1 // This file contains definitions for the 2 // x86 memory management unit (MMU). 3 4 // Eflags register 5 #define FL_CF 0x00000001 // Carry Flag 6 #define FL_PF 0x00000004 // Parity Flag 7 #define FL_AF 0x00000010 // Auxiliary carry Flag 8 #define FL_ZF 0x00000040 // Zero Flag 9 #define FL_SF 0x00000080 // Sign Flag 10 #define FL_TF 0x00000100 // Trap Flag 11 #define FL_IF 0x00000200 // Interrupt Enable 12 #define FL_DF 0x00000400 // Direction Flag 13 #define FL_OF 0x00000800 // Overflow Flag 14 #define FL_IOPL_MASK 0x00003000 // I/O Privilege Level bitmask 15 #define FL_IOPL_0 0x00000000 // IOPL == 0 16 #define FL_IOPL_1 0x00001000 // IOPL == 1 17 #define FL_IOPL_2 0x00002000 // IOPL == 2 18 #define FL_IOPL_3 0x00003000 // IOPL == 3 19 #define FL_NT 0x00004000 // Nested Task 20 #define FL_RF 0x00010000 // Resume Flag 21 #define FL_VM 0x00020000 // Virtual 8086 mode 22 #define FL_AC 0x00040000 // Alignment Check 23 #define FL_VIF 0x00080000 // Virtual Interrupt Flag 24 #define FL_VIP 0x00100000 // Virtual Interrupt Pending 25 #define FL_ID 0x00200000 // ID flag 26 27 // Segment Descriptor 28 struct segdesc { 29 uint lim_15_0 : 16; // Low bits of segment limit 30 uint base_15_0 : 16; // Low bits of segment base address 31 uint base_23_16 : 8; // Middle bits of segment base address 32 uint type : 4; // Segment type (see STS_ constants) 33 uint s : 1; // 0 = system, 1 = application 34 uint dpl : 2; // Descriptor Privilege Level 35 uint p : 1; // Present 36 uint lim_19_16 : 4; // High bits of segment limit 37 uint avl : 1; // Unused (available for software use) 38 uint rsv1 : 1; // Reserved 39 uint db : 1; // 0 = 16-bit segment, 1 = 32-bit segment 40 uint g : 1; // Granularity: limit scaled by 4K when set 41 uint base_31_24 : 8; // High bits of segment base address 42 }; 43 44 // Normal segment 45 #define SEG(type, base, lim, dpl) (struct segdesc) \ 46 { ((lim) >> 12) & 0xffff, (base) & 0xffff, ((base) >> 16) & 0xff, \ 47 type, 1, dpl, 1, (uint) (lim) >> 28, 0, 0, 1, 1, \ 48 (uint) (base) >> 24 } 49 50 #define SEG16(type, base, lim, dpl) (struct segdesc) \ 51 { (lim) & 0xffff, (base) & 0xffff, ((base) >> 16) & 0xff, \ 52 type, 1, dpl, 1, (uint) (lim) >> 16, 0, 0, 1, 0, \ 53 (uint) (base) >> 24 } 54 55 #define DPL_USER 0x3 // User DPL 56 57 // Application segment type bits 58 #define STA_X 0x8 // Executable segment 59 #define STA_E 0x4 // Expand down (non-executable segments) 60 #define STA_C 0x4 // Conforming code segment (executable only) 61 #define STA_W 0x2 // Writeable (non-executable segments) 62 #define STA_R 0x2 // Readable (executable segments) 63 #define STA_A 0x1 // Accessed 64 65 // System segment type bits 66 #define STS_T16A 0x1 // Available 16-bit TSS 67 #define STS_LDT 0x2 // Local Descriptor Table 68 #define STS_T16B 0x3 // Busy 16-bit TSS 69 #define STS_CG16 0x4 // 16-bit Call Gate 70 #define STS_TG 0x5 // Task Gate / Coum Transmitions 71 #define STS_IG16 0x6 // 16-bit Interrupt Gate 72 #define STS_TG16 0x7 // 16-bit Trap Gate 73 #define STS_T32A 0x9 // Available 32-bit TSS 74 #define STS_T32B 0xB // Busy 32-bit TSS 75 #define STS_CG32 0xC // 32-bit Call Gate 76 #define STS_IG32 0xE // 32-bit Interrupt Gate 77 #define STS_TG32 0xF // 32-bit Trap Gate 78 79 // PAGEBREAK: 40 80 // Task state segment format 81 struct taskstate { 82 uint link; // Old ts selector 83 uint esp0; // Stack pointers and segment selectors 84 ushort ss0; // after an increase in privilege level 85 ushort padding1; 86 uint *esp1; 87 ushort ss1; 88 ushort padding2; 89 uint *esp2; 90 ushort ss2; 91 ushort padding3; 92 void *cr3; // Page directory base 93 uint *eip; // Saved state from last task switch 94 uint eflags; 95 uint eax; // More saved state (registers) 96 uint ecx; 97 uint edx; 98 uint ebx; 99 uint *esp; 100 uint *ebp; 101 uint esi; 102 uint edi; 103 ushort es; // Even more saved state (segment selectors) 104 ushort padding4; 105 ushort cs; 106 ushort padding5; 107 ushort ss; 108 ushort padding6; 109 ushort ds; 110 ushort padding7; 111 ushort fs; 112 ushort padding8; 113 ushort gs; 114 ushort padding9; 115 ushort ldt; 116 ushort padding10; 117 ushort t; // Trap on task switch 118 ushort iomb; // I/O map base address 119 }; 120 121 // PAGEBREAK: 12 122 // Gate descriptors for interrupts and traps 123 struct gatedesc { 124 uint off_15_0 : 16; // low 16 bits of offset in segment 125 uint cs : 16; // code segment selector 126 uint args : 5; // # args, 0 for interrupt/trap gates 127 uint rsv1 : 3; // reserved(should be zero I guess) 128 uint type : 4; // type(STS_{TG,IG32,TG32}) 129 uint s : 1; // must be 0 (system) 130 uint dpl : 2; // descriptor(meaning new) privilege level 131 uint p : 1; // Present 132 uint off_31_16 : 16; // high bits of offset in segment 133 }; 134 135 // Set up a normal interrupt/trap gate descriptor. 136 // - istrap: 1 for a trap (= exception) gate, 0 for an interrupt gate. 137 // interrupt gate clears FL_IF, trap gate leaves FL_IF alone 138 // - sel: Code segment selector for interrupt/trap handler 139 // - off: Offset in code segment for interrupt/trap handler 140 // - dpl: Descriptor Privilege Level - 141 // the privilege level required for software to invoke 142 // this interrupt/trap gate explicitly using an int instruction. 143 #define SETGATE(gate, istrap, sel, off, d) \ 144 { \ 145 (gate).off_15_0 = (uint) (off) & 0xffff; \ 146 (gate).cs = (sel); \ 147 (gate).args = 0; \ 148 (gate).rsv1 = 0; \ 149 (gate).type = (istrap) ? STS_TG32 : STS_IG32; \ 150 (gate).s = 0; \ 151 (gate).dpl = (d); \ 152 (gate).p = 1; \ 153 (gate).off_31_16 = (uint) (off) >> 16; \ 154 } 155 156