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bpf: Introduce pinnable bpf_link abstraction

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Introduce bpf_link abstraction, representing an attachment of BPF program to
a BPF hook point (e.g., tracepoint, perf event, etc). bpf_link encapsulates
ownership of attached BPF program, reference counting of a link itself, when
reference from multiple anonymous inodes, as well as ensures that release
callback will be called from a process context, so that users can safely take
mutex locks and sleep.

Additionally, with a new abstraction it's now possible to generalize pinning
of a link object in BPF FS, allowing to explicitly prevent BPF program
detachment on process exit by pinning it in a BPF FS and let it open from
independent other process to keep working with it.

Convert two existing bpf_link-like objects (raw tracepoint and tracing BPF
program attachments) into utilizing bpf_link framework, making them pinnable
in BPF FS. More FD-based bpf_links will be added in follow up patches.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-2-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-03-02 20:31:57 -08:00 • committed by Alexei Starovoitov
parent 775a2be52d
commit 70ed506c3b
3 changed files with 237 additions and 51 deletions
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13
include/linux/bpf.h
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@ -1056,6 +1056,19 @@ extern int sysctl_unprivileged_bpf_disabled;
int bpf_map_new_fd(struct bpf_map *map, int flags);
int bpf_prog_new_fd(struct bpf_prog *prog);
struct bpf_link;
struct bpf_link_ops {
void (*release)(struct bpf_link *link);
};
void bpf_link_init(struct bpf_link *link, const struct bpf_link_ops *ops,
struct bpf_prog *prog);
void bpf_link_inc(struct bpf_link *link);
void bpf_link_put(struct bpf_link *link);
int bpf_link_new_fd(struct bpf_link *link);
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);