[bpf-next,0/2] Allow struct_ops maps with a large number of programs

Message

Kui-Feng Lee Feb. 16, 2024, 6:28 p.m. UTC

From: Kui-Feng Lee <[e-mail]>

The BPF struct_ops previously only allowed for one page to be used for
the trampolines of all links in a map. However, we have recently run
out of space due to the large number of BPF program links. By
allocating additional pages when we exhaust an existing page, we can
accommodate more links in a single map.

The variable st_map->image has been changed to st_map->image_pages,
and its type has been changed to an array of pointers to buffers of
PAGE_SIZE. The array is dynamically resized and additional pages are
allocated when all existing pages are exhausted.

The test case loads a struct_ops maps having 40 programs. Their
trampolines takes about 6.6k+ bytes over 1.5 pages on x86.

Kui-Feng Lee (2):
  bpf: struct_ops supports more than one page for trampolines.
  selftests/bpf: Test struct_ops maps with a large number of program
    links.

 kernel/bpf/bpf_struct_ops.c                   |  99 +++++++++++++----
 .../selftests/bpf/bpf_testmod/bpf_testmod.h   |  44 ++++++++
 .../prog_tests/test_struct_ops_multi_pages.c  |  24 +++++
 .../bpf/progs/struct_ops_multi_pages.c        | 102 ++++++++++++++++++
 4 files changed, 250 insertions(+), 19 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/test_struct_ops_multi_pages.c
 create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_multi_pages.c