diff mbox series

[v7,bpf-next,8/8] selftests/bpf: add test for bpf_seq_printf_btf helper

Message ID 1601292670-1616-9-git-send-email-alan.maguire@oracle.com (mailing list archive)
State Accepted
Headers show
Series bpf: add helpers to support BTF-based kernel data display | expand

Commit Message

Alan Maguire Sept. 28, 2020, 11:31 a.m. UTC 
Add a test verifying iterating over tasks and displaying BTF
representation of task_struct succeeds.

Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
 tools/testing/selftests/bpf/prog_tests/bpf_iter.c  | 74 ++++++++++++++++++++++
 .../selftests/bpf/progs/bpf_iter_task_btf.c        | 50 +++++++++++++++
 2 files changed, 124 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c

Comments

Andrii Nakryiko Sept. 29, 2020, 4:42 a.m. UTC | #1 
On Mon, Sep 28, 2020 at 4:36 AM Alan Maguire <alan.maguire@oracle.com> wrote:
>
> Add a test verifying iterating over tasks and displaying BTF
> representation of task_struct succeeds.
>
> Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> ---

Hey Alan,

These selftests rely on having struct btf_ptr and BTF_F_COMPACT (and
other) flags to be present in vmlinux.h. While there is nothing wrong
with that per se, it does break selftests builds on older kernels,
because there struct btf_ptr isn't yet present in kernel:

progs/netif_receive_skb.c:131:21: error: use of undeclared identifier
'BTF_F_NONAME'
        TEST_BTF(str, int, BTF_F_NONAME, "0", 0);
                           ^
progs/netif_receive_skb.c:131:2: error: use of undeclared identifier
'BTF_F_COMPACT'; did you mean 'TT_COMPAT'?
        TEST_BTF(str, int, BTF_F_NONAME, "0", 0);
        ^
progs/netif_receive_skb.c:50:28: note: expanded from macro 'TEST_BTF'
                __u64 _hflags = _flags | BTF_F_COMPACT;                 \
                                         ^
/data/users/andriin/linux/tools/testing/selftests/bpf/tools/include/vmlinux.h:330:2:
note: 'TT_COMPAT' declared here
        TT_COMPAT = 2,
        ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]

progs/bpf_iter_task_btf.c:21:24: error: variable has incomplete type
'struct btf_ptr'
        static struct btf_ptr ptr = { };
                              ^
/data/users/andriin/linux/tools/testing/selftests/bpf/tools/include/bpf/bpf_helper_defs.h:33:8:
note: forward declaration of 'struct btf_ptr'
struct btf_ptr;


We actually do build the very latest selftests against old kernels
(4.9 and 5.5 at the moment) as part of libbpf CI, so it would be nice
to fix this problem and keep selftests compilable.

Do you mind following up with a change to define struct btf_ptr and
those BTF_F_xxx flags explicitly for selftests only, similarly to how
we do it for bpf_iter context structs? See progs/bpf_iter.h for
examples. Thanks.

>  tools/testing/selftests/bpf/prog_tests/bpf_iter.c  | 74 ++++++++++++++++++++++
>  .../selftests/bpf/progs/bpf_iter_task_btf.c        | 50 +++++++++++++++
>  2 files changed, 124 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c
>

[...]
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index ad9de13..af15630 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -7,6 +7,7 @@ 
 #include "bpf_iter_task.skel.h"
 #include "bpf_iter_task_stack.skel.h"
 #include "bpf_iter_task_file.skel.h"
+#include "bpf_iter_task_btf.skel.h"
 #include "bpf_iter_tcp4.skel.h"
 #include "bpf_iter_tcp6.skel.h"
 #include "bpf_iter_udp4.skel.h"
@@ -167,6 +168,77 @@  static void test_task_file(void)
 	bpf_iter_task_file__destroy(skel);
 }
 
+#define TASKBUFSZ		32768
+
+static char taskbuf[TASKBUFSZ];
+
+static void do_btf_read(struct bpf_iter_task_btf *skel)
+{
+	struct bpf_program *prog = skel->progs.dump_task_struct;
+	struct bpf_iter_task_btf__bss *bss = skel->bss;
+	int iter_fd = -1, len = 0, bufleft = TASKBUFSZ;
+	struct bpf_link *link;
+	char *buf = taskbuf;
+
+	link = bpf_program__attach_iter(prog, NULL);
+	if (CHECK(IS_ERR(link), "attach_iter", "attach_iter failed\n"))
+		return;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(link));
+	if (CHECK(iter_fd < 0, "create_iter", "create_iter failed\n"))
+		goto free_link;
+
+	do {
+		len = read(iter_fd, buf, bufleft);
+		if (len > 0) {
+			buf += len;
+			bufleft -= len;
+		}
+	} while (len > 0);
+
+	if (bss->skip) {
+		printf("%s:SKIP:no __builtin_btf_type_id\n", __func__);
+		test__skip();
+		goto free_link;
+	}
+
+	if (CHECK(len < 0, "read", "read failed: %s\n", strerror(errno)))
+		goto free_link;
+
+	CHECK(strstr(taskbuf, "(struct task_struct)") == NULL,
+	      "check for btf representation of task_struct in iter data",
+	      "struct task_struct not found");
+free_link:
+	if (iter_fd > 0)
+		close(iter_fd);
+	bpf_link__destroy(link);
+}
+
+static void test_task_btf(void)
+{
+	struct bpf_iter_task_btf__bss *bss;
+	struct bpf_iter_task_btf *skel;
+
+	skel = bpf_iter_task_btf__open_and_load();
+	if (CHECK(!skel, "bpf_iter_task_btf__open_and_load",
+		  "skeleton open_and_load failed\n"))
+		return;
+
+	bss = skel->bss;
+
+	do_btf_read(skel);
+
+	if (CHECK(bss->tasks == 0, "check if iterated over tasks",
+		  "no task iteration, did BPF program run?\n"))
+		goto cleanup;
+
+	CHECK(bss->seq_err != 0, "check for unexpected err",
+	      "bpf_seq_printf_btf returned %ld", bss->seq_err);
+
+cleanup:
+	bpf_iter_task_btf__destroy(skel);
+}
+
 static void test_tcp4(void)
 {
 	struct bpf_iter_tcp4 *skel;
@@ -957,6 +1029,8 @@  void test_bpf_iter(void)
 		test_task_stack();
 	if (test__start_subtest("task_file"))
 		test_task_file();
+	if (test__start_subtest("task_btf"))
+		test_task_btf();
 	if (test__start_subtest("tcp4"))
 		test_tcp4();
 	if (test__start_subtest("tcp6"))
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c
new file mode 100644
index 0000000..a1ddc36
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c
@@ -0,0 +1,50 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020, Oracle and/or its affiliates. */
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+#include <errno.h>
+
+char _license[] SEC("license") = "GPL";
+
+long tasks = 0;
+long seq_err = 0;
+bool skip = false;
+
+SEC("iter/task")
+int dump_task_struct(struct bpf_iter__task *ctx)
+{
+	struct seq_file *seq = ctx->meta->seq;
+	struct task_struct *task = ctx->task;
+	static struct btf_ptr ptr = { };
+	long ret;
+
+#if __has_builtin(__builtin_btf_type_id)
+	ptr.type_id = bpf_core_type_id_kernel(struct task_struct);
+	ptr.ptr = task;
+
+	if (ctx->meta->seq_num == 0)
+		BPF_SEQ_PRINTF(seq, "Raw BTF task\n");
+
+	ret = bpf_seq_printf_btf(seq, &ptr, sizeof(ptr), 0);
+	switch (ret) {
+	case 0:
+		tasks++;
+		break;
+	case -ERANGE:
+		/* NULL task or task->fs, don't count it as an error. */
+		break;
+	case -E2BIG:
+		return 1;
+	default:
+		seq_err = ret;
+		break;
+	}
+#else
+	skip = true;
+#endif
+
+	return 0;
+}