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    • Alexei Starovoitov's avatar
      Merge branch 'bpf_link-XDP' · 47960ad6
      Alexei Starovoitov authored 
      Andrii Nakryiko says:

====================
Following cgroup and netns examples, implement bpf_link support for XDP.

The semantics is described in patch #2. Program and link attachments are
mutually exclusive, in the sense that neither link can replace attached
program nor program can replace attached link. Link can't replace attached
link as well, as is the case for any other bpf_link implementation.

Patch #1 refactors existing BPF program-based attachment API and centralizes
high-level query/attach decisions in generic kernel code, while drivers are
kept simple and are instructed with low-level decisions about attaching and
detaching specific bpf_prog. This also makes QUERY command unnecessary, and
patch #8 removes support for it from all kernel drivers. If that's a bad idea,
we can drop that patch altogether.

With refactoring in patch #1, adding bpf_xdp_link is completely transparent to
drivers, they are still functioning at the level of "effective" bpf_prog, that
should be called in XDP data path.

Corresponding libbpf support for BPF XDP link is added in patch #5.

v3->v4:
- fix a compilation warning in one of drivers (Jakub);

v2->v3:
- fix build when CONFIG_BPF_SYSCALL=n (kernel test robot);

v1->v2:
- fix prog refcounting bug (David);
- split dev_change_xdp_fd() changes into 2 patches (David);
- add extack messages to all user-induced errors (David).
====================
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      47960ad6
    • Andrii Nakryiko's avatar
      bpf, xdp: Remove XDP_QUERY_PROG and XDP_QUERY_PROG_HW XDP commands · e8407fde
      Andrii Nakryiko authored 
      Now that BPF program/link management is centralized in generic net_device
code, kernel code never queries program id from drivers, so
XDP_QUERY_PROG/XDP_QUERY_PROG_HW commands are unnecessary.

This patch removes all the implementations of those commands in kernel, along
the xdp_attachment_query().

This patch was compile-tested on allyesconfig.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-10-andriin@fb.com
      e8407fde
    • Andrii Nakryiko's avatar
      selftests/bpf: Add BPF XDP link selftests · fe48230c
      Andrii Nakryiko authored 
      Add selftest validating all the attachment logic around BPF XDP link. Test
also link updates and get_obj_info() APIs.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-9-andriin@fb.com
      fe48230c
    • Andrii Nakryiko's avatar
      libbpf: Add support for BPF XDP link · dc8698ca
      Andrii Nakryiko authored 
      Sync UAPI header and add support for using bpf_link-based XDP attachment.
Make xdp/ prog type set expected attach type. Kernel didn't enforce
attach_type for XDP programs before, so there is no backwards compatiblity
issues there.

Also fix section_names selftest to recognize that xdp prog types now have
expected attach type.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-8-andriin@fb.com
      dc8698ca
    • Andrii Nakryiko's avatar
      bpf: Implement BPF XDP link-specific introspection APIs · c1931c97
      Andrii Nakryiko authored 
      Implement XDP link-specific show_fdinfo and link_info to emit ifindex.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-7-andriin@fb.com
      c1931c97
    • Andrii Nakryiko's avatar
      bpf, xdp: Implement LINK_UPDATE for BPF XDP link · 026a4c28
      Andrii Nakryiko authored 
      Add support for LINK_UPDATE command for BPF XDP link to enable reliable
replacement of underlying BPF program.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-6-andriin@fb.com
      026a4c28
    • Andrii Nakryiko's avatar
      bpf, xdp: Add bpf_link-based XDP attachment API · aa8d3a71
      Andrii Nakryiko authored 
      Add bpf_link-based API (bpf_xdp_link) to attach BPF XDP program through
BPF_LINK_CREATE command.

bpf_xdp_link is mutually exclusive with direct BPF program attachment,
previous BPF program should be detached prior to attempting to create a new
bpf_xdp_link attachment (for a given XDP mode). Once BPF link is attached, it
can't be replaced by other BPF program attachment or link attachment. It will
be detached only when the last BPF link FD is closed.

bpf_xdp_link will be auto-detached when net_device is shutdown, similarly to
how other BPF links behave (cgroup, flow_dissector). At that point bpf_link
will become defunct, but won't be destroyed until last FD is closed.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-5-andriin@fb.com
      aa8d3a71
    • Andrii Nakryiko's avatar
      bpf, xdp: Extract common XDP program attachment logic · d4baa936
      Andrii Nakryiko authored 
      Further refactor XDP attachment code. dev_change_xdp_fd() is split into two
parts: getting bpf_progs from FDs and attachment logic, working with
bpf_progs. This makes attachment  logic a bit more straightforward and
prepares code for bpf_xdp_link inclusion, which will share the common logic.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-4-andriin@fb.com
      d4baa936
    • Andrii Nakryiko's avatar
      bpf, xdp: Maintain info on attached XDP BPF programs in net_device · 7f0a8382
      Andrii Nakryiko authored 
      Instead of delegating to drivers, maintain information about which BPF
programs are attached in which XDP modes (generic/skb, driver, or hardware)
locally in net_device. This effectively obsoletes XDP_QUERY_PROG command.

Such re-organization simplifies existing code already. But it also allows to
further add bpf_link-based XDP attachments without drivers having to know
about any of this at all, which seems like a good setup.
XDP_SETUP_PROG/XDP_SETUP_PROG_HW are just low-level commands to driver to
install/uninstall active BPF program. All the higher-level concerns about
prog/link interaction will be contained within generic driver-agnostic logic.

All the XDP_QUERY_PROG calls to driver in dev_xdp_uninstall() were removed.
It's not clear for me why dev_xdp_uninstall() were passing previous prog_flags
when resetting installed programs. That seems unnecessary, plus most drivers
don't populate prog_flags anyways. Having XDP_SETUP_PROG vs XDP_SETUP_PROG_HW
should be enough of an indicator of what is required of driver to correctly
reset active BPF program. dev_xdp_uninstall() is also generalized as an
iteration over all three supported mode.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-3-andriin@fb.com
      7f0a8382
    • Andrii Nakryiko's avatar
      bpf: Make bpf_link API available indepently of CONFIG_BPF_SYSCALL · 6cc7d1e8
      Andrii Nakryiko authored 
      Similarly to bpf_prog, make bpf_link and related generic API available
unconditionally to make it easier to have bpf_link support in various parts of
the kernel. Stub out init/prime/settle/cleanup and inc/put APIs.
Reported-by: default avatarkernel test robot <lkp@intel.com>
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-2-andriin@fb.com
      6cc7d1e8
    • Song Liu's avatar
      bpf: Fix build on architectures with special bpf_user_pt_regs_t · 2b9b305f
      Song Liu authored 
      Architectures like s390, powerpc, arm64, riscv have speical definition of
bpf_user_pt_regs_t. So we need to cast the pointer before passing it to
bpf_get_stack(). This is similar to bpf_get_stack_tp().

Fixes: 03d42fd2d83f ("bpf: Separate bpf_get_[stack|stackid] for perf events BPF")
Reported-by: default avatarkernel test robot <lkp@intel.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200724200503.3629591-1-songliubraving@fb.com
      2b9b305f
    • YiFei Zhu's avatar
      bpf/local_storage: Fix build without CONFIG_CGROUP · dfcdf0e9
      YiFei Zhu authored 
      local_storage.o has its compile guard as CONFIG_BPF_SYSCALL, which
does not imply that CONFIG_CGROUP is on. Including cgroup-internal.h
when CONFIG_CGROUP is off cause a compilation failure.

Fixes: f67cfc233706 ("bpf: Make cgroup storages shared between programs on the same cgroup")
Reported-by: default avatarkernel test robot <lkp@intel.com>
Signed-off-by: default avatarYiFei Zhu <zhuyifei@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200724211753.902969-1-zhuyifei1999@gmail.com
      dfcdf0e9
    • Alexei Starovoitov's avatar
      Merge branch 'shared-cgroup-storage' · 36f72484
      Alexei Starovoitov authored 
      YiFei Zhu says:

====================
To access the storage in a CGROUP_STORAGE map, one uses
bpf_get_local_storage helper, which is extremely fast due to its
use of per-CPU variables. However, its whole code is built on
the assumption that one map can only be used by one program at any
time, and this prohibits any sharing of data between multiple
programs using these maps, eliminating a lot of use cases, such
as some per-cgroup configuration storage, written to by a
setsockopt program and read by a cg_sock_addr program.

Why not use other map types? The great part of CGROUP_STORAGE map
is that it is isolated by different cgroups its attached to. When
one program uses bpf_get_local_storage, even on the same map, it
gets different storages if it were run as a result of attaching
to different cgroups. The kernel manages the storages, simplifying
BPF program or userspace. In theory, one could probably use other
maps like array or hash to do the same thing, but it would be a
major overhead / complexity. Userspace needs to know when a cgroup
is being freed in order to free up a space in the replacement map.

This patch set introduces a significant change to the semantics of
CGROUP_STORAGE map type. Instead of each storage being tied to one
single attachment, it is shared across different attachments to
the same cgroup, and persists until either the map or the cgroup
attached to is being freed.

User may use u64 as the key to the map, and the result would be
that the attach type become ignored during key comparison, and
programs of different attach types will share the same storage if
the cgroups they are attached to are the same.

How could this break existing users?
* Users that uses detach & reattach / program replacement as a
  shortcut to zeroing the storage. Since we need sharing between
  programs, we cannot zero the storage. Users that expect this
  behavior should either attach a program with a new map, or
  explicitly zero the map with a syscall.
This case is dependent on undocumented implementation details,
so the impact should be very minimal.

Patch 1 introduces a test on the old expected behavior of the map
type.

Patch 2 introduces a test showing how two programs cannot share
one such map.

Patch 3 implements the change of semantics to the map.

Patch 4 amends the new test such that it yields the behavior we
expect from the change.

Patch 5 documents the map type.

Changes since RFC:
* Clarify commit message in patch 3 such that it says the lifetime
  of the storage is ended at the freeing of the cgroup_bpf, rather
  than the cgroup itself.
* Restored an -ENOMEM check in __cgroup_bpf_attach.
* Update selftests for recent change in network_helpers API.

Changes since v1:
* s/CHECK_FAIL/CHECK/
* s/bpf_prog_attach/bpf_program__attach_cgroup/
* Moved test__start_subtest to test_cg_storage_multi.
* Removed some redundant CHECK_FAIL where they are already CHECK-ed.

Changes since v2:
* Lock cgroup_mutex during map_free.
* Publish new storages only if attach is successful, by tracking
  exactly which storages are reused in an array of bools.
* Mention bpftool map dump showing a value of zero for attach_type
  in patch 3 commit message.

Changes since v3:
* Use a much simpler lookup and allocate-if-not-exist from the fact
  that cgroup_mutex is locked during attach.
* Removed an unnecessary spinlock hold.

Changes since v4:
* Changed semantics so that if the key type is struct
  bpf_cgroup_storage_key the map retains isolation between different
  attach types. Sharing between different attach types only occur
  when key type is u64.
* Adapted tests and docs for the above change.

Changes since v5:
* Removed redundant NULL check before bpf_link__destroy.
* Free BPF object explicitly, after asserting that object failed to
  load, in the event that the object did not fail to load.
* Rename variable in bpf_cgroup_storage_key_cmp for clarity.
* Added a lot of information to Documentation, more or less copied
  from what Martin KaFai Lau wrote.
====================
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      36f72484
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