ebpf: allow bpf_ktime_get_ns_proto also for networking

As this is already exported from tracing side via commit d9847d310ab4
("tracing: Allow BPF programs to call bpf_ktime_get_ns()"), we might
as well want to move it to the core, so also networking users can make
use of it, e.g. to measure diffs for certain flows from ingress/egress.

Signed-off-by: Daniel Borkmann <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/bpf.h

···
 extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
 extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
 extern const struct bpf_func_proto bpf_tail_call_proto;
+extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
 
 #endif /* _LINUX_BPF_H */

kernel/bpf/core.c

···
 
 const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
 const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
+const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
 
 /* To execute LD_ABS/LD_IND instructions __bpf_prog_run() may call
  * skb_copy_bits(), so provide a weak definition of it for NET-less config.

kernel/bpf/helpers.c

···
 #include <linux/rcupdate.h>
 #include <linux/random.h>
 #include <linux/smp.h>
+#include <linux/ktime.h>
 
 /* If kernel subsystem is allowing eBPF programs to call this function,
  * inside its own verifier_ops->get_func_proto() callback it should return
···
 const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
 	.func		= bpf_get_smp_processor_id,
 	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+};
+
+static u64 bpf_ktime_get_ns(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	/* NMI safe access to clock monotonic */
+	return ktime_get_mono_fast_ns();
+}
+
+const struct bpf_func_proto bpf_ktime_get_ns_proto = {
+	.func		= bpf_ktime_get_ns,
+	.gpl_only	= true,
 	.ret_type	= RET_INTEGER,
 };

kernel/trace/bpf_trace.c

···
 	.arg3_type	= ARG_ANYTHING,
 };
 
-static u64 bpf_ktime_get_ns(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
-{
-	/* NMI safe access to clock monotonic */
-	return ktime_get_mono_fast_ns();
-}
-
-static const struct bpf_func_proto bpf_ktime_get_ns_proto = {
-	.func		= bpf_ktime_get_ns,
-	.gpl_only	= true,
-	.ret_type	= RET_INTEGER,
-};
-
 /*
  * limited trace_printk()
  * only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed

net/core/filter.c

···
 		return &bpf_get_smp_processor_id_proto;
 	case BPF_FUNC_tail_call:
 		return &bpf_tail_call_proto;
+	case BPF_FUNC_ktime_get_ns:
+		return &bpf_ktime_get_ns_proto;
 	default:
 		return NULL;
 	}