From patchwork Mon Dec 7 16:07:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brendan Jackman X-Patchwork-Id: 11956275 X-Patchwork-Delegate: bpf@iogearbox.net 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_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 9610BC2BBCA for ; Mon, 7 Dec 2020 16:09:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E9A623741 for ; Mon, 7 Dec 2020 16:09:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727648AbgLGQJr (ORCPT ); Mon, 7 Dec 2020 11:09:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55792 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727696AbgLGQJr (ORCPT ); Mon, 7 Dec 2020 11:09:47 -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 F1A75C0611D0 for ; Mon, 7 Dec 2020 08:08:26 -0800 (PST) Received: by mail-wm1-x349.google.com with SMTP id j62so5506387wma.4 for ; Mon, 07 Dec 2020 08:08:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=gxx2FbbCW7hbLKnAQIkI4+xIkMuXLrdGlKPV2mI9Xto=; b=f8SBI7Qe/pem04/GXA+1zz/xII3/Zl6NcNKLAEFcIyCIaSK22PqeXRDHV9BKcCzt4b nOsVbsS3083paQzlt1yE3tadJ2Bcq6l9a3YmBFV71uSNh27ZogIEURmjiwloWCAlKduc ca35FlMwDTQ3G9bXYW9beOfeTRhnj/rE0yBkVsmfocKNRjSUrTIwJGIB39MEJad3lJ6y WcGX3ya5M1I7t+yzv6JIQ6kk1+CuzAdcPTEY1xEbchEiXFkcy2DVJdd3HF//+iYzU+Qj IP/9ZOu2rpi6UAqjl7SHOkcMugWf7xZugmT0LvKZnX9EebTcRENvZID1H8TplLgXKQNo QUFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=gxx2FbbCW7hbLKnAQIkI4+xIkMuXLrdGlKPV2mI9Xto=; b=UX2zqwSGL9EqKQOnj1NRV2D7Ww44NtcwnkGGLw3HBd0HIzrGVMGUDXG5sItTh7Pp2h gmrl5Ek3ouynCALtYzrBFQnmY0BHEfDnLOvzX24UqKxSo9tikBhMRKuFrPJ5E8LoryX4 pWurK6qp6YJLZLWoLX4Mjlrd/tJ4iHl3I1+LFPfhD4PEQov4HArixilMg4MGeCM9Lc6p JDQQS0q+8C8wXw1pspeoEph9HLX2XcWbh7nhZ301yDRds9s7iSskSbq+uwZqeLlk4pdx wmQEkmIGjIvH8iFukP6kjFoXdfMPEpuOQeNwS+cIDV2bIFFbHhbAmMQCAAXZtfb5YS9J n+gA== X-Gm-Message-State: AOAM533rn8ICZm/CXjIJBPNbwwg6rLwlVAWXI7DoZUoQsEfPl6DkUEo0 6FIg+AyWvRDwdW1wXAW+5cuADKXdLFRI22BXufI9VYrUWiJmCBr3UTqDwJQ6fV4XgEc6LYHTpVY cxuv3219w64b0X9GR9v5fAwACZy6Nut8O+W6TorPZP1u6hB6C6LX0ZVpeDdUvz/g= X-Google-Smtp-Source: ABdhPJzZRoEJchhljgUUusfHGKMj4wIUtWIaFHjBLcoy3gz3zXu5QH06kDlemBFRUFoSmGszgNXOkWJdgS/W3g== 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:61c3:: with SMTP id v186mr19139744wmb.146.1607357305625; Mon, 07 Dec 2020 08:08:25 -0800 (PST) Date: Mon, 7 Dec 2020 16:07:29 +0000 In-Reply-To: <20201207160734.2345502-1-jackmanb@google.com> Message-Id: <20201207160734.2345502-7-jackmanb@google.com> Mime-Version: 1.0 References: <20201207160734.2345502-1-jackmanb@google.com> X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog Subject: [PATCH bpf-next v4 06/11] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction 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 The BPF_FETCH field can be set in bpf_insn.imm, for BPF_ATOMIC instructions, in order to have the previous value of the atomically-modified memory location loaded into the src register after an atomic op is carried out. Suggested-by: Yonghong Song Signed-off-by: Brendan Jackman Acked-by: John Fastabend --- arch/x86/net/bpf_jit_comp.c | 4 ++++ include/linux/filter.h | 1 + include/uapi/linux/bpf.h | 3 +++ kernel/bpf/core.c | 13 +++++++++++++ kernel/bpf/disasm.c | 7 +++++++ kernel/bpf/verifier.c | 33 ++++++++++++++++++++++++--------- tools/include/linux/filter.h | 11 +++++++++++ tools/include/uapi/linux/bpf.h | 3 +++ 8 files changed, 66 insertions(+), 9 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index b1829a534da1..eea7d8b0bb12 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -811,6 +811,10 @@ static int emit_atomic(u8 **pprog, u8 atomic_op, /* lock *(u32/u64*)(dst_reg + off) = src_reg */ EMIT1(simple_alu_opcodes[atomic_op]); break; + case BPF_ADD | BPF_FETCH: + /* src_reg = atomic_fetch_add(dst_reg + off, src_reg); */ + EMIT2(0x0F, 0xC1); + break; default: pr_err("bpf_jit: unknown atomic opcode %02x\n", atomic_op); return -EFAULT; diff --git a/include/linux/filter.h b/include/linux/filter.h index 45be19408f68..b5258bca10d2 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -264,6 +264,7 @@ static inline bool insn_is_zext(const struct bpf_insn *insn) * Atomic operations: * * BPF_ADD *(uint *) (dst_reg + off16) += src_reg + * BPF_ADD | BPF_FETCH src_reg = atomic_fetch_add(dst_reg + off16, src_reg); */ #define BPF_ATOMIC64(OP, DST, SRC, OFF) \ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 98161e2d389f..d5389119291e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -44,6 +44,9 @@ #define BPF_CALL 0x80 /* function call */ #define BPF_EXIT 0x90 /* function return */ +/* atomic op type fields (stored in immediate) */ +#define BPF_FETCH 0x01 /* fetch previous value into src reg */ + /* Register numbers */ enum { BPF_REG_0 = 0, diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 3abc6b250b18..61e93eb7d363 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1624,16 +1624,29 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) /* lock xadd *(u32 *)(dst_reg + off16) += src_reg */ atomic_add((u32) SRC, (atomic_t *)(unsigned long) (DST + insn->off)); + break; + case BPF_ADD | BPF_FETCH: + SRC = (u32) atomic_fetch_add( + (u32) SRC, + (atomic_t *)(unsigned long) (DST + insn->off)); + break; default: goto default_label; } CONT; + STX_ATOMIC_DW: switch (IMM) { case BPF_ADD: /* lock xadd *(u64 *)(dst_reg + off16) += src_reg */ atomic64_add((u64) SRC, (atomic64_t *)(unsigned long) (DST + insn->off)); + break; + case BPF_ADD | BPF_FETCH: + SRC = (u64) atomic64_fetch_add( + (u64) SRC, + (atomic64_t *)(s64) (DST + insn->off)); + break; default: goto default_label; } diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c index 37c8d6e9b4cc..d2e20f6d0516 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", + insn->code, insn->src_reg, + BPF_SIZE(insn->code) == BPF_DW ? "64" : "", + bpf_ldst_string[BPF_SIZE(insn->code) >> 3], + insn->dst_reg, insn->off, insn->src_reg); } else { verbose(cbs->private_data, "BUG_%02x\n", insn->code); } diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 745c53df0485..f8c4e809297d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3610,7 +3610,11 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i { int err; - if (insn->imm != BPF_ADD) { + switch (insn->imm) { + case BPF_ADD: + case BPF_ADD | BPF_FETCH: + break; + default: verbose(env, "BPF_ATOMIC uses invalid atomic opcode %02x\n", insn->imm); return -EINVAL; } @@ -3652,8 +3656,20 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i return err; /* check whether we can write into the same memory */ - return check_mem_access(env, insn_idx, insn->dst_reg, insn->off, - BPF_SIZE(insn->code), BPF_WRITE, -1, true); + err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, + BPF_SIZE(insn->code), BPF_WRITE, -1, true); + if (err) + return err; + + if (!(insn->imm & BPF_FETCH)) + return 0; + + /* check and record load of old value into src reg */ + err = check_reg_arg(env, insn->src_reg, DST_OP); + if (err) + return err; + + return 0; } static int __check_stack_boundary(struct bpf_verifier_env *env, u32 regno, @@ -9527,12 +9543,6 @@ static int do_check(struct bpf_verifier_env *env) } else if (class == BPF_STX) { enum bpf_reg_type *prev_dst_type, dst_reg_type; - if (((BPF_MODE(insn->code) != BPF_MEM && - BPF_MODE(insn->code) != BPF_ATOMIC) || insn->imm != 0)) { - verbose(env, "BPF_STX uses reserved fields\n"); - return -EINVAL; - } - if (BPF_MODE(insn->code) == BPF_ATOMIC) { err = check_atomic(env, env->insn_idx, insn); if (err) @@ -9541,6 +9551,11 @@ static int do_check(struct bpf_verifier_env *env) continue; } + if (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0) { + verbose(env, "BPF_STX uses reserved fields\n"); + return -EINVAL; + } + /* check src1 operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) diff --git a/tools/include/linux/filter.h b/tools/include/linux/filter.h index f345f12c1ff8..4e0100ba52c2 100644 --- a/tools/include/linux/filter.h +++ b/tools/include/linux/filter.h @@ -173,6 +173,7 @@ * Atomic operations: * * BPF_ADD *(uint *) (dst_reg + off16) += src_reg + * BPF_ADD | BPF_FETCH src_reg = atomic_fetch_add(dst_reg + off16, src_reg); */ #define BPF_ATOMIC64(OP, DST, SRC, OFF) \ @@ -201,6 +202,16 @@ .off = OFF, \ .imm = BPF_ADD }) +/* Atomic memory add with fetch, src_reg = atomic_fetch_add(dst_reg + off, src_reg); */ + +#define BPF_ATOMIC_FETCH_ADD(SIZE, DST, SRC, OFF) \ + ((struct bpf_insn) { \ + .code = BPF_STX | BPF_SIZE(SIZE) | BPF_ATOMIC, \ + .dst_reg = DST, \ + .src_reg = SRC, \ + .off = OFF, \ + .imm = BPF_ADD | BPF_FETCH }) + /* Memory store, *(uint *) (dst_reg + off16) = imm32 */ #define BPF_ST_MEM(SIZE, DST, OFF, IMM) \ diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 98161e2d389f..d5389119291e 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -44,6 +44,9 @@ #define BPF_CALL 0x80 /* function call */ #define BPF_EXIT 0x90 /* function return */ +/* atomic op type fields (stored in immediate) */ +#define BPF_FETCH 0x01 /* fetch previous value into src reg */ + /* Register numbers */ enum { BPF_REG_0 = 0,