46 lines
2.1 KiB
Text
46 lines
2.1 KiB
Text
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<previous description obsolete, deleted>
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Virtual memory map with 4 level page tables:
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0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
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hole caused by [48:63] sign extension
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ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor
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ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory
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ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole
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ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space
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ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole
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ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB)
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... unused hole ...
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ffffec0000000000 - fffffbffffffffff (=44 bits) kasan shadow memory (16TB)
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... unused hole ...
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ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
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... unused hole ...
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ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space
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... unused hole ...
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ffffffff80000000 - ffffffff9fffffff (=512 MB) kernel text mapping, from phys 0
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ffffffffa0000000 - ffffffffff5fffff (=1526 MB) module mapping space
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ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
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ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
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The direct mapping covers all memory in the system up to the highest
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memory address (this means in some cases it can also include PCI memory
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holes).
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vmalloc space is lazily synchronized into the different PML4 pages of
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the processes using the page fault handler, with init_level4_pgt as
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reference.
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Current X86-64 implementations support up to 46 bits of address space (64 TB),
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which is our current limit. This expands into MBZ space in the page tables.
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We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual
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memory window (this size is arbitrary, it can be raised later if needed).
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The mappings are not part of any other kernel PGD and are only available
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during EFI runtime calls.
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Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all
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physical memory, vmalloc/ioremap space and virtual memory map are randomized.
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Their order is preserved but their base will be offset early at boot time.
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-Andi Kleen, Jul 2004
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