From: Quentin Monnet <quentin.monnet@netronome.com>
Date: Sun, 7 Oct 2018 12:56:58 +0100
Subject: bpf: allow offload of programs with BPF-to-BPF function calls
Patch-mainline: v4.20-rc1
Git-commit: e4052d06a5195b29271a7af262711d69f9ecfd04
References: bsc#1109837

Now that there is at least one driver supporting BPF-to-BPF function
calls, lift the restriction, in the verifier, on hardware offload of
eBPF programs containing such calls. But prevent jit_subprogs(), still
in the verifier, from being run for offloaded programs.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/verifier.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -850,10 +850,6 @@ static int check_subprogs(struct bpf_ver
 			verbose(env, "function calls to other bpf functions are allowed for root only\n");
 			return -EPERM;
 		}
-		if (bpf_prog_is_dev_bound(env->prog->aux)) {
-			verbose(env, "function calls in offloaded programs are not supported yet\n");
-			return -EINVAL;
-		}
 		ret = add_subprog(env, i + insn[i].imm + 1);
 		if (ret < 0)
 			return ret;
@@ -5543,10 +5539,10 @@ static int fixup_call_args(struct bpf_ve
 	struct bpf_insn *insn = prog->insnsi;
 	int i, depth;
 #endif
-	int err;
+	int err = 0;
 
-	err = 0;
-	if (env->prog->jit_requested) {
+	if (env->prog->jit_requested &&
+	    !bpf_prog_is_dev_bound(env->prog->aux)) {
 		err = jit_subprogs(env);
 		if (err == 0)
 			return 0;