bpf: centre subprog information fields

It is better to centre all subprog information fields into one structure.
This structure could later serve as function node in call graph.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/linux/bpf_verifier.h

@@ -173,6 +173,11 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
 
 #define BPF_MAX_SUBPROGS 256
 
+struct bpf_subprog_info {
+	u32 start; /* insn idx of function entry point */
+	u16 stack_depth; /* max. stack depth used by this function */
+};
+
 /* single container for all structs
  * one verifier_env per bpf_check() call
  */
@@ -191,9 +196,7 @@ struct bpf_verifier_env {
 	bool seen_direct_write;
 	struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
 	struct bpf_verifier_log log;
-	u32 subprog_starts[BPF_MAX_SUBPROGS + 1];
-	/* computes the stack depth of each bpf function */
-	u16 subprog_stack_depth[BPF_MAX_SUBPROGS + 1];
+	struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
 	u32 subprog_cnt;
 };
 

kernel/bpf/verifier.c

@@ -741,18 +741,19 @@ enum reg_arg_type {
 
 static int cmp_subprogs(const void *a, const void *b)
 {
-	return *(int *)a - *(int *)b;
+	return ((struct bpf_subprog_info *)a)->start -
+	       ((struct bpf_subprog_info *)b)->start;
 }
 
 static int find_subprog(struct bpf_verifier_env *env, int off)
 {
-	u32 *p;
+	struct bpf_subprog_info *p;
 
-	p = bsearch(&off, env->subprog_starts, env->subprog_cnt,
-		    sizeof(env->subprog_starts[0]), cmp_subprogs);
+	p = bsearch(&off, env->subprog_info, env->subprog_cnt,
+		    sizeof(env->subprog_info[0]), cmp_subprogs);
 	if (!p)
 		return -ENOENT;
-	return p - env->subprog_starts;
+	return p - env->subprog_info;
 
 }
 
@@ -772,15 +773,16 @@ static int add_subprog(struct bpf_verifier_env *env, int off)
 		verbose(env, "too many subprograms\n");
 		return -E2BIG;
 	}
-	env->subprog_starts[env->subprog_cnt++] = off;
-	sort(env->subprog_starts, env->subprog_cnt,
-	     sizeof(env->subprog_starts[0]), cmp_subprogs, NULL);
+	env->subprog_info[env->subprog_cnt++].start = off;
+	sort(env->subprog_info, env->subprog_cnt,
+	     sizeof(env->subprog_info[0]), cmp_subprogs, NULL);
 	return 0;
 }
 
 static int check_subprogs(struct bpf_verifier_env *env)
 {
 	int i, ret, subprog_start, subprog_end, off, cur_subprog = 0;
+	struct bpf_subprog_info *subprog = env->subprog_info;
 	struct bpf_insn *insn = env->prog->insnsi;
 	int insn_cnt = env->prog->len;
 
@@ -810,14 +812,14 @@ static int check_subprogs(struct bpf_verifier_env *env)
 
 	if (env->log.level > 1)
 		for (i = 0; i < env->subprog_cnt; i++)
-			verbose(env, "func#%d @%d\n", i, env->subprog_starts[i]);
+			verbose(env, "func#%d @%d\n", i, subprog[i].start);
 
 	/* now check that all jumps are within the same subprog */
 	subprog_start = 0;
 	if (env->subprog_cnt == cur_subprog + 1)
 		subprog_end = insn_cnt;
 	else
-		subprog_end = env->subprog_starts[cur_subprog + 1];
+		subprog_end = subprog[cur_subprog + 1].start;
 	for (i = 0; i < insn_cnt; i++) {
 		u8 code = insn[i].code;
 
@@ -846,8 +848,7 @@ next:
 			if (env->subprog_cnt == cur_subprog + 1)
 				subprog_end = insn_cnt;
 			else
-				subprog_end =
-					env->subprog_starts[cur_subprog + 1];
+				subprog_end = subprog[cur_subprog + 1].start;
 		}
 	}
 	return 0;
@@ -1480,13 +1481,13 @@ static int update_stack_depth(struct bpf_verifier_env *env,
 			      const struct bpf_func_state *func,
 			      int off)
 {
-	u16 stack = env->subprog_stack_depth[func->subprogno];
+	u16 stack = env->subprog_info[func->subprogno].stack_depth;
 
 	if (stack >= -off)
 		return 0;
 
 	/* update known max for given subprogram */
-	env->subprog_stack_depth[func->subprogno] = -off;
+	env->subprog_info[func->subprogno].stack_depth = -off;
 	return 0;
 }
 
@@ -1498,7 +1499,8 @@ static int update_stack_depth(struct bpf_verifier_env *env,
  */
 static int check_max_stack_depth(struct bpf_verifier_env *env)
 {
-	int depth = 0, frame = 0, subprog = 0, i = 0, subprog_end;
+	int depth = 0, frame = 0, idx = 0, i = 0, subprog_end;
+	struct bpf_subprog_info *subprog = env->subprog_info;
 	struct bpf_insn *insn = env->prog->insnsi;
 	int insn_cnt = env->prog->len;
 	int ret_insn[MAX_CALL_FRAMES];
@@ -1508,17 +1510,17 @@ process_func:
 	/* round up to 32-bytes, since this is granularity
 	 * of interpreter stack size
 	 */
-	depth += round_up(max_t(u32, env->subprog_stack_depth[subprog], 1), 32);
+	depth += round_up(max_t(u32, subprog[idx].stack_depth, 1), 32);
 	if (depth > MAX_BPF_STACK) {
 		verbose(env, "combined stack size of %d calls is %d. Too large\n",
 			frame + 1, depth);
 		return -EACCES;
 	}
 continue_func:
-	if (env->subprog_cnt == subprog + 1)
+	if (env->subprog_cnt == idx + 1)
 		subprog_end = insn_cnt;
 	else
-		subprog_end = env->subprog_starts[subprog + 1];
+		subprog_end = subprog[idx + 1].start;
 	for (; i < subprog_end; i++) {
 		if (insn[i].code != (BPF_JMP | BPF_CALL))
 			continue;
@@ -1526,12 +1528,12 @@ continue_func:
 			continue;
 		/* remember insn and function to return to */
 		ret_insn[frame] = i + 1;
-		ret_prog[frame] = subprog;
+		ret_prog[frame] = idx;
 
 		/* find the callee */
 		i = i + insn[i].imm + 1;
-		subprog = find_subprog(env, i);
-		if (subprog < 0) {
+		idx = find_subprog(env, i);
+		if (idx < 0) {
 			WARN_ONCE(1, "verifier bug. No program starts at insn %d\n",
 				  i);
 			return -EFAULT;
@@ -1548,10 +1550,10 @@ continue_func:
 	 */
 	if (frame == 0)
 		return 0;
-	depth -= round_up(max_t(u32, env->subprog_stack_depth[subprog], 1), 32);
+	depth -= round_up(max_t(u32, subprog[idx].stack_depth, 1), 32);
 	frame--;
 	i = ret_insn[frame];
-	subprog = ret_prog[frame];
+	idx = ret_prog[frame];
 	goto continue_func;
 }
 
@@ -1567,7 +1569,7 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 			  start);
 		return -EFAULT;
 	}
-	return env->subprog_stack_depth[subprog];
+	return env->subprog_info[subprog].stack_depth;
 }
 #endif
 
@@ -4926,14 +4928,14 @@ process_bpf_exit:
 	verbose(env, "processed %d insns (limit %d), stack depth ",
 		insn_processed, BPF_COMPLEXITY_LIMIT_INSNS);
 	for (i = 0; i < env->subprog_cnt; i++) {
-		u32 depth = env->subprog_stack_depth[i];
+		u32 depth = env->subprog_info[i].stack_depth;
 
 		verbose(env, "%d", depth);
 		if (i + 1 < env->subprog_cnt)
 			verbose(env, "+");
 	}
 	verbose(env, "\n");
-	env->prog->aux->stack_depth = env->subprog_stack_depth[0];
+	env->prog->aux->stack_depth = env->subprog_info[0].stack_depth;
 	return 0;
 }
 
@@ -5140,9 +5142,9 @@ static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len
 	if (len == 1)
 		return;
 	for (i = 0; i < env->subprog_cnt; i++) {
-		if (env->subprog_starts[i] < off)
+		if (env->subprog_info[i].start < off)
 			continue;
-		env->subprog_starts[i] += len - 1;
+		env->subprog_info[i].start += len - 1;
 	}
 }
 
@@ -5340,7 +5342,7 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 		if (env->subprog_cnt == i + 1)
 			subprog_end = prog->len;
 		else
-			subprog_end = env->subprog_starts[i + 1];
+			subprog_end = env->subprog_info[i + 1].start;
 
 		len = subprog_end - subprog_start;
 		func[i] = bpf_prog_alloc(bpf_prog_size(len), GFP_USER);
@@ -5357,7 +5359,7 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 		 * Long term would need debug info to populate names
 		 */
 		func[i]->aux->name[0] = 'F';
-		func[i]->aux->stack_depth = env->subprog_stack_depth[i];
+		func[i]->aux->stack_depth = env->subprog_info[i].stack_depth;
 		func[i]->jit_requested = 1;
 		func[i] = bpf_int_jit_compile(func[i]);
 		if (!func[i]->jited) {