From 52875a04f4b26e7ef30a288ea096f7cfec0e93cd Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Tue, 22 Jan 2019 22:45:20 -0800 Subject: bpf: verifier: remove dead code Instead of overwriting dead code with jmp -1 instructions remove it completely for root. Adjust verifier state and line info appropriately. v2: - adjust func_info (Alexei); - make sure first instruction retains line info (Alexei). v4: (Yonghong) - remove unnecessary if (!insn to remove) checks; - always keep last line info if first live instruction lacks one. v5: (Martin Lau) - improve and clarify comments. Signed-off-by: Jakub Kicinski Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov --- kernel/bpf/core.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'kernel/bpf/core.c') diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index ad08ba341197..2a81b8af3748 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -462,6 +462,18 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off, return prog_adj; } +int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt) +{ + /* Branch offsets can't overflow when program is shrinking, no need + * to call bpf_adj_branches(..., true) here + */ + memmove(prog->insnsi + off, prog->insnsi + off + cnt, + sizeof(struct bpf_insn) * (prog->len - off - cnt)); + prog->len -= cnt; + + return WARN_ON_ONCE(bpf_adj_branches(prog, off, off + cnt, off, false)); +} + void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp) { int i; -- cgit v1.2.3