RFC: if_ndis on amd64

Ville-Pertti Keinonen will at exomi.com
Wed Jan 12 23:16:07 PST 2005

On Wed, 2005-01-12 at 15:33 -0800, David O'Brien wrote:

> What are "calling conventions that everyone else uses"??  Such things
> really don't exist as x86 CPU's don't force a particular way.  It is up
> to the compiler writer to do what he wants.

Note that I didn't even try to claim "standard" calling conventions;
however AFAIK all of the released operating systems that run on amd64
(*BSD, Linux, Solaris) use the same C ABI (SysV (ELF) ABI).

Often at least the basic C calling conventions are compatible across

> Both the AMD64 ELF and AMD64 PE (mswin) ABI's specify that the first X
> parameters are passed in registers (beyond that on the stack).  So both
> ELF (ie, FreeBSD) and MSwin passes parameters differently on 32-bit
> "i386" vs. 64-bit AMD64.

The different i386 conventions are at least partly to historical
reasons.  Since 64-bit mode is inevitably incompatible with 32-bit mode,
I was hoping 64-bit mode would be somewhat more consistent.

Anyhow, having to create wrappers isn't that bad, and should be possible
to be coerced to work correctly.  The varargs kludge I used should be
possible to eliminate by transforming the arguments into a va_list
instead of trying to preserve it as a varargs call.  Something like:

	subq	$40,%rsp
	mov	%rdi,32(%rsp)
	mov	%rsi,24(%rsp)
	mov	%r8,40+8+16(%rsp)
	mov	%r9,40+8+24(%rsp)
	movl	$48,(%rsp)
	movl	$0,4(%rsp)
	lea	40+8+16(%rsp),%rax
	mov	%rax,8(%rsp)
	mov	%rax,16(%rsp)
	mov	%rcx,%rdi
	mov	%rdx,%rsi
	mov	%rsp,%rdx
	call	vsprintf
	mov	32(%rsp),%rdi
	mov	24(%rsp),%rsi
	addq	$40,%rsp

More information about the freebsd-amd64 mailing list