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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0CBB7EE4993 for ; Tue, 22 Aug 2023 14:36:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233245AbjHVOgg (ORCPT ); Tue, 22 Aug 2023 10:36:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231316AbjHVOgg (ORCPT ); Tue, 22 Aug 2023 10:36:36 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8CF5291; Tue, 22 Aug 2023 07:36:34 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2087F63513; Tue, 22 Aug 2023 14:36:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF417C433C7; Tue, 22 Aug 2023 14:36:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692714993; bh=xQvQvrIK437NyWJbIp30mYO6bonnV3gFmgFZCl8XdxQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=lZZFW4BrrEmNyruPWDJmhRl42aB1WoBTJ7fhRqGJMCZfzxyj8jU4BFI19rFELpvRE 9IPFwsEgiTxz6tJ9AOzMZ6i1JwxtQ8Ysr4OwqCRKRHSVUn05n3ZcA6A/bvYaiYbBA0 CUkMp6nvC9coz54LQB70PdVx/dhuVVHRviwS4WDPDusKbgMb1nRgy+VxyBF9AiRnz0 eE/XRuDf8T+r1tGAs/rKED7MVzYd7leB4BIkP8Nx8purnT2/NVp7ksjz4f6gpfpjTc OhZ1sU0n5+mgkPWwkeVTKgo5gJzEME+SSi0XdeovkanNjvRehfC3NrXY9xkREF3G1M BmdAk1zLNx9Hg== Date: Tue, 22 Aug 2023 23:36:29 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: Re: [PATCH v5 3/9] tracing/probes: Add a function to search a member of a struct/union Message-Id: <20230822233629.669b3a891a0155addf52f461@kernel.org> In-Reply-To: <20230822093720.016c3554@rorschach.local.home> References: <169137686814.271367.11218568219311636206.stgit@devnote2> <169137689818.271367.4200174950023036516.stgit@devnote2> <20230822093720.016c3554@rorschach.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org On Tue, 22 Aug 2023 09:37:20 -0400 Steven Rostedt wrote: > On Mon, 7 Aug 2023 11:54:58 +0900 > "Masami Hiramatsu (Google)" wrote: > > > --- a/kernel/trace/trace_btf.c > > +++ b/kernel/trace/trace_btf.c > > @@ -50,3 +50,60 @@ const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s3 > > return NULL; > > } > > > > +#define BTF_ANON_STACK_MAX 16 > > + > > +/* > > + * Find a member of data structure/union by name and return it. > > + * Return NULL if not found, or -EINVAL if parameter is invalid. > > + * If the member is an member of anonymous union/structure, the offset > > + * of that anonymous union/structure is stored into @anon_offset. Caller > > + * can calculate the correct offset from the root data structure by > > + * adding anon_offset to the member's offset. > > + */ > > +const struct btf_member *btf_find_struct_member(struct btf *btf, > > + const struct btf_type *type, > > + const char *member_name, > > + u32 *anon_offset) > > +{ > > + struct { > > + u32 tid; > > + u32 offset; > > + } anon_stack[BTF_ANON_STACK_MAX]; > > Where is this called as the above is 128 bytes, which is a bit large > for the stack. It may not be bad if it's not that generic of a > function. But if the stack is getting tight, this could still be an > issue. OK, let me allocate an array then. Thank you, > > -- Steve > > > > + const struct btf_member *member; > > + u32 tid, cur_offset = 0; > > + const char *name; > > + int i, top = 0; > > + > > +retry: > > + if (!btf_type_is_struct(type)) > > + return ERR_PTR(-EINVAL); > > + > > + for_each_member(i, type, member) { > > + if (!member->name_off) { > > + /* Anonymous union/struct: push it for later use */ > > + type = btf_type_skip_modifiers(btf, member->type, &tid); > > + if (type && top < BTF_ANON_STACK_MAX) { > > + anon_stack[top].tid = tid; > > + anon_stack[top++].offset = > > + cur_offset + member->offset; > > + } > > + } else { > > + name = btf_name_by_offset(btf, member->name_off); > > + if (name && !strcmp(member_name, name)) { > > + if (anon_offset) > > + *anon_offset = cur_offset; > > + return member; > > + } > > + } > > + } > > + if (top > 0) { > > + /* Pop from the anonymous stack and retry */ > > + tid = anon_stack[--top].tid; > > + cur_offset = anon_stack[top].offset; > > + type = btf_type_by_id(btf, tid); > > + goto retry; > > + } > > + > > + return NULL; > > +} > > + -- Masami Hiramatsu (Google)