Add functions to pretty print the CFG and DOM table. We can also
add contrib scripts to print this dot format so tools can visualize
them. I at least found this helpful. Will add scripts in tools/bpf
follow up patch.
For development we are always printing these but should put these
noisy routines behind a verbose bit and/or only print when an error
has occured in bounded-loop logic.
Signed-off-by: John Fastabend <john.fastab...@gmail.com>
---
kernel/bpf/cfg.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
kernel/bpf/cfg.h | 5 +++++
kernel/bpf/verifier.c | 2 ++
3 files changed, 61 insertions(+)
diff --git a/kernel/bpf/cfg.c b/kernel/bpf/cfg.c
index c67541c..0d50646 100644
--- a/kernel/bpf/cfg.c
+++ b/kernel/bpf/cfg.c
@@ -62,6 +62,60 @@ static struct bb_node *bb_next(struct cfg_node_allocator
*allocator,
return (struct bb_node *)cfg_node_delink(allocator, &bb->link);
}
+void cfg_pretty_print(struct bpf_verifier_env *env,
+ struct cfg_node_allocator *allocator,
+ struct bpf_subprog_info *subprog)
+{
+ void **bb_list = (void **)&subprog->bbs;
+ struct bb_node *bb, *exit_bb;
+
+ bb = entry_bb(bb_list);
+ exit_bb = exit_bb(bb_list);
+
+ bpf_verifier_log_write(env, "CFG: ");
+ while (bb && bb != exit_bb) {
+ struct bb_node *next_bb = bb_next(allocator, bb);
+ struct edge_node *e;
+
+ e = cfg_node_delink(allocator, &bb->e_succs);
+ while (e) {
+ struct bb_node *dst = e->dst;
+ int tail = next_bb->head - 1;
+ struct bb_node *dst_next;
+ int dst_tail;
+
+ dst_next = bb_next(allocator, dst);
+ dst_tail = dst_next ? dst_next->head - 1 : 65534;
+
+ bpf_verifier_log_write(env, " %i[%i,%i] -> %i[%i,%i] ",
+ bb->idx, bb->head, tail,
dst->idx, dst->head, dst_tail);
+ e = cfg_node_delink(allocator, &e->link);
+ }
+ bb = bb_next(allocator, bb);
+ }
+ bpf_verifier_log_write(env, "\n");
+}
+
+void dom_pretty_print(struct bpf_verifier_env *env,
+ struct bpf_subprog_info *subprog)
+{
+ int lane_len, bb_num = subprog->bb_num - 2;
+ int i, j;
+
+ lane_len = BITS_TO_LONGS(bb_num);
+
+ bpf_verifier_log_write(env, "DOM:\n");
+ for (i = 0; i < bb_num; i++) {
+ for (j = 0; j < bb_num; j++) {
+ bpf_verifier_log_write(env, " %i ",
+ test_bit(j,
+ subprog->dtree + i * lane_len) ? 1 : 0);
+ }
+ bpf_verifier_log_write(env, "\n");
+ }
+ bpf_verifier_log_write(env, "\n");
+}
+
struct dom_info {
u16 *dfs_parent;
u16 *dfs_order;
diff --git a/kernel/bpf/cfg.h b/kernel/bpf/cfg.h
index 8363406..44dcabb 100644
--- a/kernel/bpf/cfg.h
+++ b/kernel/bpf/cfg.h
@@ -37,6 +37,11 @@ bool subprog_has_loop(struct cfg_node_allocator *allocator,
struct bpf_subprog_info *subprog);
int subprog_has_irreduciable_loop(struct cfg_node_allocator *allocator,
struct bpf_subprog_info *subprog);
+void cfg_pretty_print(struct bpf_verifier_env *env,
+ struct cfg_node_allocator *allocator,
+ struct bpf_subprog_info *subprog);
+void dom_pretty_print(struct bpf_verifier_env *env,
+ struct bpf_subprog_info *subprog);
int subprog_init_bb(struct cfg_node_allocator *allocator, void **bb_list,
int subprog_start, int subprog_end);
void subprog_free(struct bpf_subprog_info *subprog, int end_idx);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 49895f3..610559a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -913,6 +913,8 @@ static int check_subprogs(struct bpf_verifier_env *env)
&subprog[cur_subprog]);
if (ret < 0)
goto free_nodes;
+ cfg_pretty_print(env, &allocator,
&subprog[cur_subprog]);
+ dom_pretty_print(env, &subprog[cur_subprog]);
ret = subprog_has_irreduciable_loop(&allocator,
&subprog[cur_subprog]);
if (ret < 0)
