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bpf: Allow loading of a bpf_iter program

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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
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36
kernel/bpf/bpf_iter.c
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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;
}