From mboxrd@z Thu Jan 1 00:00:00 1970 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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 AAF63C433DF for ; Thu, 14 May 2020 20:11:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 811F420709 for ; Thu, 14 May 2020 20:11:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DYKQOwQ4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727823AbgENULw (ORCPT ); Thu, 14 May 2020 16:11:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726128AbgENULv (ORCPT ); Thu, 14 May 2020 16:11:51 -0400 Received: from mail-qk1-x743.google.com (mail-qk1-x743.google.com [IPv6:2607:f8b0:4864:20::743]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF978C061A0C; Thu, 14 May 2020 13:11:51 -0700 (PDT) Received: by mail-qk1-x743.google.com with SMTP id n14so198230qke.8; Thu, 14 May 2020 13:11:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SWTxaSNIaPrCERES4dBKm2aAsOkRsnixPtMUzOKzRpA=; b=DYKQOwQ42LSCSc47RMjHaOtJ0bCcftcelLOJjuChExKywOLSTEuLLwauis7IjyBAsq lAnb2sIOYAsvVqS9XbLtQBsLbTWzWkedESvZeOiab2GvL3IB+HSqKBZZtAWsgQFuKg5s BHgrko0arGfLjLGhku36TlTinAMm7QDQ+8KjWVp4n1NpkRUemuESdXvkZi29i1NB1MpY 7VglKdXbhjeitsmGG1tUR7PTwMJqqXZKP9MEUSFJDYyTjTQrcIZQ3ci5h025RZrrp+S3 /nCceJaQPJOCc43ASaUkVs0+tVJ6ML9faO2+aSwEO6B4FuxFkrNu1yV2kwuWJFvAKij+ hutQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SWTxaSNIaPrCERES4dBKm2aAsOkRsnixPtMUzOKzRpA=; b=FxApYEUJ/UlDfjuafU6j57rV+jILxWc9oiuIK3dX3mVWmzjPW7tzc3iQwAEhGxvGD6 QUOiMmVvTrdY6+4BDvmvB/pBFXDom9OTeVCmyKRYL/UqHtQCm5clVLkikzxC2khzOsdD XEWTIo8TtpQ2SK3lFoUwt8Dgi5tX7QxnDvWg3txCjPa+XJcCgF+vrZHwD/uSk438PkLQ f7h7ajuu5CO+2b4fneRsRSPf7oGiWyc/5hzjrTjpsjWxp00bC8m6SuZZYQeFu89ADjQC kgVZs8z++CVaXrqTQo3syQTZeqcjyZJysXz5bL6rQ76UVYlRm4FO49lAHjhnBKlYj6bW TBiA== X-Gm-Message-State: AOAM53004y+690oZAbmPDxWC+DGc8GL8LeWMJbYqAUUqPL2TSFiojHKI dPI858AYErVudjZhxVayTJgw36/1kID0XfhInJY= X-Google-Smtp-Source: ABdhPJyMrNUdVh3UMUD/6vKXwQgy5EDQ9EZiD3QuGNK3wJVF9pmeZDuaa6F+jXHsNahn6GU20CAs6cryAZQ0nqA0op8= X-Received: by 2002:ae9:e713:: with SMTP id m19mr79643qka.39.1589487110850; Thu, 14 May 2020 13:11:50 -0700 (PDT) MIME-Version: 1.0 References: <20200513192532.4058934-1-andriin@fb.com> <20200513192532.4058934-2-andriin@fb.com> <20200514165045.sk6zjlhsfzxbo6mb@bsd-mbp> In-Reply-To: <20200514165045.sk6zjlhsfzxbo6mb@bsd-mbp> From: Andrii Nakryiko Date: Thu, 14 May 2020 13:11:39 -0700 Message-ID: Subject: Re: [PATCH bpf-next 1/6] bpf: implement BPF ring buffer and verifier support for it To: Jonathan Lemon Cc: Andrii Nakryiko , bpf , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team , "Paul E . McKenney" , Jonathan Lemon Content-Type: text/plain; charset="UTF-8" Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, May 14, 2020 at 9:50 AM Jonathan Lemon wrote: > > On Wed, May 13, 2020 at 12:25:27PM -0700, Andrii Nakryiko wrote: > > +static struct bpf_ringbuf *bpf_ringbuf_restore_from_rec(void *meta_ptr) > > +{ > > + unsigned long addr = (unsigned long)meta_ptr; > > + unsigned long off = *(u32 *)(meta_ptr + 4) << PAGE_SHIFT; > > + > > + return (void*)((addr & PAGE_MASK) - off); > > +} > > + > > +static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) > > +{ > > + unsigned long cons_pos, prod_pos, new_prod_pos, flags; > > + u32 len, pg_off; > > + void *meta_ptr; > > + > > + if (unlikely(size > UINT_MAX)) > > + return NULL; > > Size should be 30 bits, not UINT_MAX, since 2 bits are reserved. Oh, good catch, thanks. Yep, should be (UINT_MAX >> 2), will add a constant for this. > > > + > > + len = round_up(size + RINGBUF_META_SZ, 8); > > + cons_pos = READ_ONCE(rb->consumer_pos); > > + > > + if (in_nmi()) { > > + if (!spin_trylock_irqsave(&rb->spinlock, flags)) > > + return NULL; > > + } else { > > + spin_lock_irqsave(&rb->spinlock, flags); > > + } > > + > > + prod_pos = rb->producer_pos; > > + new_prod_pos = prod_pos + len; > > + > > + /* check for out of ringbuf space by ensuring producer position > > + * doesn't advance more than (ringbuf_size - 1) ahead > > + */ > > + if (new_prod_pos - cons_pos > rb->mask) { > > + spin_unlock_irqrestore(&rb->spinlock, flags); > > + return NULL; > > + } > > + > > + meta_ptr = rb->data + (prod_pos & rb->mask); > > + pg_off = bpf_ringbuf_rec_pg_off(rb, meta_ptr); > > + > > + WRITE_ONCE(*(u32 *)meta_ptr, RINGBUF_BUSY_BIT | size); > > + WRITE_ONCE(*(u32 *)(meta_ptr + 4), pg_off); > > Or define a 64bit word in the structure and use: > > WRITE_ONCE(*(u64 *)meta_ptr, rec.header); yep, can do that > > > > + > > + /* ensure length prefix is written before updating producer positions */ > > + smp_wmb(); > > + WRITE_ONCE(rb->producer_pos, new_prod_pos); > > + > > + spin_unlock_irqrestore(&rb->spinlock, flags); > > + > > + return meta_ptr + RINGBUF_META_SZ; > > +} > > + > > +BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags) > > +{ > > + struct bpf_ringbuf_map *rb_map; > > + > > + if (unlikely(flags)) > > + return -EINVAL; > > + > > + rb_map = container_of(map, struct bpf_ringbuf_map, map); > > + return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size); > > +} > > + > > -- > Jonathan