nfp: bpf: prepare for call support

Add skeleton of verifier checks and translation handler
for call instructions.  Make sure jump target resolution
will not treat them as jumps.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

drivers/net/ethernet/netronome/nfp/bpf/jit.c

@@ -1930,6 +1930,15 @@ static int jne_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 	return wrp_test_reg(nfp_prog, meta, ALU_OP_XOR, BR_BNE);
 }
 
+static int call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	switch (meta->insn.imm) {
+	default:
+		WARN_ONCE(1, "verifier allowed unsupported function\n");
+		return -EOPNOTSUPP;
+	}
+}
+
 static int goto_out(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
 	wrp_br_special(nfp_prog, BR_UNC, OP_BR_GO_OUT);
@@ -2002,6 +2011,7 @@ static const instr_cb_t instr_cb[256] = {
 	[BPF_JMP | BPF_JLE | BPF_X] =	jle_reg,
 	[BPF_JMP | BPF_JSET | BPF_X] =	jset_reg,
 	[BPF_JMP | BPF_JNE | BPF_X] =	jne_reg,
+	[BPF_JMP | BPF_CALL] =		call,
 	[BPF_JMP | BPF_EXIT] =		goto_out,
 };
 
@@ -2026,6 +2036,8 @@ static int nfp_fixup_branches(struct nfp_prog *nfp_prog)
 	list_for_each_entry(meta, &nfp_prog->insns, l) {
 		if (meta->skip)
 			continue;
+		if (meta->insn.code == (BPF_JMP | BPF_CALL))
+			continue;
 		if (BPF_CLASS(meta->insn.code) != BPF_JMP)
 			continue;
 

drivers/net/ethernet/netronome/nfp/bpf/verifier.c

@@ -68,6 +68,20 @@ nfp_bpf_goto_meta(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	return meta;
 }
 
+static int
+nfp_bpf_check_call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	u32 func_id = meta->insn.imm;
+
+	switch (func_id) {
+	default:
+		pr_warn("unsupported function id: %d\n", func_id);
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
 static int
 nfp_bpf_check_exit(struct nfp_prog *nfp_prog,
 		   struct bpf_verifier_env *env)
@@ -177,6 +191,8 @@ nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 		return -EINVAL;
 	}
 
+	if (meta->insn.code == (BPF_JMP | BPF_CALL))
+		return nfp_bpf_check_call(nfp_prog, meta);
 	if (meta->insn.code == (BPF_JMP | BPF_EXIT))
 		return nfp_bpf_check_exit(nfp_prog, env);