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Date: Wed, 10 Jul 2019 10:50:30 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Jiong Wang <jiong.wang@...ronome.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
Daniel Borkmann <daniel@...earbox.net>,
Edward Cree <ecree@...arflare.com>,
"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
Andrii Nakryiko <andriin@...com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
oss-drivers@...ronome.com
Subject: Re: [RFC bpf-next 2/8] bpf: extend list based insn patching infra to
verification layer
On Thu, Jul 4, 2019 at 2:32 PM Jiong Wang <jiong.wang@...ronome.com> wrote:
>
> Verification layer also needs to handle auxiliar info as well as adjusting
> subprog start.
>
> At this layer, insns inside patch buffer could be jump, but they should
> have been resolved, meaning they shouldn't jump to insn outside of the
> patch buffer. Lineration function for this layer won't touch insns inside
> patch buffer.
>
> Adjusting subprog is finished along with adjusting jump target when the
> input will cover bpf to bpf call insn, re-register subprog start is cheap.
> But adjustment when there is insn deleteion is not considered yet.
>
> Signed-off-by: Jiong Wang <jiong.wang@...ronome.com>
> ---
> kernel/bpf/verifier.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 150 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index a2e7637..2026d64 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -8350,6 +8350,156 @@ static void opt_hard_wire_dead_code_branches(struct bpf_verifier_env *env)
> }
> }
>
> +/* Linearize bpf list insn to array (verifier layer). */
> +static struct bpf_verifier_env *
> +verifier_linearize_list_insn(struct bpf_verifier_env *env,
> + struct bpf_list_insn *list)
It's unclear why this returns env back? It's not allocating a new env,
so it's weird and unnecessary. Just return error code.
> +{
> + u32 *idx_map, idx, orig_cnt, fini_cnt = 0;
> + struct bpf_subprog_info *new_subinfo;
> + struct bpf_insn_aux_data *new_data;
> + struct bpf_prog *prog = env->prog;
> + struct bpf_verifier_env *ret_env;
> + struct bpf_insn *insns, *insn;
> + struct bpf_list_insn *elem;
> + int ret;
> +
> + /* Calculate final size. */
> + for (elem = list; elem; elem = elem->next)
> + if (!(elem->flag & LIST_INSN_FLAG_REMOVED))
> + fini_cnt++;
> +
> + orig_cnt = prog->len;
> + insns = prog->insnsi;
> + /* If prog length remains same, nothing else to do. */
> + if (fini_cnt == orig_cnt) {
> + for (insn = insns, elem = list; elem; elem = elem->next, insn++)
> + *insn = elem->insn;
> + return env;
> + }
> + /* Realloc insn buffer when necessary. */
> + if (fini_cnt > orig_cnt)
> + prog = bpf_prog_realloc(prog, bpf_prog_size(fini_cnt),
> + GFP_USER);
> + if (!prog)
> + return ERR_PTR(-ENOMEM);
> + insns = prog->insnsi;
> + prog->len = fini_cnt;
> + ret_env = env;
> +
> + /* idx_map[OLD_IDX] = NEW_IDX */
> + idx_map = kvmalloc(orig_cnt * sizeof(u32), GFP_KERNEL);
> + if (!idx_map)
> + return ERR_PTR(-ENOMEM);
> + memset(idx_map, 0xff, orig_cnt * sizeof(u32));
> +
> + /* Use the same alloc method used when allocating env->insn_aux_data. */
> + new_data = vzalloc(array_size(sizeof(*new_data), fini_cnt));
> + if (!new_data) {
> + kvfree(idx_map);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + /* Copy over insn + calculate idx_map. */
> + for (idx = 0, elem = list; elem; elem = elem->next) {
> + int orig_idx = elem->orig_idx - 1;
> +
> + if (orig_idx >= 0) {
> + idx_map[orig_idx] = idx;
> +
> + if (elem->flag & LIST_INSN_FLAG_REMOVED)
> + continue;
> +
> + new_data[idx] = env->insn_aux_data[orig_idx];
> +
> + if (elem->flag & LIST_INSN_FLAG_PATCHED)
> + new_data[idx].zext_dst =
> + insn_has_def32(env, &elem->insn);
> + } else {
> + new_data[idx].seen = true;
> + new_data[idx].zext_dst = insn_has_def32(env,
> + &elem->insn);
> + }
> + insns[idx++] = elem->insn;
> + }
> +
> + new_subinfo = kvzalloc(sizeof(env->subprog_info), GFP_KERNEL);
> + if (!new_subinfo) {
> + kvfree(idx_map);
> + vfree(new_data);
> + return ERR_PTR(-ENOMEM);
> + }
> + memcpy(new_subinfo, env->subprog_info, sizeof(env->subprog_info));
> + memset(env->subprog_info, 0, sizeof(env->subprog_info));
> + env->subprog_cnt = 0;
> + env->prog = prog;
> + ret = add_subprog(env, 0);
> + if (ret < 0) {
> + ret_env = ERR_PTR(ret);
> + goto free_all_ret;
> + }
> + /* Relocate jumps using idx_map.
> + * old_dst = jmp_insn.old_target + old_pc + 1;
> + * new_dst = idx_map[old_dst] = jmp_insn.new_target + new_pc + 1;
> + * jmp_insn.new_target = new_dst - new_pc - 1;
> + */
> + for (idx = 0, elem = list; elem; elem = elem->next) {
> + int orig_idx = elem->orig_idx;
> +
> + if (elem->flag & LIST_INSN_FLAG_REMOVED)
> + continue;
> + if ((elem->flag & LIST_INSN_FLAG_PATCHED) || !orig_idx) {
> + idx++;
> + continue;
> + }
> +
> + ret = bpf_jit_adj_imm_off(&insns[idx], orig_idx - 1, idx,
> + idx_map);
> + if (ret < 0) {
> + ret_env = ERR_PTR(ret);
> + goto free_all_ret;
> + }
> + /* Recalculate subprog start as we are at bpf2bpf call insn. */
> + if (ret > 0) {
> + ret = add_subprog(env, idx + insns[idx].imm + 1);
> + if (ret < 0) {
> + ret_env = ERR_PTR(ret);
> + goto free_all_ret;
> + }
> + }
> + idx++;
> + }
> + if (ret < 0) {
> + ret_env = ERR_PTR(ret);
> + goto free_all_ret;
> + }
> +
> + env->subprog_info[env->subprog_cnt].start = fini_cnt;
> + for (idx = 0; idx <= env->subprog_cnt; idx++)
> + new_subinfo[idx].start = env->subprog_info[idx].start;
> + memcpy(env->subprog_info, new_subinfo, sizeof(env->subprog_info));
> +
> + /* Adjust linfo.
> + * FIXME: no support for insn removal at the moment.
> + */
> + if (prog->aux->nr_linfo) {
> + struct bpf_line_info *linfo = prog->aux->linfo;
> + u32 nr_linfo = prog->aux->nr_linfo;
> +
> + for (idx = 0; idx < nr_linfo; idx++)
> + linfo[idx].insn_off = idx_map[linfo[idx].insn_off];
> + }
> + vfree(env->insn_aux_data);
> + env->insn_aux_data = new_data;
> + goto free_mem_list_ret;
> +free_all_ret:
> + vfree(new_data);
> +free_mem_list_ret:
> + kvfree(new_subinfo);
> + kvfree(idx_map);
> + return ret_env;
> +}
> +
> static int opt_remove_dead_code(struct bpf_verifier_env *env)
> {
> struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
> --
> 2.7.4
>
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