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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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57fbad15c2
In preparation for adding Clang sanitizer coverage stack depth tracking that can support stack depth callbacks: - Add the new top-level CONFIG_KSTACK_ERASE option which will be implemented either with the stackleak GCC plugin, or with the Clang stack depth callback support. - Rename CONFIG_GCC_PLUGIN_STACKLEAK as needed to CONFIG_KSTACK_ERASE, but keep it for anything specific to the GCC plugin itself. - Rename all exposed "STACKLEAK" names and files to "KSTACK_ERASE" (named for what it does rather than what it protects against), but leave as many of the internals alone as possible to avoid even more churn. While here, also split "prev_lowest_stack" into CONFIG_KSTACK_ERASE_METRICS, since that's the only place it is referenced from. Suggested-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20250717232519.2984886-1-kees@kernel.org Signed-off-by: Kees Cook <kees@kernel.org>
181 lines
13 KiB
ReStructuredText
181 lines
13 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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=================
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Memory Management
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=================
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Complete virtual memory map with 4-level page tables
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====================================================
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.. note::
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- Negative addresses such as "-23 TB" are absolute addresses in bytes, counted down
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from the top of the 64-bit address space. It's easier to understand the layout
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when seen both in absolute addresses and in distance-from-top notation.
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For example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the
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64-bit address space (ffffffffffffffff).
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Note that as we get closer to the top of the address space, the notation changes
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from TB to GB and then MB/KB.
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- "16M TB" might look weird at first sight, but it's an easier way to visualize size
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notation than "16 EB", which few will recognize at first sight as 16 exabytes.
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It also shows it nicely how incredibly large 64-bit address space is.
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::
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========================================================================================================================
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Start addr | Offset | End addr | Size | VM area description
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========================================================================================================================
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0000000000000000 | 0 | 00007fffffffefff | ~128 TB | user-space virtual memory, different per mm
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00007ffffffff000 | ~128 TB | 00007fffffffffff | 4 kB | ... guard hole
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__________________|____________|__________________|_________|___________________________________________________________
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0000800000000000 | +128 TB | 7fffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical
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| | | | virtual memory addresses up to the -8 EB
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| | | | starting offset of kernel mappings.
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| | | |
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| | | | LAM relaxes canonicallity check allowing to create aliases
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| | | | for userspace memory here.
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__________________|____________|__________________|_________|___________________________________________________________
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| Kernel-space virtual memory, shared between all processes:
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__________________|____________|__________________|_________|___________________________________________________________
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8000000000000000 | -8 EB | ffff7fffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical
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| | | | virtual memory addresses up to the -128 TB
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| | | | starting offset of kernel mappings.
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| | | |
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| | | | LAM_SUP relaxes canonicallity check allowing to create
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| | | | aliases for kernel memory here.
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____________________________________________________________|___________________________________________________________
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ffff800000000000 | -128 TB | ffff87ffffffffff | 8 TB | ... guard hole, also reserved for hypervisor
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ffff880000000000 | -120 TB | ffff887fffffffff | 0.5 TB | LDT remap for PTI
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ffff888000000000 | -119.5 TB | ffffc87fffffffff | 64 TB | direct mapping of all physical memory (page_offset_base)
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ffffc88000000000 | -55.5 TB | ffffc8ffffffffff | 0.5 TB | ... unused hole
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ffffc90000000000 | -55 TB | ffffe8ffffffffff | 32 TB | vmalloc/ioremap space (vmalloc_base)
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ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
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ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base)
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ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole
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ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory
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__________________|____________|__________________|_________|____________________________________________________________
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| Identical layout to the 56-bit one from here on:
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____________________________________________________________|____________________________________________________________
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fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole
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| | | | vaddr_end for KASLR
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fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping
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fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | ... unused hole
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ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
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ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole
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ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space
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ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole
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ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0
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ffffffff80000000 |-2048 MB | | |
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ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space
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ffffffffff000000 | -16 MB | | |
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FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
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ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI
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ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole
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__________________|____________|__________________|_________|___________________________________________________________
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Complete virtual memory map with 5-level page tables
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====================================================
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.. note::
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- With 56-bit addresses, user-space memory gets expanded by a factor of 512x,
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from 0.125 PB to 64 PB. All kernel mappings shift down to the -64 PB starting
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offset and many of the regions expand to support the much larger physical
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memory supported.
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::
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========================================================================================================================
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Start addr | Offset | End addr | Size | VM area description
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========================================================================================================================
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0000000000000000 | 0 | 00fffffffffff000 | ~64 PB | user-space virtual memory, different per mm
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00fffffffffff000 | ~64 PB | 00ffffffffffffff | 4 kB | ... guard hole
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__________________|____________|__________________|_________|___________________________________________________________
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0100000000000000 | +64 PB | 7fffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical
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| | | | virtual memory addresses up to the -8EB TB
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| | | | starting offset of kernel mappings.
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| | | |
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| | | | LAM relaxes canonicallity check allowing to create aliases
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| | | | for userspace memory here.
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__________________|____________|__________________|_________|___________________________________________________________
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| Kernel-space virtual memory, shared between all processes:
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____________________________________________________________|___________________________________________________________
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8000000000000000 | -8 EB | feffffffffffffff | ~8 EB | ... huge, almost 63 bits wide hole of non-canonical
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| | | | virtual memory addresses up to the -64 PB
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| | | | starting offset of kernel mappings.
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| | | |
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| | | | LAM_SUP relaxes canonicallity check allowing to create
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| | | | aliases for kernel memory here.
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____________________________________________________________|___________________________________________________________
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ff00000000000000 | -64 PB | ff0fffffffffffff | 4 PB | ... guard hole, also reserved for hypervisor
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ff10000000000000 | -60 PB | ff10ffffffffffff | 0.25 PB | LDT remap for PTI
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ff11000000000000 | -59.75 PB | ff90ffffffffffff | 32 PB | direct mapping of all physical memory (page_offset_base)
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ff91000000000000 | -27.75 PB | ff9fffffffffffff | 3.75 PB | ... unused hole
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ffa0000000000000 | -24 PB | ffd1ffffffffffff | 12.5 PB | vmalloc/ioremap space (vmalloc_base)
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ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole
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ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base)
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ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole
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ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory
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__________________|____________|__________________|_________|____________________________________________________________
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| Identical layout to the 47-bit one from here on:
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____________________________________________________________|____________________________________________________________
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fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole
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| | | | vaddr_end for KASLR
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fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping
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fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | ... unused hole
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ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
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ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole
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ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space
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ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole
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ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0
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ffffffff80000000 |-2048 MB | | |
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ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space
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ffffffffff000000 | -16 MB | | |
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FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
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ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI
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ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole
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__________________|____________|__________________|_________|___________________________________________________________
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Architecture defines a 64-bit virtual address. Implementations can support
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less. Currently supported are 48- and 57-bit virtual addresses. Bits 63
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through to the most-significant implemented bit are sign extended.
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This causes hole between user space and kernel addresses if you interpret them
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as unsigned.
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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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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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Be very careful vs. KASLR when changing anything here. The KASLR address
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range must not overlap with anything except the KASAN shadow area, which is
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correct as KASAN disables KASLR.
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For both 4- and 5-level layouts, the KSTACK_ERASE_POISON value in the last 2MB
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hole: ffffffffffff4111
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