On 11/10/2017 08:05 PM, Andy Lutomirski wrote: > diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h > index fbc9b7f4e35e..8a9ba5553cab 100644 > --- a/arch/x86/include/asm/fixmap.h > +++ b/arch/x86/include/asm/fixmap.h > @@ -52,6 +52,13 @@ extern unsigned long __FIXADDR_TOP; > struct cpu_entry_area > { > char gdt[PAGE_SIZE]; > + > + /* > + * The gdt is just below cpu_tss and thus serves (on x86_64) as a > + * a read-only guard page for the SYSENTER stack at the bottom > + * of the TSS region. > + */ > + struct tss_struct tss; > }; >
Aha, and here's the place that you need sizeof(tss_struct) to be nice and page-aligned. But why don't we just do: char tss_space[PAGE_SIZE*something]; ?