Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750945AbWJDTp1 (ORCPT ); Wed, 4 Oct 2006 15:45:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750949AbWJDTp1 (ORCPT ); Wed, 4 Oct 2006 15:45:27 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:57068 "EHLO e3.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1750945AbWJDTpZ (ORCPT ); Wed, 4 Oct 2006 15:45:25 -0400 Date: Wed, 4 Oct 2006 15:44:41 -0400 From: Vivek Goyal To: Franck Bui-Huu Cc: linux-kernel@vger.kernel.org, Reloc Kernel List , ebiederm@xmission.com, akpm@osdl.org, ak@suse.de, horms@verge.net.au, lace@jankratochvil.net, hpa@zytor.com, magnus.damm@gmail.com, lwang@redhat.com, dzickus@redhat.com, maneesh@in.ibm.com Subject: Re: [PATCH 4/12] i386: define __pa_symbol() Message-ID: <20061004194441.GF16218@in.ibm.com> Reply-To: vgoyal@in.ibm.com References: <20061003170032.GA30036@in.ibm.com> <20061003171055.GD3164@in.ibm.com> <45237044.8090805@innova-card.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45237044.8090805@innova-card.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2674 Lines: 79 On Wed, Oct 04, 2006 at 10:26:44AM +0200, Franck Bui-Huu wrote: > hi, > > Sorry for the late feedback... > > Vivek Goyal wrote: > > > > On x86_64 we have to be careful with calculating the physical > > address of kernel symbols. Both because of compiler odditities > > and because the symbols live in a different range of the virtual > > address space. > > > > [snip] > > > +#define __pa_symbol(x) \ > > + ({unsigned long v; \ > > + asm("" : "=r" (v) : "0" (x)); \ > > + __pa(v); }) > > Why not simply reusing RELOC_HIDE like this ? > > #define __pa_symbol(x) __pa(RELOC_HIDE(x,0)) > Thanks. Above did not work and compiler gave following warning message upon using __pa_symbol(_text) error: cast specified array type Then I specifically typecasted x to unsigned long and it seems to be fine. Regenerated patch is attached. On x86_64 we have to be careful with calculating the physical address of kernel symbols. Both because of compiler odditities and because the symbols live in a different range of the virtual address space. Having a defintition of __pa_symbol that works on both x86_64 and i386 simplifies writing code that works for both x86_64 and i386 that has these kinds of dependencies. So this patch adds the trivial i386 __pa_symbol definition. Added assembly magic similar to RELOC_HIDE as suggested by Andi Kleen. Just picked it up from x86_64. Signed-off-by: Eric W. Biederman Signed-off-by: Vivek Goyal --- include/asm-i386/page.h | 3 +++ 1 file changed, 3 insertions(+) diff -puN include/asm-i386/page.h~i386-define-__pa_symbol include/asm-i386/page.h --- linux-2.6.18-git17/include/asm-i386/page.h~i386-define-__pa_symbol 2006-10-02 14:39:18.000000000 -0400 +++ linux-2.6.18-git17-root/include/asm-i386/page.h 2006-10-04 14:48:54.000000000 -0400 @@ -124,6 +124,9 @@ extern int page_is_ram(unsigned long pag #define VMALLOC_RESERVE ((unsigned long)__VMALLOC_RESERVE) #define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE) #define __pa(x) ((unsigned long)(x)-PAGE_OFFSET) +/* __pa_symbol should be used for C visible symbols. + This seems to be the official gcc blessed way to do such arithmetic. */ +#define __pa_symbol(x) __pa(RELOC_HIDE((unsigned long)x,0)) #define __va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET)) #define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT) #ifdef CONFIG_FLATMEM _ - 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/