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
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