1991/0627/pc/mmu.c (diff list | history)

pc/mmu.c on 1991/0612
1991/0612		#include "u.h" #include "lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "io.h"
1991/0613		/*
1991/0625		* segment descriptor/gate */ typedef struct Segdesc Segdesc; struct Segdesc { ulong d0; ulong d1; }; /* * gate initializers */ #define TRAPGATE(s,o,p) { (o)&0xFFFF0000|SEGP|SEGPL(p)|SEGTG, (o)&0xFFFF|((s)<<16) } #define INTRGATE(s,o,p) { (o)&0xFFFF0000|SEGP|SEGPL(p)|SEGIG, (o)&0xFFFF|((s)<<16) } #define CALLGATE(s,o,p) { (o)&0xFFFF0000|SEGP|SEGPL(p)|SEGCG, (o)&0xFFFF|((s)<<16) } /* * segment descriptor initializers */ #define DATASEG(p) { SEGG|SEGB|(0xF<<16)|SEGP|SEGPL(p)|SEGDATA|SEGW, 0xFFFF } #define EXECSEG(p) { SEGG|SEGD|(0xF<<16)|SEGP|SEGPL(p)|SEGEXEC|SEGR, 0xFFFF } /* * task state segment. Plan 9 ignores all the task switching goo and just * uses the tss for esp0 and ss0 on gate's into the kernel, interrupts, * and exceptions. The rest is completely ignored. * * This means that we only need one tss in the whole system. */ typedef struct Tss Tss; struct Tss { ulong backlink; /* unused */ ulong esp0; /* pl0 stack pointer */ ulong ss0; /* pl0 stack selector */ ulong esp1; /* pl1 stack pointer */ ulong ss1; /* pl1 stack selector */ ulong esp2; /* pl2 stack pointer */ ulong ss2; /* pl2 stack selector */ ulong cr3; /* page table descriptor */ ulong eip; /* instruction pointer */ ulong eflags; /* processor flags */ ulong eax; /* general (hah?) registers */ ulong ecx; ulong edx; ulong ebx; ulong esp; ulong ebp; ulong esi; ulong edi; ulong es; /* segment selectors */ ulong cs; ulong ss; ulong ds; ulong fs; ulong gs; ulong ldt; /* local descriptor table */ ulong iomap; /* io map base */ }; /*
1991/0613		* global descriptor table describing all segments */ Segdesc gdt[1024] =
1991/0612		{
1991/0613		[NULLSEG] { 0, 0}, /* null descriptor */ [KESEG] EXECSEG(0), /* kernel code */ [KDSEG] DATASEG(0), /* kernel data/stack */ [UESEG] EXECSEG(3), /* user code */ [UDSEG] DATASEG(3), /* user data/stack */ [SYSGATE] CALLGATE(KESEG, syscall, 3), /* call gate for system calls */ };