libbpf: Add libbpf_set_strict_mode() API to turn on libbpf 1.0 behaviors

mainline inclusion
from mainline-5.14-rc1
commit 5981881d
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5981881d21dff612abf8fce484f8efa67f49aae4

-------------------------------------------------

Add libbpf_set_strict_mode() API that allows application to simulate libbpf
1.0 breaking changes before libbpf 1.0 is released. This will help users
migrate gradually and with confidence.

For now only ALL or NONE options are available, subsequent patches will add
more flags. This patch is preliminary for selftests/bpf changes.
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NJohn Fastabend <john.fastabend@gmail.com>
Acked-by: NToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210525035935.1461796-2-andrii@kernel.org
(cherry picked from commit 5981881d)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/Makefile

@@ -230,6 +230,7 @@ install_headers: $(BPF_HELPER_DEFS)
 		$(call do_install,btf.h,$(prefix)/include/bpf,644); \
 		$(call do_install,libbpf_util.h,$(prefix)/include/bpf,644); \
 		$(call do_install,libbpf_common.h,$(prefix)/include/bpf,644); \
+		$(call do_install,libbpf_legacy.h,$(prefix)/include/bpf,644); \
 		$(call do_install,xsk.h,$(prefix)/include/bpf,644); \
 		$(call do_install,bpf_helpers.h,$(prefix)/include/bpf,644); \
 		$(call do_install,$(BPF_HELPER_DEFS),$(prefix)/include/bpf,644); \

tools/lib/bpf/libbpf.c

@@ -151,6 +151,23 @@ static inline __u64 ptr_to_u64(const void *ptr)
 	return (__u64) (unsigned long) ptr;
 }
 
+/* this goes away in libbpf 1.0 */
+enum libbpf_strict_mode libbpf_mode = LIBBPF_STRICT_NONE;
+
+int libbpf_set_strict_mode(enum libbpf_strict_mode mode)
+{
+	/* __LIBBPF_STRICT_LAST is the last power-of-2 value used + 1, so to
+	 * get all possible values we compensate last +1, and then (2*x - 1)
+	 * to get the bit mask
+	 */
+	if (mode != LIBBPF_STRICT_ALL
+	    && (mode & ~((__LIBBPF_STRICT_LAST - 1) * 2 - 1)))
+		return errno = EINVAL, -EINVAL;
+
+	libbpf_mode = mode;
+	return 0;
+}
+
 enum kern_feature_id {
 	/* v4.14: kernel support for program & map names. */
 	FEAT_PROG_NAME,

tools/lib/bpf/libbpf.h

@@ -18,6 +18,7 @@
 #include <linux/bpf.h>
 
 #include "libbpf_common.h"
+#include "libbpf_legacy.h"
 
 #ifdef __cplusplus
 extern "C" {

tools/lib/bpf/libbpf.map

@@ -369,3 +369,8 @@ LIBBPF_0.4.0 {
 		bpf_tc_hook_destroy;
 		bpf_tc_query;
 } LIBBPF_0.3.0;
+
+LIBBPF_0.5.0 {
+	global:
+		libbpf_set_strict_mode;
+} LIBBPF_0.4.0;

tools/lib/bpf/libbpf_legacy.h

+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+
+/*
+ * Libbpf legacy APIs (either discouraged or deprecated, as mentioned in [0])
+ *
+ *   [0] https://docs.google.com/document/d/1UyjTZuPFWiPFyKk1tV5an11_iaRuec6U-ZESZ54nNTY
+ *
+ * Copyright (C) 2021 Facebook
+ */
+#ifndef __LIBBPF_LEGACY_BPF_H
+#define __LIBBPF_LEGACY_BPF_H
+
+#include <linux/bpf.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include "libbpf_common.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum libbpf_strict_mode {
+	/* Turn on all supported strict features of libbpf to simulate libbpf
+	 * v1.0 behavior.
+	 * This will be the default behavior in libbpf v1.0.
+	 */
+	LIBBPF_STRICT_ALL = 0xffffffff,
+
+	/*
+	 * Disable any libbpf 1.0 behaviors. This is the default before libbpf
+	 * v1.0. It won't be supported anymore in v1.0, please update your
+	 * code so that it handles LIBBPF_STRICT_ALL mode before libbpf v1.0.
+	 */
+	LIBBPF_STRICT_NONE = 0x00,
+
+	__LIBBPF_STRICT_LAST,
+};
+
+LIBBPF_API int libbpf_set_strict_mode(enum libbpf_strict_mode mode);
+
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* __LIBBPF_LEGACY_BPF_H */