2
0
mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-16 09:13:55 +08:00
linux-next/Documentation/riscv/vm-layout.rst
Alexandre Ghiti f7ae02333d
riscv: Move KASAN mapping next to the kernel mapping
Now that KASAN_SHADOW_OFFSET is defined at compile time as a config,
this value must remain constant whatever the size of the virtual address
space, which is only possible by pushing this region at the end of the
address space next to the kernel mapping.

Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
2022-01-19 17:54:04 -08:00

64 lines
3.5 KiB
ReStructuredText
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

.. SPDX-License-Identifier: GPL-2.0
=====================================
Virtual Memory Layout on RISC-V Linux
=====================================
:Author: Alexandre Ghiti <alex@ghiti.fr>
:Date: 12 February 2021
This document describes the virtual memory layout used by the RISC-V Linux
Kernel.
RISC-V Linux Kernel 32bit
=========================
RISC-V Linux Kernel SV32
------------------------
TODO
RISC-V Linux Kernel 64bit
=========================
The RISC-V privileged architecture document states that the 64bit addresses
"must have bits 6348 all equal to bit 47, or else a page-fault exception will
occur.": that splits the virtual address space into 2 halves separated by a very
big hole, the lower half is where the userspace resides, the upper half is where
the RISC-V Linux Kernel resides.
RISC-V Linux Kernel SV39
------------------------
::
========================================================================================================================
Start addr | Offset | End addr | Size | VM area description
========================================================================================================================
| | | |
0000000000000000 | 0 | 0000003fffffffff | 256 GB | user-space virtual memory, different per mm
__________________|____________|__________________|_________|___________________________________________________________
| | | |
0000004000000000 | +256 GB | ffffffbfffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
| | | | virtual memory addresses up to the -256 GB
| | | | starting offset of kernel mappings.
__________________|____________|__________________|_________|___________________________________________________________
|
| Kernel-space virtual memory, shared between all processes:
____________________________________________________________|___________________________________________________________
| | | |
ffffffc6fee00000 | -228 GB | ffffffc6feffffff | 2 MB | fixmap
ffffffc6ff000000 | -228 GB | ffffffc6ffffffff | 16 MB | PCI io
ffffffc700000000 | -228 GB | ffffffc7ffffffff | 4 GB | vmemmap
ffffffc800000000 | -224 GB | ffffffd7ffffffff | 64 GB | vmalloc/ioremap space
ffffffd800000000 | -160 GB | fffffff6ffffffff | 124 GB | direct mapping of all physical memory
fffffff700000000 | -36 GB | fffffffeffffffff | 32 GB | kasan
__________________|____________|__________________|_________|____________________________________________________________
|
|
____________________________________________________________|____________________________________________________________
| | | |
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
__________________|____________|__________________|_________|____________________________________________________________