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Re: [PATCH v4 0/4] Application Data Integrity feature introduced by SPARC M7

From David Miller <davem@davemloft.net>
Newsgroups linux.kernel
Subject Re: [PATCH v4 0/4] Application Data Integrity feature introduced by SPARC M7
Date 2017-01-17 05:50 +0100
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From: Dave Hansen <dave.hansen@linux.intel.com>
Date: Wed, 11 Jan 2017 10:13:54 -0800

> For memory shared by two different processes, do they have to agree on
> what the tags are, or can they differ?

Whoever allocates the memory (does the mmap()+mprotect() or whatever),
decides on the tag.  They set it, and this determines which virtual
address is valid to access that mapping.

It's like kmalloc() returns pointers with some weird bits set in the
upper bits of the address.  Behind the scenes kmalloc() sets the
TAG bits appropriately.

It doesn't, in that sense, matter where in the non-tagged virtual
address space the memory is mapped.  All that matters is that, for
a given page, the TAG bits in the virtual address used for loads
and stores to that mapping are set properly.

I think the fundamental thing being missed is that the TAG bits in the
virtual address are not interpreted by the TLB.  They are chopped off
before virtual address translation occurs.

The TAG bits of the virtual address serve only to indicate what ADI
value the load or store thinks is valid to use for access to that
piece of memory.

Or something like that... :-)

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Thread

[PATCH v4 0/4] Application Data Integrity feature introduced by SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-11 17:20 +0100
  [PATCH v4 1/4] signals, sparc: Add signal codes for ADI violations Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-11 17:20 +0100
  Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-11 17:40 +0100
    Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-11 18:00 +0100
      Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-11 19:20 +0100
        Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-11 20:00 +0100
          Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-11 20:20 +0100
            Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-12 01:30 +0100
              Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-12 01:50 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-12 18:00 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-12 19:00 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-13 01:30 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Rob Gardner <rob.gardner@oracle.com> - 2017-01-13 02:40 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-13 15:50 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Rob Gardner <rob.gardner@oracle.com> - 2017-01-13 16:40 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-13 17:10 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Rob Gardner <rob.gardner@oracle.com> - 2017-01-13 18:40 +0100
                Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-13 17:10 +0100
        Re: [PATCH v4 0/4] Application Data Integrity feature introduced  by SPARC M7 David Miller <davem@davemloft.net> - 2017-01-17 05:50 +0100
          Re: [PATCH v4 0/4] Application Data Integrity feature introduced by  SPARC M7 Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-17 22:50 +0100
    Re: [PATCH v4 0/4] Application Data Integrity feature introduced  by SPARC M7 David Miller <davem@davemloft.net> - 2017-01-17 06:00 +0100
  Re: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data  Integrity) David Miller <davem@davemloft.net> - 2017-01-17 05:40 +0100
    Re: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data  Integrity) Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-17 20:40 +0100
      Re: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data  Integrity) David Miller <davem@davemloft.net> - 2017-01-17 21:00 +0100
        Re: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data  Integrity) Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-17 21:20 +0100
    Re: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data  Integrity) Khalid Aziz <khalid.aziz@oracle.com> - 2017-01-18 01:20 +0100

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