From 89f7f1b114c1bbea3ad62808bf3653e1d2337d1f Mon Sep 17 00:00:00 2001 From: Aleksa Vučković Date: Wed, 27 Oct 2021 11:44:12 +0200 Subject: Added paging --- src/c/paging.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 src/c/paging.c (limited to 'src/c/paging.c') diff --git a/src/c/paging.c b/src/c/paging.c new file mode 100644 index 0000000..b256b74 --- /dev/null +++ b/src/c/paging.c @@ -0,0 +1,51 @@ +#include"../include/types.h" + +extern void loadPageDirectory(uint32_t*); +extern void enablePaging(); + +uint32_t page_directory[1024] __attribute__((aligned(4096))); + +void set_pd() +{ + //set each entry to not present + for(size_t i=0;i<1024;i++) + { + // This sets the following flags to the pages: + // Supervisor: Only kernel-mode can access them + // Write Enabled: It can be both read from and written to + // Not Present: The page table is not present + page_directory[i] = 0x00000002; + } +} + +uint32_t first_page_table[1024] __attribute__((aligned(4096))); + +void set_pt() +{ + // holds the physical address where we want to start mapping these pages to. + // in this case, we want to map these pages to the very beginning of memory. + unsigned int i; + + //we will fill all 1024 entries in the table, mapping 4 megabytes + for(i = 0; i < 1024; i++) + { + // As the address is page aligned, it will always leave 12 bits zeroed. + // Those bits are used by the attributes ;) + first_page_table[i] = (i * 0x1000) | 3; // attributes: supervisor level, read/write, present. + } +} + +void put_pt() +{ + // attributes: supervisor level, read/write, present + page_directory[0] = ((uint32_t)first_page_table) | 3; +} + +void set_paging() +{ + set_pd(); + set_pt(); + put_pt(); + loadPageDirectory(page_directory); + enablePaging(); +} -- cgit v1.2.3