€•ÿƒŒsphinx.addnodes”Œdocument”“”)”}”(Œ rawsource”Œ”Œchildren”]”(Œ translations”Œ LanguagesNode”“”)”}”(hhh]”(hŒ pending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ refdomain”Œstd”Œreftype”Œdoc”Œ reftarget”Œ&/translations/zh_CN/arch/x86/x86_64/mm”Œmodname”NŒ classname”NŒ refexplicit”ˆuŒtagname”hhh ubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ&/translations/zh_TW/arch/x86/x86_64/mm”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ&/translations/it_IT/arch/x86/x86_64/mm”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ&/translations/ja_JP/arch/x86/x86_64/mm”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ&/translations/ko_KR/arch/x86/x86_64/mm”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ&/translations/sp_SP/arch/x86/x86_64/mm”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h hhŒ _document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ xml:space”Œpreserve”uh1h¡hhhžhhŸŒ@/var/lib/git/docbuild/linux/Documentation/arch/x86/x86_64/mm.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒMemory Management”h]”hŒMemory Management”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ4Complete virtual memory map with 4-level page tables”h]”hŒ4Complete virtual memory map with 4-level page tables”…””}”(hhÌhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhÉhžhhŸh³h KubhŒnote”“”)”}”(hXÎ- Negative addresses such as "-23 TB" are absolute addresses in bytes, counted down from the top of the 64-bit address space. It's easier to understand the layout when seen both in absolute addresses and in distance-from-top notation. For example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the 64-bit address space (ffffffffffffffff). Note that as we get closer to the top of the address space, the notation changes from TB to GB and then MB/KB. - "16M TB" might look weird at first sight, but it's an easier way to visualize size notation than "16 EB", which few will recognize at first sight as 16 exabytes. It also shows it nicely how incredibly large 64-bit address space is.”h]”hŒ bullet_list”“”)”}”(hhh]”(hŒ list_item”“”)”}”(hXÒNegative addresses such as "-23 TB" are absolute addresses in bytes, counted down from the top of the 64-bit address space. It's easier to understand the layout when seen both in absolute addresses and in distance-from-top notation. For example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the 64-bit address space (ffffffffffffffff). Note that as we get closer to the top of the address space, the notation changes from TB to GB and then MB/KB. ”h]”(hŒ paragraph”“”)”}”(hŒèNegative addresses such as "-23 TB" are absolute addresses in bytes, counted down from the top of the 64-bit address space. It's easier to understand the layout when seen both in absolute addresses and in distance-from-top notation.”h]”hŒîNegative addresses such as “-23 TB†are absolute addresses in bytes, counted down from the top of the 64-bit address space. It’s easier to understand the layout when seen both in absolute addresses and in distance-from-top notation.”…””}”(hhíhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K hhçubhì)”}”(hŒwFor example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the 64-bit address space (ffffffffffffffff).”h]”hŒyFor example 0xffffe90000000000 == -23 TB, it’s 23 TB lower than the top of the 64-bit address space (ffffffffffffffff).”…””}”(hhûhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Khhçubhì)”}”(hŒnNote that as we get closer to the top of the address space, the notation changes from TB to GB and then MB/KB.”h]”hŒnNote that as we get closer to the top of the address space, the notation changes from TB to GB and then MB/KB.”…””}”(hj hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Khhçubeh}”(h]”h ]”h"]”h$]”h&]”uh1håhhâubhæ)”}”(hŒç"16M TB" might look weird at first sight, but it's an easier way to visualize size notation than "16 EB", which few will recognize at first sight as 16 exabytes. It also shows it nicely how incredibly large 64-bit address space is.”h]”hì)”}”(hŒç"16M TB" might look weird at first sight, but it's an easier way to visualize size notation than "16 EB", which few will recognize at first sight as 16 exabytes. It also shows it nicely how incredibly large 64-bit address space is.”h]”hŒñ“16M TB†might look weird at first sight, but it’s an easier way to visualize size notation than “16 EBâ€, which few will recognize at first sight as 16 exabytes. It also shows it nicely how incredibly large 64-bit address space is.”…””}”(hj!hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Khjubah}”(h]”h ]”h"]”h$]”h&]”uh1håhhâubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1hàhŸh³h K hhÜubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhhÉhžhhŸNh NubhŒ literal_block”“”)”}”(hX™======================================================================================================================== Start addr | Offset | End addr | Size | VM area description ======================================================================================================================== | | | | 0000000000000000 | 0 | 00007fffffffefff | ~128 TB | user-space virtual memory, different per mm 00007ffffffff000 | ~128 TB | 00007fffffffffff | 4 kB | ... guard hole __________________|____________|__________________|_________|___________________________________________________________ | | | | 0000800000000000 | +128 TB | 7fffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -8 EB | | | | starting offset of kernel mappings. | | | | | | | | LAM relaxes canonicallity check allowing to create aliases | | | | for userspace memory here. __________________|____________|__________________|_________|___________________________________________________________ | | Kernel-space virtual memory, shared between all processes: __________________|____________|__________________|_________|___________________________________________________________ | | | | 8000000000000000 | -8 EB | ffff7fffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -128 TB | | | | starting offset of kernel mappings. | | | | | | | | LAM_SUP relaxes canonicallity check allowing to create | | | | aliases for kernel memory here. ____________________________________________________________|___________________________________________________________ | | | | 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 __________________|____________|__________________|_________|___________________________________________________________”h]”hX™======================================================================================================================== Start addr | Offset | End addr | Size | VM area description ======================================================================================================================== | | | | 0000000000000000 | 0 | 00007fffffffefff | ~128 TB | user-space virtual memory, different per mm 00007ffffffff000 | ~128 TB | 00007fffffffffff | 4 kB | ... guard hole __________________|____________|__________________|_________|___________________________________________________________ | | | | 0000800000000000 | +128 TB | 7fffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -8 EB | | | | starting offset of kernel mappings. | | | | | | | | LAM relaxes canonicallity check allowing to create aliases | | | | for userspace memory here. __________________|____________|__________________|_________|___________________________________________________________ | | Kernel-space virtual memory, shared between all processes: __________________|____________|__________________|_________|___________________________________________________________ | | | | 8000000000000000 | -8 EB | ffff7fffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -128 TB | | | | starting offset of kernel mappings. | | | | | | | | LAM_SUP relaxes canonicallity check allowing to create | | | | aliases for kernel memory here. ____________________________________________________________|___________________________________________________________ | | | | 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 __________________|____________|__________________|_________|___________________________________________________________”…””}”hjEsbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jChŸh³h KhhÉhžhubeh}”(h]”Œ4complete-virtual-memory-map-with-4-level-page-tables”ah ]”h"]”Œ4complete virtual memory map with 4-level page tables”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ4Complete virtual memory map with 5-level page tables”h]”hŒ4Complete virtual memory map with 5-level page tables”…””}”(hj^hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj[hžhhŸh³h KXubhÛ)”}”(hŒý- 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 PB starting offset and many of the regions expand to support the much larger physical memory supported.”h]”há)”}”(hhh]”hæ)”}”(hŒõWith 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 PB starting offset and many of the regions expand to support the much larger physical memory supported.”h]”hì)”}”(hŒõWith 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 PB starting offset and many of the regions expand to support the much larger physical memory supported.”h]”hŒõWith 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 PB starting offset and many of the regions expand to support the much larger physical memory supported.”…””}”(hjwhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K\hjsubah}”(h]”h ]”h"]”h$]”h&]”uh1håhjpubah}”(h]”h ]”h"]”h$]”h&]”j;j<uh1hàhŸh³h K\hjlubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhj[hžhhŸNh NubjD)”}”(hX\======================================================================================================================== Start addr | Offset | End addr | Size | VM area description ======================================================================================================================== | | | | 0000000000000000 | 0 | 00fffffffffff000 | ~64 PB | user-space virtual memory, different per mm 00fffffffffff000 | ~64 PB | 00ffffffffffffff | 4 kB | ... guard hole __________________|____________|__________________|_________|___________________________________________________________ | | | | 0100000000000000 | +64 PB | 7fffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -8EB TB | | | | starting offset of kernel mappings. | | | | | | | | LAM relaxes canonicallity check allowing to create aliases | | | | for userspace memory here. __________________|____________|__________________|_________|___________________________________________________________ | | Kernel-space virtual memory, shared between all processes: ____________________________________________________________|___________________________________________________________ 8000000000000000 | -8 EB | feffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -64 PB | | | | starting offset of kernel mappings. | | | | | | | | LAM_SUP relaxes canonicallity check allowing to create | | | | aliases for kernel memory here. ____________________________________________________________|___________________________________________________________ | | | | 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 | fffffbffffffffff | ~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 __________________|____________|__________________|_________|___________________________________________________________”h]”hX\======================================================================================================================== Start addr | Offset | End addr | Size | VM area description ======================================================================================================================== | | | | 0000000000000000 | 0 | 00fffffffffff000 | ~64 PB | user-space virtual memory, different per mm 00fffffffffff000 | ~64 PB | 00ffffffffffffff | 4 kB | ... guard hole __________________|____________|__________________|_________|___________________________________________________________ | | | | 0100000000000000 | +64 PB | 7fffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -8EB TB | | | | starting offset of kernel mappings. | | | | | | | | LAM relaxes canonicallity check allowing to create aliases | | | | for userspace memory here. __________________|____________|__________________|_________|___________________________________________________________ | | Kernel-space virtual memory, shared between all processes: ____________________________________________________________|___________________________________________________________ 8000000000000000 | -8 EB | feffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical | | | | virtual memory addresses up to the -64 PB | | | | starting offset of kernel mappings. | | | | | | | | LAM_SUP relaxes canonicallity check allowing to create | | | | aliases for kernel memory here. ____________________________________________________________|___________________________________________________________ | | | | 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 | fffffbffffffffff | ~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 __________________|____________|__________________|_________|___________________________________________________________”…””}”hj—sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jChŸh³h Kchj[hžhubhì)”}”(hX1Architecture defines a 64-bit virtual address. Implementations can support less. Currently supported are 48- and 57-bit virtual addresses. Bits 63 through to the most-significant implemented bit are sign extended. This causes hole between user space and kernel addresses if you interpret them as unsigned.”h]”hX1Architecture defines a 64-bit virtual address. Implementations can support less. Currently supported are 48- and 57-bit virtual addresses. Bits 63 through to the most-significant implemented bit are sign extended. This causes hole between user space and kernel addresses if you interpret them as unsigned.”…””}”(hj¥hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h Kœhj[hžhubhì)”}”(hŒ”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).”h]”hŒ”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).”…””}”(hj³hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K¢hj[hžhubhì)”}”(hŒõWe map EFI runtime services in the 'efi_pgd' PGD in a 64GB large virtual memory window (this size is arbitrary, it can be raised later if needed). The mappings are not part of any other kernel PGD and are only available during EFI runtime calls.”h]”hŒùWe map EFI runtime services in the ‘efi_pgd’ PGD in a 64GB large virtual memory window (this size is arbitrary, it can be raised later if needed). The mappings are not part of any other kernel PGD and are only available during EFI runtime calls.”…””}”(hjÁhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K¦hj[hžhubhì)”}”(hŒãNote 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.”h]”hŒãNote 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.”…””}”(hjÏhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hëhŸh³h K«hj[hžhubhì)”}”(hŒµBe 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.”h]”hŒµBe very careful vs. KASLR when changing anything here. 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