1 2<previous description obsolete, deleted> 3 4Virtual memory map with 4 level page tables: 5 60000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm 7hole caused by [48:63] sign extension 8ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor 9ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory 10ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole 11ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space 12ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole 13ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB) 14... unused hole ... 15ffffec0000000000 - fffffbffffffffff (=44 bits) kasan shadow memory (16TB) 16... unused hole ... 17ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks 18... unused hole ... 19ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space 20... unused hole ... 21ffffffff80000000 - ffffffff9fffffff (=512 MB) kernel text mapping, from phys 0 22ffffffffa0000000 - ffffffffff5fffff (=1526 MB) module mapping space 23ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls 24ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole 25 26The direct mapping covers all memory in the system up to the highest 27memory address (this means in some cases it can also include PCI memory 28holes). 29 30vmalloc space is lazily synchronized into the different PML4 pages of 31the processes using the page fault handler, with init_level4_pgt as 32reference. 33 34Current X86-64 implementations support up to 46 bits of address space (64 TB), 35which is our current limit. This expands into MBZ space in the page tables. 36 37We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual 38memory window (this size is arbitrary, it can be raised later if needed). 39The mappings are not part of any other kernel PGD and are only available 40during EFI runtime calls. 41 42Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all 43physical memory, vmalloc/ioremap space and virtual memory map are randomized. 44Their order is preserved but their base will be offset early at boot time. 45 46-Andi Kleen, Jul 2004 47