214 lines
6.9 KiB
C
214 lines
6.9 KiB
C
/*
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* This file contains definitions for the x86 memory management unit (MMU),
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* including paging- and segmentation-related data structures and constants,
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* the %cr0, %cr4, and %eflags registers, and traps.
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*/
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/*
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* Register flags and fundamental constants.
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*/
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#define PGSIZE 4096 // bytes mapped by a page
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// Eflags register
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#define FL_CF 0x00000001 // Carry Flag
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#define FL_PF 0x00000004 // Parity Flag
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#define FL_AF 0x00000010 // Auxiliary carry Flag
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#define FL_ZF 0x00000040 // Zero Flag
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#define FL_SF 0x00000080 // Sign Flag
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#define FL_TF 0x00000100 // Trap Flag
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#define FL_IF 0x00000200 // Interrupt Flag
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#define FL_DF 0x00000400 // Direction Flag
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#define FL_OF 0x00000800 // Overflow Flag
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#define FL_IOPL_MASK 0x00003000 // I/O Privilege Level bitmask
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#define FL_IOPL_0 0x00000000 // IOPL == 0
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#define FL_IOPL_1 0x00001000 // IOPL == 1
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#define FL_IOPL_2 0x00002000 // IOPL == 2
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#define FL_IOPL_3 0x00003000 // IOPL == 3
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#define FL_NT 0x00004000 // Nested Task
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#define FL_RF 0x00010000 // Resume Flag
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#define FL_VM 0x00020000 // Virtual 8086 mode
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#define FL_AC 0x00040000 // Alignment Check
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#define FL_VIF 0x00080000 // Virtual Interrupt Flag
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#define FL_VIP 0x00100000 // Virtual Interrupt Pending
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#define FL_ID 0x00200000 // ID flag
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// Page fault error codes
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#define FEC_PR 0x1 // Page fault caused by protection violation
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#define FEC_WR 0x2 // Page fault caused by a write
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#define FEC_U 0x4 // Page fault occured while in user mode
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/*
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*
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* Segmentation data structures and constants.
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*
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*/
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#ifdef __ASSEMBLER__
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/*
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* Macros to build GDT entries in assembly.
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*/
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#define SEG_NULL \
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.word 0, 0; \
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.byte 0, 0, 0, 0
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#define SEG(type,base,lim) \
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.word (((lim) >> 12) & 0xffff), ((base) & 0xffff); \
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.byte (((base) >> 16) & 0xff), (0x90 | (type)), \
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(0xC0 | (((lim) >> 28) & 0xf)), (((base) >> 24) & 0xff)
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#else // not __ASSEMBLER__
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// Segment Descriptors
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struct segdesc {
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uint lim_15_0 : 16; // Low bits of segment limit
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uint base_15_0 : 16; // Low bits of segment base address
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uint base_23_16 : 8; // Middle bits of segment base address
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uint type : 4; // Segment type (see STS_ constants)
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uint s : 1; // 0 = system, 1 = application
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uint dpl : 2; // Descriptor Privilege Level
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uint p : 1; // Present
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uint lim_19_16 : 4; // High bits of segment limit
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uint avl : 1; // Unused (available for software use)
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uint rsv1 : 1; // Reserved
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uint db : 1; // 0 = 16-bit segment, 1 = 32-bit segment
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uint g : 1; // Granularity: limit scaled by 4K when set
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uint base_31_24 : 8; // High bits of segment base address
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};
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// Null segment
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#define SEG_NULL (struct segdesc){ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }
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// Segment that is loadable but faults when used
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#define SEG_FAULT (struct segdesc){ 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0 }
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// Normal segment
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#define SEG(type, base, lim, dpl) (struct segdesc) \
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{ ((lim) >> 12) & 0xffff, (base) & 0xffff, ((base) >> 16) & 0xff, \
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type, 1, dpl, 1, (uint) (lim) >> 28, 0, 0, 1, 1, \
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(uint) (base) >> 24 }
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#define SEG16(type, base, lim, dpl) (struct segdesc) \
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{ (lim) & 0xffff, (base) & 0xffff, ((base) >> 16) & 0xff, \
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type, 1, dpl, 1, (uint) (lim) >> 16, 0, 0, 1, 0, \
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(uint) (base) >> 24 }
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#endif /* !__ASSEMBLER__ */
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// Application segment type bits
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#define STA_X 0x8 // Executable segment
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#define STA_E 0x4 // Expand down (non-executable segments)
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#define STA_C 0x4 // Conforming code segment (executable only)
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#define STA_W 0x2 // Writeable (non-executable segments)
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#define STA_R 0x2 // Readable (executable segments)
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#define STA_A 0x1 // Accessed
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// System segment type bits
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#define STS_T16A 0x1 // Available 16-bit TSS
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#define STS_LDT 0x2 // Local Descriptor Table
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#define STS_T16B 0x3 // Busy 16-bit TSS
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#define STS_CG16 0x4 // 16-bit Call Gate
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#define STS_TG 0x5 // Task Gate / Coum Transmitions
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#define STS_IG16 0x6 // 16-bit Interrupt Gate
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#define STS_TG16 0x7 // 16-bit Trap Gate
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#define STS_T32A 0x9 // Available 32-bit TSS
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#define STS_T32B 0xB // Busy 32-bit TSS
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#define STS_CG32 0xC // 32-bit Call Gate
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#define STS_IG32 0xE // 32-bit Interrupt Gate
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#define STS_TG32 0xF // 32-bit Trap Gate
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/*
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*
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* Traps.
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*
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*/
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#ifndef __ASSEMBLER__
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// Task state segment format (as described by the Pentium architecture book)
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struct taskstate {
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uint32_t link; // Old ts selector
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uintptr_t esp0; // Stack pointers and segment selectors
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uint16_t ss0; // after an increase in privilege level
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uint16_t padding1;
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uintptr_t esp1;
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uint16_t ss1;
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uint16_t padding2;
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uintptr_t esp2;
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uint16_t ss2;
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uint16_t padding3;
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physaddr_t cr3; // Page directory base
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uintptr_t eip; // Saved state from last task switch
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uint32_t eflags;
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uint32_t eax; // More saved state (registers)
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uint32_t ecx;
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uint32_t edx;
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uint32_t ebx;
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uintptr_t esp;
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uintptr_t ebp;
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uint32_t esi;
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uint32_t edi;
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uint16_t es; // Even more saved state (segment selectors)
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uint16_t padding4;
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uint16_t cs;
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uint16_t padding5;
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uint16_t ss;
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uint16_t padding6;
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uint16_t ds;
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uint16_t padding7;
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uint16_t fs;
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uint16_t padding8;
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uint16_t gs;
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uint16_t padding9;
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uint16_t ldt;
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uint16_t padding10;
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uint16_t t; // Trap on task switch
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uint16_t iomb; // I/O map base address
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};
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// Gate descriptors for interrupts and traps
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struct gatedesc {
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uint off_15_0 : 16; // low 16 bits of offset in segment
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uint ss : 16; // segment selector
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uint args : 5; // # args, 0 for interrupt/trap gates
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uint rsv1 : 3; // reserved(should be zero I guess)
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uint type : 4; // type(STS_{TG,IG32,TG32})
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uint s : 1; // must be 0 (system)
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uint dpl : 2; // descriptor(meaning new) privilege level
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uint p : 1; // Present
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uint off_31_16 : 16; // high bits of offset in segment
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};
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// Set up a normal interrupt/trap gate descriptor.
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// - istrap: 1 for a trap (= exception) gate, 0 for an interrupt gate.
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// - sel: Code segment selector for interrupt/trap handler
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// - off: Offset in code segment for interrupt/trap handler
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// - dpl: Descriptor Privilege Level -
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// the privilege level required for software to invoke
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// this interrupt/trap gate explicitly using an int instruction.
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#define SETGATE(gate, istrap, sel, off, d) \
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{ \
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(gate).off_15_0 = (uint32_t) (off) & 0xffff; \
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(gate).ss = (sel); \
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(gate).args = 0; \
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(gate).rsv1 = 0; \
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(gate).type = (istrap) ? STS_TG32 : STS_IG32; \
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(gate).s = 0; \
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(gate).dpl = (d); \
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(gate).p = 1; \
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(gate).off_31_16 = (uint32_t) (off) >> 16; \
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}
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// Set up a call gate descriptor.
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#define SETCALLGATE(gate, ss, off, d) \
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{ \
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(gate).off_15_0 = (uint32_t) (off) & 0xffff; \
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(gate).ss = (ss); \
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(gate).args = 0; \
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(gate).rsv1 = 0; \
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(gate).type = STS_CG32; \
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(gate).s = 0; \
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(gate).dpl = (d); \
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(gate).p = 1; \
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(gate).off_31_16 = (uint32_t) (off) >> 16; \
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}
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#endif /* !__ASSEMBLER__ */
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