add lab4 spoc discuss

related_info/lab4/lab4-spoc-discuss/boot/asm.h

@@ -0,0 +1,26 @@
+#ifndef __BOOT_ASM_H__
+#define __BOOT_ASM_H__
+
+/* Assembler macros to create x86 segments */
+
+/* Normal segment */
+#define SEG_NULLASM                                             \
+    .word 0, 0;                                                 \
+    .byte 0, 0, 0, 0
+
+#define SEG_ASM(type,base,lim)                                  \
+    .word (((lim) >> 12) & 0xffff), ((base) & 0xffff);          \
+    .byte (((base) >> 16) & 0xff), (0x90 | (type)),             \
+        (0xC0 | (((lim) >> 28) & 0xf)), (((base) >> 24) & 0xff)
+
+
+/* Application segment type bits */
+#define STA_X       0x8     // Executable segment
+#define STA_E       0x4     // Expand down (non-executable segments)
+#define STA_C       0x4     // Conforming code segment (executable only)
+#define STA_W       0x2     // Writeable (non-executable segments)
+#define STA_R       0x2     // Readable (executable segments)
+#define STA_A       0x1     // Accessed
+
+#endif /* !__BOOT_ASM_H__ */
+