diff options
| -rw-r--r-- | Documentation/x86/x86_64/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/x86/x86_64/mm.rst | 161 | ||||
| -rw-r--r-- | Documentation/x86/x86_64/mm.txt | 153 |
3 files changed, 162 insertions, 153 deletions
diff --git a/Documentation/x86/x86_64/index.rst b/Documentation/x86/x86_64/index.rst index ddfa1f9d4193..4b65d29ef459 100644 --- a/Documentation/x86/x86_64/index.rst +++ b/Documentation/x86/x86_64/index.rst @@ -9,3 +9,4 @@ x86_64 Support boot-options uefi + mm diff --git a/Documentation/x86/x86_64/mm.rst b/Documentation/x86/x86_64/mm.rst new file mode 100644 index 000000000000..52020577b8de --- /dev/null +++ b/Documentation/x86/x86_64/mm.rst @@ -0,0 +1,161 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================ +Memory Managment +================ + +Complete virtual memory map with 4-level page tables +==================================================== + +.. note:: + + - 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 | ffff887fffffffff | 0.5 TB | LDT remap for PTI + ffff888000000000 | -119.5 TB | ffffc87fffffffff | 64 TB | direct mapping of all physical memory (page_offset_base) + ffffc88000000000 | -55.5 TB | ffffc8ffffffffff | 0.5 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 + __________________|____________|__________________|_________|____________________________________________________________ + | + | Identical layout to the 56-bit one from here on: + ____________________________________________________________|____________________________________________________________ + | | | | + 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 + 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 +==================================================== + +.. note:: + + - 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 -64 PB + | | | | 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 | ff10ffffffffffff | 0.25 PB | LDT remap for PTI + ff11000000000000 | -59.75 PB | ff90ffffffffffff | 32 PB | direct mapping of all physical memory (page_offset_base) + ff91000000000000 | -27.75 PB | ff9fffffffffffff | 3.75 PB | ... unused hole + 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 + __________________|____________|__________________|_________|____________________________________________________________ + | + | Identical layout to the 47-bit one from here on: + ____________________________________________________________|____________________________________________________________ + | | | | + 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 + 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 +through to the most-significant implemented bit are sign extended. +This causes hole between user space and kernel addresses if you interpret them +as unsigned. + +The direct mapping covers all memory in the system up to the highest +memory address (this means in some cases it can also include PCI memory +holes). + +vmalloc space is lazily synchronized into the different PML4/PML5 pages of +the processes using the page fault handler, with init_top_pgt as +reference. + +We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual +memory window (this size is arbitrary, it can be raised later if needed). +The mappings are not part of any other kernel PGD and are only available +during EFI runtime calls. + +Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all +physical memory, vmalloc/ioremap space and virtual memory map are randomized. +Their order is preserved but their base will be offset early at boot time. + +Be very careful vs. KASLR when changing anything here. The KASLR address +range must not overlap with anything except the KASAN shadow area, which is +correct as KASAN disables KASLR. + +For both 4- and 5-level layouts, the STACKLEAK_POISON value in the last 2MB +hole: ffffffffffff4111 diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt deleted file mode 100644 index 804f9426ed17..000000000000 --- a/Documentation/x86/x86_64/mm.txt +++ /dev/null @@ -1,153 +0,0 @@ -==================================================== -Complete virtual memory map with 4-level page tables -==================================================== - -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 | ffff887fffffffff | 0.5 TB | LDT remap for PTI - ffff888000000000 | -119.5 TB | ffffc87fffffffff | 64 TB | direct mapping of all physical memory (page_offset_base) - ffffc88000000000 | -55.5 TB | ffffc8ffffffffff | 0.5 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 -__________________|____________|__________________|_________|____________________________________________________________ - | - | Identical layout to the 56-bit one from here on: -____________________________________________________________|____________________________________________________________ - | | | | - 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 - 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 -64 PB - | | | | 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 | ff10ffffffffffff | 0.25 PB | LDT remap for PTI - ff11000000000000 | -59.75 PB | ff90ffffffffffff | 32 PB | direct mapping of all physical memory (page_offset_base) - ff91000000000000 | -27.75 PB | ff9fffffffffffff | 3.75 PB | ... unused hole - 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 -__________________|____________|__________________|_________|____________________________________________________________ - | - | Identical layout to the 47-bit one from here on: -____________________________________________________________|____________________________________________________________ - | | | | - 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 - 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 -through to the most-significant implemented bit are sign extended. -This causes hole between user space and kernel addresses if you interpret them -as unsigned. - -The direct mapping covers all memory in the system up to the highest -memory address (this means in some cases it can also include PCI memory -holes). - -vmalloc space is lazily synchronized into the different PML4/PML5 pages of -the processes using the page fault handler, with init_top_pgt as -reference. - -We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual -memory window (this size is arbitrary, it can be raised later if needed). -The mappings are not part of any other kernel PGD and are only available -during EFI runtime calls. - -Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all -physical memory, vmalloc/ioremap space and virtual memory map are randomized. -Their order is preserved but their base will be offset early at boot time. - -Be very careful vs. KASLR when changing anything here. The KASLR address -range must not overlap with anything except the KASAN shadow area, which is -correct as KASAN disables KASLR. - -For both 4- and 5-level layouts, the STACKLEAK_POISON value in the last 2MB -hole: ffffffffffff4111 |