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 | 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"))
+ 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"))
+ goto cleanup;
+
+cleanup:
+ if (raw_data && raw_data != MAP_FAILED)
+ munmap(raw_data, btf_size);
+ if (btf)
+ 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);
+}
--
2.49.0On Mon, May 5, 2025 at 11:39 AM Lorenz Bauer <lmb@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 <lmb@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
>
On Tue, May 6, 2025 at 10:39 PM Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote: > > + raw_data = mmap(NULL, end, PROT_READ, MAP_PRIVATE, fd, 0); > > + if (!ASSERT_NEQ(raw_data, MAP_FAILED, "mmap_btf")) > > ASSERT_OK_PTR()? Don't think that mmap follows libbpf_get_error conventions? I'd keep it as it is. > > + btf = btf__new_split(raw_data, btf_size, base); > > + if (!ASSERT_NEQ(btf, NULL, "parse_btf")) > > ASSERT_OK_PTR() Ack. > Do you intend to add more subtests? if not, why even using a subtest structure The original intention was to add kmod support, but that didn't pan out, see my discussion with Alexei. I can drop the subtest if you want, but I'd probably keep the helper as it is.
On Wed, May 7, 2025 at 2:14 AM Lorenz Bauer <lmb@isovalent.com> wrote: > > On Tue, May 6, 2025 at 10:39 PM Andrii Nakryiko > <andrii.nakryiko@gmail.com> wrote: > > > > + raw_data = mmap(NULL, end, PROT_READ, MAP_PRIVATE, fd, 0); > > > + if (!ASSERT_NEQ(raw_data, MAP_FAILED, "mmap_btf")) > > > > ASSERT_OK_PTR()? > > Don't think that mmap follows libbpf_get_error conventions? I'd keep > it as it is. ASSERT_OK_PTR() isn't libbpf specific (and libbpf is actually returning a NULL or valid pointer for all public APIs, since libbpf 1.0). But if you look at the implementation, "an OK" pointer is a non-NULL pointer that is also not a small negative value. NULL is a bad pointer, -1 (MAP_FAILED) is a bad pointer, and so on. So it's a pretty universal check for anything pointer-related. Please do use OK_PTR, it's semantically better in tests > > > > + btf = btf__new_split(raw_data, btf_size, base); > > > + if (!ASSERT_NEQ(btf, NULL, "parse_btf")) > > > > ASSERT_OK_PTR() > > Ack. > > > Do you intend to add more subtests? if not, why even using a subtest structure > > The original intention was to add kmod support, but that didn't pan > out, see my discussion with Alexei. I can drop the subtest if you > want, but I'd probably keep the helper as it is. yeah, let's drop the subtest, it's a bit easier to work with non-subtest tests, IMO
© 2016 - 2025 Red Hat, Inc.