+++ /dev/null
-/*
-pcboot - bootable PC demo/game kernel
-Copyright (C) 2018 John Tsiombikas <nuclear@member.fsf.org>
-
-This program is free software: you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation, either version 3 of the License, or
-(at your option) any later version.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY, without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with this program. If not, see <https://www.gnu.org/licenses/>.
-*/
-#include <stdio.h>
-#include <string.h>
-#include "config.h"
-#include "panic.h"
-#include "mem.h"
-#include "intr.h"
-
-#define FREE 0
-#define USED 1
-
-#define BM_IDX(pg) ((pg) / 32)
-#define BM_BIT(pg) ((pg) & 0x1f)
-
-#define IS_FREE(pg) ((bitmap[BM_IDX(pg)] & (1 << BM_BIT(pg))) == 0)
-
-#define MEM_START ((uint32_t)&_mem_start)
-
-
-struct mem_range {
- uint32_t start;
- uint32_t size;
-};
-
-void move_stack(uint32_t newaddr); /* defined in startup.s */
-
-static void mark_page(int pg, int used);
-static void add_memory(uint32_t start, size_t size);
-
-#define MAX_MAP_SIZE 16
-extern struct mem_range boot_mem_map[MAX_MAP_SIZE];
-extern int boot_mem_map_size;
-
-/* linker supplied symbol, points to the end of the kernel image */
-extern uint32_t _mem_start;
-
-
-/* A bitmap is used to track which physical memory pages are used, and which
- * are available for allocation by alloc_ppage.
- *
- * last_alloc_idx keeps track of the last 32bit element in the bitmap array
- * where a free page was found. It's guaranteed that all the elements before
- * this have no free pages, but it doesn't imply that there will be another
- * free page there. So it's used as a starting point for the search.
- */
-static uint32_t *bitmap;
-static int bmsize, last_alloc_idx;
-
-
-
-void init_mem(void)
-{
- int i, pg, max_used_pg, end_pg = 0;
- uint32_t used_end, start, end, sz, total = 0, rem;
- const char *suffix[] = {"bytes", "KB", "MB", "GB"};
-
- last_alloc_idx = 0;
-
- /* the allocation bitmap starts right at the end of the kernel image */
- bitmap = (uint32_t*)&_mem_start;
-
- /* start by marking all posible pages (2**20) as used. We do not "reserve"
- * all this space. Pages beyond the end of the useful bitmap area
- * ((char*)bitmap + bmsize), which will be determined after we traverse the
- * memory map, are going to be marked as available for allocation.
- */
- memset(bitmap, 0xff, 1024 * 1024 / 8);
-
-
- if(boot_mem_map_size <= 0 || boot_mem_map_size > MAX_MAP_SIZE) {
- panic("invalid memory map size reported by the boot loader: %d\n", boot_mem_map_size);
- }
-
- printf("Memory map:\n");
- for(i=0; i<boot_mem_map_size; i++) {
- printf(" start: %08x - size: %08x\n", (unsigned int)boot_mem_map[i].start,
- (unsigned int)boot_mem_map[i].size);
-
- start = boot_mem_map[i].start;
- sz = boot_mem_map[i].size & 0xfffffffc;
- end = start + sz;
- if(end < sz) {
- end = 0xfffffffc;
- sz = end - start;
- }
-
- /* ignore any memory ranges which end before the end of the kernel image */
- if(end < MEM_START) continue;
- if(start < MEM_START) {
- start = MEM_START;
- }
-
- add_memory(start, sz);
- total += sz;
-
- pg = ADDR_TO_PAGE(end);
- if(end_pg < pg) {
- end_pg = pg;
- }
- }
-
- i = 0;
- while(total > 1024) {
- rem = total & 0x3ff;
- total >>= 10;
- ++i;
- }
- printf("Total usable RAM: %u.%u %s\n", total, 100 * rem / 1024, suffix[i]);
-
- /* size of the useful part of the bitmap in bytes padded to 4-byte
- * boundaries to allow 32bit at a time operations.
- */
- bmsize = (end_pg / 32) * 4;
-
- /* mark all pages occupied by the bitmap as used */
- used_end = (uint32_t)bitmap + bmsize - 1;
-
- max_used_pg = ADDR_TO_PAGE(used_end);
- printf("marking pages up to %x (page: %d) as used\n", used_end, max_used_pg);
- for(i=0; i<=max_used_pg; i++) {
- mark_page(i, USED);
- }
-
-#ifdef MOVE_STACK_RAMTOP
- /* allocate space for the stack at the top of RAM and move it there */
- if((pg = alloc_ppages(STACK_PAGES, MEM_STACK)) != -1) {
- printf("moving stack-top to: %x (%d pages)\n", PAGE_TO_ADDR(end_pg) - 4, STACK_PAGES);
- move_stack(PAGE_TO_ADDR(pg + STACK_PAGES) - 4);
- }
-#endif
-}
-
-int alloc_ppage(int area)
-{
- return alloc_ppages(1, area);
-}
-
-/* free_ppage marks the physical page, free in the allocation bitmap.
- *
- * CAUTION: no checks are done that this page should actually be freed or not.
- * If you call free_ppage with the address of some part of memory that was
- * originally reserved due to it being in a memory hole or part of the kernel
- * image or whatever, it will be subsequently allocatable by alloc_ppage.
- */
-void free_ppage(int pg)
-{
- int bmidx = BM_IDX(pg);
-
- int intr_state = get_intr_flag();
- disable_intr();
-
- if(IS_FREE(pg)) {
- panic("free_ppage(%d): I thought that was already free!\n", pg);
- }
-
- mark_page(pg, FREE);
- if(bmidx < last_alloc_idx) {
- last_alloc_idx = bmidx;
- }
-
- set_intr_flag(intr_state);
-}
-
-
-int alloc_ppages(int count, int area)
-{
- int i, dir, pg, idx, max, intr_state, found_free = 0;
-
- intr_state = get_intr_flag();
- disable_intr();
-
- if(area == MEM_STACK) {
- idx = (bmsize - 1) / 4;
- max = -1;
- dir = -1;
- } else {
- idx = last_alloc_idx;
- max = bmsize / 4;
- dir = 1;
- }
-
- while(idx != max) {
- /* if at least one bit is 0 then we have at least
- * one free page. find it and try to allocate a range starting from there
- */
- if(bitmap[idx] != 0xffffffff) {
- pg = idx * 32;
- if(dir < 0) pg += 31;
-
- for(i=0; i<32; i++) {
- if(IS_FREE(pg)) {
- if(!found_free && dir > 0) {
- last_alloc_idx = idx;
- found_free = 1;
- }
-
- if(alloc_ppage_range(pg, count) != -1) {
- set_intr_flag(intr_state);
- return pg;
- }
- }
- pg += dir;
- }
- }
- idx += dir;
- }
-
- set_intr_flag(intr_state);
- return -1;
-}
-
-void free_ppages(int pg0, int count)
-{
- int i;
-
- for(i=0; i<count; i++) {
- free_ppage(pg0++);
- }
-}
-
-int alloc_ppage_range(int start, int size)
-{
- int i, pg = start;
- int intr_state;
-
- intr_state = get_intr_flag();
- disable_intr();
-
- /* first validate that no page in the requested range is allocated */
- for(i=0; i<size; i++) {
- if(!IS_FREE(pg)) {
- return -1;
- }
- ++pg;
- }
-
- /* all is well, mark them as used */
- pg = start;
- for(i=0; i<size; i++) {
- mark_page(pg++, USED);
- }
-
- set_intr_flag(intr_state);
- return 0;
-}
-
-int free_ppage_range(int start, int size)
-{
- int i, pg = start;
-
- for(i=0; i<size; i++) {
- free_ppage(pg++);
- }
- return 0;
-}
-
-/* adds a range of physical memory to the available pool. used during init_mem
- * when traversing the memory map.
- */
-static void add_memory(uint32_t start, size_t sz)
-{
- int i, szpg, pg;
-
- szpg = ADDR_TO_PAGE(sz + 4095);
- pg = ADDR_TO_PAGE(start);
-
- for(i=0; i<szpg; i++) {
- mark_page(pg++, FREE);
- }
-}
-
-/* maps a page as used or free in the allocation bitmap */
-static void mark_page(int pg, int used)
-{
- int idx = BM_IDX(pg);
- int bit = BM_BIT(pg);
-
- if(used) {
- bitmap[idx] |= 1 << bit;
- } else {
- bitmap[idx] &= ~(1 << bit);
- }
-}
-
-void print_page_bitmap(void)
-{
- int i;
-
- for(i=0; i<bmsize/4; i++) {
- if((i & 3) == 0) {
- uint32_t pg = i * 32;
- uint32_t addr = PAGE_TO_ADDR(pg);
- printf("\n%5d [%08x]:", (int)pg, (unsigned long)addr);
- }
- printf(" %08x", bitmap[i]);
- }
- printf("\n");
-}
projects / com32 / blobdiff