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Commit | Line | Data |
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1da177e4 LT |
1 | |
2 | <previous description obsolete, deleted> | |
3 | ||
4 | Virtual memory map with 4 level page tables: | |
5 | ||
57d30772 | 6 | 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm |
4c7c4483 | 7 | hole caused by [47:63] sign extension |
beb9147e | 8 | ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor |
2feceeff | 9 | ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory |
c898faf9 RR |
10 | ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole |
11 | ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space | |
12 | ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole | |
13 | ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB) | |
ef7f0d6a | 14 | ... unused hole ... |
9d9cce7f | 15 | ffffec0000000000 - fffffbffffffffff (=44 bits) kasan shadow memory (16TB) |
1da177e4 | 16 | ... unused hole ... |
3891a04a PA |
17 | ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks |
18 | ... unused hole ... | |
9d9cce7f | 19 | ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space |
ff3d0a12 | 20 | ... unused hole ... |
9d9cce7f | 21 | ffffffff80000000 - ffffffff9fffffff (=512 MB) kernel text mapping, from phys 0 |
f06bdd40 | 22 | ffffffffa0000000 - ffffffffff5fffff (=1526 MB) module mapping space (variable) |
aca91bfc BP |
23 | ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls |
24 | ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole | |
1da177e4 | 25 | |
4c7c4483 KS |
26 | Virtual memory map with 5 level page tables: |
27 | ||
28 | 0000000000000000 - 00ffffffffffffff (=56 bits) user space, different per mm | |
29 | hole caused by [56:63] sign extension | |
30 | ff00000000000000 - ff0fffffffffffff (=52 bits) guard hole, reserved for hypervisor | |
31 | ff10000000000000 - ff8fffffffffffff (=55 bits) direct mapping of all phys. memory | |
32 | ff90000000000000 - ff91ffffffffffff (=49 bits) hole | |
33 | ff92000000000000 - ffd1ffffffffffff (=54 bits) vmalloc/ioremap space | |
34 | ffd2000000000000 - ffd3ffffffffffff (=49 bits) hole | |
35 | ffd4000000000000 - ffd5ffffffffffff (=49 bits) virtual memory map (512TB) | |
36 | ... unused hole ... | |
2ce42815 | 37 | ffdf000000000000 - fffffc0000000000 (=53 bits) kasan shadow memory (8PB) |
4c7c4483 KS |
38 | ... unused hole ... |
39 | ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks | |
40 | ... unused hole ... | |
41 | ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space | |
42 | ... unused hole ... | |
43 | ffffffff80000000 - ffffffff9fffffff (=512 MB) kernel text mapping, from phys 0 | |
44 | ffffffffa0000000 - ffffffffff5fffff (=1526 MB) module mapping space | |
45 | ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls | |
46 | ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole | |
47 | ||
48 | Architecture defines a 64-bit virtual address. Implementations can support | |
49 | less. Currently supported are 48- and 57-bit virtual addresses. Bits 63 | |
50 | through to the most-significant implemented bit are set to either all ones | |
51 | or all zero. This causes hole between user space and kernel addresses. | |
52 | ||
57d30772 | 53 | The direct mapping covers all memory in the system up to the highest |
8315eca2 | 54 | memory address (this means in some cases it can also include PCI memory |
57d30772 | 55 | holes). |
8315eca2 | 56 | |
4c7c4483 KS |
57 | vmalloc space is lazily synchronized into the different PML4/PML5 pages of |
58 | the processes using the page fault handler, with init_top_pgt as | |
1da177e4 LT |
59 | reference. |
60 | ||
78b0634d JG |
61 | Current X86-64 implementations support up to 46 bits of address space (64 TB), |
62 | which is our current limit. This expands into MBZ space in the page tables. | |
1da177e4 | 63 | |
ff3d0a12 MF |
64 | We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual |
65 | memory window (this size is arbitrary, it can be raised later if needed). | |
66 | The mappings are not part of any other kernel PGD and are only available | |
67 | during EFI runtime calls. | |
d2f7cbe7 | 68 | |
f06bdd40 TG |
69 | The module mapping space size changes based on the CONFIG requirements for the |
70 | following fixmap section. | |
71 | ||
0483e1fa TG |
72 | Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all |
73 | physical memory, vmalloc/ioremap space and virtual memory map are randomized. | |
74 | Their order is preserved but their base will be offset early at boot time. | |
75 | ||
1da177e4 | 76 | -Andi Kleen, Jul 2004 |