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
This commit is contained in:
Yonghong Song 2020-05-09 10:59:00 -07:00 committed by Alexei Starovoitov
parent ae24345da5
commit 15d83c4d7c
5 changed files with 62 additions and 0 deletions

View File

@ -1127,6 +1127,8 @@ struct bpf_link *bpf_link_get_from_fd(u32 ufd);
int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
int bpf_obj_get_user(const char __user *pathname, int flags);
#define BPF_ITER_FUNC_PREFIX "__bpf_iter__"
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data);
typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
@ -1140,6 +1142,7 @@ struct bpf_iter_reg {
int bpf_iter_reg_target(struct bpf_iter_reg *reg_info);
void bpf_iter_unreg_target(const char *target);
bool bpf_iter_prog_supported(struct bpf_prog *prog);
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);

View File

@ -218,6 +218,7 @@ enum bpf_attach_type {
BPF_TRACE_FEXIT,
BPF_MODIFY_RETURN,
BPF_LSM_MAC,
BPF_TRACE_ITER,
__MAX_BPF_ATTACH_TYPE
};

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@ -12,6 +12,7 @@ struct bpf_iter_target_info {
bpf_iter_init_seq_priv_t init_seq_private;
bpf_iter_fini_seq_priv_t fini_seq_private;
u32 seq_priv_size;
u32 btf_id; /* cached value */
};
static struct list_head targets = LIST_HEAD_INIT(targets);
@ -57,3 +58,38 @@ void bpf_iter_unreg_target(const char *target)
WARN_ON(found == false);
}
static void cache_btf_id(struct bpf_iter_target_info *tinfo,
struct bpf_prog *prog)
{
tinfo->btf_id = prog->aux->attach_btf_id;
}
bool bpf_iter_prog_supported(struct bpf_prog *prog)
{
const char *attach_fname = prog->aux->attach_func_name;
u32 prog_btf_id = prog->aux->attach_btf_id;
const char *prefix = BPF_ITER_FUNC_PREFIX;
struct bpf_iter_target_info *tinfo;
int prefix_len = strlen(prefix);
bool supported = false;
if (strncmp(attach_fname, prefix, prefix_len))
return false;
mutex_lock(&targets_mutex);
list_for_each_entry(tinfo, &targets, list) {
if (tinfo->btf_id && tinfo->btf_id == prog_btf_id) {
supported = true;
break;
}
if (!strcmp(attach_fname + prefix_len, tinfo->target)) {
cache_btf_id(tinfo, prog);
supported = true;
break;
}
}
mutex_unlock(&targets_mutex);
return supported;
}

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@ -7101,6 +7101,10 @@ static int check_return_code(struct bpf_verifier_env *env)
return 0;
range = tnum_const(0);
break;
case BPF_PROG_TYPE_TRACING:
if (env->prog->expected_attach_type != BPF_TRACE_ITER)
return 0;
break;
default:
return 0;
}
@ -10481,6 +10485,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
struct bpf_prog *tgt_prog = prog->aux->linked_prog;
u32 btf_id = prog->aux->attach_btf_id;
const char prefix[] = "btf_trace_";
struct btf_func_model fmodel;
int ret = 0, subprog = -1, i;
struct bpf_trampoline *tr;
const struct btf_type *t;
@ -10622,6 +10627,22 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
prog->aux->attach_func_proto = t;
prog->aux->attach_btf_trace = true;
return 0;
case BPF_TRACE_ITER:
if (!btf_type_is_func(t)) {
verbose(env, "attach_btf_id %u is not a function\n",
btf_id);
return -EINVAL;
}
t = btf_type_by_id(btf, t->type);
if (!btf_type_is_func_proto(t))
return -EINVAL;
prog->aux->attach_func_name = tname;
prog->aux->attach_func_proto = t;
if (!bpf_iter_prog_supported(prog))
return -EINVAL;
ret = btf_distill_func_proto(&env->log, btf, t,
tname, &fmodel);
return ret;
default:
if (!prog_extension)
return -EINVAL;

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@ -218,6 +218,7 @@ enum bpf_attach_type {
BPF_TRACE_FEXIT,
BPF_MODIFY_RETURN,
BPF_LSM_MAC,
BPF_TRACE_ITER,
__MAX_BPF_ATTACH_TYPE
};