diff mbox series

[bpf-next,v2,4/4] selftests/bpf: Add test for abnormal cnt during multi-kprobe attachment

Message ID 20231213112531.3775079-5-houtao@huaweicloud.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Fix warnings in kvmalloc_node() | expand

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Commit Message

Hou Tao Dec. 13, 2023, 11:25 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

If an abnormally huge cnt is used for multi-kprobes attachment, the
following warning will be reported:

  ------------[ cut here ]------------
  WARNING: CPU: 1 PID: 392 at mm/util.c:632 kvmalloc_node+0xd9/0xe0
  Modules linked in: bpf_testmod(O)
  CPU: 1 PID: 392 Comm: test_progs Tainted: G ...... 6.7.0-rc3+ #32
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
  ......
  RIP: 0010:kvmalloc_node+0xd9/0xe0
   ? __warn+0x89/0x150
   ? kvmalloc_node+0xd9/0xe0
   bpf_kprobe_multi_link_attach+0x87/0x670
   __sys_bpf+0x2a28/0x2bc0
   __x64_sys_bpf+0x1a/0x30
   do_syscall_64+0x36/0xb0
   entry_SYSCALL_64_after_hwframe+0x6e/0x76
  RIP: 0033:0x7fbe067f0e0d
  ......
   </TASK>
  ---[ end trace 0000000000000000 ]---

So add a test to ensure the warning is fixed.

Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 .../selftests/bpf/prog_tests/kprobe_multi_test.c   | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

Comments

Andrii Nakryiko Dec. 13, 2023, 11:33 p.m. UTC | #1 
On Wed, Dec 13, 2023 at 3:24 AM Hou Tao <houtao@huaweicloud.com> wrote:
>
> From: Hou Tao <houtao1@huawei.com>
>
> If an abnormally huge cnt is used for multi-kprobes attachment, the
> following warning will be reported:
>
>   ------------[ cut here ]------------
>   WARNING: CPU: 1 PID: 392 at mm/util.c:632 kvmalloc_node+0xd9/0xe0
>   Modules linked in: bpf_testmod(O)
>   CPU: 1 PID: 392 Comm: test_progs Tainted: G ...... 6.7.0-rc3+ #32
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>   ......
>   RIP: 0010:kvmalloc_node+0xd9/0xe0
>    ? __warn+0x89/0x150
>    ? kvmalloc_node+0xd9/0xe0
>    bpf_kprobe_multi_link_attach+0x87/0x670
>    __sys_bpf+0x2a28/0x2bc0
>    __x64_sys_bpf+0x1a/0x30
>    do_syscall_64+0x36/0xb0
>    entry_SYSCALL_64_after_hwframe+0x6e/0x76
>   RIP: 0033:0x7fbe067f0e0d
>   ......
>    </TASK>
>   ---[ end trace 0000000000000000 ]---
>
> So add a test to ensure the warning is fixed.
>
> Signed-off-by: Hou Tao <houtao1@huawei.com>
> ---
>  .../selftests/bpf/prog_tests/kprobe_multi_test.c   | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> index 4041cfa670eb..802554d4ee24 100644
> --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> @@ -300,6 +300,20 @@ static void test_attach_api_fails(void)
>         if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_5_error"))
>                 goto cleanup;
>
> +       /* fail_6 - abnormal cnt */
> +       opts.addrs = (const unsigned long *) addrs;
> +       opts.syms = NULL;
> +       opts.cnt = INT_MAX;
> +       opts.cookies = NULL;
> +
> +       link = bpf_program__attach_kprobe_multi_opts(skel->progs.test_kprobe_manual,
> +                                                    NULL, &opts);
> +       if (!ASSERT_ERR_PTR(link, "fail_6"))
> +               goto cleanup;
> +
> +       if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_6_error"))

this is unreliable, store errno right after the operation before
ASSERT_xxx() macros

> +               goto cleanup;
> +
>  cleanup:
>         bpf_link__destroy(link);
>         kprobe_multi__destroy(skel);
> --
> 2.29.2
>
Hou Tao Dec. 14, 2023, 1:44 a.m. UTC | #2 
Hi,

On 12/14/2023 7:33 AM, Andrii Nakryiko wrote:
> On Wed, Dec 13, 2023 at 3:24 AM Hou Tao <houtao@huaweicloud.com> wrote:
>> From: Hou Tao <houtao1@huawei.com>
>>
>> If an abnormally huge cnt is used for multi-kprobes attachment, the
>> following warning will be reported:
>>
>>   ------------[ cut here ]------------
>>   WARNING: CPU: 1 PID: 392 at mm/util.c:632 kvmalloc_node+0xd9/0xe0
>>   Modules linked in: bpf_testmod(O)
>>   CPU: 1 PID: 392 Comm: test_progs Tainted: G ...... 6.7.0-rc3+ #32
>>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>>   ......
>>   RIP: 0010:kvmalloc_node+0xd9/0xe0
>>    ? __warn+0x89/0x150
>>    ? kvmalloc_node+0xd9/0xe0
>>    bpf_kprobe_multi_link_attach+0x87/0x670
>>    __sys_bpf+0x2a28/0x2bc0
>>    __x64_sys_bpf+0x1a/0x30
>>    do_syscall_64+0x36/0xb0
>>    entry_SYSCALL_64_after_hwframe+0x6e/0x76
>>   RIP: 0033:0x7fbe067f0e0d
>>   ......
>>    </TASK>
>>   ---[ end trace 0000000000000000 ]---
>>
>> So add a test to ensure the warning is fixed.
>>
>> Signed-off-by: Hou Tao <houtao1@huawei.com>
>> ---
>>  .../selftests/bpf/prog_tests/kprobe_multi_test.c   | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
>> index 4041cfa670eb..802554d4ee24 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
>> @@ -300,6 +300,20 @@ static void test_attach_api_fails(void)
>>         if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_5_error"))
>>                 goto cleanup;
>>
>> +       /* fail_6 - abnormal cnt */
>> +       opts.addrs = (const unsigned long *) addrs;
>> +       opts.syms = NULL;
>> +       opts.cnt = INT_MAX;
>> +       opts.cookies = NULL;
>> +
>> +       link = bpf_program__attach_kprobe_multi_opts(skel->progs.test_kprobe_manual,
>> +                                                    NULL, &opts);
>> +       if (!ASSERT_ERR_PTR(link, "fail_6"))
>> +               goto cleanup;
>> +
>> +       if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_6_error"))
> this is unreliable, store errno right after the operation before
> ASSERT_xxx() macros

I didn't fully follow the reason why it is unreliable. Do you mean
ASSERT_ERR_PTR() macro may overwrite errno, right ? But _CHECK() already
saves and restores errno before invoking fprintf(), so I think it is OK
to use libbpf_get_error() to get the errno here ?
>
>> +               goto cleanup;
>> +
>>  cleanup:
>>         bpf_link__destroy(link);
>>         kprobe_multi__destroy(skel);
>> --
>> 2.29.2
>>
Andrii Nakryiko Dec. 14, 2023, 4:26 a.m. UTC | #3 
On Wed, Dec 13, 2023 at 5:44 PM Hou Tao <houtao@huaweicloud.com> wrote:
>
> Hi,
>
> On 12/14/2023 7:33 AM, Andrii Nakryiko wrote:
> > On Wed, Dec 13, 2023 at 3:24 AM Hou Tao <houtao@huaweicloud.com> wrote:
> >> From: Hou Tao <houtao1@huawei.com>
> >>
> >> If an abnormally huge cnt is used for multi-kprobes attachment, the
> >> following warning will be reported:
> >>
> >>   ------------[ cut here ]------------
> >>   WARNING: CPU: 1 PID: 392 at mm/util.c:632 kvmalloc_node+0xd9/0xe0
> >>   Modules linked in: bpf_testmod(O)
> >>   CPU: 1 PID: 392 Comm: test_progs Tainted: G ...... 6.7.0-rc3+ #32
> >>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
> >>   ......
> >>   RIP: 0010:kvmalloc_node+0xd9/0xe0
> >>    ? __warn+0x89/0x150
> >>    ? kvmalloc_node+0xd9/0xe0
> >>    bpf_kprobe_multi_link_attach+0x87/0x670
> >>    __sys_bpf+0x2a28/0x2bc0
> >>    __x64_sys_bpf+0x1a/0x30
> >>    do_syscall_64+0x36/0xb0
> >>    entry_SYSCALL_64_after_hwframe+0x6e/0x76
> >>   RIP: 0033:0x7fbe067f0e0d
> >>   ......
> >>    </TASK>
> >>   ---[ end trace 0000000000000000 ]---
> >>
> >> So add a test to ensure the warning is fixed.
> >>
> >> Signed-off-by: Hou Tao <houtao1@huawei.com>
> >> ---
> >>  .../selftests/bpf/prog_tests/kprobe_multi_test.c   | 14 ++++++++++++++
> >>  1 file changed, 14 insertions(+)
> >>
> >> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> >> index 4041cfa670eb..802554d4ee24 100644
> >> --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> >> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> >> @@ -300,6 +300,20 @@ static void test_attach_api_fails(void)
> >>         if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_5_error"))
> >>                 goto cleanup;
> >>
> >> +       /* fail_6 - abnormal cnt */
> >> +       opts.addrs = (const unsigned long *) addrs;
> >> +       opts.syms = NULL;
> >> +       opts.cnt = INT_MAX;
> >> +       opts.cookies = NULL;
> >> +
> >> +       link = bpf_program__attach_kprobe_multi_opts(skel->progs.test_kprobe_manual,
> >> +                                                    NULL, &opts);
> >> +       if (!ASSERT_ERR_PTR(link, "fail_6"))
> >> +               goto cleanup;
> >> +
> >> +       if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_6_error"))
> > this is unreliable, store errno right after the operation before
> > ASSERT_xxx() macros
>
> I didn't fully follow the reason why it is unreliable. Do you mean
> ASSERT_ERR_PTR() macro may overwrite errno, right ? But _CHECK() already
> saves and restores errno before invoking fprintf(), so I think it is OK
> to use libbpf_get_error() to get the errno here ?

We shouldn't be using libbpf_get_error() in new code, it's legacy and
not advised to be used. If ASSERT_xxx() macro guarantee to
save/restore errno, then it might be actually fine, but it still feels
better to save errno explicitly right after the operation, just like
you'd do in normal code.

> >
> >> +               goto cleanup;
> >> +
> >>  cleanup:
> >>         bpf_link__destroy(link);
> >>         kprobe_multi__destroy(skel);
> >> --
> >> 2.29.2
> >>
>
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
index 4041cfa670eb..802554d4ee24 100644
--- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
@@ -300,6 +300,20 @@  static void test_attach_api_fails(void)
 	if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_5_error"))
 		goto cleanup;
 
+	/* fail_6 - abnormal cnt */
+	opts.addrs = (const unsigned long *) addrs;
+	opts.syms = NULL;
+	opts.cnt = INT_MAX;
+	opts.cookies = NULL;
+
+	link = bpf_program__attach_kprobe_multi_opts(skel->progs.test_kprobe_manual,
+						     NULL, &opts);
+	if (!ASSERT_ERR_PTR(link, "fail_6"))
+		goto cleanup;
+
+	if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_6_error"))
+		goto cleanup;
+
 cleanup:
 	bpf_link__destroy(link);
 	kprobe_multi__destroy(skel);