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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id i9sm12810706wrs.70.2020.12.08.01.26.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Dec 2020 01:26:54 -0800 (PST) Date: Tue, 8 Dec 2020 09:26:50 +0000 From: Brendan Jackman To: John Fastabend Cc: bpf@vger.kernel.org, Alexei Starovoitov , Yonghong Song , Daniel Borkmann , KP Singh , Florent Revest , linux-kernel@vger.kernel.org, Jann Horn Subject: Re: [PATCH bpf-next v4 04/11] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm Message-ID: References: <20201207160734.2345502-1-jackmanb@google.com> <20201207160734.2345502-5-jackmanb@google.com> <5fcea525c4971_5a96208bd@john-XPS-13-9370.notmuch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5fcea525c4971_5a96208bd@john-XPS-13-9370.notmuch> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi John, thanks a lot for the reviews! On Mon, Dec 07, 2020 at 01:56:53PM -0800, John Fastabend wrote: > Brendan Jackman wrote: > > A subsequent patch will add additional atomic operations. These new > > operations will use the same opcode field as the existing XADD, with > > the immediate discriminating different operations. > > > > In preparation, rename the instruction mode BPF_ATOMIC and start > > calling the zero immediate BPF_ADD. > > > > This is possible (doesn't break existing valid BPF progs) because the > > immediate field is currently reserved MBZ and BPF_ADD is zero. > > > > All uses are removed from the tree but the BPF_XADD definition is > > kept around to avoid breaking builds for people including kernel > > headers. > > > > Signed-off-by: Brendan Jackman > > --- > > Documentation/networking/filter.rst | 30 ++++++++----- > > arch/arm/net/bpf_jit_32.c | 7 ++- > > arch/arm64/net/bpf_jit_comp.c | 16 +++++-- > > arch/mips/net/ebpf_jit.c | 11 +++-- > > arch/powerpc/net/bpf_jit_comp64.c | 25 ++++++++--- > > arch/riscv/net/bpf_jit_comp32.c | 20 +++++++-- > > arch/riscv/net/bpf_jit_comp64.c | 16 +++++-- > > arch/s390/net/bpf_jit_comp.c | 27 ++++++----- > > arch/sparc/net/bpf_jit_comp_64.c | 17 +++++-- > > arch/x86/net/bpf_jit_comp.c | 45 ++++++++++++++----- > > arch/x86/net/bpf_jit_comp32.c | 6 +-- > > drivers/net/ethernet/netronome/nfp/bpf/jit.c | 14 ++++-- > > drivers/net/ethernet/netronome/nfp/bpf/main.h | 4 +- > > .../net/ethernet/netronome/nfp/bpf/verifier.c | 15 ++++--- > > include/linux/filter.h | 29 ++++++++++-- > > include/uapi/linux/bpf.h | 5 ++- > > kernel/bpf/core.c | 31 +++++++++---- > > kernel/bpf/disasm.c | 6 ++- > > kernel/bpf/verifier.c | 24 +++++----- > > lib/test_bpf.c | 14 +++--- > > samples/bpf/bpf_insn.h | 4 +- > > samples/bpf/cookie_uid_helper_example.c | 6 +-- > > samples/bpf/sock_example.c | 2 +- > > samples/bpf/test_cgrp2_attach.c | 5 ++- > > tools/include/linux/filter.h | 28 ++++++++++-- > > tools/include/uapi/linux/bpf.h | 5 ++- > > .../bpf/prog_tests/cgroup_attach_multi.c | 4 +- > > .../selftests/bpf/test_cgroup_storage.c | 2 +- > > tools/testing/selftests/bpf/verifier/ctx.c | 7 ++- > > .../bpf/verifier/direct_packet_access.c | 4 +- > > .../testing/selftests/bpf/verifier/leak_ptr.c | 10 ++--- > > .../selftests/bpf/verifier/meta_access.c | 4 +- > > tools/testing/selftests/bpf/verifier/unpriv.c | 3 +- > > .../bpf/verifier/value_illegal_alu.c | 2 +- > > tools/testing/selftests/bpf/verifier/xadd.c | 18 ++++---- > > 35 files changed, 317 insertions(+), 149 deletions(-) > > > > [...] > > > +++ a/arch/mips/net/ebpf_jit.c > > [...] > > > - if (BPF_MODE(insn->code) == BPF_XADD) { > > + if (BPF_MODE(insn->code) == BPF_ATOMIC) { > > + if (insn->imm != BPF_ADD) { > > + pr_err("ATOMIC OP %02x NOT HANDLED\n", insn->imm); > > + return -EINVAL; > > + } > > + > > /* > [...] > > +++ b/arch/powerpc/net/bpf_jit_comp64.c > > > - case BPF_STX | BPF_XADD | BPF_W: > > + case BPF_STX | BPF_ATOMIC | BPF_W: > > + if (insn->imm != BPF_ADD) { > > + pr_err_ratelimited( > > + "eBPF filter atomic op code %02x (@%d) unsupported\n", > > + code, i); > > + return -ENOTSUPP; > > + } > [...] > > @@ -699,8 +707,15 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, > > - case BPF_STX | BPF_XADD | BPF_DW: > > + case BPF_STX | BPF_ATOMIC | BPF_DW: > > + if (insn->imm != BPF_ADD) { > > + pr_err_ratelimited( > > + "eBPF filter atomic op code %02x (@%d) unsupported\n", > > + code, i); > > + return -ENOTSUPP; > > + } > [...] > > + case BPF_STX | BPF_ATOMIC | BPF_W: > > + if (insn->imm != BPF_ADD) { > > + pr_info_once( > > + "bpf-jit: not supported: atomic operation %02x ***\n", > > + insn->imm); > > + return -EFAULT; > > + } > [...] > > + case BPF_STX | BPF_ATOMIC | BPF_W: > > + case BPF_STX | BPF_ATOMIC | BPF_DW: > > + if (insn->imm != BPF_ADD) { > > + pr_err("bpf-jit: not supported: atomic operation %02x ***\n", > > + insn->imm); > > + return -EINVAL; > > + } > > Can we standardize the error across jits and the error return code? It seems > odd that we use pr_err, pr_info_once, pr_err_ratelimited and then return > ENOTSUPP, EFAULT or EINVAL. That would be a noble cause but I don't think it makes sense in this patchset: they are already inconsistent, so here I've gone for intra-JIT consistency over inter-JIT consistency. I think it would be more annoying, for example, if the s390 JIT returned -EOPNOTSUPP for a bad atomic but -1 for other unsupported ops, than it is already that the s390 JIT returns -1 where the MIPS returns -EINVAL. > granted the error codes might not propagate all the way out at the moment but > still shouldn't hurt. > > > diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c > > index 0a4182792876..f973e2ead197 100644 > > --- a/arch/s390/net/bpf_jit_comp.c > > +++ b/arch/s390/net/bpf_jit_comp.c > > @@ -1205,18 +1205,23 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, > > For example this will return -1 regardless of error from insn->imm != BPF_ADD. > [...] > > + case BPF_STX | BPF_ATOMIC | BPF_DW: > > + case BPF_STX | BPF_ATOMIC | BPF_W: > > + if (insn->imm != BPF_ADD) { > > + pr_err("Unknown atomic operation %02x\n", insn->imm); > > + return -1; > > + } > > + > [...] > > > --- a/include/linux/filter.h > > +++ b/include/linux/filter.h > > @@ -259,15 +259,38 @@ static inline bool insn_is_zext(const struct bpf_insn *insn) > > .off = OFF, \ > > .imm = 0 }) > > > > -/* Atomic memory add, *(uint *)(dst_reg + off16) += src_reg */ > > + > > +/* > > + * Atomic operations: > > + * > > + * BPF_ADD *(uint *) (dst_reg + off16) += src_reg > > + */ > > + > > +#define BPF_ATOMIC64(OP, DST, SRC, OFF) \ > > + ((struct bpf_insn) { \ > > + .code = BPF_STX | BPF_DW | BPF_ATOMIC, \ > > + .dst_reg = DST, \ > > + .src_reg = SRC, \ > > + .off = OFF, \ > > + .imm = OP }) > > + > > +#define BPF_ATOMIC32(OP, DST, SRC, OFF) \ > > + ((struct bpf_insn) { \ > > + .code = BPF_STX | BPF_W | BPF_ATOMIC, \ > > + .dst_reg = DST, \ > > + .src_reg = SRC, \ > > + .off = OFF, \ > > + .imm = OP }) > > + > > +/* Legacy equivalent of BPF_ATOMIC{64,32}(BPF_ADD, ...) */ > > Not sure I care too much. Does seem more natural to follow > below pattern and use, > > BPF_ATOMIC(OP, SIZE, DST, SRC, OFF) > > > > > #define BPF_STX_XADD(SIZE, DST, SRC, OFF) \ > > ((struct bpf_insn) { \ > > - .code = BPF_STX | BPF_SIZE(SIZE) | BPF_XADD, \ > > + .code = BPF_STX | BPF_SIZE(SIZE) | BPF_ATOMIC, \ > > .dst_reg = DST, \ > > .src_reg = SRC, \ > > .off = OFF, \ > > - .imm = 0 }) > > + .imm = BPF_ADD }) > > > > /* Memory store, *(uint *) (dst_reg + off16) = imm32 */ > > > > [...] > > Otherwise LGTM, I'll try to get the remaining patches reviewed tonight > I need to jump onto something else this afternoon. Thanks!