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tools: bpftool: add out edges for each basic-block
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This patch adds out edges for each basic-block. We will need these out
edges to finish the .dot graph drawing.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Jiong Wang authored and Alexei Starovoitov committed Mar 2, 2018
1 parent 0824611 commit 6e9eb7e
Showing 1 changed file with 160 additions and 2 deletions.
162 changes: 160 additions & 2 deletions tools/bpf/bpftool/cfg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,15 +58,32 @@ struct func_node {

struct bb_node {
struct list_head l;
struct list_head e_prevs;
struct list_head e_succs;
struct bpf_insn *head;
struct bpf_insn *tail;
int idx;
};

#define EDGE_FLAG_EMPTY 0x0
#define EDGE_FLAG_FALLTHROUGH 0x1
#define EDGE_FLAG_JUMP 0x2
struct edge_node {
struct list_head l;
struct bb_node *src;
struct bb_node *dst;
int flags;
};

#define ENTRY_BLOCK_INDEX 0
#define EXIT_BLOCK_INDEX 1
#define NUM_FIXED_BLOCKS 2
#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 entry_bb(func) func_first_bb(func)
#define exit_bb(func) func_last_bb(func)
#define cfg_first_func(cfg) \
list_first_entry(&cfg->funcs, struct func_node, l)
#define cfg_last_func(cfg) \
Expand Down Expand Up @@ -120,11 +137,30 @@ static struct bb_node *func_append_bb(struct func_node *func,
return NULL;
}
new_bb->head = insn;
INIT_LIST_HEAD(&new_bb->e_prevs);
INIT_LIST_HEAD(&new_bb->e_succs);
list_add(&new_bb->l, &bb->l);

return new_bb;
}

static struct bb_node *func_insert_dummy_bb(struct list_head *after)
{
struct bb_node *bb;

bb = calloc(1, sizeof(*bb));
if (!bb) {
p_err("OOM when allocating BB node");
return NULL;
}

INIT_LIST_HEAD(&bb->e_prevs);
INIT_LIST_HEAD(&bb->e_succs);
list_add(&bb->l, after);

return bb;
}

static bool cfg_partition_funcs(struct cfg *cfg, struct bpf_insn *cur,
struct bpf_insn *end)
{
Expand Down Expand Up @@ -190,8 +226,8 @@ static bool func_partition_bb_head(struct func_node *func)

static void func_partition_bb_tail(struct func_node *func)
{
unsigned int bb_idx = NUM_FIXED_BLOCKS;
struct bb_node *bb, *last;
unsigned int bb_idx = 0;

last = func_last_bb(func);
last->tail = func->end;
Expand All @@ -205,6 +241,23 @@ static void func_partition_bb_tail(struct func_node *func)
func->bb_num = bb_idx;
}

static bool func_add_special_bb(struct func_node *func)
{
struct bb_node *bb;

bb = func_insert_dummy_bb(&func->bbs);
if (!bb)
return true;
bb->idx = ENTRY_BLOCK_INDEX;

bb = func_insert_dummy_bb(&func_last_bb(func)->l);
if (!bb)
return true;
bb->idx = EXIT_BLOCK_INDEX;

return false;
}

static bool func_partition_bb(struct func_node *func)
{
if (func_partition_bb_head(func))
Expand All @@ -215,6 +268,96 @@ static bool func_partition_bb(struct func_node *func)
return false;
}

static struct bb_node *func_search_bb_with_head(struct func_node *func,
struct bpf_insn *insn)
{
struct bb_node *bb;

list_for_each_entry(bb, &func->bbs, l) {
if (bb->head == insn)
return bb;
}

return NULL;
}

static struct edge_node *new_edge(struct bb_node *src, struct bb_node *dst,
int flags)
{
struct edge_node *e;

e = calloc(1, sizeof(*e));
if (!e) {
p_err("OOM when allocating edge node");
return NULL;
}

if (src)
e->src = src;
if (dst)
e->dst = dst;

e->flags |= flags;

return e;
}

static bool func_add_bb_edges(struct func_node *func)
{
struct bpf_insn *insn;
struct edge_node *e;
struct bb_node *bb;

bb = entry_bb(func);
e = new_edge(bb, bb_next(bb), EDGE_FLAG_FALLTHROUGH);
if (!e)
return true;
list_add_tail(&e->l, &bb->e_succs);

bb = exit_bb(func);
e = new_edge(bb_prev(bb), bb, EDGE_FLAG_FALLTHROUGH);
if (!e)
return true;
list_add_tail(&e->l, &bb->e_prevs);

bb = entry_bb(func);
bb = bb_next(bb);
list_for_each_entry_from(bb, &exit_bb(func)->l, l) {
e = new_edge(bb, NULL, EDGE_FLAG_EMPTY);
if (!e)
return true;
e->src = bb;

insn = bb->tail;
if (BPF_CLASS(insn->code) != BPF_JMP ||
BPF_OP(insn->code) == BPF_EXIT) {
e->dst = bb_next(bb);
e->flags |= EDGE_FLAG_FALLTHROUGH;
list_add_tail(&e->l, &bb->e_succs);
continue;
} else if (BPF_OP(insn->code) == BPF_JA) {
e->dst = func_search_bb_with_head(func,
insn + insn->off + 1);
e->flags |= EDGE_FLAG_JUMP;
list_add_tail(&e->l, &bb->e_succs);
continue;
}

e->dst = bb_next(bb);
e->flags |= EDGE_FLAG_FALLTHROUGH;
list_add_tail(&e->l, &bb->e_succs);

e = new_edge(bb, NULL, EDGE_FLAG_JUMP);
if (!e)
return true;
e->src = bb;
e->dst = func_search_bb_with_head(func, insn + insn->off + 1);
list_add_tail(&e->l, &bb->e_succs);
}

return false;
}

static bool cfg_build(struct cfg *cfg, struct bpf_insn *insn, unsigned int len)
{
int cnt = len / sizeof(*insn);
Expand All @@ -226,7 +369,10 @@ static bool cfg_build(struct cfg *cfg, struct bpf_insn *insn, unsigned int len)
return true;

list_for_each_entry(func, &cfg->funcs, l) {
if (func_partition_bb(func))
if (func_partition_bb(func) || func_add_special_bb(func))
return true;

if (func_add_bb_edges(func))
return true;
}

Expand All @@ -241,6 +387,18 @@ static void cfg_destroy(struct cfg *cfg)
struct bb_node *bb, *bb2;

list_for_each_entry_safe(bb, bb2, &func->bbs, l) {
struct edge_node *e, *e2;

list_for_each_entry_safe(e, e2, &bb->e_prevs, l) {
list_del(&e->l);
free(e);
}

list_for_each_entry_safe(e, e2, &bb->e_succs, l) {
list_del(&e->l);
free(e);
}

list_del(&bb->l);
free(bb);
}
Expand Down

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