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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 4E7CDC433DF for ; Tue, 4 Aug 2020 20:59:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 392102086A for ; Tue, 4 Aug 2020 20:59:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728624AbgHDU7E (ORCPT ); Tue, 4 Aug 2020 16:59:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:42174 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728095AbgHDU6Q (ORCPT ); Tue, 4 Aug 2020 16:58:16 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 539FA22CB2; Tue, 4 Aug 2020 20:58:14 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1k340j-006HDS-Af; Tue, 04 Aug 2020 16:58:13 -0400 Message-ID: <20200804205813.223522602@goodmis.org> User-Agent: quilt/0.66 Date: Tue, 04 Aug 2020 16:57:52 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Ingo Molnar , Miguel Ojeda , stable@vger.kernel.org, Tim Murray , Simon MacMullen , Greg Hackmann , Nick Desaulniers Subject: [for-linus][PATCH 09/17] tracepoint: Mark __tracepoint_strings __used References: <20200804205743.419135730@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nick Desaulniers __tracepoint_string's have their string data stored in .rodata, and an address to that data stored in the "__tracepoint_str" section. Functions that refer to those strings refer to the symbol of the address. Compiler optimization can replace those address references with references directly to the string data. If the address doesn't appear to have other uses, then it appears dead to the compiler and is removed. This can break the /tracing/printk_formats sysfs node which iterates the addresses stored in the "__tracepoint_str" section. Like other strings stored in custom sections in this header, mark these __used to inform the compiler that there are other non-obvious users of the address, so they should still be emitted. Link: https://lkml.kernel.org/r/20200730224555.2142154-2-ndesaulniers@google.com Cc: Ingo Molnar Cc: Miguel Ojeda Cc: stable@vger.kernel.org Fixes: 102c9323c35a8 ("tracing: Add __tracepoint_string() to export string pointers") Reported-by: Tim Murray Reported-by: Simon MacMullen Suggested-by: Greg Hackmann Signed-off-by: Nick Desaulniers Signed-off-by: Steven Rostedt (VMware) --- include/linux/tracepoint.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index a1fecf311621..3a5b717d92e8 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -361,7 +361,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) static const char *___tp_str __tracepoint_string = str; \ ___tp_str; \ }) -#define __tracepoint_string __attribute__((section("__tracepoint_str"))) +#define __tracepoint_string __attribute__((section("__tracepoint_str"), used)) #else /* * tracepoint_string() is used to save the string address for userspace -- 2.26.2