On Mon, Nov 8, 2021 at 4:31 PM Hao Luo <haoluo@xxxxxxxxxx> wrote:
>
> This test verifies that a ksym of non-struct can not be directly
> updated.
>
> Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
> ---
Love the simplicity of the test.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Changes since v2:
> - Rebase
>
> Changes since v1:
> - Replaced CHECK() with ASSERT_ERR_PTR()
> - Commented in the test for the reason of verification failure.
>
> .../selftests/bpf/prog_tests/ksyms_btf.c | 14 +++++++++
> .../bpf/progs/test_ksyms_btf_write_check.c | 29 +++++++++++++++++++
> 2 files changed, 43 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> index 79f6bd1e50d6..f6933b06daf8 100644
> --- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> @@ -8,6 +8,7 @@
> #include "test_ksyms_btf_null_check.skel.h"
> #include "test_ksyms_weak.skel.h"
> #include "test_ksyms_weak.lskel.h"
> +#include "test_ksyms_btf_write_check.skel.h"
>
> static int duration;
>
> @@ -137,6 +138,16 @@ static void test_weak_syms_lskel(void)
> test_ksyms_weak_lskel__destroy(skel);
> }
>
> +static void test_write_check(void)
> +{
> + struct test_ksyms_btf_write_check *skel;
> +
> + skel = test_ksyms_btf_write_check__open_and_load();
> + ASSERT_ERR_PTR(skel, "unexpected load of a prog writing to ksym memory\n");
> +
> + test_ksyms_btf_write_check__destroy(skel);
> +}
> +
> void test_ksyms_btf(void)
> {
> int percpu_datasec;
> @@ -167,4 +178,7 @@ void test_ksyms_btf(void)
>
> if (test__start_subtest("weak_ksyms_lskel"))
> test_weak_syms_lskel();
> +
> + if (test__start_subtest("write_check"))
> + test_write_check();
> }
> diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
> new file mode 100644
> index 000000000000..2180c41cd890
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
> @@ -0,0 +1,29 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2021 Google */
> +
> +#include "vmlinux.h"
> +
> +#include <bpf/bpf_helpers.h>
> +
> +extern const int bpf_prog_active __ksym; /* int type global var. */
> +
> +SEC("raw_tp/sys_enter")
> +int handler(const void *ctx)
> +{
> + int *active;
> + __u32 cpu;
> +
> + cpu = bpf_get_smp_processor_id();
> + active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
> + if (active) {
> + /* Kernel memory obtained from bpf_{per,this}_cpu_ptr
> + * is read-only, should _not_ pass verification.
> + */
> + /* WRITE_ONCE */
> + *(volatile int *)active = -1;
> + }
> +
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.34.0.rc0.344.g81b53c2807-goog
>
