内存容量检查（2）

09_day/bootpack.c

@@ -3,6 +3,8 @@
 #include "bootpack.h"
 #include <stdio.h>
 
+unsigned int memtest(unsigned int start, unsigned int end);
+
 void HariMain(void)
 {
 	struct BOOTINFO *binfo = (struct BOOTINFO *) ADR_BOOTINFO;
@@ -20,6 +22,7 @@ void HariMain(void)
 	io_out8(PIC1_IMR, 0xef); /* 开放鼠标中断(11101111) */
 
 	init_keyboard();
+	enable_mouse(&mdec);
 
 	init_palette();
 	init_screen8(binfo->vram, binfo->scrnx, binfo->scrny);
@@ -30,7 +33,9 @@ void HariMain(void)
 	sprintf(s, "(%d, %d)", mx, my);
 	putfonts8_asc(binfo->vram, binfo->scrnx, 0, 0, COL8_FFFFFF, s);
 
-	enable_mouse(&mdec);
+	i = memtest(0x00400000, 0xbfffffff) / (1024 * 1024);
+	sprintf(s, "memory %dMB", i);
+	putfonts8_asc(binfo->vram, binfo->scrnx, 0, 32, COL8_FFFFFF, s);
 
 	for (;;) {
 		io_cli();
@@ -86,3 +91,40 @@ void HariMain(void)
 	}
 }
 
+#define EFLAGS_AC_BIT			0x00040000
+#define CR0_CACHE_DISABLE	0x60000000
+
+unsigned int memtest(unsigned int start, unsigned int end) 
+{
+	char flg486 = 0;
+	unsigned int eflg, cr0, i;
+
+	/* 确认CPU是386还是486以上的 */
+	eflg = io_load_eflags();
+	eflg |= EFLAGS_AC_BIT; /* AC-bit = 1 */
+	io_store_eflags(eflg);
+	eflg = io_load_eflags();
+	if ((eflg & EFLAGS_AC_BIT) != 0) {
+		/* 如果是386，即使设定AC=1，AC的值还会自动回到0 */
+		flg486 = 1;
+	}
+
+	eflg &= ~EFLAGS_AC_BIT; /* AC-bit = 0 */
+	io_store_eflags(eflg);
+
+	if (flg486 != 0) {
+		cr0 = load_cr0();
+		cr0 |= CR0_CACHE_DISABLE; /* 禁止缓存 */ 
+		store_cr0(cr0);
+	}
+
+	i = memtest_sub(start, end);
+
+	if (flg486 != 0) {
+		cr0 = load_cr0();
+		cr0 &= ~CR0_CACHE_DISABLE; /* 允许缓存 */
+		store_cr0(cr0);
+	}
+
+	return i;
+}

09_day/naskfunc.nas

@@ -11,7 +11,9 @@
 		GLOBAL	_io_out8, _io_out16, _io_out32
 		GLOBAL	_io_load_eflags, _io_store_eflags
 		GLOBAL	_load_gdtr, _load_idtr
+		GLOBAL	_load_cr0, _store_cr0
 		GLOBAL	_asm_inthandler21, _asm_inthandler27, _asm_inthandler2c
+		GLOBAL	_memtest_sub
 		EXTERN	_inthandler21, _inthandler27, _inthandler2c
 
 [SECTION .text]
@@ -91,6 +93,15 @@ _load_idtr:		; void load_idtr(int limit, int addr);
 		LIDT	[ESP+6]
 		RET
 
+_load_cr0:		; int load_cr0(void);
+		MOV		EAX,CR0
+		RET
+
+_store_cr0:		; void store_cr0(int cr0);
+		MOV		EAX,[ESP+4]
+		MOV		CR0,EAX
+		RET
+
 _asm_inthandler21:
 		PUSH	ES
 		PUSH	DS
@@ -138,3 +149,36 @@ _asm_inthandler2c:
 		POP		DS
 		POP		ES
 		IRETD
+
+_memtest_sub:	; unsigned int memtest_sub(unsigned int start, unsigned int end)
+		PUSH	EDI						; （由于还要使用EBX, ESI, EDI）
+		PUSH	ESI
+		PUSH	EBX
+		MOV		ESI,0xaa55aa55			; pat0 = 0xaa55aa55;
+		MOV		EDI,0x55aa55aa			; pat1 = 0x55aa55aa;
+		MOV		EAX,[ESP+12+4]			; i = start;
+mts_loop:
+		MOV		EBX,EAX
+		ADD		EBX,0xffc				; p = i + 0xffc;
+		MOV		EDX,[EBX]				; old = *p;
+		MOV		[EBX],ESI				; *p = pat0;
+		XOR		DWORD [EBX],0xffffffff	; *p ^= 0xffffffff;
+		CMP		EDI,[EBX]				; if (*p != pat1) goto fin;
+		JNE		mts_fin
+		XOR		DWORD [EBX],0xffffffff	; *p ^= 0xffffffff;
+		CMP		ESI,[EBX]				; if (*p != pat0) goto fin;
+		JNE		mts_fin
+		MOV		[EBX],EDX				; *p = old;
+		ADD		EAX,0x1000				; i += 0x1000;
+		CMP		EAX,[ESP+12+8]			; if (i <= end) goto mts_loop;
+		JBE		mts_loop
+		POP		EBX
+		POP		ESI
+		POP		EDI
+		RET
+mts_fin:
+		MOV		[EBX],EDX				; *p = old;
+		POP		EBX
+		POP		ESI
+		POP		EDI
+		RET