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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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