On 12/19, Daniel Borkmann wrote:

On 12/17/2018 07:25 PM, Stanislav Fomichev wrote:

quoted

Export bpf_map_type_supported() and bpf_prog_type_supported() which
return true/false to indicate kernel support for the appropriate
program or map type. These helpers will be used in the next commits
to selectively skip test_verifier/test_maps tests.

bpf_map_type_supported() supports only limited set of maps for which we
do fixups in the test_verifier, for unknown maps it falls back to
'supported'.

Signed-off-by: Stanislav Fomichev <redacted>
---
 tools/testing/selftests/bpf/probe_helpers.c | 68 +++++++++++++++++++++
 tools/testing/selftests/bpf/probe_helpers.h | 10 +++
 2 files changed, 78 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/probe_helpers.c
 create mode 100644 tools/testing/selftests/bpf/probe_helpers.h

diff --git a/tools/testing/selftests/bpf/probe_helpers.c b/tools/testing/selftests/bpf/probe_helpers.c
new file mode 100644
index 000000000000..00467fdda813
--- /dev/null
+++ b/tools/testing/selftests/bpf/probe_helpers.c

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+#include <unistd.h>
+#include <bpf/bpf.h>
+
+#include "cgroup_helpers.h"
+#include "bpf_util.h"
+#include "../../../include/linux/filter.h"
+
+bool bpf_prog_type_supported(enum bpf_prog_type prog_type)
+{
+	struct bpf_load_program_attr attr;
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int ret;
+
+	if (prog_type == BPF_PROG_TYPE_UNSPEC)
+		return true;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.prog_type = prog_type;
+	attr.insns = insns;
+	attr.insns_cnt = ARRAY_SIZE(insns);
+	attr.license = "GPL";
+
+	ret = bpf_load_program_xattr(&attr, NULL, 0);
+	if (ret < 0)
+		return false;
+	close(ret);
+
+	return true;
+}
+
+bool bpf_map_type_supported(enum bpf_map_type map_type)
+{
+	int key_size, value_size, max_entries;
+	int fd;
+
+	key_size = sizeof(__u32);
+	value_size = sizeof(__u32);
+	max_entries = 1;
+
+	/* limited set of maps for test_verifier.c and test_maps.c */
+	switch (map_type) {
+	case BPF_MAP_TYPE_SOCKMAP:
+	case BPF_MAP_TYPE_SOCKHASH:
+	case BPF_MAP_TYPE_XSKMAP:
+		break;
+	case BPF_MAP_TYPE_STACK_TRACE:
+		value_size = sizeof(__u64);
+	case BPF_MAP_TYPE_CGROUP_STORAGE:
+	case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE:
+		key_size = sizeof(struct bpf_cgroup_storage_key);
+		value_size = sizeof(__u64);
+		max_entries = 0;
+		break;
+	default:
+		return true;

Given bpf_map_type_supported() is mainly called in the "unexpected" failure
case, it's probably okay to have this less restricted here. Also, ideally we
shouldn't need an explicit opt-in for every newly added map type to probe in
future. But presumably both limitation will be removed when using libbpf API.

Yes, both of these problems should go away when converted to libbpf API.
I wanted to have something simple and tailed to a particular
usecase here.

quoted

+	}
+
+	fd = bpf_create_map(map_type, key_size, value_size, max_entries, 0);
+	if (fd < 0)
+		return false;
+	close(fd);
+
+	return true;
+}

diff --git a/tools/testing/selftests/bpf/probe_helpers.h b/tools/testing/selftests/bpf/probe_helpers.h
new file mode 100644
index 000000000000..9a107d6fe936
--- /dev/null
+++ b/tools/testing/selftests/bpf/probe_helpers.h

@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+#ifndef __PROBE_HELPERS_H
+#define __PROBE_HELPERS_H
+
+#include <linux/bpf.h>
+
+bool bpf_prog_type_supported(enum bpf_prog_type prog_type);
+bool bpf_map_type_supported(enum bpf_map_type map_type);
+
+#endif