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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 7BA88C433DF for ; Thu, 20 Aug 2020 10:19:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DDCF2067C for ; Thu, 20 Aug 2020 10:19:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597918785; bh=0dL8pYVd9qMBr7zVzJoGqGXN8Z9c9tLEAYuKy1M5Sao=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lZyTe9LTfvX3/7spyjNDdMrzG2oj9+GnPLYxVbbVq2JeFkN3mmwZXhdq06SaRAr2F nvvMeypJjs9a3NyQlxQ7o5lWmVc1zFLD1U/X/rScs75cQOSUXzE8ph3m4Vvdr3WVQS m4+dqFWz8Gh5vcBwvpifXSiXr+mmnJ8rz4hjNGLI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731450AbgHTKTo (ORCPT ); Thu, 20 Aug 2020 06:19:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:42492 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731366AbgHTKTN (ORCPT ); Thu, 20 Aug 2020 06:19:13 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 50DF12067C; Thu, 20 Aug 2020 10:19:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597918752; bh=0dL8pYVd9qMBr7zVzJoGqGXN8Z9c9tLEAYuKy1M5Sao=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y7m/U16TdyGLKiUpZ6bivOW1Jasf+OXXJmjyiY2zTUtozMHohQt4ELOWS60wc+nFh 84FckLpFG5r4EuhlQlDajcAHjjctx/vYPHDIAhS5DQ9HMOVemvZizVWHL2q3zcmNjr NZtiM4I686bXnZtTFlA9HRqMADUeBauZOIGEKgZE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ingo Molnar , Miguel Ojeda , Tim Murray , Simon MacMullen , Greg Hackmann , Nick Desaulniers , "Steven Rostedt (VMware)" Subject: [PATCH 4.4 054/149] tracepoint: Mark __tracepoint_strings __used Date: Thu, 20 Aug 2020 11:22:11 +0200 Message-Id: <20200820092128.347118822@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820092125.688850368@linuxfoundation.org> References: <20200820092125.688850368@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nick Desaulniers commit f3751ad0116fb6881f2c3c957d66a9327f69cefb upstream. __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) Signed-off-by: Greg Kroah-Hartman --- include/linux/tracepoint.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -328,7 +328,7 @@ extern void syscall_unregfunc(void); 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