[PATCH bpf-next v4 00/10] Introduce load-acquire and store-release BPF instructions

Peilin Ye
2025-03-03T05:36:55Z

Hi all!

This patchset adds kernel support for BPF load-acquire and store-release
instructions (for background, please see [1]), including core/verifier,
arm64/x86-64 JIT compiler and Documentation/ changes, as well as
selftests. riscv64 is also planned to be supported. The corresponding
LLVM changes can be found at:

https://github.com/llvm/llvm-project/pull/108636

Please refer to the LLVM PR and individual kernel patches for details.
Thanks!

v3: https://lore.kernel.org/bpf/cover.1740009184.git.yepeilin@google.com/
v3..v4 notable changes:

o (Alexei) add x86-64 JIT support (including arena)
o add Acked-by: tags from Xu

v2: https://lore.kernel.org/bpf/cover.1738888641.git.yepeilin@google.com/
v2..v3 notable changes:

o (Alexei) change encoding to BPF_LOAD_ACQ=0x100, BPF_STORE_REL=0x110
o add Acked-by: tags from Ilya and Eduard
o make new selftests depend on:
* __clang_major__ >= 18, and
* ENABLE_ATOMICS_TESTS is defined (currently this means -mcpu=v3 or
v4), and
* JIT supports load_acq/store_rel (currenty only arm64)
o work around llvm-17 CI job failure by conditionally define
__arena_global variables as 64-bit if __clang_major__ < 18, to make
sure .addr_space.1 has no holes
o add Google copyright notice in new files

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

[1] https://lore.kernel.org/all/20240729183246.4110549-1-yepeilin@google.com/

Thanks,
Peilin Ye (10):
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
bpf, x86: 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 | 78 ++++--
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 | 86 +++++-
arch/s390/net/bpf_jit_comp.c | 14 +-
arch/x86/net/bpf_jit_comp.c | 95 ++++++-
include/linux/bpf.h | 15 +
include/linux/filter.h | 2 +
include/uapi/linux/bpf.h | 3 +
kernel/bpf/core.c | 63 ++++-
kernel/bpf/disasm.c | 12 +
kernel/bpf/verifier.c | 234 +++++++++++-----
tools/include/uapi/linux/bpf.h | 3 +
.../selftests/bpf/prog_tests/arena_atomics.c | 66 ++++-
.../selftests/bpf/prog_tests/verifier.c | 4 +
.../selftests/bpf/progs/arena_atomics.c | 121 +++++++-
.../bpf/progs/verifier_load_acquire.c | 197 +++++++++++++
.../selftests/bpf/progs/verifier_precision.c | 49 ++++
.../bpf/progs/verifier_store_release.c | 264 ++++++++++++++++++
20 files changed, 1246 insertions(+), 121 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