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  1. 09 Mar, 2020 9 commits
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  7. 03 Mar, 2020 6 commits
    • Alexei Starovoitov's avatar
      Merge branch 'bpf_link' · abbc61a5
      Alexei Starovoitov authored 
      Andrii Nakryiko says:

====================
This patch series adds bpf_link abstraction, analogous to libbpf's already
existing bpf_link abstraction. This formalizes and makes more uniform existing
bpf_link-like BPF program link (attachment) types (raw tracepoint and tracing
links), which are FD-based objects that are automatically detached when last
file reference is closed. These types of BPF program links are switched to
using bpf_link framework.

FD-based bpf_link approach provides great safety guarantees, by ensuring there
is not going to be an abandoned BPF program attached, if user process suddenly
exits or forgets to clean up after itself. This is especially important in
production environment and is what all the recent new BPF link types followed.

One of the previously existing  inconveniences of FD-based approach, though,
was the scenario in which user process wants to install BPF link and exit, but
let attached BPF program run. Now, with bpf_link abstraction in place, it's
easy to support pinning links in BPF FS, which is done as part of the same
patch #1. This allows FD-based BPF program links to survive exit of a user
process and original file descriptor being closed, by creating an file entry
in BPF FS. This provides great safety by default, with simple way to opt out
for cases where it's needed.

Corresponding libbpf APIs are added in the same patch set, as well as
selftests for this functionality.

Other types of BPF program attachments (XDP, cgroup, perf_event, etc) are
going to be converted in subsequent patches to follow similar approach.

v1->v2:
- use bpf_link_new_fd() uniformly (Alexei).
====================
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      abbc61a5
    • Andrii Nakryiko's avatar
      selftests/bpf: Add link pinning selftests · 6489b8e1
      Andrii Nakryiko authored 
      Add selftests validating link pinning/unpinning and associated BPF link
(attachment) lifetime.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-4-andriin@fb.com
      6489b8e1
    • Andrii Nakryiko's avatar
      libbpf: Add bpf_link pinning/unpinning · c016b68e
      Andrii Nakryiko authored 
      With bpf_link abstraction supported by kernel explicitly, add
pinning/unpinning API for links. Also allow to create (open) bpf_link from BPF
FS file.

This API allows to have an "ephemeral" FD-based BPF links (like raw tracepoint
or fexit/freplace attachments) surviving user process exit, by pinning them in
a BPF FS, which is an important use case for long-running BPF programs.

As part of this, expose underlying FD for bpf_link. While legacy bpf_link's
might not have a FD associated with them (which will be expressed as
a bpf_link with fd=-1), kernel's abstraction is based around FD-based usage,
so match it closely. This, subsequently, allows to have a generic
pinning/unpinning API for generalized bpf_link. For some types of bpf_links
kernel might not support pinning, in which case bpf_link__pin() will return
error.

With FD being part of generic bpf_link, also get rid of bpf_link_fd in favor
of using vanialla bpf_link.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-3-andriin@fb.com
      c016b68e
    • Andrii Nakryiko's avatar
      bpf: Introduce pinnable bpf_link abstraction · 70ed506c
      Andrii Nakryiko authored 
      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: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-2-andriin@fb.com
      70ed506c
    • Toke Høiland-Jørgensen's avatar
      selftests/bpf: Declare bpf_log_buf variables as static · 775a2be5
      Toke Høiland-Jørgensen authored 
      The cgroup selftests did not declare the bpf_log_buf variable as static, leading
to a linker error with GCC 10 (which defaults to -fno-common). Fix this by
adding the missing static declarations.

Fixes: 257c8855 ("selftests/bpf: Convert test_cgroup_attach to prog_tests")
Signed-off-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrey Ignatov <rdna@fb.com>
Link: https://lore.kernel.org/bpf/20200302145348.559177-1-toke@redhat.com
      775a2be5
    • Andrii Nakryiko's avatar
      bpf: Reliably preserve btf_trace_xxx types · 441420a1
      Andrii Nakryiko authored 
      btf_trace_xxx types, crucial for tp_btf BPF programs (raw tracepoint with
verifier-checked direct memory access), have to be preserved in kernel BTF to
allow verifier do its job and enforce type/memory safety. It was reported
([0]) that for kernels built with Clang current type-casting approach doesn't
preserve these types.

This patch fixes it by declaring an anonymous union for each registered
tracepoint, capturing both struct bpf_raw_event_map information, as well as
recording btf_trace_##call type reliably. Structurally, it's still the same
content as for a plain struct bpf_raw_event_map, so no other changes are
necessary.

  [0] https://github.com/iovisor/bcc/issues/2770#issuecomment-591007692

Fixes: e8c423fb ("bpf: Add typecast to raw_tracepoints to help BTF generation")
Reported-by: default avatarWenbo Zhang <ethercflow@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200301081045.3491005-2-andriin@fb.com
      441420a1
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