diff options
| -rw-r--r-- | Documentation/x86/x86_64/mm.txt | 171 |
1 files changed, 120 insertions, 51 deletions
diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt index b4bc95c9790e..702898633b00 100644 --- a/Documentation/x86/x86_64/mm.txt +++ b/Documentation/x86/x86_64/mm.txt @@ -1,55 +1,124 @@ +==================================================== +Complete virtual memory map with 4-level page tables +==================================================== -Virtual memory map with 4 level page tables: - -0000000000000000 - 00007fffffffffff (=47 bits, 128 TB) user space, different per mm - hole caused by [47:63] sign extension -ffff800000000000 - ffff87ffffffffff (=43 bits, 8 TB) guard hole, reserved for hypervisor -ffff880000000000 - ffffc7ffffffffff (=46 bits, 64 TB) direct mapping of all phys. memory (page_offset_base) -ffffc80000000000 - ffffc8ffffffffff (=40 bits, 1 TB) unused hole -ffffc90000000000 - ffffe8ffffffffff (=45 bits, 32 TB) vmalloc/ioremap space (vmalloc_base) -ffffe90000000000 - ffffe9ffffffffff (=40 bits, 1 TB) unused hole -ffffea0000000000 - ffffeaffffffffff (=40 bits, 1 TB) virtual memory map (vmemmap_base) -ffffeb0000000000 - ffffebffffffffff (=40 bits, 1 TB) unused hole -ffffec0000000000 - fffffbffffffffff (=44 bits, 16 TB) kasan shadow memory -fffffc0000000000 - fffffdffffffffff (=41 bits, 2 TB) unused hole - vaddr_end for KASLR -fffffe0000000000 - fffffe7fffffffff (=39 bits, 512 GB) cpu_entry_area mapping -fffffe8000000000 - fffffeffffffffff (=39 bits, 512 GB) LDT remap for PTI -ffffff0000000000 - ffffff7fffffffff (=39 bits, 512 GB) %esp fixup stacks -ffffff8000000000 - fffffffeefffffff (~39 bits, ~507 GB) unused hole -ffffffef00000000 - fffffffeffffffff (=36 bits, 64 GB) EFI region mapping space -ffffffff00000000 - ffffffff7fffffff (=31 bits, 2 GB) unused hole -ffffffff80000000 - ffffffff9fffffff (=29 bits, 512 MB) kernel text mapping, from phys 0 -ffffffffa0000000 - fffffffffeffffff (~31 bits, 1520 MB) module mapping space -[fixmap start] - ffffffffff5fffff kernel-internal fixmap range -ffffffffff600000 - ffffffffff600fff ( =4 kB) legacy vsyscall ABI -ffffffffffe00000 - ffffffffffffffff ( =2 MB) unused hole - -Virtual memory map with 5 level page tables: - -0000000000000000 - 00ffffffffffffff (=56 bits, 64 PB) user space, different per mm - hole caused by [56:63] sign extension -ff00000000000000 - ff0fffffffffffff (=52 bits, 4 PB) guard hole, reserved for hypervisor -ff10000000000000 - ff8fffffffffffff (=55 bits, 32 PB) direct mapping of all phys. memory (page_offset_base) -ff90000000000000 - ff9fffffffffffff (=52 bits, 4 PB) LDT remap for PTI -ffa0000000000000 - ffd1ffffffffffff (=53 bits, 12800 TB) vmalloc/ioremap space (vmalloc_base) -ffd2000000000000 - ffd3ffffffffffff (=49 bits, 512 TB) unused hole -ffd4000000000000 - ffd5ffffffffffff (=49 bits, 512 TB) virtual memory map (vmemmap_base) -ffd6000000000000 - ffdeffffffffffff (~51 bits, 2304 TB) unused hole -ffdf000000000000 - fffffdffffffffff (~53 bits, ~8 PB) kasan shadow memory -fffffc0000000000 - fffffdffffffffff (=41 bits, 2 TB) unused hole - vaddr_end for KASLR -fffffe0000000000 - fffffe7fffffffff (=39 bits, 512 GB) cpu_entry_area mapping -fffffe8000000000 - fffffeffffffffff (=39 bits, 512 GB) unused hole -ffffff0000000000 - ffffff7fffffffff (=39 bits, 512 GB) %esp fixup stacks -ffffff8000000000 - ffffffeeffffffff (~39 bits, 444 GB) unused hole -ffffffef00000000 - fffffffeffffffff (=36 bits, 64 GB) EFI region mapping space -ffffffff00000000 - ffffffff7fffffff (31 bits, 2 GB) unused hole -ffffffff80000000 - ffffffff9fffffff (=29 bits, 512 MB) kernel text mapping, from phys 0 -ffffffffa0000000 - fffffffffeffffff (~31 bits, 1520 MB) module mapping space -[fixmap start] - ffffffffff5fffff kernel-internal fixmap range -ffffffffff600000 - ffffffffff600fff ( =4 kB) legacy vsyscall ABI -ffffffffffe00000 - ffffffffffffffff ( =2 MB) unused hole +Notes: + + - Negative addresses such as "-23 TB" are absolute addresses in bytes, counted down + from the top of the 64-bit address space. It's easier to understand the layout + when seen both in absolute addresses and in distance-from-top notation. + + For example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the + 64-bit address space (ffffffffffffffff). + + Note that as we get closer to the top of the address space, the notation changes + from TB to GB and then MB/KB. + + - "16M TB" might look weird at first sight, but it's an easier to visualize size + notation than "16 EB", which few will recognize at first sight as 16 exabytes. + It also shows it nicely how incredibly large 64-bit address space is. + +======================================================================================================================== + Start addr | Offset | End addr | Size | VM area description +======================================================================================================================== + | | | | + 0000000000000000 | 0 | 00007fffffffffff | 128 TB | user-space virtual memory, different per mm +__________________|____________|__________________|_________|___________________________________________________________ + | | | | + 0000800000000000 | +128 TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical + | | | | virtual memory addresses up to the -128 TB + | | | | starting offset of kernel mappings. +__________________|____________|__________________|_________|___________________________________________________________ + | + | Kernel-space virtual memory, shared between all processes: +____________________________________________________________|___________________________________________________________ + | | | | + ffff800000000000 | -128 TB | ffff87ffffffffff | 8 TB | ... guard hole, also reserved for hypervisor + ffff880000000000 | -120 TB | ffffc7ffffffffff | 64 TB | direct mapping of all physical memory (page_offset_base) + ffffc80000000000 | -56 TB | ffffc8ffffffffff | 1 TB | ... unused hole + ffffc90000000000 | -55 TB | ffffe8ffffffffff | 32 TB | vmalloc/ioremap space (vmalloc_base) + ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole + ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base) + ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole + ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory + fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole + | | | | vaddr_end for KASLR + fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping + fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | LDT remap for PTI + ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks +__________________|____________|__________________|_________|____________________________________________________________ + | + | Identical layout to the 47-bit one from here on: +____________________________________________________________|____________________________________________________________ + | | | | + ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole + ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space + ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole + ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0 + ffffffff80000000 |-2048 MB | | | + ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space + ffffffffff000000 | -16 MB | | | + FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset + ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI + ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole +__________________|____________|__________________|_________|___________________________________________________________ + + +==================================================== +Complete virtual memory map with 5-level page tables +==================================================== + +Notes: + + - With 56-bit addresses, user-space memory gets expanded by a factor of 512x, + from 0.125 PB to 64 PB. All kernel mappings shift down to the -64 PT starting + offset and many of the regions expand to support the much larger physical + memory supported. + +======================================================================================================================== + Start addr | Offset | End addr | Size | VM area description +======================================================================================================================== + | | | | + 0000000000000000 | 0 | 00ffffffffffffff | 64 PB | user-space virtual memory, different per mm +__________________|____________|__________________|_________|___________________________________________________________ + | | | | + 0000800000000000 | +64 PB | ffff7fffffffffff | ~16K PB | ... huge, still almost 64 bits wide hole of non-canonical + | | | | virtual memory addresses up to the -128 TB + | | | | starting offset of kernel mappings. +__________________|____________|__________________|_________|___________________________________________________________ + | + | Kernel-space virtual memory, shared between all processes: +____________________________________________________________|___________________________________________________________ + | | | | + ff00000000000000 | -64 PB | ff0fffffffffffff | 4 PB | ... guard hole, also reserved for hypervisor + ff10000000000000 | -60 PB | ff8fffffffffffff | 32 PB | direct mapping of all physical memory (page_offset_base) + ff90000000000000 | -28 PB | ff9fffffffffffff | 4 PB | LDT remap for PTI + ffa0000000000000 | -24 PB | ffd1ffffffffffff | 12.5 PB | vmalloc/ioremap space (vmalloc_base) + ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole + ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base) + ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole + ffdf000000000000 | -8.25 PB | fffffdffffffffff | ~8 PB | KASAN shadow memory + fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole + | | | | vaddr_end for KASLR + fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping + fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | ... unused hole + ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks +__________________|____________|__________________|_________|____________________________________________________________ + | + | Identical layout to the 47-bit one from here on: +____________________________________________________________|____________________________________________________________ + | | | | + ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole + ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space + ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole + ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0 + ffffffff80000000 |-2048 MB | | | + ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space + ffffffffff000000 | -16 MB | | | + FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset + ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI + ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole +__________________|____________|__________________|_________|___________________________________________________________ Architecture defines a 64-bit virtual address. Implementations can support less. Currently supported are 48- and 57-bit virtual addresses. Bits 63 |