[PATCH bpf-next 0/2] bpf: enable x86 fentry on tail-called programs

[Takeru Hayasaka <hayatake396@gmail.com>]

This series enables fentry on x86 BPF programs reached via tail calls
and adds a focused selftest for the expected behavior.

Patch 1 fixes the x86 mirrored text-poke lookup so the tail-call landing
slot is patched on both IBT and non-IBT JITs.

Patch 2 adds a selftest that checks both direct entry and tail-called
entry for a tailcall callee with fentry attached.

Takeru Hayasaka (2):
  bpf, x86: patch tail-call fentry slot on non-IBT JITs
  selftests/bpf: cover fentry on tailcalled programs

 arch/x86/net/bpf_jit_comp.c                   |  47 +++++++-
 .../selftests/bpf/prog_tests/tailcalls.c      | 110 ++++++++++++++++++
 .../bpf/progs/tailcall_fentry_probe.c         |  16 +++
 .../bpf/progs/tailcall_fentry_target.c        |  27 +++++
 4 files changed, 197 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/tailcall_fentry_probe.c
 create mode 100644 tools/testing/selftests/bpf/progs/tailcall_fentry_target.c

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2.43.0