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bpf: Allow loading of a bpf_iter program
A bpf_iter program is a tracing program with attach type BPF_TRACE_ITER. The load attribute attach_btf_id is used by the verifier against a particular kernel function, which represents a target, e.g., __bpf_iter__bpf_map for target bpf_map which is implemented later. The program return value must be 0 or 1 for now. 0 : successful, except potential seq_file buffer overflow which is handled by seq_file reader. 1 : request to restart the same object In the future, other return values may be used for filtering or teminating the iterator. Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20200509175900.2474947-1-yhs@fb.com
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@ -1127,6 +1127,8 @@ struct bpf_link *bpf_link_get_from_fd(u32 ufd);
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int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
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int bpf_obj_get_user(const char __user *pathname, int flags);
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#define BPF_ITER_FUNC_PREFIX "__bpf_iter__"
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typedef int (*bpf_iter_init_seq_priv_t)(void *private_data);
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typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
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@ -1140,6 +1142,7 @@ struct bpf_iter_reg {
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int bpf_iter_reg_target(struct bpf_iter_reg *reg_info);
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void bpf_iter_unreg_target(const char *target);
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bool bpf_iter_prog_supported(struct bpf_prog *prog);
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int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
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int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
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@ -218,6 +218,7 @@ enum bpf_attach_type {
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BPF_TRACE_FEXIT,
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BPF_MODIFY_RETURN,
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BPF_LSM_MAC,
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BPF_TRACE_ITER,
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__MAX_BPF_ATTACH_TYPE
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};
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@ -12,6 +12,7 @@ struct bpf_iter_target_info {
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bpf_iter_init_seq_priv_t init_seq_private;
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bpf_iter_fini_seq_priv_t fini_seq_private;
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u32 seq_priv_size;
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u32 btf_id; /* cached value */
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};
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static struct list_head targets = LIST_HEAD_INIT(targets);
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@ -57,3 +58,38 @@ void bpf_iter_unreg_target(const char *target)
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WARN_ON(found == false);
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}
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static void cache_btf_id(struct bpf_iter_target_info *tinfo,
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struct bpf_prog *prog)
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{
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tinfo->btf_id = prog->aux->attach_btf_id;
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}
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bool bpf_iter_prog_supported(struct bpf_prog *prog)
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{
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const char *attach_fname = prog->aux->attach_func_name;
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u32 prog_btf_id = prog->aux->attach_btf_id;
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const char *prefix = BPF_ITER_FUNC_PREFIX;
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struct bpf_iter_target_info *tinfo;
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int prefix_len = strlen(prefix);
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bool supported = false;
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if (strncmp(attach_fname, prefix, prefix_len))
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return false;
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mutex_lock(&targets_mutex);
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list_for_each_entry(tinfo, &targets, list) {
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if (tinfo->btf_id && tinfo->btf_id == prog_btf_id) {
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supported = true;
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break;
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}
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if (!strcmp(attach_fname + prefix_len, tinfo->target)) {
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cache_btf_id(tinfo, prog);
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supported = true;
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break;
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}
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}
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mutex_unlock(&targets_mutex);
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return supported;
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}
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@ -7101,6 +7101,10 @@ static int check_return_code(struct bpf_verifier_env *env)
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return 0;
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range = tnum_const(0);
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break;
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case BPF_PROG_TYPE_TRACING:
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if (env->prog->expected_attach_type != BPF_TRACE_ITER)
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return 0;
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break;
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default:
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return 0;
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}
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@ -10481,6 +10485,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
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struct bpf_prog *tgt_prog = prog->aux->linked_prog;
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u32 btf_id = prog->aux->attach_btf_id;
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const char prefix[] = "btf_trace_";
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struct btf_func_model fmodel;
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int ret = 0, subprog = -1, i;
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struct bpf_trampoline *tr;
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const struct btf_type *t;
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@ -10622,6 +10627,22 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
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prog->aux->attach_func_proto = t;
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prog->aux->attach_btf_trace = true;
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return 0;
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case BPF_TRACE_ITER:
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if (!btf_type_is_func(t)) {
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verbose(env, "attach_btf_id %u is not a function\n",
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btf_id);
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return -EINVAL;
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}
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t = btf_type_by_id(btf, t->type);
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if (!btf_type_is_func_proto(t))
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return -EINVAL;
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prog->aux->attach_func_name = tname;
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prog->aux->attach_func_proto = t;
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if (!bpf_iter_prog_supported(prog))
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return -EINVAL;
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ret = btf_distill_func_proto(&env->log, btf, t,
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tname, &fmodel);
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return ret;
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default:
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if (!prog_extension)
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return -EINVAL;
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@ -218,6 +218,7 @@ enum bpf_attach_type {
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BPF_TRACE_FEXIT,
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BPF_MODIFY_RETURN,
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BPF_LSM_MAC,
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BPF_TRACE_ITER,
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__MAX_BPF_ATTACH_TYPE
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};
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