Messages in this thread |  | | Date | Sat, 25 Nov 2017 18:03:36 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 20/43] x86/entry: Clean up SYSENTER_stack code |
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On Sat, 25 Nov 2017, Andy Lutomirski wrote: > > 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.
Btw, I don't think you have to worry about making it RO. The SDM is blurry about that for 64bit. RW is a must for 32bit though.
> Maybe I should rename cpu_tss to cpu_tss_rw in that patch.
For clarity that would be nice.
Thanks,
tglx
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