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 lmb@isovalent.com --- tools/testing/selftests/bpf/prog_tests/btf_sysfs.c | 79 ++++++++++++++++++++++ 1 file changed, 79 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..8dffed136b4757779028ec0971b56ff541f2218c --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c @@ -0,0 +1,79 @@ +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-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> + +#define BTF_MAGIC 0xeB9F + +static const char *btf_path = "/sys/kernel/btf/vmlinux"; + +void test_btf_sysfs(void) +{ + struct stat st; + __u64 btf_size; + void *raw_data = NULL; + int fd = -1; + size_t trailing; + long page_size; + + page_size = sysconf(_SC_PAGESIZE); + if (!ASSERT_GE(page_size, 0, "get_page_size")) + goto cleanup; + + if (!ASSERT_OK(stat(btf_path, &st), "stat_btf")) + goto cleanup; + + btf_size = st.st_size; + trailing = page_size - (btf_size % page_size) % page_size; + + fd = open(btf_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, btf_size + trailing + 1, PROT_READ, MAP_PRIVATE, fd, 0); + if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_invalid_size")) + goto cleanup; + + raw_data = mmap(NULL, btf_size, PROT_READ, MAP_PRIVATE, fd, 0); + if (!ASSERT_NEQ(raw_data, MAP_FAILED, "mmap_btf")) + 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 BTF magic value */ + if (!ASSERT_EQ(*(__u16 *)raw_data, BTF_MAGIC, "btf_magic")) + goto cleanup; + + /* Check padding is zeroed */ + for (int i = 0; i < trailing; i++) { + if (((__u8 *)raw_data)[btf_size + i] != 0) { + PRINT_FAIL("tail of BTF is not zero at page offset %d\n", i); + goto cleanup; + } + } + +cleanup: + if (raw_data && raw_data != MAP_FAILED) + munmap(raw_data, btf_size); + if (fd >= 0) + close(fd); +}