xv6: xv6/asm.h Source File

00001 //
00002 // assembler macros to create x86 segments
00003 //
00004 
00005 #define SEG_NULLASM                                             \
00006         .word 0, 0;                                             \
00007         .byte 0, 0, 0, 0
00008 
00009 #define SEG_ASM(type,base,lim)                                  \
00010         .word (((lim) >> 12) & 0xffff), ((base) & 0xffff);      \
00011         .byte (((base) >> 16) & 0xff), (0x90 | (type)),         \
00012                 (0xC0 | (((lim) >> 28) & 0xf)), (((base) >> 24) & 0xff)
00013 
00014 #define STA_X     0x8       // Executable segment
00015 #define STA_E     0x4       // Expand down (non-executable segments)
00016 #define STA_C     0x4       // Conforming code segment (executable only)
00017 #define STA_W     0x2       // Writeable (non-executable segments)
00018 #define STA_R     0x2       // Readable (executable segments)
00019 #define STA_A     0x1       // Accessed