bpf: table based bpf_insn_successors()

Converting bpf_insn_successors() to use lookup table makes it ~1.5
times faster.

Also remove unnecessary conditionals:
- `idx + 1 < prog->len` is unnecessary because after check_cfg() all
  jump targets are guaranteed to be within a program;
- `i == 0 || succ[0] != dst` is unnecessary because any client of
  bpf_insn_successors() can handle duplicate edges:
  - compute_live_registers()
  - compute_scc()

Moving bpf_insn_successors() to liveness.c allows its inlining in
liveness.c:__update_stack_liveness().
Such inlining speeds up __update_stack_liveness() by ~40%.
bpf_insn_successors() is used in both verifier.c and liveness.c.
perf shows such move does not negatively impact users in verifier.c,
as these are executed only once before main varification pass.
Unlike __update_stack_liveness() which can be triggered multiple
times.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250918-callchain-sensitive-liveness-v3-10-c3cd27bacc60@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c7515da8500c..4c497e839526 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -1049,6 +1049,7 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
 		      u32 frameno);
 
 struct bpf_subprog_info *bpf_find_containing_subprog(struct bpf_verifier_env *env, int off);
+int bpf_jmp_offset(struct bpf_insn *insn);
 int bpf_insn_successors(struct bpf_prog *prog, u32 idx, u32 succ[2]);
 void bpf_fmt_stack_mask(char *buf, ssize_t buf_sz, u64 stack_mask);
 bool bpf_calls_callback(struct bpf_verifier_env *env, int insn_idx);