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Commit 0824611f authored by Jiong Wang's avatar Jiong Wang Committed by Alexei Starovoitov
Browse files

tools: bpftool: partition basic-block for each function in the CFG 



This patch partition basic-block for each function in the CFG. The
algorithm is simple, we identify basic-block head in a first traversal,
then second traversal to identify the tail.

We could build extended basic-block (EBB) in next steps. EBB could make the
graph more readable when the eBPF sequence is big.

Signed-off-by: default avatarJiong Wang <jiong.wang@netronome.com>
Acked-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 80331752

tools/bpf/bpftool/cfg.c

+117 −1
Original line number Diff line number Diff line
@@ -49,17 +49,32 @@ struct cfg { 


struct func_node {

	struct list_head l;

	struct list_head bbs;

	struct bpf_insn *start;

	struct bpf_insn *end;

	int idx;

	int bb_num;

};



struct bb_node {

	struct list_head l;

	struct bpf_insn *head;

	struct bpf_insn *tail;

	int idx;

};



#define func_prev(func)		list_prev_entry(func, l)

#define func_next(func)		list_next_entry(func, l)

#define bb_prev(bb)		list_prev_entry(bb, l)

#define bb_next(bb)		list_next_entry(bb, l)

#define cfg_first_func(cfg)	\

	list_first_entry(&cfg->funcs, struct func_node, l)

#define cfg_last_func(cfg)	\

	list_last_entry(&cfg->funcs, struct func_node, l)

#define func_first_bb(func)	\

	list_first_entry(&func->bbs, struct bb_node, l)

#define func_last_bb(func)	\

	list_last_entry(&func->bbs, struct bb_node, l)



static struct func_node *cfg_append_func(struct cfg *cfg, struct bpf_insn *insn)

{
@@ -86,6 +101,30 @@ static struct func_node *cfg_append_func(struct cfg *cfg, struct bpf_insn *insn) 
	return new_func;

}



static struct bb_node *func_append_bb(struct func_node *func,

				      struct bpf_insn *insn)

{

	struct bb_node *new_bb, *bb;



	list_for_each_entry(bb, &func->bbs, l) {

		if (bb->head == insn)

			return bb;

		else if (bb->head > insn)

			break;

	}



	bb = bb_prev(bb);

	new_bb = calloc(1, sizeof(*new_bb));

	if (!new_bb) {

		p_err("OOM when allocating BB node");

		return NULL;

	}

	new_bb->head = insn;

	list_add(&new_bb->l, &bb->l);



	return new_bb;

}



static bool cfg_partition_funcs(struct cfg *cfg, struct bpf_insn *cur,

				struct bpf_insn *end)

{
@@ -115,13 +154,83 @@ static bool cfg_partition_funcs(struct cfg *cfg, struct bpf_insn *cur, 
	return false;

}



static bool func_partition_bb_head(struct func_node *func)

{

	struct bpf_insn *cur, *end;

	struct bb_node *bb;



	cur = func->start;

	end = func->end;

	INIT_LIST_HEAD(&func->bbs);

	bb = func_append_bb(func, cur);

	if (!bb)

		return true;



	for (; cur <= end; cur++) {

		if (BPF_CLASS(cur->code) == BPF_JMP) {

			u8 opcode = BPF_OP(cur->code);



			if (opcode == BPF_EXIT || opcode == BPF_CALL)

				continue;



			bb = func_append_bb(func, cur + cur->off + 1);

			if (!bb)

				return true;



			if (opcode != BPF_JA) {

				bb = func_append_bb(func, cur + 1);

				if (!bb)

					return true;

			}

		}

	}



	return false;

}



static void func_partition_bb_tail(struct func_node *func)

{

	struct bb_node *bb, *last;

	unsigned int bb_idx = 0;



	last = func_last_bb(func);

	last->tail = func->end;

	bb = func_first_bb(func);

	list_for_each_entry_from(bb, &last->l, l) {

		bb->tail = bb_next(bb)->head - 1;

		bb->idx = bb_idx++;

	}



	last->idx = bb_idx++;

	func->bb_num = bb_idx;

}



static bool func_partition_bb(struct func_node *func)

{

	if (func_partition_bb_head(func))

		return true;



	func_partition_bb_tail(func);



	return false;

}



static bool cfg_build(struct cfg *cfg, struct bpf_insn *insn, unsigned int len)

{

	int cnt = len / sizeof(*insn);

	struct func_node *func;



	INIT_LIST_HEAD(&cfg->funcs);



	return cfg_partition_funcs(cfg, insn, insn + cnt);

	if (cfg_partition_funcs(cfg, insn, insn + cnt))

		return true;



	list_for_each_entry(func, &cfg->funcs, l) {

		if (func_partition_bb(func))

			return true;

	}



	return false;

}



static void cfg_destroy(struct cfg *cfg)
@@ -129,6 +238,13 @@ static void cfg_destroy(struct cfg *cfg) 
	struct func_node *func, *func2;



	list_for_each_entry_safe(func, func2, &cfg->funcs, l) {

		struct bb_node *bb, *bb2;



		list_for_each_entry_safe(bb, bb2, &func->bbs, l) {

			list_del(&bb->l);

			free(bb);

		}



		list_del(&func->l);

		free(func);

	}