Re: [stable-4.4.y] compile error with KAISER and no vsyscall emulation

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sat, Feb 10, 2018 at 04:24:10PM -0800, Hugh Dickins wrote:
> On Sat, 10 Feb 2018, Tobias Jakobi wrote:
> > Hello,
> > 
> > I noticed a compile error with a recent version (4.4.115) of the 4.4.y branch:
> > arch/x86/mm/kaiser.c: In function ‘kaiser_init’:
> > arch/x86/mm/kaiser.c:348:8: error: ‘vsyscall_pgprot’ undeclared (first use in
> > this function)
> > 
> > It seems like my combination of kernel options doesn't work for KAISER.
> > X86_VSYSCALL_EMULATION is not set on my system, while LEGACY_VSYSCALL is set to
> > NONE (LEGACY_VSYSCALL_NONE=y). I have managed to get things compiling again, by
> > moving the 'extern unsigned long vsyscall_pgprot' outside of the preprocessor
> > statement. This works for me, I guess because the code in question is never
> > called during runtime anyway (vsyscall_enabled() always returns false).
> > 
> > With best wishes,
> > Tobias
> 
> Yes, sorry about that, thanks Tobias. Same error on 4.9 too.
> Here's the patch that you correctly suggest, and it's good for both:
> 
> 
> [PATCH 4.4 and 4.9] kaiser: fix compile error without vsyscall

Thanks, now queued up.

greg k-h