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RISC-V Linux 上的虚拟内存布局¶
- 作者:
Alexandre Ghiti <alex@ghiti.fr>
- 日期:
2021 年 2 月 12 日
本文档描述了 RISC-V Linux 内核使用的虚拟内存布局。
RISC-V Linux 内核 32 位¶
RISC-V Linux 内核 SV32¶
待办
RISC-V Linux 内核 64 位¶
RISC-V 特权架构文档指出，64 位地址“必须使位 63-48 都等于位 47，否则将发生页面错误异常。”：这会将虚拟地址空间分成两个半部分，中间由一个非常大的空洞分隔，下半部分是用户空间所在的位置，上半部分是 RISC-V Linux 内核所在的位置。
RISC-V Linux 内核 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:
____________________________________________________________|___________________________________________________________
| | | |
ffffffc4fea00000 | -236 GB | ffffffc4feffffff | 6 MB | fixmap
ffffffc4ff000000 | -236 GB | ffffffc4ffffffff | 16 MB | PCI io
ffffffc500000000 | -236 GB | ffffffc5ffffffff | 4 GB | vmemmap
ffffffc600000000 | -232 GB | ffffffd5ffffffff | 64 GB | vmalloc/ioremap space
ffffffd600000000 | -168 GB | fffffff5ffffffff | 128 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
__________________|____________|__________________|_________|____________________________________________________________
RISC-V Linux 内核 SV48¶
========================================================================================================================
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:
____________________________________________________________|___________________________________________________________
| | | |
ffff8d7ffea00000 | -114.5 TB | ffff8d7ffeffffff | 6 MB | fixmap
ffff8d7fff000000 | -114.5 TB | ffff8d7fffffffff | 16 MB | PCI io
ffff8d8000000000 | -114.5 TB | ffff8f7fffffffff | 2 TB | vmemmap
ffff8f8000000000 | -112.5 TB | ffffaf7fffffffff | 32 TB | vmalloc/ioremap space
ffffaf8000000000 | -80.5 TB | ffffef7fffffffff | 64 TB | direct mapping of all physical memory
ffffef8000000000 | -16.5 TB | fffffffeffffffff | 16.5 TB | kasan
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 39-bit one from here on:
____________________________________________________________|____________________________________________________________
| | | |
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
__________________|____________|__________________|_________|____________________________________________________________
RISC-V Linux 内核 SV57¶
========================================================================================================================
Start addr | Offset | End addr | Size | VM area description
========================================================================================================================
| | | |
0000000000000000 | 0 | 00ffffffffffffff | 64 PB | user-space virtual memory, different per mm
__________________|____________|__________________|_________|___________________________________________________________
| | | |
0100000000000000 | +64 PB | feffffffffffffff | ~16K PB | ... huge, 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:
____________________________________________________________|___________________________________________________________
| | | |
ff1bfffffea00000 | -57 PB | ff1bfffffeffffff | 6 MB | fixmap
ff1bffffff000000 | -57 PB | ff1bffffffffffff | 16 MB | PCI io
ff1c000000000000 | -57 PB | ff1fffffffffffff | 1 PB | vmemmap
ff20000000000000 | -56 PB | ff5fffffffffffff | 16 PB | vmalloc/ioremap space
ff60000000000000 | -40 PB | ffdeffffffffffff | 32 PB | direct mapping of all physical memory
ffdf000000000000 | -8 PB | fffffffeffffffff | 8 PB | kasan
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 39-bit one from here on:
____________________________________________________________|____________________________________________________________
| | | |
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
__________________|____________|__________________|_________|____________________________________________________________