asm-x86/byteorder.h, CONFIG_X86_BSWAP leaks to userland

asm-x86/byteorder.h, CONFIG_X86_BSWAP leaks to userland

[Olaf Hering]

What is the purpose of CONFIG_X86_BSWAP in asm-x86/byteorder.h?

An undefined CONFIG_foo defaults to 0 (I think), so bswap is never used.
Is this done on purpose, or can the CONFIG_ foo be moved inside
__KERNEL__ somehow?

Olaf

Re: asm-x86/byteorder.h, CONFIG_X86_BSWAP leaks to userland

[Arjan van de Ven]

On Sat, 26 Jul 2008 12:48:31 -0400
"H. Peter Anvin" <hpa@zytor.com> w
> > I'm not sure if it's time yet to make the bswap ones be exported,
> > as they would no longer be usable for those early machines.  X86
> > guys CC:d.
> 
> On i386 we still default to i386-compatible binaries; I *think* gcc
> has macros telling you if the user has used -march=i486 etc.

It is also not the kernels job to provide this sort of functionality to
userspace programs. At all. This is gcc/glibc/etc's job.

Rule of thumb: the kernel does not provide code for compiling inside
userspace programs.

(As opposed to providing datastructures that userspace programs can use
to talk to the kernel).



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Re: asm-x86/byteorder.h, CONFIG_X86_BSWAP leaks to userland

[H. Peter Anvin]

Arjan van de Ven wrote:
\>
> It is also not the kernels job to provide this sort of functionality to
> userspace programs. At all. This is gcc/glibc/etc's job.
> 
> Rule of thumb: the kernel does not provide code for compiling inside
> userspace programs.
> 
> (As opposed to providing datastructures that userspace programs can use
> to talk to the kernel).
> 

That's a fine rule of thumb, but we have 17 years of legacy to deal with 
here, too.

	-hpa