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Tue, 23 Jun 2020 18:57:34 +0000 Subject: Re: [PATCH bpf-next 3/3] selftests/bpf: add bpf_iter test with bpf_get_task_stack_trace() To: Song Liu , , CC: , , , , References: <20200623070802.2310018-1-songliubraving@fb.com> <20200623070802.2310018-4-songliubraving@fb.com> From: Yonghong Song Message-ID: <445e1e04-882f-7ff7-9bd4-ebcf679cebbb@fb.com> Date: Tue, 23 Jun 2020 11:57:32 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 In-Reply-To: <20200623070802.2310018-4-songliubraving@fb.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR07CA0002.namprd07.prod.outlook.com (2603:10b6:a02:bc::15) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c085:21d6::1377] (2620:10d:c090:400::5:7789) by BYAPR07CA0002.namprd07.prod.outlook.com (2603:10b6:a02:bc::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3131.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: ad330c03-956a-4aae-f83b-08d817a74a18 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jun 2020 18:57:34.4691 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: TNgePXGA09336nPt9PysrmTOg3o9Aq7b7uKeuxt2cf8QiDgE89jMOFy/MaTVf6c2 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3192 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-23_12:2020-06-23,2020-06-23 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 clxscore=1015 impostorscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 priorityscore=1501 mlxscore=0 lowpriorityscore=0 adultscore=0 spamscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006120000 definitions=main-2006230129 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 6/23/20 12:08 AM, Song Liu wrote: > The new test is similar to other bpf_iter tests. > > Signed-off-by: Song Liu > --- > .../selftests/bpf/prog_tests/bpf_iter.c | 17 +++++++ > .../selftests/bpf/progs/bpf_iter_task_stack.c | 50 +++++++++++++++++++ > 2 files changed, 67 insertions(+) > create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > index 87c29dde1cf96..baa83328f810d 100644 > --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > @@ -5,6 +5,7 @@ > #include "bpf_iter_netlink.skel.h" > #include "bpf_iter_bpf_map.skel.h" > #include "bpf_iter_task.skel.h" > +#include "bpf_iter_task_stack.skel.h" > #include "bpf_iter_task_file.skel.h" > #include "bpf_iter_test_kern1.skel.h" > #include "bpf_iter_test_kern2.skel.h" > @@ -106,6 +107,20 @@ static void test_task(void) > bpf_iter_task__destroy(skel); > } > > +static void test_task_stack(void) > +{ > + struct bpf_iter_task_stack *skel; > + > + skel = bpf_iter_task_stack__open_and_load(); > + if (CHECK(!skel, "bpf_iter_task_stack__open_and_load", > + "skeleton open_and_load failed\n")) > + return; > + > + do_dummy_read(skel->progs.dump_task_stack); > + > + bpf_iter_task_stack__destroy(skel); > +} > + > static void test_task_file(void) > { > struct bpf_iter_task_file *skel; > @@ -392,6 +407,8 @@ void test_bpf_iter(void) > test_bpf_map(); > if (test__start_subtest("task")) > test_task(); > + if (test__start_subtest("task_stack")) > + test_task_stack(); > if (test__start_subtest("task_file")) > test_task_file(); > if (test__start_subtest("anon")) > diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > new file mode 100644 > index 0000000000000..4fc939e0fca77 > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > @@ -0,0 +1,50 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2020 Facebook */ > +/* "undefine" structs in vmlinux.h, because we "override" them below */ > +#define bpf_iter_meta bpf_iter_meta___not_used > +#define bpf_iter__task bpf_iter__task___not_used > +#include "vmlinux.h" > +#undef bpf_iter_meta > +#undef bpf_iter__task > +#include > +#include > + > +char _license[] SEC("license") = "GPL"; > + > +struct bpf_iter_meta { > + struct seq_file *seq; > + __u64 session_id; > + __u64 seq_num; > +} __attribute__((preserve_access_index)); > + > +struct bpf_iter__task { > + struct bpf_iter_meta *meta; > + struct task_struct *task; > +} __attribute__((preserve_access_index)); > + > +#define MAX_STACK_TRACE_DEPTH 64 > +unsigned long entries[MAX_STACK_TRACE_DEPTH]; > + > +SEC("iter/task") > +int dump_task_stack(struct bpf_iter__task *ctx) > +{ > + struct seq_file *seq = ctx->meta->seq; > + struct task_struct *task = ctx->task; > + unsigned int i, num_entries; > + > + if (task == (void *)0) > + return 0; > + > + num_entries = bpf_get_task_stack_trace(task, entries, MAX_STACK_TRACE_DEPTH); > + > + BPF_SEQ_PRINTF(seq, "pid: %8u\n", task->pid); > + > + for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) { > + if (num_entries > i) > + BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]); We may have an issue on 32bit issue. On 32bit system, the following is called in the kernel + return stack_trace_save_tsk(task, (unsigned long *)entries, size, 0); it will pack addresses at 4 byte increment. But in BPF program, the reading is in 8 byte increment. If "entries" are handled in user space, user space can just using "long *" pointer and will be able to correctly retrieve the stack addresses. Maybe add some comments to clarify this prog only works for 64bit system. > + } > + > + BPF_SEQ_PRINTF(seq, "\n"); > + > + return 0; > +} >