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SubjectRe: [PATCH 12/14] x86: remove address space overrides using set_fs()
On Fri, Sep 04, 2020 at 03:55:10AM +0100, Al Viro wrote:
> On Thu, Sep 03, 2020 at 04:22:40PM +0200, Christoph Hellwig wrote:
>
> > diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
> > index c8a85b512796e1..94f7be4971ed04 100644
> > --- a/arch/x86/lib/getuser.S
> > +++ b/arch/x86/lib/getuser.S
> > @@ -35,10 +35,19 @@
> > #include <asm/smap.h>
> > #include <asm/export.h>
> >
> > +#ifdef CONFIG_X86_5LEVEL
> > +#define LOAD_TASK_SIZE_MINUS_N(n) \
> > + ALTERNATIVE "mov $((1 << 47) - 4096 - (n)),%rdx", \
> > + "mov $((1 << 56) - 4096 - (n)),%rdx", X86_FEATURE_LA57
> > +#else
> > +#define LOAD_TASK_SIZE_MINUS_N(n) \
> > + mov $(TASK_SIZE_MAX - (n)),%_ASM_DX
> > +#endif
>
> Wait a sec... how is that supposed to build with X86_5LEVEL? Do you mean
>
> #define LOAD_TASK_SIZE_MINUS_N(n) \
> ALTERNATIVE __stringify(mov $((1 << 47) - 4096 - (n)),%rdx), \
> __stringify(mov $((1 << 56) - 4096 - (n)),%rdx), X86_FEATURE_LA57
>
> there?

Don't ask me about the how, but it builds and works with X86_5LEVEL,
and the style is copied from elsewhere..

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