From: Brendan Jackman <jackmanb@google.com>
To: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
KP Singh <kpsingh@chromium.org>,
Florent Revest <revest@chromium.org>,
linux-kernel@vger.kernel.org, Jann Horn <jannh@google.com>
Subject: Re: [PATCH bpf-next v3 07/14] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction
Date: Fri, 4 Dec 2020 09:12:21 +0000 [thread overview]
Message-ID: <X8n9dTz8oofFVWzM@google.com> (raw)
In-Reply-To: <45b3d69d-7356-2c28-e507-897889be564c@fb.com>
On Thu, Dec 03, 2020 at 09:27:04PM -0800, Yonghong Song wrote:
> On 12/3/20 8:02 AM, Brendan Jackman wrote:
[...]
> > diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c
> > index 37c8d6e9b4cc..3ee2246a52ef 100644
> > --- a/kernel/bpf/disasm.c
> > +++ b/kernel/bpf/disasm.c
> > @@ -160,6 +160,13 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
> > bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
> > insn->dst_reg, insn->off,
> > insn->src_reg);
> > + } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
> > + insn->imm == (BPF_ADD | BPF_FETCH)) {
> > + verbose(cbs->private_data, "(%02x) r%d = atomic%s_fetch_add(*(%s *)(r%d %+d), r%d)\n",
>
> We should not do dereference here (withough first *), right? since the input
> is actually an address. something like below?
> r2 = atomic[64]_fetch_add((u64/u32 *)(r3 +40), r2)
Ah yep - thanks!
[...]
> > diff --git a/tools/include/linux/filter.h b/tools/include/linux/filter.h
> > index 95ff51d97f25..ac7701678e1a 100644
> > --- a/tools/include/linux/filter.h
> > +++ b/tools/include/linux/filter.h
> > @@ -180,6 +180,16 @@
> > .imm = BPF_ADD })
> > #define BPF_STX_XADD BPF_ATOMIC_ADD /* alias */
> > +/* Atomic memory add with fetch, src_reg = atomic_fetch_add(*(dst_reg + off), src_reg); */
>
> Maybe src_reg = atomic_fetch_add(dst_reg + off, src_reg)?
Yep - and the same for the bitwise ops in the later patch.
next prev parent reply other threads:[~2020-12-04 9:13 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 16:02 [PATCH bpf-next v3 00/14] Atomics for eBPF Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 01/14] bpf: x86: Factor out emission of ModR/M for *(reg + off) Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 02/14] bpf: x86: Factor out emission of REX byte Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 03/14] bpf: x86: Factor out function to emit NEG Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 04/14] bpf: x86: Factor out a lookup table for some ALU opcodes Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 05/14] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm Brendan Jackman
2020-12-04 4:49 ` Yonghong Song
2020-12-03 16:02 ` [PATCH bpf-next v3 06/14] bpf: Move BPF_STX reserved field check into BPF_STX verifier code Brendan Jackman
2020-12-04 4:51 ` Yonghong Song
2020-12-03 16:02 ` [PATCH bpf-next v3 07/14] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction Brendan Jackman
2020-12-04 5:02 ` Yonghong Song
2020-12-04 5:27 ` Yonghong Song
2020-12-04 9:12 ` Brendan Jackman [this message]
2020-12-03 16:02 ` [PATCH bpf-next v3 08/14] bpf: Add instructions for atomic_[cmp]xchg Brendan Jackman
2020-12-04 5:34 ` Yonghong Song
2020-12-04 9:26 ` Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 09/14] bpf: Pull out a macro for interpreting atomic ALU operations Brendan Jackman
2020-12-04 6:30 ` Yonghong Song
2020-12-04 9:29 ` Brendan Jackman
2020-12-04 15:20 ` Yonghong Song
2020-12-03 16:02 ` [PATCH bpf-next v3 10/14] bpf: Add bitwise atomic instructions Brendan Jackman
2020-12-04 6:42 ` Yonghong Song
2020-12-04 9:36 ` Brendan Jackman
2020-12-04 15:21 ` Yonghong Song
2020-12-07 11:28 ` Brendan Jackman
2020-12-07 15:58 ` Yonghong Song
2020-12-07 16:14 ` Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 11/14] tools build: Implement feature check for BPF atomics in Clang Brendan Jackman
2020-12-03 21:02 ` Andrii Nakryiko
2020-12-03 16:02 ` [PATCH bpf-next v3 12/14] bpf: Pull tools/build/feature biz into selftests Makefile Brendan Jackman
2020-12-03 21:01 ` Andrii Nakryiko
2020-12-04 9:41 ` Brendan Jackman
2020-12-04 19:00 ` Andrii Nakryiko
2020-12-07 11:00 ` Brendan Jackman
2020-12-08 2:19 ` Andrii Nakryiko
2020-12-08 17:04 ` Brendan Jackman
2020-12-08 18:31 ` Andrii Nakryiko
2020-12-03 16:02 ` [PATCH bpf-next v3 13/14] bpf: Add tests for new BPF atomic operations Brendan Jackman
2020-12-04 7:06 ` Yonghong Song
2020-12-04 9:45 ` Brendan Jackman
2020-12-04 15:28 ` Yonghong Song
2020-12-04 19:49 ` Andrii Nakryiko
2020-12-07 15:48 ` Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 14/14] bpf: Document new atomic instructions Brendan Jackman
2020-12-03 16:10 ` [PATCH bpf-next v3 00/14] Atomics for eBPF Brendan Jackman
2020-12-04 4:46 ` Yonghong Song
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