Messages in this thread | | | Subject | Re: [RFC 2/2] x86/pti/64: Remove the SYSCALL64 entry trampoline | From | Dave Hansen <> | Date | Mon, 23 Jul 2018 05:59:24 -0700 |
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On 07/22/2018 10:45 AM, Andy Lutomirski wrote: > static void __init pti_clone_user_shared(void) > { > + unsigned cpu; > + > pti_clone_p4d(CPU_ENTRY_AREA_BASE); > + > + for_each_possible_cpu(cpu) { > + /* > + * The SYSCALL64 entry code needs to be able to find the > + * thread stack and needs one word of scratch space in which > + * to spill a register. All of this lives in the TSS, in > + * the sp1 and sp2 slots. > + */
I had to remind myself about the r/o cpu_entry_area alias here. Should we maybe call it out explicitly?
/* * The TSS is also mapped read-only into the cpu_entry_area. * The cpu_entry_area copy is used r/o by the hardware for the * hardware stack switching, like interrupt entry. * * The copies being mapped here are the normal r/w per-cpu * areas. We need r/w because we spill a register here. */
BTW, since we have this alias, do we still *need* the r/o cpu_entry_area alias? Or do we still get some value from keeping the thing referenced by hardware r/o?
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