[PATCH bpf-next v3 0/2] bpf,riscv: Add support for BPF Arena

[Puranjay Mohan]

Changes in V3
V2: https://lore.kernel.org/bpf/20240325155434.65589-1-puranjay12@xxxxxxxxx/
- Use REG_DONT_CLEAR_MARKER in place of DONT_CLEAR as the name.
- Use RV_REG_ZERO for the above as it is guaranteed to be never used in as
  dst/src register in BPF LDX/STX/ST instructions.
- Use #define RV_REG_ARENA for RV_REG_S7

Changes in V2
V1: https://lore.kernel.org/bpf/20240323154652.54572-1-puranjay12@xxxxxxxxx/
- Used S7 in place of S11 for storing the kernel_vm_start
- Used 17 in place of 16 for DONT_CLEAR marker
- Remove an unused variable
- Removed some misleading information from the commit message.

This series adds the support for PROBE_MEM32 and bpf_addr_space_cast
instructions to the RISCV BPF JIT. These two instructions allow the
enablement of BPF Arena.

All arena related selftests are passing:

  root@rv-tester:~/bpf# uname -p
  riscv64
  root@rv-tester:~/bpf# ./test_progs -a "*arena*"
  #3/1     arena_htab/arena_htab_llvm:OK
  #3/2     arena_htab/arena_htab_asm:OK
  #3       arena_htab:OK
  #4/1     arena_list/arena_list_1:OK
  #4/2     arena_list/arena_list_1000:OK
  #4       arena_list:OK
  #434/1   verifier_arena/basic_alloc1:OK
  #434/2   verifier_arena/basic_alloc2:OK
  #434/3   verifier_arena/basic_alloc3:OK
  #434/4   verifier_arena/iter_maps1:OK
  #434/5   verifier_arena/iter_maps2:OK
  #434/6   verifier_arena/iter_maps3:OK
  #434     verifier_arena:OK
  Summary: 3/10 PASSED, 0 SKIPPED, 0 FAILED

This feature needs the following two fixes in the bpf/bpf.git to work
properly:

f7f5d1808b1b6 ("bpf: verifier: fix addr_space_cast from as(1) to as(0)")
443574b033876 ("riscv, bpf: Fix kfunc parameters incompatibility between bpf and riscv abi")

There is a lot of code repetition for LDX, STX, and ST. I will be sending a
follow-up patch to refactor these.

Puranjay Mohan (2):
  bpf,riscv: Implement PROBE_MEM32 pseudo instructions
  bpf,riscv: Implement bpf_addr_space_cast instruction

 arch/riscv/net/bpf_jit.h        |   2 +
 arch/riscv/net/bpf_jit_comp64.c | 205 +++++++++++++++++++++++++++++++-
 arch/riscv/net/bpf_jit_core.c   |   2 +
 3 files changed, 207 insertions(+), 2 deletions(-)

-- 
2.40.1