>>> On 30.04.18 at 18:23, <boris.ostrovsky@xxxxxxxxxx> wrote: > --- a/arch/x86/xen/xen-pvh.S > +++ b/arch/x86/xen/xen-pvh.S > @@ -54,6 +54,9 @@ > * charge of setting up it's own stack, GDT and IDT. > */ > > +#define PVH_GDT_ENTRY_CANARY 4 > +#define PVH_CANARY_SEL (PVH_GDT_ENTRY_CANARY * 8) I can only advise against doing it this way: There's no safeguard against someone changing asm/segment.h without changing this value (in fact this applies to all of the GDT selectors populated in this file). At the very least tie this to GDT_ENTRY_BOOT_TSS / __BOOT_TSS? > @@ -64,6 +67,9 @@ ENTRY(pvh_start_xen) > mov %eax,%es > mov %eax,%ss > > + mov $(PVH_CANARY_SEL),%eax > + mov %eax,%gs > + > /* Stash hvm_start_info. */ > mov $_pa(pvh_start_info), %edi > mov %ebx, %esi > @@ -150,6 +156,7 @@ gdt_start: > .quad 0x00cf9a000000ffff /* __BOOT_CS */ > #endif > .quad 0x00cf92000000ffff /* __BOOT_DS */ > + .quad 0x0040900000000018 /* PVH_CANARY_SEL */ Without any further code before loading the selector, this points at physical address 0. Don't you need to add in the base address of the per-CPU stack_canary? Jan
