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

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Date: Tue, 26 Mar 2024 22:49:41 +0000
From: Puranjay Mohan <puranjay12@...il.com>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Björn Töpel <bjorn@...nel.org>,
	Luke Nelson <luke.r.nels@...il.com>,
	Xi Wang <xi.wang@...il.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	bpf@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Pu Lehui <pulehui@...weicloud.com>
Cc: puranjay12@...il.com
Subject: [PATCH bpf-next v3 0/2] bpf,riscv: Add support for BPF Arena

Changes in V3
V2: https://lore.kernel.org/bpf/20240325155434.65589-1-puranjay12@gmail.com/
- 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@gmail.com/
- 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@...tester:~/bpf# uname -p
  riscv64
  root@...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