[RFC PATCH RESEND bpf-next 0/4] Support bpf trampoline for RV64

[Pu Lehui]

BPF trampoline is the critical infrastructure of the bpf
subsystem, acting as a mediator between kernel functions
and BPF programs. Numerous important features, such as
using ebpf program for zero overhead kernel introspection,
rely on this key component. We can't wait to support bpf
trampoline on RV64. The implementation of bpf trampoline
was closely to x86 and arm64 for future development.

As most of riscv cpu support unaligned memory accesses,
we temporarily use patch [1] to facilitate testing. The
test results are as follow, and test_verifier with no
new failure ceses.

- fexit_test:OK
- fentry_test:OK
- fentry_fexit:OK
- fexit_stress:OK
- fexit_bpf2bpf:OK
- dummy_st_ops:OK
- modify_return:OK
- get_func_ip_test:OK
- get_func_args_test:OK
- trampoline_count:OK

[1] https://lore.kernel.org/linux-riscv/20210916130855.4054926-2-chenhuang5@xxxxxxxxxx/

Pu Lehui (4):
  bpf: Rollback to text_poke when arch not supported ftrace direct call
  riscv, bpf: Factor out emit_call for kernel and bpf context
  riscv, bpf: Add bpf_arch_text_poke support for RV64
  riscv, bpf: Add bpf trampoline support for RV64

 arch/riscv/net/bpf_jit.h        |   5 +
 arch/riscv/net/bpf_jit_comp64.c | 483 ++++++++++++++++++++++++++++++--
 kernel/bpf/trampoline.c         |   8 +-
 3 files changed, 471 insertions(+), 25 deletions(-)

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2.25.1