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=-0.8 required=3.0 tests=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 1CD5EC433E1 for ; Thu, 14 May 2020 16:57:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E9268206A5 for ; Thu, 14 May 2020 16:57:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726327AbgENQ5a (ORCPT ); Thu, 14 May 2020 12:57:30 -0400 Received: from smtp4.emailarray.com ([65.39.216.22]:24927 "EHLO smtp4.emailarray.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726287AbgENQ53 (ORCPT ); Thu, 14 May 2020 12:57:29 -0400 Received: (qmail 57254 invoked by uid 89); 14 May 2020 16:50:48 -0000 Received: from unknown (HELO localhost) (amxlbW9uQGZsdWdzdmFtcC5jb21AMTYzLjExNC4xMzIuMw==) (POLARISLOCAL) by smtp4.emailarray.com with SMTP; 14 May 2020 16:50:48 -0000 Date: Thu, 14 May 2020 09:50:45 -0700 From: Jonathan Lemon To: Andrii Nakryiko Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, ast@fb.com, daniel@iogearbox.net, andrii.nakryiko@gmail.com, kernel-team@fb.com, "Paul E . McKenney" , Jonathan Lemon Subject: Re: [PATCH bpf-next 1/6] bpf: implement BPF ring buffer and verifier support for it Message-ID: <20200514165045.sk6zjlhsfzxbo6mb@bsd-mbp> References: <20200513192532.4058934-1-andriin@fb.com> <20200513192532.4058934-2-andriin@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200513192532.4058934-2-andriin@fb.com> Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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. > + > + 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); > + > + /* 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