From patchwork Thu Dec 3 16:02:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brendan Jackman X-Patchwork-Id: 11949051 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4BAFCC433FE for ; Thu, 3 Dec 2020 16:04:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB0B1207AD for ; Thu, 3 Dec 2020 16:04:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389271AbgLCQDv (ORCPT ); Thu, 3 Dec 2020 11:03:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389110AbgLCQDv (ORCPT ); Thu, 3 Dec 2020 11:03:51 -0500 Received: from mail-wm1-x349.google.com (mail-wm1-x349.google.com [IPv6:2a00:1450:4864:20::349]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03511C061A4F for ; Thu, 3 Dec 2020 08:03:11 -0800 (PST) Received: by mail-wm1-x349.google.com with SMTP id n18so1550302wmk.0 for ; Thu, 03 Dec 2020 08:03:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=Umt6coDnn4aZpAALuE3BNX1YhLXZCr34hXrUZ71njTk=; b=C3HBhRolseNEzsSxkUobwV6xR5RqddG0sq+ojtufOrz8uZMgV4OTse5wwhhFQtV6WE F4XNOoTPIJdC1LQ+a4N7SLUj9rfaAhc8gyOldkg0TSVPsokmAs/CDr93hjrvJkkTwj/b DYoyHS/Og/vzFT1cef/YEsJqTws3yLnj1CNVWbG/fZ/t16TLFVWZ56moJHvypdl+7dG9 l/gWP5wgRyEplBhYtmi3CfKGSwbeHTj+nIju0Gd7l54w3CJscCiN8wYDMT6ocpUGnGhK lv3Yk01Y3c7BfKPXQmAAh0HSqDz111vRJWuQ1DVbhFhyqsI0ATkRhpamSCTYE+wTQ4rz g1vQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=Umt6coDnn4aZpAALuE3BNX1YhLXZCr34hXrUZ71njTk=; b=NqR2GcwH8pCerVxo9yUL0AsavBsZQIzx8XR596WmDvJI3GvNPqtu9O03+vmTSsmJr8 PyDUUNne6nUorwLbE82KaVdjZKLSgE9W3RE1Pes4jT+ME0KMsWXJupNVHI47qhqw9s2V lwNsO/m04Odg5onJxDfdlCHB8LAwgnqCgoojho4lqf0WEiFOKR6wQVuhUrdhtZrj0W+Y +Mn7O+Nv0pgDrEQh7lqPk1L1Lft934Ke2CIjKIa5P2um2T5bJyhVFCCTW0TiovKLwpmW 4MBGaj1neRNKJZd7OFIY1msxKomuaaAITAoRxdTBIExxiSDk/u6fOkdDMNCPpW3jEBVg 9WjQ== X-Gm-Message-State: AOAM532/uO1QHnu2D5d4j9bKoiJGEAt/NS8zusBoIZ5Fl1/YwBTGG/i6 aLwUC70iJnqKCwYOPbnXHYJGhr7+osaON2LrwS+Pm0j8ukmbsvellrnNbXV7DfNXL2dmbcXEZC3 RgVdLvRObN53Tpi2t1ttu2/pIJFgJrnI3cINo3WMCxHUraTWIC+zMNtojVeuQdUU= X-Google-Smtp-Source: ABdhPJzFt8qBiRvs5wq+69dJNKDvJH0zM4rlkm9pKh5y+4L6Qbvp1Dc/OIlZVrhocfA12YWxMT0WCX75hUXkFA== Sender: "jackmanb via sendgmr" X-Received: from beeg.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:11db]) (user=jackmanb job=sendgmr) by 2002:a1c:2b03:: with SMTP id r3mr4146344wmr.184.1607011388856; Thu, 03 Dec 2020 08:03:08 -0800 (PST) Date: Thu, 3 Dec 2020 16:02:31 +0000 Message-Id: <20201203160245.1014867-1-jackmanb@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.29.2.454.gaff20da3a2-goog Subject: [PATCH bpf-next v3 00/14] Atomics for eBPF From: Brendan Jackman To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Yonghong Song , Daniel Borkmann , KP Singh , Florent Revest , linux-kernel@vger.kernel.org, Jann Horn , Brendan Jackman Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Status of the patches ===================== Thanks for the reviews! Differences from v2->v3 [1]: * More minor fixes and naming/comment changes * Dropped atomic subtract: compilers can implement this by preceding an atomic add with a NEG instruction (which is what the x86 JIT did under the hood anyway). * Dropped the use of -mcpu=v4 in the Clang BPF command-line; there is no longer an architecture version bump. Instead a feature test is added to Kbuild - it builds a source file to check if Clang supports BPF atomics. * Fixed the prog_test so it no longer breaks test_progs-no_alu32. This requires some ifdef acrobatics to avoid complicating the prog_tests model where the same userspace code exercises both the normal and no_alu32 BPF test objects, using the same skeleton header. Differences from v1->v2 [1]: * Fixed mistakes in the netronome driver * Addd sub, add, or, xor operations * The above led to some refactors to keep things readable. (Maybe I should have just waited until I'd implemented these before starting the review...) * Replaced BPF_[CMP]SET | BPF_FETCH with just BPF_[CMP]XCHG, which include the BPF_FETCH flag * Added a bit of documentation. Suggestions welcome for more places to dump this info... The prog_test that's added depends on Clang/LLVM features added by Yonghong in https://reviews.llvm.org/D72184 This only includes a JIT implementation for x86_64 - I don't plan to implement JIT support myself for other architectures. Operations ========== This patchset adds atomic operations to the eBPF instruction set. The use-case that motivated this work was a trivial and efficient way to generate globally-unique cookies in BPF progs, but I think it's obvious that these features are pretty widely applicable. The instructions that are added here can be summarised with this list of kernel operations: * atomic[64]_[fetch_]add * atomic[64]_[fetch_]and * atomic[64]_[fetch_]or * atomic[64]_xchg * atomic[64]_cmpxchg The following are left out of scope for this effort: * 16 and 8 bit operations * Explicit memory barriers Encoding ======== I originally planned to add new values for bpf_insn.opcode. This was rather unpleasant: the opcode space has holes in it but no entire instruction classes[2]. Yonghong Song had a better idea: use the immediate field of the existing STX XADD instruction to encode the operation. This works nicely, without breaking existing programs, because the immediate field is currently reserved-must-be-zero, and extra-nicely because BPF_ADD happens to be zero. Note that this of course makes immediate-source atomic operations impossible. It's hard to imagine a measurable speedup from such instructions, and if it existed it would certainly not benefit x86, which has no support for them. The BPF_OP opcode fields are re-used in the immediate, and an additional flag BPF_FETCH is used to mark instructions that should fetch a pre-modification value from memory. So, BPF_XADD is now called BPF_ATOMIC (the old name is kept to avoid breaking userspace builds), and where we previously had .imm = 0, we now have .imm = BPF_ADD (which is 0). Operands ======== Reg-source eBPF instructions only have two operands, while these atomic operations have up to four. To avoid needing to encode additional operands, then: - One of the input registers is re-used as an output register (e.g. atomic_fetch_add both reads from and writes to the source register). - Where necessary (i.e. for cmpxchg) , R0 is "hard-coded" as one of the operands. This approach also allows the new eBPF instructions to map directly to single x86 instructions. [1] Previous patchset: https://lore.kernel.org/bpf/20201123173202.1335708-1-jackmanb@google.com/ [2] Visualisation of eBPF opcode space: https://gist.github.com/bjackman/00fdad2d5dfff601c1918bc29b16e778 Brendan Jackman (14): bpf: x86: Factor out emission of ModR/M for *(reg + off) bpf: x86: Factor out emission of REX byte bpf: x86: Factor out function to emit NEG bpf: x86: Factor out a lookup table for some ALU opcodes bpf: Rename BPF_XADD and prepare to encode other atomics in .imm bpf: Move BPF_STX reserved field check into BPF_STX verifier code bpf: Add BPF_FETCH field / create atomic_fetch_add instruction bpf: Add instructions for atomic_[cmp]xchg bpf: Pull out a macro for interpreting atomic ALU operations bpf: Add bitwise atomic instructions tools build: Implement feature check for BPF atomics in Clang bpf: Pull tools/build/feature biz into selftests Makefile bpf: Add tests for new BPF atomic operations bpf: Document new atomic instructions Documentation/networking/filter.rst | 56 +++- 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 | 241 +++++++++++----- 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 | 97 ++++++- include/uapi/linux/bpf.h | 8 +- kernel/bpf/core.c | 66 ++++- kernel/bpf/disasm.c | 43 ++- kernel/bpf/verifier.c | 75 +++-- lib/test_bpf.c | 2 +- samples/bpf/bpf_insn.h | 4 +- samples/bpf/sock_example.c | 2 +- samples/bpf/test_cgrp2_attach.c | 4 +- tools/build/feature/Makefile | 4 + tools/build/feature/test-clang-bpf-atomics.c | 9 + tools/include/linux/filter.h | 97 ++++++- tools/include/uapi/linux/bpf.h | 8 +- tools/testing/selftests/bpf/.gitignore | 1 + tools/testing/selftests/bpf/Makefile | 42 +++ .../selftests/bpf/prog_tests/atomics_test.c | 262 ++++++++++++++++++ .../bpf/prog_tests/cgroup_attach_multi.c | 4 +- .../selftests/bpf/progs/atomics_test.c | 154 ++++++++++ .../selftests/bpf/verifier/atomic_and.c | 77 +++++ .../selftests/bpf/verifier/atomic_cmpxchg.c | 96 +++++++ .../selftests/bpf/verifier/atomic_fetch_add.c | 106 +++++++ .../selftests/bpf/verifier/atomic_or.c | 77 +++++ .../selftests/bpf/verifier/atomic_xchg.c | 46 +++ .../selftests/bpf/verifier/atomic_xor.c | 77 +++++ tools/testing/selftests/bpf/verifier/ctx.c | 7 +- .../testing/selftests/bpf/verifier/leak_ptr.c | 4 +- tools/testing/selftests/bpf/verifier/unpriv.c | 3 +- tools/testing/selftests/bpf/verifier/xadd.c | 2 +- 42 files changed, 1666 insertions(+), 186 deletions(-) create mode 100644 tools/build/feature/test-clang-bpf-atomics.c create mode 100644 tools/testing/selftests/bpf/prog_tests/atomics_test.c create mode 100644 tools/testing/selftests/bpf/progs/atomics_test.c create mode 100644 tools/testing/selftests/bpf/verifier/atomic_and.c create mode 100644 tools/testing/selftests/bpf/verifier/atomic_cmpxchg.c create mode 100644 tools/testing/selftests/bpf/verifier/atomic_fetch_add.c create mode 100644 tools/testing/selftests/bpf/verifier/atomic_or.c create mode 100644 tools/testing/selftests/bpf/verifier/atomic_xchg.c create mode 100644 tools/testing/selftests/bpf/verifier/atomic_xor.c base-commit: 97306be45fbe7a02461c3c2a57e666cf662b1aaf --- 2.29.2.454.gaff20da3a2-goog