[PATCH bpf-next v1 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. Since RV64 does not support ftrace
direct call yet, the current RV64 bpf trampoline is only
used in bpf context.

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_bpf2bpf:OK
- dummy_st_ops:OK
- xdp_bpf2bpf:OK

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

v1:
- Remove the logic of bpf_arch_text_poke supported for
  kernel functions. (Kuohai and Björn)
- Extend patch_text for multiple instructions. (Björn)
- Fix OOB issue when image too big. (Björn)

RFC:
https://lore.kernel.org/bpf/20230103090756.1993820-1-pulehui@xxxxxxxxxxxxxxx/

Pu Lehui (4):
  riscv: Extend patch_text for multiple instructions
  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/include/asm/patch.h     |   2 +-
 arch/riscv/kernel/patch.c          |  19 +-
 arch/riscv/kernel/probes/kprobes.c |  15 +-
 arch/riscv/net/bpf_jit.h           |   5 +
 arch/riscv/net/bpf_jit_comp64.c    | 437 +++++++++++++++++++++++++++--
 5 files changed, 444 insertions(+), 34 deletions(-)

-- 
2.25.1