xv6/asm.h

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C
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2023-01-04 17:04:31 +01:00
//
// assembler macros to create x86 segments
//
#define SEG_NULLASM \
.word 0, 0; \
.byte 0, 0, 0, 0
// The 0xC0 means the limit is in 4096-byte units
// and (for executable segments) 32-bit mode.
#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)
#define STA_X 0x8 // Executable segment
#define STA_W 0x2 // Writeable (non-executable segments)
#define STA_R 0x2 // Readable (executable segments)