108 lines
2.6 KiB
C
108 lines
2.6 KiB
C
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/*
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Copyright (C) 2015-2019 The University of Notre Dame
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This software is distributed under the GNU General Public License.
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See the file LICENSE for details.
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*/
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#include "console.h"
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#include "kernel/types.h"
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#include "page.h"
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#include "string.h"
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#include "memorylayout.h"
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#include "kernelcore.h"
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static uint32_t pages_free = 0;
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static uint32_t pages_total = 0;
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static uint32_t *freemap = 0;
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static uint32_t freemap_bits = 0;
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static uint32_t freemap_bytes = 0;
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static uint32_t freemap_cells = 0;
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static uint32_t freemap_pages = 0;
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static void *main_memory_start = (void *) MAIN_MEMORY_START;
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#define CELL_BITS (8*sizeof(*freemap))
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void page_init()
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{
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int i;
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pages_total = (total_memory * 1024 * 1024 - MAIN_MEMORY_START) / PAGE_SIZE;
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pages_free = pages_total;
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printf("memory: %d MB (%d KB) total\n", (pages_free * PAGE_SIZE) / MEGA, (pages_free * PAGE_SIZE) / KILO);
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freemap = main_memory_start;
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freemap_bits = pages_total;
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freemap_bytes = 1 + freemap_bits / 8;
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freemap_cells = 1 + freemap_bits / CELL_BITS;
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freemap_pages = 1 + freemap_bytes / PAGE_SIZE;
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printf("memory: %d bits %d bytes %d cells %d pages\n", freemap_bits, freemap_bytes, freemap_cells, freemap_pages);
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memset(freemap, 0xff, freemap_bytes);
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for(i = 0; i < freemap_pages; i++)
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page_alloc(0);
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// This is ahack that I don't understand yet.
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// vmware doesn't like the use of a particular page
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// close to 1MB, but what it is used for I don't know.
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freemap[0] = 0x0;
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printf("memory: %d MB (%d KB) available\n", (pages_free * PAGE_SIZE) / MEGA, (pages_free * PAGE_SIZE) / KILO);
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}
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void page_stats( uint32_t *nfree, uint32_t *ntotal )
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{
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*nfree = pages_free;
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*ntotal = pages_total;
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}
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void *page_alloc(bool zeroit)
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{
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uint32_t i, j;
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uint32_t cellmask;
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uint32_t pagenumber;
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void *pageaddr;
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if(!freemap) {
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printf("memory: not initialized yet!\n");
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return 0;
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}
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for(i = 0; i < freemap_cells; i++) {
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if(freemap[i] != 0) {
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for(j = 0; j < CELL_BITS; j++) {
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cellmask = (1 << j);
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if(freemap[i] & cellmask) {
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freemap[i] &= ~cellmask;
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pagenumber = i * CELL_BITS + j;
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pageaddr = (pagenumber << PAGE_BITS) + main_memory_start;
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if(zeroit)
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memset(pageaddr, 0, PAGE_SIZE);
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pages_free--;
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//printf("page: alloc %d\n",pages_free);
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return pageaddr;
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}
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}
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}
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}
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printf("memory: WARNING: everything allocated\n");
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halt();
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return 0;
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}
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void page_free(void *pageaddr)
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{
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uint32_t pagenumber = (pageaddr - main_memory_start) >> PAGE_BITS;
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uint32_t cellnumber = pagenumber / CELL_BITS;
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uint32_t celloffset = pagenumber % CELL_BITS;
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uint32_t cellmask = (1 << celloffset);
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freemap[cellnumber] |= cellmask;
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pages_free++;
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//printf("page: free %d\n",pages_free);
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}
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