bpfloader: Support <4.14 kernels

Change-Id: I3d6573c102c1d64a64209bf61ecb8ed0c4ecb64c
diff --git a/bpfloader/BpfLoader.cpp b/bpfloader/BpfLoader.cpp
index f153b40..29da777 100644
--- a/bpfloader/BpfLoader.cpp
+++ b/bpfloader/BpfLoader.cpp
@@ -192,12 +192,14 @@
     //  kernel does not have CONFIG_BPF_JIT=y)
     // BPF_JIT is required by R VINTF (which means 4.14/4.19/5.4 kernels),
     // but 4.14/4.19 were released with P & Q, and only 5.4 is new in R+.
-    if (writeProcSysFile("/proc/sys/net/core/bpf_jit_enable", "1\n")) return 1;
+    if (writeProcSysFile("/proc/sys/net/core/bpf_jit_enable", "1\n") &&
+        android::bpf::isAtLeastKernelVersion(4, 14, 0)) return 1;
 
     // Enable JIT kallsyms export for privileged users only
     // (Note: this (open) will fail with ENOENT 'No such file or directory' if
     //  kernel does not have CONFIG_HAVE_EBPF_JIT=y)
-    if (writeProcSysFile("/proc/sys/net/core/bpf_jit_kallsyms", "1\n")) return 1;
+    if (writeProcSysFile("/proc/sys/net/core/bpf_jit_kallsyms", "1\n") &&
+        android::bpf::isAtLeastKernelVersion(4, 14, 0)) return 1;
 
     // Create all the pin subdirectories
     // (this must be done first to allow selinux_context and pin_subdir functionality,