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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 B70BCC4727E for ; Fri, 25 Sep 2020 00:33:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EC3723977 for ; Fri, 25 Sep 2020 00:33:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="qolVVq1I" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726807AbgIYAd3 (ORCPT ); Thu, 24 Sep 2020 20:33:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726631AbgIYAd3 (ORCPT ); Thu, 24 Sep 2020 20:33:29 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A6042C0613CE; Thu, 24 Sep 2020 17:33:28 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id g29so1027240pgl.2; Thu, 24 Sep 2020 17:33:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=heSZ+vYMpgFHhWomcOAQ0pB3xOxWwgLlUEvkB5nligg=; b=qolVVq1IXAH2KQsr1j+mJ189ZPsIRozzGguGVAMYYXukIe7sljhxPZT+XB3Z4bB0mh 1nMqK1+EN03THQFbpx6SY1wavqCTlq3Jd8q9ehUKXQfwrKIGfJNmPo/M7XpfoUAhe5mS skl1yghN9442sSafo5zZml7QG5D6QMWG4kYn5xW8TTRFrvuQjp0TRXLR2I1UNoIJpVE2 pUCUl71FFEaJLNeCWT7X/o3URttG5Sc9kK7uclod8TPYVNywP4UpAXyKy3QaAwy9g9NY LwaMVHdhWQwBdhkLSUTWoThubO+wLdUH0wZ+4YgfvsmRQeu74S2CyaKZYO/4cCt/nwoD FF8A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=heSZ+vYMpgFHhWomcOAQ0pB3xOxWwgLlUEvkB5nligg=; b=UiXn4GtBcrC1SWJmj5aGGrXGfpDKs7/vDwYELr59/4vjwuYFBbudwkQqE22UAwR0vr 13zYeC1HbcQRVjr+FJFC0B2+lJK4uSrPlChgIOdswov2pmaGs8RoWnRtwGRoDfWVp6ul 09RjRJELF0N/CJbGL98KS+8M1DeVpInZ/zYwWqGwShg3TT8qyrFrOpBQjgp9qkw7X8Sy J5tI+pH2cahxsJdFHM6v6eMY/hAEnQNXZYoyCyg48xloaFeElDpezeHAq1+S0fM0WZIX FXTR6Z2YyWkmcFfovrzxSpz0ixHkqBAIdrcv1cmAOlci7naPoqvmEub7ts+yyjBMQG0u g4eQ== X-Gm-Message-State: AOAM530nhcGjOm/glfGznAi4j2NG02syU9jAtnVMWD6lwu2DrYjb4uom p4mIYe42dguNWTRy9aO0VQk= X-Google-Smtp-Source: ABdhPJzAV7rIzcHLywe8VSGKzhq95U0ycxS2I81hHRVEYrbo3sKMnkRgNi8ea0dj1c2XdBuo85vX0w== X-Received: by 2002:aa7:9986:0:b029:142:2501:39db with SMTP id k6-20020aa799860000b0290142250139dbmr1599765pfh.42.1600994008051; Thu, 24 Sep 2020 17:33:28 -0700 (PDT) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:400::5:49ed]) by smtp.gmail.com with ESMTPSA id z7sm594743pfj.75.2020.09.24.17.33.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Sep 2020 17:33:27 -0700 (PDT) Date: Thu, 24 Sep 2020 17:33:23 -0700 From: Alexei Starovoitov To: Alan Maguire Cc: ast@kernel.org, daniel@iogearbox.net, andriin@fb.com, yhs@fb.com, linux@rasmusvillemoes.dk, andriy.shevchenko@linux.intel.com, pmladek@suse.com, kafai@fb.com, songliubraving@fb.com, john.fastabend@gmail.com, kpsingh@chromium.org, shuah@kernel.org, rdna@fb.com, scott.branden@broadcom.com, quentin@isovalent.com, cneirabustos@gmail.com, jakub@cloudflare.com, mingo@redhat.com, rostedt@goodmis.org, bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, acme@kernel.org Subject: Re: [PATCH v6 bpf-next 2/6] bpf: move to generic BTF show support, apply it to seq files/strings Message-ID: <20200925003323.u2s2vyyqq2uhtij7@ast-mbp.dhcp.thefacebook.com> References: <1600883188-4831-1-git-send-email-alan.maguire@oracle.com> <1600883188-4831-3-git-send-email-alan.maguire@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1600883188-4831-3-git-send-email-alan.maguire@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 23, 2020 at 06:46:24PM +0100, Alan Maguire wrote: > > +/* Chunk size we use in safe copy of data to be shown. */ > +#define BTF_SHOW_OBJ_SAFE_SIZE 256 sizeof(struct btf_show) == 472 It's allocated on stack and called from bpf prog. It's a leaf function, but it still worries me a bit. I've trimmed it down to 32 and everything seems to be printing fine. There will be more calls to copy_from_kernel_nofault(), but so what? Is there a downside to make it that small? Similarly state.name is 128 bytes. May be use 80 there? I think that should be plenty still. > + * Another problem is we want to ensure the data for display is safe to > + * access. To support this, the "struct obj" is used to track the data 'struct obj' doesn't exist. It's an anon field 'struct {} obj;' inside btf_show that you're referring to, right? Would be good to fix this comment. > +struct btf_show { > + u64 flags; > + void *target; /* target of show operation (seq file, buffer) */ > + void (*showfn)(struct btf_show *show, const char *fmt, ...); buildbot complained that this field needs to be annotated. > +#define btf_show(show, ...) \ > + do { \ > + if (!show->state.depth_check) \ > + show->showfn(show, __VA_ARGS__); \ > + } while (0) Does it have to be a macro? What are you gaining from macro instead of vararg function? > +static inline const char *__btf_show_indent(struct btf_show *show) please remove all 'inline' from .c file. There is no need to give such hints to the compiler. > +#define btf_show_indent(show) \ > + ((show->flags & BTF_SHOW_COMPACT) ? "" : __btf_show_indent(show)) > + > +#define btf_show_newline(show) \ > + ((show->flags & BTF_SHOW_COMPACT) ? "" : "\n") > + > +#define btf_show_delim(show) \ > + (show->state.depth == 0 ? "" : \ > + ((show->flags & BTF_SHOW_COMPACT) && show->state.type && \ > + BTF_INFO_KIND(show->state.type->info) == BTF_KIND_UNION) ? "|" : ",") > + > +#define btf_show_type_value(show, fmt, value) \ > + do { \ > + if ((value) != 0 || (show->flags & BTF_SHOW_ZERO) || \ > + show->state.depth == 0) { \ > + btf_show(show, "%s%s" fmt "%s%s", \ > + btf_show_indent(show), \ > + btf_show_name(show), \ > + value, btf_show_delim(show), \ > + btf_show_newline(show)); \ > + if (show->state.depth > show->state.depth_to_show) \ > + show->state.depth_to_show = show->state.depth; \ > + } \ > + } while (0) > + > +#define btf_show_type_values(show, fmt, ...) \ > + do { \ > + btf_show(show, "%s%s" fmt "%s%s", btf_show_indent(show), \ > + btf_show_name(show), \ > + __VA_ARGS__, btf_show_delim(show), \ > + btf_show_newline(show)); \ > + if (show->state.depth > show->state.depth_to_show) \ > + show->state.depth_to_show = show->state.depth; \ > + } while (0) > + > +/* How much is left to copy to safe buffer after @data? */ > +#define btf_show_obj_size_left(show, data) \ > + (show->obj.head + show->obj.size - data) > + > +/* Is object pointed to by @data of @size already copied to our safe buffer? */ > +#define btf_show_obj_is_safe(show, data, size) \ > + (data >= show->obj.data && \ > + (data + size) < (show->obj.data + BTF_SHOW_OBJ_SAFE_SIZE)) > + > +/* > + * If object pointed to by @data of @size falls within our safe buffer, return > + * the equivalent pointer to the same safe data. Assumes > + * copy_from_kernel_nofault() has already happened and our safe buffer is > + * populated. > + */ > +#define __btf_show_obj_safe(show, data, size) \ > + (btf_show_obj_is_safe(show, data, size) ? \ > + show->obj.safe + (data - show->obj.data) : NULL) Similarly I don't understand the benefit of macros. They all could have been normal functions. > +static inline void *btf_show_obj_safe(struct btf_show *show, > + const struct btf_type *t, > + void *data) drop 'inline' pls. > +{ > + int size_left, size; > + void *safe = NULL; > + > + if (show->flags & BTF_SHOW_UNSAFE) > + return data; > + > + (void) btf_resolve_size(show->btf, t, &size); Is this ok to ignore the error?