Xv6 Page Table

最新推荐文章于 2024-06-23 16:35:37 发布

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最新推荐文章于 2024-06-23 16:35:37 发布

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分类专栏： Xv6 文章标签： unix os 操作系统 xv6

本文链接：https://blog.youkuaiyun.com/u012419550/article/details/114580005

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本文详细介绍了运行在Sv39 RISC-V架构上的Xv6页表机制。内容包括分页硬件、内核地址空间、创建地址空间、物理内存分配、物理内存分配器、进程地址空间、sbrk以及exec系统调用的工作原理。通过阅读，可以深入理解Xv6操作系统的内存管理和虚拟地址到物理地址的转换过程。

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Meaning Unknown's Head Image

Learning xv6-riscv-book Chapter 3 Page tables

Isolate different process’s address spaces and to multiplex them onto a single physical memory.

Sv39 RISC-V:

Xv6 runs on Sv39 RISC-V: only the bottom 39 bits of a 64-bit virtual address are used; the top 25 bits are not used.
a RISC-V page table: an array of $2^{27}$ page table entries (PTEs)
a PTE: a 44-bit physical page number (PPN) and flags.

[Logically] The paging hardware: virtual address => physical address:

handle a 39-bit virtual address
- top 27 bits of the 39 bits: index into the page table to find a PTE
- bottom 12 bits: do not change
making a 56-bit physical address:
- top 44 bits come from the PPN in the PTE
- bottom 12 bits are copied from the original virtual address.