Re: [PATCH bpf-next 4/4] selftests/bpf: Add test for abnormal cnt during multi-uprobe attachment

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Dec 11, 2023 at 07:28:43PM +0800, Hou Tao wrote:
> From: Hou Tao <houtao1@huawei.com>
> 
> If an abnormally huge cnt is used for multi-uprobes attachment, the
> following warning will be reported:
> 
>   ------------[ cut here ]------------
>   WARNING: CPU: 7 PID: 406 at mm/util.c:632 kvmalloc_node+0xd9/0xe0
>   Modules linked in: bpf_testmod(O)
>   CPU: 7 PID: 406 Comm: test_progs Tainted: G ...... 6.7.0-rc3+ #32
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ......
>   RIP: 0010:kvmalloc_node+0xd9/0xe0
>   ......
>   Call Trace:
>    <TASK>
>    ? __warn+0x89/0x150
>    ? kvmalloc_node+0xd9/0xe0
>    bpf_uprobe_multi_link_attach+0x14a/0x480
>    __sys_bpf+0x14a9/0x2bc0
>    do_syscall_64+0x36/0xb0
>    entry_SYSCALL_64_after_hwframe+0x6e/0x76
>    ......
>    </TASK>
>   ---[ end trace 0000000000000000 ]---
> 
> So add a test to ensure the warning is fixed.
> 
> Signed-off-by: Hou Tao <houtao1@huawei.com>
> ---
>  .../bpf/prog_tests/uprobe_multi_test.c        | 43 ++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> index ece260cf2c0b..379ee9cc6221 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> @@ -234,6 +234,45 @@ static void test_attach_api_syms(void)
>  	test_attach_api("/proc/self/exe", NULL, &opts);
>  }
>  
> +static void test_failed_link_api(void)
> +{
> +	LIBBPF_OPTS(bpf_link_create_opts, opts);
> +	const char *path = "/proc/self/exe";
> +	struct uprobe_multi *skel = NULL;
> +	unsigned long *offsets = NULL;
> +	const char *syms[3] = {
> +		"uprobe_multi_func_1",
> +		"uprobe_multi_func_2",
> +		"uprobe_multi_func_3",
> +	};
> +	int link_fd = -1, err;
> +
> +	err = elf_resolve_syms_offsets(path, 3, syms, (unsigned long **) &offsets, STT_FUNC);
> +	if (!ASSERT_OK(err, "elf_resolve_syms_offsets"))
> +		return;

we should not need any symbols/offset for this tests right?

the allocation takes place before the offsets are checked,
so I think using just some pointer != NULL should be enough?

thanks,
jirka

> +
> +	skel = uprobe_multi__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "uprobe_multi__open_and_load"))
> +		goto cleanup;
> +
> +	/* abnormal cnt */
> +	opts.uprobe_multi.path = path;
> +	opts.uprobe_multi.offsets = offsets;
> +	opts.uprobe_multi.cnt = INT_MAX;
> +	opts.kprobe_multi.flags = 0;
> +	link_fd = bpf_link_create(bpf_program__fd(skel->progs.uprobe), 0,
> +				  BPF_TRACE_UPROBE_MULTI, &opts);
> +	if (!ASSERT_ERR(link_fd, "link_fd"))
> +		goto cleanup;
> +	if (!ASSERT_EQ(link_fd, -ENOMEM, "no mem fail"))
> +		goto cleanup;
> +cleanup:
> +	if (link_fd >= 0)
> +		close(link_fd);
> +	uprobe_multi__destroy(skel);
> +	free(offsets);
> +}
> +
>  static void __test_link_api(struct child *child)
>  {
>  	int prog_fd, link1_fd = -1, link2_fd = -1, link3_fd = -1, link4_fd = -1;
> @@ -311,7 +350,7 @@ static void __test_link_api(struct child *child)
>  	free(offsets);
>  }
>  
> -void test_link_api(void)
> +static void test_link_api(void)
>  {
>  	struct child *child;
>  
> @@ -408,6 +447,8 @@ void test_uprobe_multi_test(void)
>  		test_attach_api_syms();
>  	if (test__start_subtest("link_api"))
>  		test_link_api();
> +	if (test__start_subtest("failed_link_api"))
> +		test_failed_link_api();
>  	if (test__start_subtest("bench_uprobe"))
>  		test_bench_attach_uprobe();
>  	if (test__start_subtest("bench_usdt"))
> -- 
> 2.29.2
>