bpf: cleanup register_is_null()

don't pass large struct bpf_reg_state by value.
Instead pass it by pointer.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

kernel/bpf/verifier.c

@@ -1265,9 +1265,9 @@ static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_ins
 }
 
 /* Does this register contain a constant zero? */
-static bool register_is_null(struct bpf_reg_state reg)
+static bool register_is_null(struct bpf_reg_state *reg)
 {
-	return reg.type == SCALAR_VALUE && tnum_equals_const(reg.var_off, 0);
+	return reg->type == SCALAR_VALUE && tnum_equals_const(reg->var_off, 0);
 }
 
 /* when register 'regno' is passed into function that will read 'access_size'
@@ -1280,31 +1280,31 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
 				int access_size, bool zero_size_allowed,
 				struct bpf_call_arg_meta *meta)
 {
+	struct bpf_reg_state *reg = cur_regs(env) + regno;
 	struct bpf_verifier_state *state = env->cur_state;
-	struct bpf_reg_state *regs = state->regs;
 	int off, i, slot, spi;
 
-	if (regs[regno].type != PTR_TO_STACK) {
+	if (reg->type != PTR_TO_STACK) {
 		/* Allow zero-byte read from NULL, regardless of pointer type */
 		if (zero_size_allowed && access_size == 0 &&
-		    register_is_null(regs[regno]))
+		    register_is_null(reg))
 			return 0;
 
 		verbose(env, "R%d type=%s expected=%s\n", regno,
-			reg_type_str[regs[regno].type],
+			reg_type_str[reg->type],
 			reg_type_str[PTR_TO_STACK]);
 		return -EACCES;
 	}
 
 	/* Only allow fixed-offset stack reads */
-	if (!tnum_is_const(regs[regno].var_off)) {
+	if (!tnum_is_const(reg->var_off)) {
 		char tn_buf[48];
 
-		tnum_strn(tn_buf, sizeof(tn_buf), regs[regno].var_off);
+		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
 		verbose(env, "invalid variable stack read R%d var_off=%s\n",
 			regno, tn_buf);
 	}
-	off = regs[regno].off + regs[regno].var_off.value;
+	off = reg->off + reg->var_off.value;
 	if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
 	    access_size < 0 || (access_size == 0 && !zero_size_allowed)) {
 		verbose(env, "invalid stack type R%d off=%d access_size=%d\n",
@@ -1412,7 +1412,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 		 * passed in as argument, it's a SCALAR_VALUE type. Final test
 		 * happens during stack boundary checking.
 		 */
-		if (register_is_null(*reg) &&
+		if (register_is_null(reg) &&
 		    arg_type == ARG_PTR_TO_MEM_OR_NULL)
 			/* final test in check_stack_boundary() */;
 		else if (!type_is_pkt_pointer(type) &&