linux-kernel - Re: [RFC] [PATCH] asm-generic/unistd.h: handle symbol prefixes in cond

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Date:	Fri, 24 Feb 2012 11:19:42 -0500
From:	Mike Frysinger <vapier@...too.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	James Hogan <james.hogan@...tec.com>, linux-arch@...r.kernel.org,
	"linux-kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] [PATCH] asm-generic/unistd.h: handle symbol prefixes in cond_syscall

On Friday 24 February 2012 09:24:07 Arnd Bergmann wrote:
> On Friday 24 February 2012, James Hogan wrote:
> > Some architectures have symbol prefixes and set CONFIG_SYMBOL_PREFIX,
> > but this wasn't taken into account by the generic cond_syscall. It's
> > easy enough to fix in a generic fashion, so add the symbol prefix to
> > symbol names in cond_syscall when CONFIG_SYMBOL_PREFIX is set.
> > 
> >  include/asm-generic/unistd.h |    9 ++++++++-
> >  1 files changed, 8 insertions(+), 1 deletions(-)
> > 
> > --- a/include/asm-generic/unistd.h
> > +++ b/include/asm-generic/unistd.h
> >  
> >  #ifndef cond_syscall
> > -#define cond_syscall(x) asm(".weak\t" #x "\n\t.set\t" #x
> > ",sys_ni_syscall")
> > +#ifdef CONFIG_SYMBOL_PREFIX
> > +#define __SYMBOL_PREFIX CONFIG_SYMBOL_PREFIX
> > +#else
> > +#define __SYMBOL_PREFIX
> > +#endif
> > +#define cond_syscall(x) asm(".weak\t" __SYMBOL_PREFIX #x "\n\t" \
> > +                           ".set\t" __SYMBOL_PREFIX #x "," \
> > +                           __SYMBOL_PREFIX "sys_ni_syscall")
> > 
> >  #endif
> 
> Our trend is to move away from arch specific Kconfig symbols and
> __ARCH_HAS_* macros towards just defining whatever you need in the
> architecture as an override for the generic definition.

i don't see how __ARCH_HAS_xxx would help here.  the symbol prefix is a string, 
not a bool value.  it's also already used by linux/export.h, asm-
generic/vmlinux.lds.h, and module code in scripts/.

> Just provide your own unistd.h that does

the point of asm-generic is so that arches don't have to keep copying & 
pasting things that they really don't care about.  James' proposed patch looks 
good to me.  it might be nice to go even further and add logic to a core 
header so that CONFIG_SYMBOL_PREFIX is always defined ...
-mike

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