On Thu, 19 Mar 2020, Jan Beulich wrote: > On 19.03.2020 10:56, Miroslav Benes wrote: > > The unwinder reports the boot CPU idle task's stack on XEN PV as > > unreliable, which affects at least live patching. There are two reasons > > for this. First, the task does not follow the x86 convention that its > > stack starts at the offset right below saved pt_regs. It allows the > > unwinder to easily detect the end of the stack and verify it. Second, > > startup_xen() function does not store the return address before jumping > > to xen_start_kernel() which confuses the unwinder. > > > > Amend both issues by moving the starting point of initial stack in > > startup_xen() and storing the return address before the jump, which is > > exactly what call instruction does. > > > > Signed-off-by: Miroslav Benes <mbenes@xxxxxxx> > > --- > > arch/x86/xen/xen-head.S | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S > > index 1d0cee3163e4..edc776af0e0a 100644 > > --- a/arch/x86/xen/xen-head.S > > +++ b/arch/x86/xen/xen-head.S > > @@ -35,7 +35,11 @@ SYM_CODE_START(startup_xen) > > rep __ASM_SIZE(stos) > > > > mov %_ASM_SI, xen_start_info > > - mov $init_thread_union+THREAD_SIZE, %_ASM_SP > > +#ifdef CONFIG_X86_64 > > + mov initial_stack(%rip), %_ASM_SP > > +#else > > + mov pa(initial_stack), %_ASM_SP > > +#endif > > If you need to distinguish the two anyway, why not use %rsp and > %esp respectively? I could, I just preferred the unification instead. Will change it if you think it would be better. Miroslav
