Merge branch 'add-kfunc-bpf_xdp_pull_data'

Amery Hung says:

====================
Add kfunc bpf_xdp_pull_data

v7 -> v6
  patch 5 (new patch)
  - Rename variables in bpf_prog_test_run_xdp()

  patch 6
  - Fix bugs (Martin)

v6 -> v5
  patch 6
  - v5 selftest failed on S390 when changing how tailroom occupied by
    skb_shared_info is calculated. Revert selftest to v4, where we get
    SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) by running an XDP
    program

Link: https://lore.kernel.org/bpf/20250919230952.3628709-1-ameryhung@gmail.com/
v5 -> v4
  patch 1
  - Add a new patch clearing pfmemalloc bit in xdp->frags when all frags
    are freed in bpf_xdp_adjust_tail() (Maciej)

  patch 2
  - Refactor bpf_xdp_shrink_data() (Maciej)

  patch 3
  - Clear pfmemalloc when all frags are freed in bpf_xdp_pull_data()
    (Maciej)

  patch 6
  - Use BTF to get sizes of skb_shared_info and xdp_frame (Maciej)

Link: https://lore.kernel.org/bpf/20250919182100.1925352-1-ameryhung@gmail.com/
v3 -> v4
  patch 2
  - Improve comments (Jakub)
  - Drop new_end and len_free to simplify code (Jakub)

  patch 4
  - Instead of adding is_xdp to bpf_test_init, move lower-bound check
    of user_size to callers (Martin)
  - Simplify linear data size calculation (Martin)

  patch 5
  - Add static function identifier (Martin)
  - Free calloc-ed buf (Martin)

Link: https://lore.kernel.org/bpf/20250917225513.3388199-1-ameryhung@gmail.com/
v2 -> v3
  Separate mlx5 fixes from the patchset

  patch 2
  - Use headroom for pulling data by shifting metadata and data down
    (Jakub)
  - Drop the flags argument (Martin)

  patch 4
  - Support empty linear xdp data for BPF_PROG_TEST_RUN

Link: https://lore.kernel.org/bpf/20250915224801.2961360-1-ameryhung@gmail.com/
v1 -> v2
  Rebase onto bpf-next

  Try to build on top of the mlx5 patchset that avoids copying payload
  to linear part by Christoph but got a kernel panic. Will rebase on
  that patchset if it got merged first, or separate the mlx5 fix
  from this set.

  patch 1
  - Remove the unnecessary head frag search (Dragos)
  - Rewind the end frag pointer to simplify the change (Dragos)
  - Rewind the end frag pointer and recalculate truesize only when the
    number of frags changed (Dragos)

  patch 3
  - Fix len == zero behavior. To mirror bpf_skb_pull_data() correctly,
    the kfunc should do nothing (Stanislav)
  - Fix a pointer wrap around bug (Jakub)
  - Use memmove() when moving sinfo->frags (Jakub)

Link: https://lore.kernel.org/bpf/20250905173352.3759457-1-ameryhung@gmail.com/
====================

Link: https://patch.msgid.link/20250922233356.3356453-1-ameryhung@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>