From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46104) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b6Hyj-0002zx-1l for qemu-devel@nongnu.org; Fri, 27 May 2016 09:39:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b6Hye-0003ge-Qq for qemu-devel@nongnu.org; Fri, 27 May 2016 09:39:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51779) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b6Hye-0003gY-Kx for qemu-devel@nongnu.org; Fri, 27 May 2016 09:39:00 -0400 Date: Fri, 27 May 2016 14:38:58 +0100 From: "Richard W.M. Jones" Message-ID: <20160527133858.GR1683@redhat.com> References: <1464343604-517-1-git-send-email-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PULL 00/31] Misc changes for 2016-05-27 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Paolo Bonzini , QEMU Developers , Marc =?iso-8859-1?Q?Mar=ED?= On Fri, May 27, 2016 at 02:04:52PM +0100, Peter Maydell wrote: > With V=1: > > i686-w64-mingw32-ld -m i386pe -Ttext 0 -e _start -s -o > linuxboot_dma.img linuxboot_dma.o > linuxboot_dma.o:linuxboot_dma.c:(.text+0x57): undefined reference to > `load_kernel' > > Building an image for the target using our host compiler seems like > an odd choice, Which compiler should I be using? > but the makefile obviously intends to support it > since it has specific ifdef CONFIG_WIN32 code to adjust the linker > command line. > > I suspect this is a mismatch between the symbol the native asm is > using and the one that the C compiler wants: > > $ nm build/w32-new/pc-bios/optionrom/linuxboot_dma.o |grep load_kernel > 000005dd T _load_kernel > U load_kernel > > since name mangling rules are different for Linux and Windows ABIs. One way to solve this (which works for me) is as below. There are some other approaches, eg. using -fno-leading-underscore, or using a conditional macro to mangle the name. However I have no idea if there is some preferred way. Rich. diff --git a/pc-bios/optionrom/linuxboot_dma.c b/pc-bios/optionrom/linuxboot_dma.c index 86ef1ce..8509b28 100644 --- a/pc-bios/optionrom/linuxboot_dma.c +++ b/pc-bios/optionrom/linuxboot_dma.c @@ -213,6 +213,9 @@ static uint32_t get_e801_addr(void) return ret; } +/* Force the asm name without leading underscore, even on Win32. */ +extern void load_kernel(void) asm("load_kernel"); + void load_kernel(void) { void *setup_addr; -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org