bpf_helpers.h: add load_byte/half/word() llvm/clang asm magic

see kernel's
  samples/bpf/bpf_helpers.h
or
  tools/testing/selftests/bpf/bpf_legacy.h

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Id331fb9abcd87df8bf87c5a86749acf0144ffbde
diff --git a/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h b/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
index 4d48720..8c66b91 100644
--- a/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
+++ b/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
@@ -277,6 +277,11 @@
     DEFINE_BPF_MAP_UGM(the_map, TYPE, KeyType, ValueType, num_entries, \
                        DEFAULT_BPF_MAP_UID, gid, 0660)
 
+// LLVM eBPF builtins: they directly generate BPF_LD_ABS/BPF_LD_IND (skb may be ignored?)
+unsigned long long load_byte(void* skb, unsigned long long off) asm("llvm.bpf.load.byte");
+unsigned long long load_half(void* skb, unsigned long long off) asm("llvm.bpf.load.half");
+unsigned long long load_word(void* skb, unsigned long long off) asm("llvm.bpf.load.word");
+
 static int (*bpf_probe_read)(void* dst, int size, void* unsafe_ptr) = (void*) BPF_FUNC_probe_read;
 static int (*bpf_probe_read_str)(void* dst, int size, void* unsafe_ptr) = (void*) BPF_FUNC_probe_read_str;
 static unsigned long long (*bpf_ktime_get_ns)(void) = (void*) BPF_FUNC_ktime_get_ns;