3;
+       permute_ids[5 - start_id] = 3;
+       permute_ids[6 - start_id] = 6;
+       err = btf__permute(split_btf, permute_ids, ARRAY_SIZE(permute_ids), NULL);
+       if (!ASSERT_ERR(err, "btf__permute_split"))
+               goto cleanup;
+       /* BTF is not modified */
+       permute_split_check(split_btf);
+
+       /* Can not map to base ID */
+       permute_ids[3 - start_id] = 4;
+       permute_ids[4 - start_id] = 2;
+       permute_ids[5 - start_id] = 5;
+       permute_ids[6 - start_id] = 6;
+       err = btf__permute(split_btf, permute_ids, ARRAY_SIZE(permute_ids), NULL);
+       if (!ASSERT_ERR(err, "btf__permute_split"))
+               goto cleanup;
+       /* BTF is not modified */
+       permute_split_check(split_btf);
+
+cleanup:
+       btf__free(split_btf);
+       btf__free(base_btf);
+}
+
+void test_btf_permute(void)
+{
+       if (test__start_subtest("permute_base"))
+               test_permute_base();
+       if (test__start_subtest("permute_split"))
+               test_permute_split();
+}