nfp: bpf: ignore helper-related checks for BPF calls in nfp verifier

The checks related to eBPF helper calls are performed each time the nfp
driver meets a BPF_JUMP | BPF_CALL instruction. However, these checks
are not relevant for BPF-to-BPF call (same instruction code, different
value in source register), so just skip the checks for such calls.

While at it, rename the function that runs those checks to make it clear
they apply to _helper_ calls only.
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>

drivers/net/ethernet/netronome/nfp/bpf/main.h

@@ -423,6 +423,14 @@ static inline bool is_mbpf_div(const struct nfp_insn_meta *meta)
 	return is_mbpf_alu(meta) && mbpf_op(meta) == BPF_DIV;
 }
 
+static inline bool is_mbpf_helper_call(const struct nfp_insn_meta *meta)
+{
+	struct bpf_insn insn = meta->insn;
+
+	return insn.code == (BPF_JMP | BPF_CALL) &&
+		insn.src_reg != BPF_PSEUDO_CALL;
+}
+
 /**
  * struct nfp_bpf_subprog_info - nfp BPF sub-program (a.k.a. function) info
  * @stack_depth:	maximum stack depth used by this sub-program

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

@@ -155,8 +155,9 @@ nfp_bpf_map_call_ok(const char *fname, struct bpf_verifier_env *env,
 }
 
 static int
-nfp_bpf_check_call(struct nfp_prog *nfp_prog, struct bpf_verifier_env *env,
-		   struct nfp_insn_meta *meta)
+nfp_bpf_check_helper_call(struct nfp_prog *nfp_prog,
+			  struct bpf_verifier_env *env,
+			  struct nfp_insn_meta *meta)
 {
 	const struct bpf_reg_state *reg1 = cur_regs(env) + BPF_REG_1;
 	const struct bpf_reg_state *reg2 = cur_regs(env) + BPF_REG_2;
@@ -620,8 +621,8 @@ 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, env, meta);
+	if (is_mbpf_helper_call(meta))
+		return nfp_bpf_check_helper_call(nfp_prog, env, meta);
 	if (meta->insn.code == (BPF_JMP | BPF_EXIT))
 		return nfp_bpf_check_exit(nfp_prog, env);