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提交 9aa0337d 创建 作者: Frans Kaashoek's avatar Frans Kaashoek
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Map kernel high

Very important to give qemu memory through PHYSTOP :(
上级 dccb9152
隐藏空白字符变更
内嵌 并排
正在显示 包含 207 行增加 和 70 行删除
Makefile
浏览文件 @ 9aa0337d
......@@ -109,7 +109,7 @@ initcode: initcode.S
$(OBJDUMP) -S initcode.o > initcode.asm
kernel: $(OBJS) multiboot.o data.o bootother initcode
$(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernel multiboot.o data.o $(OBJS) -b binary initcode bootother
$(LD) $(LDFLAGS) -T kernel.ld -e multiboot_entry -o kernel multiboot.o data.o $(OBJS) -b binary initcode bootother
$(OBJDUMP) -S kernel > kernel.asm
$(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
......@@ -200,7 +200,7 @@ QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
ifndef CPUS
CPUS := 2
endif
QEMUOPTS = -hdb fs.img xv6.img -smp $(CPUS)
QEMUOPTS = -hdb fs.img xv6.img -smp $(CPUS) -m 512
qemu: fs.img xv6.img
$(QEMU) -serial mon:stdio $(QEMUOPTS)
......
bootmain.c
浏览文件 @ 9aa0337d
......@@ -8,6 +8,7 @@
#include "types.h"
#include "elf.h"
#include "x86.h"
#include "memlayout.h"
#define SECTSIZE 512
......@@ -19,7 +20,7 @@ bootmain(void)
struct elfhdr *elf;
struct proghdr *ph, *eph;
void (*entry)(void);
uchar* va;
uchar* pa;
elf = (struct elfhdr*)0x10000; // scratch space
......@@ -34,15 +35,15 @@ bootmain(void)
ph = (struct proghdr*)((uchar*)elf + elf->phoff);
eph = ph + elf->phnum;
for(; ph < eph; ph++){
va = (uchar*)ph->va;
readseg(va, ph->filesz, ph->offset);
pa = (uchar*)ph->pa;
readseg(pa, ph->filesz, ph->offset);
if(ph->memsz > ph->filesz)
stosb(va + ph->filesz, 0, ph->memsz - ph->filesz);
stosb(pa + ph->filesz, 0, ph->memsz - ph->filesz);
}
// Call the entry point from the ELF header.
// Does not return!
entry = (void(*)(void))(elf->entry);
entry = (void(*)(void))(elf->entry & 0xFFFFFF);
entry();
}
......
bootother.S
浏览文件 @ 9aa0337d
#include "asm.h"
#include "memlayout.h"
# Each non-boot CPU ("AP") is started up in response to a STARTUP
# IPI from the boot CPU. Section B.4.2 of the Multi-Processor
......@@ -24,6 +25,8 @@
#define CR0_PE 1
#define RELOC1(x) ((x) + KERNBASE) // same as V2P, but without casts
.code16
.globl start
start:
......@@ -40,7 +43,7 @@ start:
movl %eax, %cr0
//PAGEBREAK!
ljmp $(SEG_KCODE<<3), $start32
ljmpl $(SEG_KCODE<<3), $(start32+KERNBASE)
.code32
start32:
......@@ -53,10 +56,10 @@ start32:
movw %ax, %gs
# switch to the stack allocated by bootothers()
movl start-4, %esp
movl RELOC1(start-4), %esp
# call mpmain()
call *(start-8)
call *(RELOC1(start)-8)
movw $0x8a00, %ax
movw %ax, %dx
......@@ -69,8 +72,9 @@ spin:
.p2align 2
gdt:
SEG_NULLASM
SEG_ASM(STA_X|STA_R, 0x0, 0xffffffff)
SEG_ASM(STA_W, 0x0, 0xffffffff)
SEG_ASM(STA_X|STA_R, -KERNBASE, 0xffffffff)
SEG_ASM(STA_W, -KERNBASE, 0xffffffff)
gdtdesc:
.word (gdtdesc - gdt - 1)
......
console.c
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......@@ -9,6 +9,7 @@
#include "spinlock.h"
#include "fs.h"
#include "file.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
......@@ -60,6 +61,9 @@ cprintf(char *fmt, ...)
if(locking)
acquire(&cons.lock);
if (fmt == 0)
panic("null fmt");
argp = (uint*)(void*)(&fmt + 1);
state = 0;
for(i = 0; (c = fmt[i] & 0xff) != 0; i++){
......@@ -121,7 +125,7 @@ panic(char *s)
//PAGEBREAK: 50
#define BACKSPACE 0x100
#define CRTPORT 0x3d4
static ushort *crt = (ushort*)0xb8000; // CGA memory
static ushort *crt = (ushort*)P2V(0xb8000); // CGA memory
static void
cgaputc(int c)
......
defs.h
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......@@ -62,6 +62,7 @@ extern uchar ioapicid;
void ioapicinit(void);
// kalloc.c
char* pgalloc(void);
char* kalloc(void);
void kfree(char*);
void kinit(void);
......@@ -160,6 +161,7 @@ void uartintr(void);
void uartputc(int);
// vm.c
void pginit(char* (*alloc)());
void seginit(void);
void kvmalloc(void);
void vmenable(void);
......
exec.c
浏览文件 @ 9aa0337d
#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
......
ide.c
浏览文件 @ 9aa0337d
......@@ -3,6 +3,7 @@
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
......
kalloc.c
浏览文件 @ 9aa0337d
......@@ -5,6 +5,7 @@
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "spinlock.h"
......@@ -18,6 +19,20 @@ struct {
} kmem;
extern char end[]; // first address after kernel loaded from ELF file
char *newend;
// simple page allocator to get off the ground during boot
char *
pgalloc(void)
{
if (newend == 0)
newend = end;
void *p = (void*)PGROUNDUP((uint)newend);
memset(p, 0, PGSIZE);
newend = newend + PGSIZE;
return p;
}
// Initialize free list of physical pages.
void
......@@ -26,8 +41,8 @@ kinit(void)
char *p;
initlock(&kmem.lock, "kmem");
p = (char*)PGROUNDUP((uint)end);
for(; p + PGSIZE <= (char*)PHYSTOP; p += PGSIZE)
p = (char*)PGROUNDUP((uint)newend);
for(; p + PGSIZE <= (char*)p2v(PHYSTOP); p += PGSIZE)
kfree(p);
}
......@@ -41,7 +56,7 @@ kfree(char *v)
{
struct run *r;
if((uint)v % PGSIZE || v < end || (uint)v >= PHYSTOP)
if((uint)v % PGSIZE || v < end || v2p(v) >= PHYSTOP)
panic("kfree");
// Fill with junk to catch dangling refs.
......@@ -67,6 +82,7 @@ kalloc(void)
if(r)
kmem.freelist = r->next;
release(&kmem.lock);
cprintf("kalloc: 0x%x\n", r);
return (char*)r;
}
main.c
浏览文件 @ 9aa0337d
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
......@@ -9,6 +10,8 @@ static void bootothers(void);
static void mpmain(void);
void jmpkstack(void) __attribute__((noreturn));
void mainc(void);
static volatile int newpgdir;
// Bootstrap processor starts running C code here.
// Allocate a real stack and switch to it, first
......@@ -16,6 +19,7 @@ void mainc(void);
int
main(void)
{
pginit(pgalloc);
mpinit(); // collect info about this machine
lapicinit(mpbcpu());
seginit(); // set up segments
......@@ -46,7 +50,6 @@ mainc(void)
ioapicinit(); // another interrupt controller
consoleinit(); // I/O devices & their interrupts
uartinit(); // serial port
kvmalloc(); // initialize the kernel page table
pinit(); // process table
tvinit(); // trap vectors
binit(); // buffer cache
......@@ -57,7 +60,8 @@ mainc(void)
timerinit(); // uniprocessor timer
userinit(); // first user process
bootothers(); // start other processors
kvmalloc(); // new kernel page table wo. bottom mapped
newpgdir = 1;
// Finish setting up this processor in mpmain.
mpmain();
}
......@@ -66,16 +70,25 @@ mainc(void)
// Bootstrap CPU comes here from mainc().
// Other CPUs jump here from bootother.S.
static void
mpmain(void)
mpboot(void)
{
if(cpunum() != mpbcpu()){
seginit();
lapicinit(cpunum());
}
vmenable(); // turn on paging
seginit();
lapicinit(cpunum());
mpmain();
}
// Common CPU setup code.
// Bootstrap CPU comes here from mainc().
// Other CPUs jump here from bootother.S.
static void
mpmain(void)
{
cprintf("cpu%d: starting\n", cpu->id);
idtinit(); // load idt register
xchg(&cpu->booted, 1); // tell bootothers() we're up
while (!newpgdir) ; // wait until we have new page dir
switchkvm(); // switch to new page dir
scheduler(); // start running processes
}
......@@ -91,7 +104,7 @@ bootothers(void)
// Write bootstrap code to unused memory at 0x7000.
// The linker has placed the image of bootother.S in
// _binary_bootother_start.
code = (uchar*)0x7000;
code = p2v(0x7000);
memmove(code, _binary_bootother_start, (uint)_binary_bootother_size);
for(c = cpus; c < cpus+ncpu; c++){
......@@ -103,9 +116,9 @@ bootothers(void)
// its first instruction.
stack = kalloc();
*(void**)(code-4) = stack + KSTACKSIZE;
*(void**)(code-8) = mpmain;
*(void**)(code-8) = mpboot;
lapicstartap(c->id, (uint)code);
lapicstartap(c->id, v2p(code));
// Wait for cpu to finish mpmain()
while(c->booted == 0)
......
mmu.h
浏览文件 @ 9aa0337d
......@@ -106,18 +106,10 @@ struct segdesc {
// construct linear address from indexes and offset
#define PGADDR(d, t, o) ((uint)((d) << PDXSHIFT | (t) << PTXSHIFT | (o)))
// turn a kernel linear address into a physical address.
// all of the kernel data structures have linear and
// physical addresses that are equal.
#define PADDR(a) ((uint)(a))
// Page directory and page table constants.
#define NPDENTRIES 1024 // page directory entries per page directory
#define NPTENTRIES 1024 // page table entries per page table
#define PGSIZE 4096 // bytes mapped by a page
#define PGSHIFT 12 // log2(PGSIZE)
#define PTXSHIFT 12 // offset of PTX in a linear address
#define PDXSHIFT 22 // offset of PDX in a linear address
......
mp.c
浏览文件 @ 9aa0337d
......@@ -5,6 +5,7 @@
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mp.h"
#include "x86.h"
#include "mmu.h"
......@@ -39,6 +40,7 @@ mpsearch1(uchar *addr, int len)
{
uchar *e, *p;
addr = p2v((uint) addr);
e = addr+len;
for(p = addr; p < e; p += sizeof(struct mp))
if(memcmp(p, "_MP_", 4) == 0 && sum(p, sizeof(struct mp)) == 0)
......@@ -83,7 +85,7 @@ mpconfig(struct mp **pmp)
if((mp = mpsearch()) == 0 || mp->physaddr == 0)
return 0;
conf = (struct mpconf*)mp->physaddr;
conf = (struct mpconf*) p2v((uint) mp->physaddr);
if(memcmp(conf, "PCMP", 4) != 0)
return 0;
if(conf->version != 1 && conf->version != 4)
......
multiboot.S
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......@@ -15,6 +15,9 @@
# }
#include "asm.h"
#include "memlayout.h"
#define RELOC(x) ((x) - KERNBASE) // same as V2P, but without casts
#define STACK 4096
......@@ -42,7 +45,7 @@ multiboot_header:
# boot loader - bootasm.S - sets up.
.globl multiboot_entry
multiboot_entry:
lgdt gdtdesc
lgdt RELOC(gdtdesc)
ljmp $(SEG_KCODE<<3), $mbstart32
mbstart32:
......@@ -65,11 +68,11 @@ spin:
.p2align 2 # force 4 byte alignment
gdt:
SEG_NULLASM # null seg
SEG_ASM(STA_X|STA_R, 0x0, 0xffffffff) # code seg
SEG_ASM(STA_W, 0x0, 0xffffffff) # data seg
SEG_ASM(STA_X|STA_R, -KERNBASE, 0xffffffff) # code seg
SEG_ASM(STA_W, -KERNBASE, 0xffffffff) # data seg
gdtdesc:
.word (gdtdesc - gdt - 1) # sizeof(gdt) - 1
.long gdt # address gdt
.long RELOC(gdt) # address gdt
.comm stack, STACK
param.h
浏览文件 @ 9aa0337d
......@@ -7,8 +7,6 @@
#define NINODE 50 // maximum number of active i-nodes
#define NDEV 10 // maximum major device number
#define ROOTDEV 1 // device number of file system root disk
#define USERTOP 0xA0000 // end of user address space
#define PHYSTOP 0x1000000 // use phys mem up to here as free pool
#define MAXARG 32 // max exec arguments
#define LOGSIZE 10 // size of log
proc.c
浏览文件 @ 9aa0337d
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "x86.h"
#include "proc.h"
......
spinlock.c
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......@@ -4,6 +4,7 @@
#include "defs.h"
#include "param.h"
#include "x86.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "spinlock.h"
......@@ -71,7 +72,7 @@ getcallerpcs(void *v, uint pcs[])
ebp = (uint*)v - 2;
for(i = 0; i < 10; i++){
if(ebp == 0 || ebp < (uint*)0x100000 || ebp == (uint*)0xffffffff)
if(ebp == 0 || ebp < (uint*)KERNBASE || ebp == (uint*)0xffffffff)
break;
pcs[i] = ebp[1]; // saved %eip
ebp = (uint*)ebp[0]; // saved %ebp
......
syscall.c
浏览文件 @ 9aa0337d
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
......
sysproc.c
浏览文件 @ 9aa0337d
......@@ -2,6 +2,7 @@
#include "x86.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
......
trap.c
浏览文件 @ 9aa0337d
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
......
vm.c
浏览文件 @ 9aa0337d
......@@ -2,20 +2,71 @@
#include "types.h"
#include "defs.h"
#include "x86.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "elf.h"
extern char data[]; // defined in data.S
static pde_t *kpgdir; // for use in scheduler()
struct segdesc gdt[NSEGS];
// Allocate one page table for the machine for the kernel address
// space for scheduler processes.
// page map for during boot
// XXX build a static page table in assembly
static void
pgmap(void *va, void *last, uint pa)
{
pde_t *pde;
pte_t *pgtab;
pte_t *pte;
for(;;){
pde = &kpgdir[PDX(va)];
pde_t pdev = *pde;
if (pdev == 0) {
pgtab = (pte_t *) pgalloc();
*pde = v2p(pgtab) | PTE_P | PTE_W;
} else {
pgtab = (pte_t*)p2v(PTE_ADDR(pdev));
}
pte = &pgtab[PTX(va)];
*pte = pa | PTE_W | PTE_P;
if(va == last)
break;
va += PGSIZE;
pa += PGSIZE;
}
}
// set up a page table to get off the ground
void
kvmalloc(void)
pginit(char* (*alloc)(void))
{
kpgdir = setupkvm();
uint cr0;
kpgdir = (pde_t *) alloc();
pgmap((void *) 0, (void *) PHYSTOP, 0); // map pa 0 at va 0
pgmap((void *) KERNBASE, (void *) (KERNBASE+PHYSTOP), 0); // map pa 0 at va KERNBASE
pgmap((void*)0xFE000000, 0, 0xFE000000);
switchkvm(); // load kpgdir into cr3
cr0 = rcr0();
cr0 |= CR0_PG;
lcr0(cr0); // paging on
// new gdt
gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, 0);
gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
lgdt((void *)v2p(gdt), sizeof(gdt));
loadgs(SEG_KDATA << 3);
loadfs(SEG_KDATA << 3);
loades(SEG_KDATA << 3);
loadds(SEG_KDATA << 3);
loadss(SEG_KDATA << 3);
__asm volatile("ljmp %0,$1f\n 1:\n" :: "i" (SEG_KCODE << 3)); // reload cs
}
// Set up CPU's kernel segment descriptors.
......@@ -57,7 +108,7 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
pde = &pgdir[PDX(va)];
if(*pde & PTE_P){
pgtab = (pte_t*)PTE_ADDR(*pde);
pgtab = (pte_t*)p2v(PTE_ADDR(*pde));
} else {
if(!create || (pgtab = (pte_t*)kalloc()) == 0)
return 0;
......@@ -66,7 +117,7 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
// The permissions here are overly generous, but they can
// be further restricted by the permissions in the page table
// entries, if necessary.
*pde = PADDR(pgtab) | PTE_P | PTE_W | PTE_U;
*pde = v2p(pgtab) | PTE_P | PTE_W | PTE_U;
}
return &pgtab[PTX(va)];
}
......@@ -105,29 +156,30 @@ mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
// page protection bits prevent it from using anything other
// than its memory.
//
//
// setupkvm() and exec() set up every page table like this:
// 0..640K : user memory (text, data, stack, heap)
// 640K..1M : mapped direct (for IO space)
// 1M..end : mapped direct (for the kernel's text and data)
// end..PHYSTOP : mapped direct (kernel heap and user pages)
// 0..KERNBASE : user memory (text, data, stack, heap), mapped to some phys mem
// KERNBASE+640K..KERNBASE+1M: mapped to 640K..1M
// KERNBASE+1M..KERNBASE+end : mapped to 1M..end
// KERNBASE+end..KERBASE+PHYSTOP : mapped to end..PHYSTOP (free memory)
// 0xfe000000..0 : mapped direct (devices such as ioapic)
//
// The kernel allocates memory for its heap and for user memory
// between kernend and the end of physical memory (PHYSTOP).
// The virtual address space of each user program includes the kernel
// (which is inaccessible in user mode). The user program addresses
// range from 0 till 640KB (USERTOP), which where the I/O hole starts
// (both in physical memory and in the kernel's virtual address
// space).
// (which is inaccessible in user mode). The user program sits in
// the bottom of the address space, and the kernel at the top at KERNBASE.
static struct kmap {
void *p;
void *e;
void *l;
uint p;
uint e;
int perm;
} kmap[] = {
{(void*)USERTOP, (void*)0x100000, PTE_W}, // I/O space
{(void*)0x100000, data, 0 }, // kernel text, rodata
{data, (void*)PHYSTOP, PTE_W}, // kernel data, memory
{(void*)0xFE000000, 0, PTE_W}, // device mappings
{ (void *)IOSPACEB, IOSPACEB, IOSPACEE, PTE_W}, // I/O space
{ P2V(IOSPACEB), IOSPACEB, IOSPACEE, PTE_W}, // I/O space
{ (void *)KERNLINK, V2P(KERNLINK), V2P(data), 0}, // kernel text, rodata
{ data, V2P(data), PHYSTOP, PTE_W}, // kernel data, memory
{ (void*)0xFE000000, 0xFE000000, 0, PTE_W}, // device mappings
};
// Set up kernel part of a page table.
......@@ -142,12 +194,21 @@ setupkvm(void)
memset(pgdir, 0, PGSIZE);
k = kmap;
for(k = kmap; k < &kmap[NELEM(kmap)]; k++)
if(mappages(pgdir, k->p, k->e - k->p, (uint)k->p, k->perm) < 0)
if(mappages(pgdir, k->l, k->e - k->p, (uint)k->p, k->perm) < 0)
return 0;
return pgdir;
}
// Allocate one page table for the machine for the kernel address
// space for scheduler processes.
void
kvmalloc(void)
{
kpgdir = setupkvm();
switchkvm();
}
// Turn on paging.
void
vmenable(void)
......@@ -158,6 +219,16 @@ vmenable(void)
cr0 = rcr0();
cr0 |= CR0_PG;
lcr0(cr0);
struct cpu *c = &cpus[0];
lgdt((void *)v2p((void *)(c->gdt)), sizeof(c->gdt));
loadgs(SEG_KCPU << 3);
loadfs(SEG_KDATA << 3);
loades(SEG_KDATA << 3);
loadds(SEG_KDATA << 3);
loadss(SEG_KDATA << 3);
__asm volatile("ljmp %0,$1f\n 1:\n" :: "i" (SEG_KCODE << 3)); // reload cs
}
// Switch h/w page table register to the kernel-only page table,
......@@ -165,7 +236,7 @@ vmenable(void)
void
switchkvm(void)
{
lcr3(PADDR(kpgdir)); // switch to the kernel page table
lcr3(v2p(kpgdir)); // switch to the kernel page table
}
// Switch TSS and h/w page table to correspond to process p.
......@@ -180,7 +251,7 @@ switchuvm(struct proc *p)
ltr(SEG_TSS << 3);
if(p->pgdir == 0)
panic("switchuvm: no pgdir");
lcr3(PADDR(p->pgdir)); // switch to new address space
lcr3(v2p(p->pgdir)); // switch to new address space
popcli();
}
......@@ -195,7 +266,7 @@ inituvm(pde_t *pgdir, char *init, uint sz)
panic("inituvm: more than a page");
mem = kalloc();
memset(mem, 0, PGSIZE);
mappages(pgdir, 0, PGSIZE, PADDR(mem), PTE_W|PTE_U);
mappages(pgdir, 0, PGSIZE, v2p(mem), PTE_W|PTE_U);
memmove(mem, init, sz);
}
......@@ -245,7 +316,7 @@ allocuvm(pde_t *pgdir, uint oldsz, uint newsz)
return 0;
}
memset(mem, 0, PGSIZE);
mappages(pgdir, (char*)a, PGSIZE, PADDR(mem), PTE_W|PTE_U);
mappages(pgdir, (char*)a, PGSIZE, v2p(mem), PTE_W|PTE_U);
}
return newsz;
}
......@@ -289,7 +360,7 @@ freevm(pde_t *pgdir)
deallocuvm(pgdir, USERTOP, 0);
for(i = 0; i < NPDENTRIES; i++){
if(pgdir[i] & PTE_P)
kfree((char*)PTE_ADDR(pgdir[i]));
kfree(p2v(PTE_ADDR(pgdir[i])));
}
kfree((char*)pgdir);
}
......@@ -315,7 +386,7 @@ copyuvm(pde_t *pgdir, uint sz)
if((mem = kalloc()) == 0)
goto bad;
memmove(mem, (char*)pa, PGSIZE);
if(mappages(d, (void*)i, PGSIZE, PADDR(mem), PTE_W|PTE_U) < 0)
if(mappages(d, (void*)i, PGSIZE, v2p(mem), PTE_W|PTE_U) < 0)
goto bad;
}
return d;
......
x86.h
浏览文件 @ 9aa0337d
......@@ -96,6 +96,30 @@ loadgs(ushort v)
asm volatile("movw %0, %%gs" : : "r" (v));
}
static inline void
loadfs(ushort v)
{
__asm volatile("movw %0, %%fs" : : "r" (v));
}
static inline void
loades(ushort v)
{
__asm volatile("movw %0, %%es" : : "r" (v));
}
static inline void
loadds(ushort v)
{
__asm volatile("movw %0, %%ds" : : "r" (v));
}
static inline void
loadss(ushort v)
{
__asm volatile("movw %0, %%ss" : : "r" (v));
}
static inline uint
rebp(void)
{
......
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