On Sun, Nov 27, 2022 at 11:26 PM Viktor Malik <vmalik@xxxxxxxxxx> wrote:
>
> Adds a new test that tries to attach a program to fentry of two
> functions of the same name, one located in vmlinux and the other in
> bpf_testmod.
>
> To avoid conflicts with existing tests, a new function
> "bpf_fentry_shadow_test" was created both in vmlinux and in bpf_testmod.
>
> The previous commit fixed a bug which caused this test to fail. The
> verifier would always use the vmlinux function's address as the target
> trampoline address, hence trying to attach two programs to the same
> trampoline.
>
> Signed-off-by: Viktor Malik <vmalik@xxxxxxxxxx>
> ---
<...>
> diff --git a/tools/testing/selftests/bpf/prog_tests/module_attach_shadow.c b/tools/testing/selftests/bpf/prog_tests/module_attach_shadow.c
> new file mode 100644
> index 000000000000..0c604a0f22ca
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/module_attach_shadow.c
> @@ -0,0 +1,120 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Red Hat */
> +#include <test_progs.h>
> +#include <bpf/btf.h>
> +#include "bpf/libbpf_internal.h"
> +#include "cgroup_helpers.h"
> +
> +static const char *module_name = "bpf_testmod";
> +static const char *symbol_name = "bpf_fentry_shadow_test";
> +
> +int get_bpf_testmod_btf_fd(void)
> +{
> + struct bpf_btf_info info;
> + char name[64];
> + __u32 id, len;
We need to initialize 'id'.
> + int err, fd;
<...>
> +}
> +
> +void test_module_fentry_shadow(void)
> +{
<...>
> +
> + btf_id[0] = btf__find_by_name(vmlinux_btf, symbol_name);
> + if (!ASSERT_GT(btf_id[0], 0, "btf_find_by_name"))
> + goto out;
> +
> + btf_id[1] = btf__find_by_name(mod_btf, symbol_name);
btf__find_by_name_kind() may be better. It skips the name comparison
if the kind doesn't match.
> + if (!ASSERT_GT(btf_id[1], 0, "btf_find_by_name"))
> + goto out;
> +
<...>
> + err = bpf_prog_test_run_opts(prog_fd[0], &test_opts);
> + ASSERT_OK(err, "running test");
> +
> +out:
We also need to btf__free vmlinux_btf and mod_btf.
> + for (i = 0; i < 2; i++) {
> + if (btf_fd[i])
> + close(btf_fd[i]);
> + if (prog_fd[i])
> + close(prog_fd[i]);
> + if (link_fd[i])
> + close(link_fd[i]);
> + }
> +}
> --
> 2.38.1
>
