From 9f6b20778c444923d18b1638cdbcb86e648adf02 Mon Sep 17 00:00:00 2001 From: 0xAX Date: Sat, 28 Feb 2015 18:47:49 +0600 Subject: [PATCH] Update Paging.md --- Theory/Paging.md | 2 -- 1 file changed, 2 deletions(-) diff --git a/Theory/Paging.md b/Theory/Paging.md index 2700966..1461dba 100644 --- a/Theory/Paging.md +++ b/Theory/Paging.md @@ -176,8 +176,6 @@ This solution is `sign extension`. Here we can see that low 48 bits of a virtual Userspace occupies the lower part of the virtual address space, from `0x000000000000000` to `0x00007fffffffffff` and kernel space occupies the highest part from the `0xffff8000000000` to `0xffffffffffffffff`. Note that bits `63:48` is 0 for userspace and 1 for kernel space. All addresses which are in kernel space and in userspace or in another words which higher `63:48` bits zero or one calls `canonical` addresses. There is `non-canonical` area between these memory regions. Together this two memory regions (kernel space and user space) are exactly `2^48` bits. We can find virtual memory map with 4 level page tables in the [Documentation/x86/x86_64/mm.txt](https://github.com/torvalds/linux/blob/master/Documentation/x86/x86_64/mm.txt): ``` -Virtual memory map with 4 level page tables: - 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm hole caused by [48:63] sign extension ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor