Merge branch 'bpf: Support multi-attach for freplace'

Toke Høiland-Jørgensen says:

====================
This series adds support attaching freplace BPF programs to multiple targets.
This is needed to support incremental attachment of multiple XDP programs using
the libxdp dispatcher model.

Patch 1 moves prog_aux->linked_prog and the trampoline to be embedded in
bpf_tracing_link on attach, and freed by the link release logic, and introduces
a mutex to protect the writing of the pointers in prog->aux.

Based on this refactoring (and previously applied patches), it becomes pretty
straight-forward to support multiple-attach for freplace programs (patch 2).
This is simply a matter of creating a second bpf_tracing_link if a target is
supplied. However, for API consistency with other types of link attach, this
option is added to the BPF_LINK_CREATE API instead of extending
bpf_raw_tracepoint_open().

Patch 3 is a port of Jiri Olsa's patch to support fentry/fexit on freplace
programs. His approach of getting the target type from the target program
reference no longer works after we've gotten rid of linked_prog (because the
bpf_tracing_link reference disappears on attach). Instead, we used the saved
reference to the target prog type that is also used to verify compatibility on
secondary freplace attachment.

Patch 4 is the accompanying libbpf update, and patches 5-7 are selftests: patch
5 tests for the multi-freplace functionality itself; patch 6 is Jiri's previous
selftest for the fentry-to-freplace fix; patch 7 is a test for the change
introduced in the previously-applied patches, blocking MODIFY_RETURN functions
from attaching to other BPF programs.

With this series, libxdp and xdp-tools can successfully attach multiple programs
one at a time. To play with this, use the 'freplace-multi-attach' branch of
xdp-tools:

$ git clone --recurse-submodules --branch freplace-multi-attach https://github.com/xdp-project/xdp-tools
$ cd xdp-tools/xdp-loader
$ make
$ sudo ./xdp-loader load veth0 ../lib/testing/xdp_drop.o
$ sudo ./xdp-loader load veth0 ../lib/testing/xdp_pass.o
$ sudo ./xdp-loader status

The series is also available here:
https://git.kernel.org/pub/scm/linux/kernel/git/toke/linux.git/log/?h=bpf-freplace-multi-attach-alt-10

Changelog:

v10:
  - Dial back the s/tgt_/dst_/ replacement a bit
  - Fix smatch warning (from ktest robot)
  - Rebase to bpf-next, drop already-applied patches

v9:
  - Clarify commit message of patch 3
  - Add new struct bpf_attach_target_info for returning from
    bpf_check_attach_target() and passing to bpf_trampoline_get()
  - Move trampoline key computation into a helper
  - Make sure we don't break bpffs debug umh
  - Add some comment blocks explaining the logic flow in
    bpf_tracing_prog_attach()
  - s/tgt_/dst_/ in prog->aux, and for local variables using those members
  - Always drop dst_trampoline and dst_prog from prog->aux on first attach
  - Don't remove syscall fmod_ret test from selftest benchmarks
  - Add saved_ prefix to dst_{prog,attach}_type members in prog_aux
  - Drop prog argument from check_attach_modify_return()
  - Add comment about possible NULL of tr_link->tgt_prog on link_release()

v8:
  - Add a separate error message when trying to attach FMOD_REPLACE to tgt_prog
  - Better error messages in bpf_program__attach_freplace()
  - Don't lock mutex when setting tgt_* pointers in prog create and verifier
  - Remove fmod_ret programs from benchmarks in selftests (new patch 11)
  - Fix a few other nits in selftests

v7:
  - Add back missing ptype == prog->type check in link_create()
  - Use tracing_bpf_link_attach() instead of separate freplace_bpf_link_attach()
  - Don't break attachment of bpf_iters in libbpf (by clobbering link_create.iter_info)

v6:
  - Rebase to latest bpf-next
  - Simplify logic in bpf_tracing_prog_attach()
  - Don't create a new attach_type for link_create(), disambiguate on prog->type
    instead
  - Use raw_tracepoint_open() in libbpf bpf_program__attach_ftrace() if called
    with NULL target
  - Switch bpf_program__attach_ftrace() to take function name as parameter
    instead of btf_id
  - Add a patch disallowing MODIFY_RETURN programs from attaching to other BPF
    programs, and an accompanying selftest (patches 1 and 10)

v5:
  - Fix typo in inline function definition of bpf_trampoline_get()
  - Don't put bpf_tracing_link in prog->aux, use a mutex to protect tgt_prog and
    trampoline instead, and move them to the link on attach.
  - Restore Jiri as author of the last selftest patch

v4:
  - Cleanup the refactored check_attach_btf_id() to make the logic easier to follow
  - Fix cleanup paths for bpf_tracing_link
  - Use xchg() for removing the bpf_tracing_link from prog->aux and restore on (some) failures
  - Use BPF_LINK_CREATE operation to create link with target instead of extending raw_tracepoint_open
  - Fold update of tools/ UAPI header into main patch
  - Update arg dereference patch to use skeletons and set_attach_target()

v3:
  - Get rid of prog_aux->linked_prog entirely in favour of a bpf_tracing_link
  - Incorporate Jiri's fix for attaching fentry to freplace programs

v2:
  - Drop the log arguments from bpf_raw_tracepoint_open
  - Fix kbot errors
  - Rebase to latest bpf-next
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

0 files changed, 0 insertions, 0 deletions