[bpf-next,v3,0/2] Add 12-argument support for RV64 bpf trampoline

Message

Pu Lehui April 3, 2024, 7:28 a.m. UTC

This patch adds 12 function arguments support for riscv64 bpf
trampoline. The current bpf trampoline supports <= sizeof(u64) bytes
scalar arguments [0] and <= 16 bytes struct arguments [1]. Therefore, we
focus on the situation where scalars are at most XLEN bits and
aggregates whose total size does not exceed 2×XLEN bits in the riscv
calling convention [2].

Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6184 [0]
Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6769 [1]
Link: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/releases/download/draft-20230929-e5c800e661a53efe3c2678d71a306323b60eb13b/riscv-abi.pdf [2]

v3:
- Variable and macro name alignment:
  nr_reg_args: number of args in reg
  nr_stack_args: number of args on stack
  RV_MAX_REG_ARGS: macro for riscv max args in reg

v2: https://lore.kernel.org/all/[e-mail]/
- Add tracing_struct to DENYLIST.aarch64 while aarch64 does not yet support
  bpf trampoline with more than 8 args.
- Change the macro RV_MAX_ARG_REGS to RV_MAX_ARGS_REG to synchronize with
  the variable definition below.
- Add some comments for stk_arg_off and magic number of skip slots for loading
  args on stack.

v1: https://lore.kernel.org/all/[e-mail]/

Pu Lehui (2):
  riscv, bpf: Add 12-argument support for RV64 bpf trampoline
  selftests/bpf: Add testcase where 7th argment is struct

 arch/riscv/net/bpf_jit_comp64.c               | 65 +++++++++++++------
 tools/testing/selftests/bpf/DENYLIST.aarch64  |  1 +
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   | 19 ++++++
 .../selftests/bpf/prog_tests/tracing_struct.c | 13 ++++
 .../selftests/bpf/progs/tracing_struct.c      | 35 ++++++++++
 5 files changed, 114 insertions(+), 19 deletions(-)