Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265269AbUAJRfR (ORCPT ); Sat, 10 Jan 2004 12:35:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265267AbUAJRfQ (ORCPT ); Sat, 10 Jan 2004 12:35:16 -0500 Received: from bender.bawue.de ([193.7.176.20]:56014 "EHLO bender.bawue.de") by vger.kernel.org with ESMTP id S265278AbUAJRdQ (ORCPT ); Sat, 10 Jan 2004 12:33:16 -0500 To: Tim Cambrant Cc: Mario Vanoni , Linux Kernel Mailing List Subject: Re: 2.6.1-mm2: compiler warning In-Reply-To: <20040110155626.GA20684@cambrant.com> (Tim Cambrant's message of "Sat, 10 Jan 2004 16:56:26 +0100") References: <40001CEE.5050206@bluewin.ch> <20040110155626.GA20684@cambrant.com> From: Hans Ulrich Niedermann Date: Sat, 10 Jan 2004 18:31:42 +0100 Message-ID: <86r7y7pv5t.fsf@n-dimensional.de> User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Reasonable Discussion, linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2872 Lines: 90 Tim Cambrant writes: > On Sat, Jan 10, 2004 at 04:40:30PM +0100, Mario Vanoni wrote: >> Compiling the kernel under 2.6.1-mm2, gcc-3.3.2 >> (same messages as under 2.6.1-rc1-mm1, re-tested), >> >> arch/i386/boot/setup.S: Assembler messages: >> arch/i386/boot/setup.S:165: Warning: value 0x37ffffff truncated to >> 0x37ffffff >> > If you've got a fix, it would surely be included in the kernel. Hmm... let's see... The assembler calculates in arch/i386/boot/setup.S (with the definition of MAXMEM from include/asm-i386/page.h): - 0xC0000000 - 0x08000000 - 1 This obviously is a negative number which is what the assembler warns us about. As there are no negative memory addresses anyway, the number we really want is the positive number (1 << 32) - 0xC0000000 - 0x08000000 - 1 which is the same in modulo (1 << 32) arithmetic, of course. Original arch/i386/boot/setup.o (subtract from 0): 0000002c : 2c: ff (bad) 2d: ff (bad) 2e: ff 37 pushl (%edi) Patched arch/i386/boot/setup.o (subtract from (1<<32)): 0000002c : 2c: ff (bad) 2d: ff (bad) 2e: ff 37 pushl (%edi) This looks OK to me so far. However, a few issues remain: - There probably are some nasty side effects in other places which I haven't thought about. - I didn't try to boot the patched kernel yet. - As I don't know whether the C compiler might get confused about that, I re-used the #ifdef in include/asm-i386/page.h. Subtracting UL constants from (0UL) shouldn't make a difference, even if subtracting from 0x100000000UL might. - __MAXMEM_ADDRSPACE_MAX should probably be defined using a constant from somewhere else. (Where from?) Regards, Uli --- linux-2.6.1/include/asm-i386/page.h.orig Sat Jan 10 18:01:31 2004 +++ linux-2.6.1/include/asm-i386/page.h Sat Jan 10 18:03:48 2004 @@ -116,14 +116,16 @@ #ifdef __ASSEMBLY__ #define __PAGE_OFFSET (0xC0000000) +#define __MAXMEM_ADDRSPACE_MAX (1 << 32) #else #define __PAGE_OFFSET (0xC0000000UL) +#define __MAXMEM_ADDRSPACE_MAX (0UL) #endif #define PAGE_OFFSET ((unsigned long)__PAGE_OFFSET) #define VMALLOC_RESERVE ((unsigned long)__VMALLOC_RESERVE) -#define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE) +#define MAXMEM (__MAXMEM_ADDRSPACE_MAX-__PAGE_OFFSET-__VMALLOC_RESERVE) #define __pa(x) ((unsigned long)(x)-PAGE_OFFSET) #define __va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET)) #define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT) - 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/