Messages in this thread | | | Subject | Re: [PATCH 20/43] x86/entry: Clean up SYSENTER_stack code | From | Andy Lutomirski <> | Date | Sat, 25 Nov 2017 09:55:15 -0700 |
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> On Nov 25, 2017, at 9:50 AM, Thomas Gleixner <tglx@linutronix.de> wrote: > > On Sat, 25 Nov 2017, Borislav Petkov wrote: >>> - >>> + wrmsr(MSR_IA32_SYSENTER_ESP, (unsigned long)(cpu_SYSENTER_stack(cpu) + 1), 0); >>> wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long)entry_SYSENTER_32, 0); >> >> Right, so we have now two TSS thingies, AFAICT: >> >> tss = &per_cpu(cpu_tss, cpu); >> >> which is cpu_tss and then indirectly, we have also: >> >> &get_cpu_entry_area((cpu))->tss >> >> And those are two different things in my guest here: >> >> [ 0.044002] tss: 0xf5747000 >> [ 0.044706] entry area tss: 0xffef1000 >> >> What is the logic here? We carry two TSSs per CPU - one which is RO >> for the entry area and the other is the actual cpu_tss thing? Or am I >> misreading it? > > entry area tss is a alias mapping of cpu_tss > > + set_percpu_fixmap_pages(get_cpu_entry_area_index(cpu, tss), > + &per_cpu(cpu_tss, cpu), > + sizeof(struct tss_struct) / PAGE_SIZE, > + PAGE_KERNEL); >
Exactly. And, in the patch I haven't emailed, the alias is RO on x86_64.
Maybe I should rename cpu_tss to cpu_tss_rw in that patch.
> Thanks, > > tglx
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