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Message-ID: <cover.1738888641.git.yepeilin@google.com>
Date: Fri, 7 Feb 2025 02:04:54 +0000
From: Peilin Ye <yepeilin@...gle.com>
To: bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: Peilin Ye <yepeilin@...gle.com>, bpf@...f.org, Xu Kuohai <xukuohai@...weicloud.com>,
Eduard Zingerman <eddyz87@...il.com>, David Vernet <void@...ifault.com>,
Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 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@...ichev.me>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Jonathan Corbet <corbet@....net>,
"Paul E. McKenney" <paulmck@...nel.org>, Puranjay Mohan <puranjay@...nel.org>,
Ilya Leoshkevich <iii@...ux.ibm.com>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Quentin Monnet <qmo@...nel.org>, Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
Ihor Solodrai <ihor.solodrai@...ux.dev>, Yingchi Long <longyingchi24s@....ac.cn>,
Josh Don <joshdon@...gle.com>, Barret Rhoden <brho@...gle.com>, Neel Natu <neelnatu@...gle.com>,
Benjamin Segall <bsegall@...gle.com>, linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 0/9] Introduce load-acquire and store-release BPF instructions
Hi all!
This patchset adds kernel support for BPF load-acquire and store-release
instructions (for background, please see [1]), mainly including
core/verifier, arm64 JIT compiler, and Documentation/ changes. x86-64
and riscv64 are also planned to be supported. The corresponding LLVM
changes can be found at:
https://github.com/llvm/llvm-project/pull/108636
An atomic load/store is a BPF_STX | BPF_ATOMIC instruction, with the
lowest 8 bits of the 'imm' field in the following format:
+-+-+-+-+-+-+-+-+
| type | order |
+-+-+-+-+-+-+-+-+
o 'type' indicates ATOMIC_LOAD (0x1) or ATOMIC_STORE (0x2)
o 'order' is one of RELAXED (0x0), ACQUIRE (0x1), RELEASE (0x2),
ACQ_REL (0x3, acquire-and-release) and SEQ_CST (0x4, sequentially
consistent)
Currently only two combinations are legal:
o LOAD_ACQ (0x11: ATOMIC_LOAD, ACQUIRE)
o STORE_REL (0x22: ATOMIC_STORE, RELEASE)
During v1 there was a discussion on whether it is necessary to have a
dedicated 'order' field and define all possible values, considering that
we only allow two combinations at the moment. Please refer to [2] for
more context.
v1: https://lore.kernel.org/all/cover.1737763916.git.yepeilin@google.com/
v1..v2 notable changes:
o (Eduard) for x86 and s390, make
bpf_jit_supports_insn(..., /*in_arena=*/true) return false
for load_acq/store_rel
o add Eduard's Acked-by: tag
o (Eduard) extract LDX and non-ATOMIC STX handling into helpers, see
PATCH v2 3/9
o allow unpriv programs to store-release pointers to stack
o (Alexei) make it clearer in the interpreter code (PATCH v2 4/9) that
only W and DW are supported for atomic RMW
o test misaligned load_acq/store_rel
o (Eduard) other selftests/ changes:
* test load_acq/store_rel with !atomic_ptr_type_ok() pointers:
- PTR_TO_CTX, for is_ctx_reg()
- PTR_TO_PACKET, for is_pkt_reg()
- PTR_TO_FLOW_KEYS, for is_flow_key_reg()
- PTR_TO_SOCKET, for is_sk_reg()
* drop atomics/ tests
* delete unnecessary 'pid' checks from arena_atomics/ tests
* avoid depending on __BPF_FEATURE_LOAD_ACQ_STORE_REL, use
__imm_insn() and inline asm macros instead
RFC v1: https://lore.kernel.org/all/cover.1734742802.git.yepeilin@google.com
RFC v1..v1 notable changes:
o 1-2/8: minor verifier.c refactoring patches
o 3/8: core/verifier changes
* (Eduard) handle load-acquire properly in backtrack_insn()
* (Eduard) avoid skipping checks (e.g.,
bpf_jit_supports_insn()) for load-acquires
* track the value stored by store-releases, just like how
non-atomic STX instructions are handled
* (Eduard) add missing link in commit message
* (Eduard) always print 'r' for disasm.c changes
o 4/8: arm64/insn: avoid treating load_acq/store_rel as
load_ex/store_ex
o 5/8: arm64/insn: add load_acq/store_rel
* (Xu) include Should-Be-One (SBO) bits in "mask" and "value",
to avoid setting fixed bits during runtime (JIT-compile
time)
o 6/8: arm64 JIT compiler changes
* (Xu) use emit_a64_add_i() for "pointer + offset" to optimize
code emission
o 7/8: selftests
* (Eduard) avoid adding new tests to the 'test_verifier' runner
* add more tests, e.g., checking mark_precise logic
o 8/8: instruction-set.rst changes
Please see the individual kernel patches (and LLVM commits) for details.
The LLVM GitHub PR will be split into three (each containing a single
commit) soon. Feedback is much appreciated!
[1] https://lore.kernel.org/all/20240729183246.4110549-1-yepeilin@google.com/
[2] https://lore.kernel.org/bpf/Z5srM--fdH_JAgYT@google.com
Thanks,
Peilin Ye (9):
bpf/verifier: Factor out atomic_ptr_type_ok()
bpf/verifier: Factor out check_atomic_rmw()
bpf/verifier: Factor out check_load_mem() and check_store_reg()
bpf: Introduce load-acquire and store-release instructions
arm64: insn: Add BIT(23) to {load,store}_ex's mask
arm64: insn: Add load-acquire and store-release instructions
bpf, arm64: Support load-acquire and store-release instructions
selftests/bpf: Add selftests for load-acquire and store-release
instructions
bpf, docs: Update instruction-set.rst for load-acquire and
store-release instructions
.../bpf/standardization/instruction-set.rst | 114 ++++++--
arch/arm64/include/asm/insn.h | 12 +-
arch/arm64/lib/insn.c | 29 ++
arch/arm64/net/bpf_jit.h | 20 ++
arch/arm64/net/bpf_jit_comp.c | 87 +++++-
arch/s390/net/bpf_jit_comp.c | 14 +-
arch/x86/net/bpf_jit_comp.c | 4 +
include/linux/bpf.h | 11 +
include/linux/filter.h | 2 +
include/uapi/linux/bpf.h | 13 +
kernel/bpf/core.c | 63 ++++-
kernel/bpf/disasm.c | 12 +
kernel/bpf/verifier.c | 234 +++++++++++-----
tools/include/uapi/linux/bpf.h | 13 +
.../selftests/bpf/prog_tests/arena_atomics.c | 50 ++++
.../selftests/bpf/prog_tests/verifier.c | 4 +
.../selftests/bpf/progs/arena_atomics.c | 88 ++++++
.../bpf/progs/verifier_load_acquire.c | 190 +++++++++++++
.../selftests/bpf/progs/verifier_precision.c | 47 ++++
.../bpf/progs/verifier_store_release.c | 262 ++++++++++++++++++
20 files changed, 1164 insertions(+), 105 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/verifier_load_acquire.c
create mode 100644 tools/testing/selftests/bpf/progs/verifier_store_release.c
--
2.48.1.502.g6dc24dfdaf-goog
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