X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fmem.c;h=a01360777d7b5096a74b84406eb4f620a37835b9;hp=1d5db9e87b6efd653980188b2a68a810ff26dac8;hb=81c11bdd80190ec319a82b0402173cfb65fcbf72;hpb=79be435fcf61613617025a2c4ef5fddf00a09178

diff --git a/src/mem.c b/src/mem.c
index 1d5db9e..a013607 100644
--- a/src/mem.c
+++ b/src/mem.c
@@ -16,21 +16,72 @@ 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;
+	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);
@@ -40,5 +91,224 @@ void init_mem(void)
 	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");
 }