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SubjectRe: [patch] arch-specific cond_syscall usage issues
On Fri, Jan 09, 2004 at 09:21:08PM -0800, Pete Zaitcev wrote:
> On Fri, 9 Jan 2004 19:37:53 -0800
> Andrew Morton <akpm@osdl.org> wrote:
>
> > > Experimenting with trying to use cond_syscall for a few arch-specific
> > > syscalls, I discovered that it can't actually be used outside the file
> > > in which sys_ni_syscall is declared because the assembler doesn't feel
> > > obliged to output the symbol in that case:
>
> > > One arch (PPC) is apparently trying to use cond_syscall this way
> > > anyway, though it's probably never been actually tested as the above
> > > test was done on a PPC.
> >
> > So why does the PPC kernel successfully link?
>
> Perhaps it never was tested right when the change went in.

On closer inspection, PPC has this:

config PCI
bool "PCI support" if 40x || 8260
default y if !40x && !8260 && !8xx && !APUS
default PCI_PERMEDIA if !4xx && !8260 && !8xx && APUS
default PCI_QSPAN if !4xx && !8260 && 8xx
which suggests that non-PCI PPC are limited to very old and/or
embedded boxes. And indeed compiling it for one of these (...much time
elapses...) gets us:

arch/ppc/kernel/built-in.o(.data+0x380):arch/ppc/kernel/entry.S:
undefined reference to `sys_pciconfig_iobase'

> The patch is easy. The hard road would be to take it to binutils people
> like H.J.Lu and see what they say.

I believe Dave M mentioned that gcc uses weak symbols similarly, so
they've probably decided that the necessary smarts to do what we
originally wanted are too much trouble.

--
Matt Mackall : http://www.selenic.com : Linux development and consulting
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