Messages in this thread | | | Subject | Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI) | From | Rob Gardner <> | Date | Mon, 7 Mar 2016 17:31:23 -0800 |
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On 03/07/2016 10:39 AM, Khalid Aziz wrote: > On 03/07/2016 11:12 AM, Dave Hansen wrote: >> On 03/07/2016 09:53 AM, Andy Lutomirski wrote: >>> Also, what am I missing? Tying these tags to the physical page seems >>> like a poor design to me. This seems really awkward to use. >> >> Yeah, can you describe the structures that store these things? Surely >> the hardware has some kind of lookup tables for them and stores them in >> memory _somewhere_. >> > > Version tags are tied to virtual addresses, not physical pages. > > Where exactly are the tags stored is part of processor architecture > and I am not privy to that. MMU stores these lookup tables somewhere > and uses it to authenticate access to virtual addresses. It really is > irrelevant to kernel how MMU implements access controls as long as we > have access to the knowledge of how to use it.
The tags are stored in physical memory, and you can write a tag directly to that memory via stxa with ASI_MCD_REAL and completely bypass the MMU. When you do that, the tag will still be seen by any virtual address that maps to that physical address.
Rob
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