root@odroid64-pre:~/crash-7.1.4# ./crash --minimal
crash> rd linux_banner 30
ffffffc00186a090:  0000001600000102 0000000000005018   .........P......
ffffffc00186a0a0:  00000000000115f9 0000001600000102   ................
ffffffc00186a0b0:  0000000000003e11 0000000000011606   .>..............
ffffffc00186a0c0:  0000001600000102 00000000000048d4   .........H......
ffffffc00186a0d0:  0000000000011614 0000001600000102   ................
ffffffc00186a0e0:  000000000000c2f1 0000000000011648   ........H.......
ffffffc00186a0f0:  0000001600000102 00000000000048d4   .........H......
ffffffc00186a100:  0000000000011656 0000001600000102   V...............
ffffffc00186a110:  0000000000009225 000000000001167d   %.......}.......
ffffffc00186a120:  0000001600000102 000000000000080f   ................
ffffffc00186a130:  0000000000011688 0000001600000102   ................
ffffffc00186a140:  0000000000006e9f 0000000000011695   .n..............
ffffffc00186a150:  0000001600000102 000000000000619c   .........a......
ffffffc00186a160:  00000000000116a2 0000001600000102   ................
ffffffc00186a170:  000000000000574a 00000000000116af   JW..............
crash>
crash>  help -m | grep -e page_offset -e phys_offset
           page_offset: ffffffc000000000
           phys_offset: 1000000

debug: 4
crash> rd linux_banner
<addr: ffffffc00186a090 count: 1 flag: 490 (KVADDR)>
<readmem: ffffffc00186a090, KVADDR, "64-bit KVADDR", 8, (FOE), 7ff6123398>
<read_dev_mem: addr: ffffffc00186a090 paddr: 286a090 cnt: 8>
ffffffc00186a090:  0000001600000102                    ........
crash>


>Are there more than one "System RAM" sections in your /proc/iomem?
Just one, the specs on this arm64 board are 2gb of ram
sparse memory is configured.
root@odroid64-pre:~/linux# grep -i sparse .config
CONFIG_SPARSE_IRQ=y
CONFIG_ARCH_SPARSEMEM_ENABLE=y
CONFIG_ARCH_SPARSEMEM_DEFAULT=y
CONFIG_SPARSEMEM_MANUAL=y
CONFIG_SPARSEMEM=y
CONFIG_SPARSEMEM_EXTREME=y
CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
CONFIG_SPARSEMEM_VMEMMAP=y
# CONFIG_INPUT_SPARSEKMAP is not set
# CONFIG_SPARSE_RCU_POINTER is not set

root@odroid64-pre:~/crash-7.1.4# cat /proc/iomem
01000000-0fffffff : System RAM
  01080000-01b21e83 : Kernel code
  01bff000-01ffefff : Kernel data
10200000-77ffffff : System RAM
c11084c0-c11084d3 : c11084c0.serial
c1108500-c110851f : /i2c@c1108500
c1108680-c11086af : c1108680.saradc
c11087c0-c11087df : /i2c@c11087c0
c1109880-c110988f : /pinmux
c8013000-c80137ff : /mhu@c883c400
c8100014-c810001b : mux
c8100024-c810002b : gpio
c810002c-c810002f : pull
c81004c0-c81004d3 : c81004c0.serial
c8834120-c8834133 : pull-enable
c8834430-c883446f : gpio
c88344b0-c88344d7 : mux
c88344e8-c88344fb : pull
c8834540-c8834547 : /ethernet@0xc9410000
c8838000-c88383ff : c8838000.canvas
c883c3d8-c883c3df : c1108680.saradc
c883c400-c883c44b : /mhu@c883c400
c9410000-c941ffff : /ethernet@0xc9410000

I backported about 15 arm64 patches from upstream to the 3.14 kernel we are on and
while doing so noticed a few patches regarding PTE calculations
(I would have to go back and see if any would apply)
Most appeared to be part of bigger changes to the memory layout