Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964791Ab1EWUBd (ORCPT ); Mon, 23 May 2011 16:01:33 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:62537 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933960Ab1EWUB3 (ORCPT ); Mon, 23 May 2011 16:01:29 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=H0SQ9LPhRnoMPuFRi7ATz4V8JyldPTkgy3DhehHieyI8JsqDGmQtYKrBpNUJEHICzO njdaA0KxvWne1we0qxhOe1dLmPZgVCngo3MkOOleIYeZxNmYnaY+5qolIXBycr0EJkfJ yw7NNUQ3DCjjXGg1fdV5aBSIaDdTsDSGvI0/s= Date: Mon, 23 May 2011 22:01:23 +0200 (CEST) From: John Kacur X-X-Sender: jkacur@localhost6.localdomain6 To: Steven Rostedt cc: "H. Peter Anvin" , Eduardo Silva , Frederic Weisbecker , Ingo Molnar , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kernel: Fix ftrace.c compiler warning when calling ftrace_nop_replace() In-Reply-To: <1306156114.1465.37.camel@gandalf.stny.rr.com> Message-ID: References: <1306113548.29789.2.camel@monotop> <4DD9BA2F.9000303@zytor.com> <1306156114.1465.37.camel@gandalf.stny.rr.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-1463803646-1583054631-1306180886=:4933" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4569 Lines: 130 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---1463803646-1583054631-1306180886=:4933 Content-Type: TEXT/PLAIN; charset=ISO-8859-7 Content-Transfer-Encoding: 8BIT On Mon, 23 May 2011, Steven Rostedt wrote: > On Sun, 2011-05-22 at 18:36 -0700, H. Peter Anvin wrote: > > On 05/22/2011 06:19 PM, Eduardo Silva wrote: > > > the function ftrace_nop_replace() returns a 'static const unsigned char *' > > > value, so when the caller perform a direct assignment to a > > > 'static unsigned char *', the compiler raise the following warning message: > > > > > > ftrace.c:308:6: warning: assignment discards qualifiers from pointer target type > > > ftrace.c:318:6: warning: assignment discards qualifiers from pointer target type > > > > > > Adding the proper casts the message goes away. > > > > > > Signed-off-by: Eduardo Silva > > > > This quiets a warning of something that potentially looks like a real > > bug. Perhaps "new" should be const? > > Although there is no real bug here, I hate these "hide the warning" > patches. > > The real solution is to change all the users into const *. This should > be doable as the new and old pointers are not modified. > > And remember: > > char *changes; > const char *no_changes; > > no_changes = changes; /* is OK! (no compiler warnings) */ > > changes = no_changes; /* is not OK. (compiler will warn). */ > > -- Steve The following needs some testing, just compile tested for now. >From 71d6e5971cc90a03fd2d7bf8aaa2b81932bd0c7c Mon Sep 17 00:00:00 2001 From: John Kacur Date: Mon, 23 May 2011 21:24:27 +0200 Subject: [PATCH] ftrace: Change unsigned char *new, *old to const MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This removes the warning: arch/x86/kernel/ftrace.c: In function ?ftrace_make_nop?: /arch/x86/kernel/ftrace.c:308: warning: assignment discards qualifiers from pointer target type Steven Rostedt suggested to make these pointers const pointers. This patch assumes that https://patchwork.kernel.org/patch/798172/ is applied first. Reported-by: Eduardo Silva Signed-off-by: John Kacur --- arch/x86/kernel/ftrace.c | 12 ++++++------ 1 files changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 0ba15a6..e4f23d1 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -123,7 +123,7 @@ static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr) static atomic_t nmi_running = ATOMIC_INIT(0); static int mod_code_status; /* holds return value of text write */ static void *mod_code_ip; /* holds the IP to write to */ -static void *mod_code_newcode; /* holds the text to write to the IP */ +static const void *mod_code_newcode; /* holds the text to write to the IP */ static unsigned nmi_wait_count; static atomic_t nmi_update_count = ATOMIC_INIT(0); @@ -225,7 +225,7 @@ within(unsigned long addr, unsigned long start, unsigned long end) } static int -do_ftrace_mod_code(unsigned long ip, void *new_code) +do_ftrace_mod_code(unsigned long ip, const void *new_code) { /* * On x86_64, kernel text mappings are mapped read-only with @@ -266,8 +266,8 @@ static const unsigned char *ftrace_nop_replace(void) } static int -ftrace_modify_code(unsigned long ip, unsigned char *old_code, - unsigned char *new_code) +ftrace_modify_code(unsigned long ip, const unsigned char *old_code, + const unsigned char *new_code) { unsigned char replaced[MCOUNT_INSN_SIZE]; @@ -301,7 +301,7 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code, int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - unsigned char *new, *old; + const unsigned char *new, *old; unsigned long ip = rec->ip; old = ftrace_call_replace(ip, addr); @@ -312,7 +312,7 @@ int ftrace_make_nop(struct module *mod, int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { - unsigned char *new, *old; + const unsigned char *new, *old; unsigned long ip = rec->ip; old = ftrace_nop_replace(); -- 1.7.2.3 ---1463803646-1583054631-1306180886=:4933-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/