[bpf-next,v2,0/4] Mixing bpf2bpf and tailcalls for RV64

Message

Pu Lehui Jan. 30, 2024, 4:09 a.m. UTC

From: Pu Lehui <[e-mail]>

In the current RV64 JIT, if we just don't initialize the TCC in subprog,
the TCC can be propagated from the parent process to the subprocess, but
the TCC of the parent process cannot be restored when the subprocess
exits. Since the RV64 TCC is initialized before saving the callee saved
registers into the stack, we cannot use the callee saved register to
pass the TCC, otherwise the original value of the callee saved register
will be destroyed. So we implemented mixing bpf2bpf and tailcalls
similar to x86_64, i.e. using a non-callee saved register to transfer
the TCC between functions, and saving that register to the stack to
protect the TCC value. At the same time, we also consider the scenario
of mixing trampoline.

In addition, some code cleans are also attached to this patchset.

Tests test_bpf.ko and test_verifier have passed, as well as the relative
testcases of test_progs*.

v2:
- Fix emit restore RV_REG_TCC double times when `flags & BPF_TRAMP_F_CALL_ORIG`
- Use bpf_is_subprog helper

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

Pu Lehui (4):
  riscv, bpf: Remove redundant ctx->offset initialization
  riscv, bpf: Using kvcalloc to allocate cache buffer
  riscv, bpf: Add RV_TAILCALL_OFFSET macro to format tailcall offset
  riscv, bpf: Mixing bpf2bpf and tailcalls

 arch/riscv/net/bpf_jit.h        |   1 +
 arch/riscv/net/bpf_jit_comp64.c | 102 ++++++++++++++------------------
 arch/riscv/net/bpf_jit_core.c   |   9 +--
 3 files changed, 46 insertions(+), 66 deletions(-)