On Mon, May 5, 2025 at 11:39 AM Lorenz Bauer <l...@isovalent.com> wrote:
>
> Add a basic test for the ability to mmap /sys/kernel/btf/vmlinux. Since
> libbpf doesn't have an API to parse BTF from memory we do some basic
> sanity checks ourselves.
>
> Signed-off-by: Lorenz Bauer <l...@isovalent.com>
> ---
> tools/testing/selftests/bpf/prog_tests/btf_sysfs.c | 83
> ++++++++++++++++++++++
> 1 file changed, 83 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c
> b/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..3319cf758897d46cefa8ca25e16acb162f4e9889
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
> +/* Copyright (c) 2025 Isovalent */
> +
> +#include <test_progs.h>
> +#include <bpf/btf.h>
> +#include <sys/stat.h>
> +#include <sys/mman.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +
> +static void test_btf_mmap_sysfs(const char *path, struct btf *base)
> +{
> + struct stat st;
> + __u64 btf_size, end;
> + void *raw_data = NULL;
> + int fd = -1;
> + long page_size;
> + struct btf *btf = NULL;
> +
> + page_size = sysconf(_SC_PAGESIZE);
> + if (!ASSERT_GE(page_size, 0, "get_page_size"))
> + goto cleanup;
> +
> + if (!ASSERT_OK(stat(path, &st), "stat_btf"))
> + goto cleanup;
> +
> + btf_size = st.st_size;
> + end = (btf_size + page_size - 1) / page_size * page_size;
> +
> + fd = open(path, O_RDONLY);
> + if (!ASSERT_GE(fd, 0, "open_btf"))
> + goto cleanup;
> +
> + raw_data = mmap(NULL, btf_size, PROT_READ | PROT_WRITE, MAP_PRIVATE,
> fd, 0);
> + if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_writable"))
> + goto cleanup;
> +
> + raw_data = mmap(NULL, btf_size, PROT_READ, MAP_SHARED, fd, 0);
> + if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_shared"))
> + goto cleanup;
> +
> + raw_data = mmap(NULL, end + 1, PROT_READ, MAP_PRIVATE, fd, 0);
> + if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_invalid_size"))
> + goto cleanup;
> +
> + raw_data = mmap(NULL, end, PROT_READ, MAP_PRIVATE, fd, 0);
> + if (!ASSERT_NEQ(raw_data, MAP_FAILED, "mmap_btf"))
ASSERT_OK_PTR()?
> + goto cleanup;
> +
> + if (!ASSERT_EQ(mprotect(raw_data, btf_size, PROT_READ | PROT_WRITE),
> -1,
> + "mprotect_writable"))
> + goto cleanup;
> +
> + if (!ASSERT_EQ(mprotect(raw_data, btf_size, PROT_READ | PROT_EXEC),
> -1,
> + "mprotect_executable"))
> + goto cleanup;
> +
> + /* Check padding is zeroed */
> + for (int i = btf_size; i < end; i++) {
> + if (((__u8 *)raw_data)[i] != 0) {
> + PRINT_FAIL("tail of BTF is not zero at page offset
> %d\n", i);
> + goto cleanup;
> + }
> + }
> +
> + btf = btf__new_split(raw_data, btf_size, base);
> + if (!ASSERT_NEQ(btf, NULL, "parse_btf"))
ASSERT_OK_PTR()
> + goto cleanup;
> +
> +cleanup:
> + if (raw_data && raw_data != MAP_FAILED)
> + munmap(raw_data, btf_size);
> + if (btf)
no need to check this, all libbpf destructor APIs deal with NULL
correctly (ignoring them)
> + btf__free(btf);
> + if (fd >= 0)
> + close(fd);
> +}
> +
> +void test_btf_sysfs(void)
> +{
> + if (test__start_subtest("vmlinux"))
> + test_btf_mmap_sysfs("/sys/kernel/btf/vmlinux", NULL);
Do you intend to add more subtests? if not, why even using a subtest structure
> +}
>
> --
> 2.49.0
>
