Task State Segment (TSS) for a 486 31 16 15 <- bits 0 +------------------------+------------------------+ | 0000 0000 0000 0000 | BACK LINK | 0 (TSS base) | ESP0 | 4 | 0000 0000 0000 0000 | SS0 | 8 | ESP1 | C | 0000 0000 0000 0000 | SS1 | 10 | ESP2 | 14 | 0000 0000 0000 0000 | SS2 | 18 | CR3 | 1C | EIP | 20 | EFLAGS | 24 | EAX | 28 | ECX | 2C | EDX | 30 | EBX | 34 | ESP | 38 | EBP | 3C | ESI | 40 | EDI | 44 | 0000 0000 0000 0000 | ES | 48 | 0000 0000 0000 0000 | CS | 4C | 0000 0000 0000 0000 | SS | 50 | 0000 0000 0000 0000 | DS | 54 | 0000 0000 0000 0000 | FS | 58 | 0000 0000 0000 0000 | GS | 5C | 0000 0000 0000 0000 | LDT | 60 | BIT_MAP_OFFSET(15:0) | 0000 0000 0000 000 |T| 64 T= debug trap bit +------------------------+------------------------+ | Available | | SYSTEM STATUS, ETC. | \\ \\ \\ ... \\ | | +------------------------+------------------------+ |31 24|23 16|15 8|7 0| BIT_MAP_OFFSET |63 56|55 48|47 40|39 32| BIT_MAP_OFFSET + 4 |95 88|87 80|79 72|71 64| BIT_MAP_OFFSET + 8 \\ ... \\ etc. \\ \\ |65471 | | | 65440| BIT_MAP_OFFSET + 1FF4 |65503 | | | 65472| BIT_MAP_OFFSET + 1FF8 |65535 | | | 65504| BIT_MAP_OFFSET + 1FFC +-----------+------------+------------| "FFh" | BIT_MAP_OFFSET + 2000 +-----------+ Notes: 1. ESP0-3, and SS0-3 are the stacks for CPL 0,1 and 2 2. BIT_MAP_OFFSET must be <= DFFFh 3. The I/O Permission bitmap uses one bit per I/O port address and may be truncated using the TSS limit in the TSS Register. 4. The backlink is a pointer to the previous TSS. It is used when a CALL or INT instruction causes a task switch.
file: /Techref/intel/80486/tss.htm, 3KB, , updated: 2000/2/16 12:35, local time: 2024/11/30 17:20,
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