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bpf: Change uapi for bpf iterator map elements

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Commit a5cbe05a66 ("bpf: Implement bpf iterator for
map elements") added bpf iterator support for
map elements. The map element bpf iterator requires
info to identify a particular map. In the above
commit, the attr->link_create.target_fd is used
to carry map_fd and an enum bpf_iter_link_info
is added to uapi to specify the target_fd actually
representing a map_fd:
    enum bpf_iter_link_info {
	BPF_ITER_LINK_UNSPEC = 0,
	BPF_ITER_LINK_MAP_FD = 1,

	MAX_BPF_ITER_LINK_INFO,
    };

This is an extensible approach as we can grow
enumerator for pid, cgroup_id, etc. and we can
unionize target_fd for pid, cgroup_id, etc.
But in the future, there are chances that
more complex customization may happen, e.g.,
for tasks, it could be filtered based on
both cgroup_id and user_id.

This patch changed the uapi to have fields
	__aligned_u64	iter_info;
	__u32		iter_info_len;
for additional iter_info for link_create.
The iter_info is defined as
	union bpf_iter_link_info {
		struct {
			__u32   map_fd;
		} map;
	};

So future extension for additional customization
will be easier. The bpf_iter_link_info will be
passed to target callback to validate and generic
bpf_iter framework does not need to deal it any
more.

Note that map_fd = 0 will be considered invalid
and -EBADF will be returned to user space.

Fixes: a5cbe05a66 ("bpf: Implement bpf iterator for map elements")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200805055056.1457463-1-yhs@fb.com
This commit is contained in:
Yonghong Song
2020-08-04 22:50:56 -07:00
committed by Alexei Starovoitov
parent 6bcaf41f96
commit 5e7b30205c
6 changed files with 102 additions and 57 deletions
Download Patch File Download Diff File Expand all files Collapse all files

58
kernel/bpf/bpf_iter.c
View File

@@ -338,8 +338,8 @@ static void bpf_iter_link_release(struct bpf_link *link)
struct bpf_iter_link *iter_link =
container_of(link, struct bpf_iter_link, link);
if (iter_link->aux.map)
bpf_map_put_with_uref(iter_link->aux.map);
if (iter_link->tinfo->reg_info->detach_target)
iter_link->tinfo->reg_info->detach_target(&iter_link->aux);
}
static void bpf_iter_link_dealloc(struct bpf_link *link)
@@ -390,15 +390,35 @@ bool bpf_link_is_iter(struct bpf_link *link)
int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
union bpf_iter_link_info __user *ulinfo;
struct bpf_link_primer link_primer;
struct bpf_iter_target_info *tinfo;
struct bpf_iter_aux_info aux = {};
union bpf_iter_link_info linfo;
struct bpf_iter_link *link;
u32 prog_btf_id, target_fd;
u32 prog_btf_id, linfo_len;
bool existed = false;
struct bpf_map *map;
int err;
if (attr->link_create.target_fd || attr->link_create.flags)
return -EINVAL;
memset(&linfo, 0, sizeof(union bpf_iter_link_info));
ulinfo = u64_to_user_ptr(attr->link_create.iter_info);
linfo_len = attr->link_create.iter_info_len;
if (!ulinfo ^ !linfo_len)
return -EINVAL;
if (ulinfo) {
err = bpf_check_uarg_tail_zero(ulinfo, sizeof(linfo),
linfo_len);
if (err)
return err;
linfo_len = min_t(u32, linfo_len, sizeof(linfo));
if (copy_from_user(&linfo, ulinfo, linfo_len))
return -EFAULT;
}
prog_btf_id = prog->aux->attach_btf_id;
mutex_lock(&targets_mutex);
list_for_each_entry(tinfo, &targets, list) {
@@ -411,13 +431,6 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
if (!existed)
return -ENOENT;
/* Make sure user supplied flags are target expected. */
target_fd = attr->link_create.target_fd;
if (attr->link_create.flags != tinfo->reg_info->req_linfo)
return -EINVAL;
if (!attr->link_create.flags && target_fd)
return -EINVAL;
link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
if (!link)
return -ENOMEM;
@@ -431,28 +444,15 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
return err;
}
if (tinfo->reg_info->req_linfo == BPF_ITER_LINK_MAP_FD) {
map = bpf_map_get_with_uref(target_fd);
if (IS_ERR(map)) {
err = PTR_ERR(map);
goto cleanup_link;
}
aux.map = map;
err = tinfo->reg_info->check_target(prog, &aux);
if (tinfo->reg_info->attach_target) {
err = tinfo->reg_info->attach_target(prog, &linfo, &link->aux);
if (err) {
bpf_map_put_with_uref(map);
goto cleanup_link;
bpf_link_cleanup(&link_primer);
return err;
}
link->aux.map = map;
}
return bpf_link_settle(&link_primer);
cleanup_link:
bpf_link_cleanup(&link_primer);
return err;
}
static void init_seq_meta(struct bpf_iter_priv_data *priv_data,