From 0824611f9b38d556327916ed0702a7323a88c58b Mon Sep 17 00:00:00 2001 From: Jiong Wang Date: Thu, 1 Mar 2018 18:01:19 -0800 Subject: [PATCH] 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: Jiong Wang Acked-by: Jakub Kicinski Signed-off-by: Alexei Starovoitov --- tools/bpf/bpftool/cfg.c | 118 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 117 insertions(+), 1 deletion(-) diff --git a/tools/bpf/bpftool/cfg.c b/tools/bpf/bpftool/cfg.c index 8330dedb3576..152df904d421 100644 --- a/tools/bpf/bpftool/cfg.c +++ b/tools/bpf/bpftool/cfg.c @@ -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); } -- GitLab