1 files changed, 40 insertions, 9 deletions

diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index f804f210244e..54a50699bbfd 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -1,12 +1,6 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __BPF_HELPERS_H
-#define __BPF_HELPERS_H
-
-/* helper macro to place programs, maps, license in
- * different sections in elf_bpf file. Section names
- * are interpreted by elf_bpf loader
- */
-#define SEC(NAME) __attribute__((section(NAME), used))
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+#ifndef __BPF_HELPERS__
+#define __BPF_HELPERS__
 
 #define __uint(name, val) int (*name)[val]
 #define __type(name, val) val *name
@@ -19,6 +13,14 @@
 			 ##__VA_ARGS__);		\
 })
 
+#ifdef __clang__
+
+/* helper macro to place programs, maps, license in
+ * different sections in elf_bpf file. Section names
+ * are interpreted by elf_bpf loader
+ */
+#define SEC(NAME) __attribute__((section(NAME), used))
+
 /* helper functions called from eBPF programs written in C */
 static void *(*bpf_map_lookup_elem)(void *map, const void *key) =
 	(void *) BPF_FUNC_map_lookup_elem;
@@ -228,6 +230,9 @@ static void *(*bpf_sk_storage_get)(void *map, struct bpf_sock *sk,
 static int (*bpf_sk_storage_delete)(void *map, struct bpf_sock *sk) =
 	(void *)BPF_FUNC_sk_storage_delete;
 static int (*bpf_send_signal)(unsigned sig) = (void *)BPF_FUNC_send_signal;
+static long long (*bpf_tcp_gen_syncookie)(struct bpf_sock *sk, void *ip,
+					  int ip_len, void *tcp, int tcp_len) =
+	(void *) BPF_FUNC_tcp_gen_syncookie;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions
@@ -253,6 +258,12 @@ struct bpf_map_def {
 	unsigned int numa_node;
 };
 
+#else
+
+#include <bpf-helpers.h>
+
+#endif
+
 #define BPF_ANNOTATE_KV_PAIR(name, type_key, type_val)		\
 	struct ____btf_map_##name {				\
 		type_key key;					\
@@ -501,4 +512,24 @@ struct pt_regs;
 				(void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
 #endif
 
+/*
+ * BPF_CORE_READ abstracts away bpf_probe_read() call and captures offset
+ * relocation for source address using __builtin_preserve_access_index()
+ * built-in, provided by Clang.
+ *
+ * __builtin_preserve_access_index() takes as an argument an expression of
+ * taking an address of a field within struct/union. It makes compiler emit
+ * a relocation, which records BTF type ID describing root struct/union and an
+ * accessor string which describes exact embedded field that was used to take
+ * an address. See detailed description of this relocation format and
+ * semantics in comments to struct bpf_offset_reloc in libbpf_internal.h.
+ *
+ * This relocation allows libbpf to adjust BPF instruction to use correct
+ * actual field offset, based on target kernel BTF type that matches original
+ * (local) BTF, used to record relocation.
+ */
+#define BPF_CORE_READ(dst, src)						\
+	bpf_probe_read((dst), sizeof(*(src)),				\
+		       __builtin_preserve_access_index(src))
+
 #endif