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This commit is contained in:
Frans Kaashoek 2010-08-26 08:03:18 -04:00
commit d55b2fac07
21 changed files with 352 additions and 168 deletions
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2
Makefile
View file

@ -38,7 +38,7 @@ AS = $(TOOLPREFIX)gas
LD = $(TOOLPREFIX)ld
OBJCOPY = $(TOOLPREFIX)objcopy
OBJDUMP = $(TOOLPREFIX)objdump
CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32
CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror
CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
ASFLAGS = -m32 -gdwarf-2
# FreeBSD ld wants ``elf_i386_fbsd''

2
asm.h
View file

@ -6,6 +6,8 @@
.word 0, 0; \
.byte 0, 0, 0, 0
// The 0xC0 means the limit is in 4096-byte units
// and (for executable segments) 32-bit mode.
#define SEG_ASM(type,base,lim) \
.word (((lim) >> 12) & 0xffff), ((base) & 0xffff); \
.byte (((base) >> 16) & 0xff), (0x90 | (type)), \

6
bootasm.S
View file

@ -51,8 +51,10 @@ seta20.2:
orl $CR0_PE, %eax
movl %eax, %cr0
# Jump to next instruction, but in 32-bit code segment.
# Switches processor into 32-bit mode.
# This ljmp is how you load the CS (Code Segment) register.
# SEG_ASM produces segment descriptors with the 32-bit mode
# flag set (the D flag), so addresses and word operands will
# default to 32 bits after this jump.
ljmp $(SEG_KCODE<<3), $start32
.code32 # Assemble for 32-bit mode

6
bootother.S
View file

@ -45,8 +45,10 @@ start:
orl $CR0_PE, %eax
movl %eax, %cr0
# Jump to next instruction, but in 32-bit code segment.
# Switches processor into 32-bit mode.
# This ljmp is how you load the CS (Code Segment) register.
# SEG_ASM produces segment descriptors with the 32-bit mode
# flag set (the D flag), so addresses and word operands will
# default to 32 bits after this jump.
ljmp $(SEG_KCODE<<3), $start32
.code32 # Assemble for 32-bit mode

12
defs.h
View file

@ -110,7 +110,6 @@ void yield(void);
// swtch.S
void swtch(struct context**, struct context*);
void jstack(uint);
// spinlock.c
void acquire(struct spinlock*);
@ -143,7 +142,7 @@ void timerinit(void);
// trap.c
void idtinit(void);
extern int ticks;
extern uint ticks;
void tvinit(void);
extern struct spinlock tickslock;
@ -153,23 +152,20 @@ void uartintr(void);
void uartputc(int);
// vm.c
#define PGROUNDUP(sz) ((sz+PGSIZE-1) & ~(PGSIZE-1))
extern pde_t *kpgdir;
void pminit(void);
void ksegment(void);
void kvmalloc(void);
void vminit(void);
void jkstack();
void printstack(void);
void printpgdir(pde_t *);
pde_t* setupkvm(void);
char* uva2ka(pde_t*, char*);
int allocuvm(pde_t*, char*, uint);
int deallocuvm(pde_t *pgdir, char *addr, uint sz);
void freevm(pde_t*);
void inituvm(pde_t*, char*, char*, uint);
int loaduvm(pde_t*, char*, struct inode *ip, uint, uint);
pde_t* copyuvm(pde_t*,uint);
void loadvm(struct proc*);
void switchuvm(struct proc*);
void switchkvm();
// number of elements in fixed-size array
#define NELEM(x) (sizeof(x)/sizeof((x)[0]))

7
exec.c
View file

@ -43,13 +43,16 @@ exec(char *path, char **argv)
goto bad;
if (!allocuvm(pgdir, (char *)ph.va, ph.memsz))
goto bad;
sz += PGROUNDUP(ph.memsz);
if(ph.va + ph.memsz > sz)
sz = ph.va + ph.memsz;
if (!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
goto bad;
}
iunlockput(ip);
// Allocate and initialize stack at sz
sz = PGROUNDUP(sz);
sz += PGSIZE; // leave an invalid page
if (!allocuvm(pgdir, (char *)sz, PGSIZE))
goto bad;
mem = uva2ka(pgdir, (char *)sz);
@ -95,7 +98,7 @@ exec(char *path, char **argv)
proc->tf->eip = elf.entry; // main
proc->tf->esp = sp;
loadvm(proc);
switchuvm(proc);
freevm(oldpgdir);

9
kalloc.c
View file

@ -1,9 +1,8 @@
// Physical memory allocator, intended to allocate
// memory for user processes. Allocates in 4096-byte "pages".
// memory for user processes. Allocates in 4096-byte pages.
// Free list is kept sorted and combines adjacent pages into
// long runs, to make it easier to allocate big segments.
// One reason the page size is 4k is that the x86 segment size
// granularity is 4k.
// This combining is not useful now that xv6 uses paging.
#include "types.h"
#include "defs.h"
@ -24,14 +23,10 @@ struct {
int nfreemem;
// Initialize free list of physical pages.
// This code cheats by just considering one megabyte of
// pages after end. Real systems would determine the
// amount of memory available in the system and use it all.
void
kinit(char *p, uint len)
{
initlock(&kmem.lock, "kmem");
cprintf("end 0x%x free = %d(0x%x)\n", p, len);
nfreemem = 0;
kfree(p, len);
}

40
main.c
View file

@ -8,6 +8,7 @@
static void bootothers(void);
static void mpmain(void);
void jkstack(void) __attribute__((noreturn));
void mainc(void);
// Bootstrap processor starts running C code here.
int
@ -15,21 +16,32 @@ main(void)
{
mpinit(); // collect info about this machine
lapicinit(mpbcpu());
ksegment();
ksegment(); // set up segments
picinit(); // interrupt controller
ioapicinit(); // another interrupt controller
consoleinit(); // I/O devices & their interrupts
uartinit(); // serial port
pminit(); // physical memory for kernel
jkstack(); // Jump to mainc on a proper-allocated kernel stack
pminit(); // discover how much memory there is
jkstack(); // call mainc() on a properly-allocated stack
}
void
jkstack(void)
{
char *kstack = kalloc(PGSIZE);
if (!kstack)
panic("jkstack\n");
char *top = kstack + PGSIZE;
asm volatile("movl %0,%%esp" : : "r" (top));
asm volatile("call mainc");
panic("jkstack");
}
void
mainc(void)
{
cprintf("cpus %p cpu %p\n", cpus, cpu);
cprintf("\ncpu%d: starting xv6\n\n", cpu->id);
kvmalloc(); // allocate the kernel page table
kvmalloc(); // initialze the kernel page table
pinit(); // process table
tvinit(); // trap vectors
binit(); // buffer cache
@ -45,22 +57,21 @@ mainc(void)
mpmain();
}
// Bootstrap processor gets here after setting up the hardware.
// Additional processors start here.
// Common CPU setup code.
// Bootstrap CPU comes here from mainc().
// Other CPUs jump here from bootother.S.
static void
mpmain(void)
{
if(cpunum() != mpbcpu()) {
ksegment();
cprintf("other cpu\n");
lapicinit(cpunum());
}
vminit(); // Run with paging on each processor
cprintf("cpu%d: mpmain\n", cpu->id);
idtinit();
vminit(); // turn on paging
cprintf("cpu%d: starting\n", cpu->id);
idtinit(); // load idt register
xchg(&cpu->booted, 1);
cprintf("cpu%d: scheduling\n", cpu->id);
scheduler();
scheduler(); // start running processes
}
static void
@ -75,6 +86,7 @@ bootothers(void)
// placed the start of bootother.S there.
code = (uchar *) 0x7000;
memmove(code, _binary_bootother_start, (uint)_binary_bootother_size);
for(c = cpus; c < cpus+ncpu; c++){
if(c == cpus+cpunum()) // We've started already.
continue;
@ -85,7 +97,7 @@ bootothers(void)
*(void**)(code-8) = mpmain;
lapicstartap(c->id, (uint)code);
// Wait for cpu to get through bootstrap.
// Wait for cpu to finish mpmain()
while(c->booted == 0)
;
}

33
mmu.h
View file

@ -85,32 +85,20 @@ struct segdesc {
// | Page Directory | Page Table | Offset within Page |
// | Index | Index | |
// +----------------+----------------+---------------------+
// \--- PDX(la) --/ \--- PTX(la) --/ \---- PGOFF(la) ----/
// \----------- PPN(la) -----------/
//
// The PDX, PTX, PGOFF, and PPN macros decompose linear addresses as shown.
// To construct a linear address la from PDX(la), PTX(la), and PGOFF(la),
// use PGADDR(PDX(la), PTX(la), PGOFF(la)).
// page number field of address
#define PPN(la) (((uint) (la)) >> PTXSHIFT)
#define VPN(la) PPN(la) // used to index into vpt[]
// \--- PDX(la) --/ \--- PTX(la) --/
// page directory index
#define PDX(la) ((((uint) (la)) >> PDXSHIFT) & 0x3FF)
#define VPD(la) PDX(la) // used to index into vpd[]
// page table index
#define PTX(la) ((((uint) (la)) >> PTXSHIFT) & 0x3FF)
// offset in page
#define PGOFF(la) (((uint) (la)) & 0xFFF)
// construct linear address from indexes and offset
#define PGADDR(d, t, o) ((uint) ((d) << PDXSHIFT | (t) << PTXSHIFT | (o)))
// mapping from physical addresses to virtual addresses is the identity one
// (really linear addresses, but we map linear to physical also directly)
// 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.
@ -120,12 +108,12 @@ struct segdesc {
#define PGSIZE 4096 // bytes mapped by a page
#define PGSHIFT 12 // log2(PGSIZE)
#define PTSIZE (PGSIZE*NPTENTRIES) // bytes mapped by a page directory entry
#define PTSHIFT 22 // log2(PTSIZE)
#define PTXSHIFT 12 // offset of PTX in a linear address
#define PDXSHIFT 22 // offset of PDX in a linear address
#define PGROUNDUP(sz) (((sz)+PGSIZE-1) & ~(PGSIZE-1))
#define PGROUNDDOWN(a) ((char*)((((unsigned int)a) & ~(PGSIZE-1))))
// Page table/directory entry flags.
#define PTE_P 0x001 // Present
#define PTE_W 0x002 // Writeable
@ -137,13 +125,6 @@ struct segdesc {
#define PTE_PS 0x080 // Page Size
#define PTE_MBZ 0x180 // Bits must be zero
// The PTE_AVAIL bits aren't used by the kernel or interpreted by the
// hardware, so user processes are allowed to set them arbitrarily.
#define PTE_AVAIL 0xE00 // Available for software use
// Only flags in PTE_USER may be used in system calls.
#define PTE_USER (PTE_AVAIL | PTE_P | PTE_W | PTE_U)
// Address in page table or page directory entry
#define PTE_ADDR(pte) ((uint) (pte) & ~0xFFF)

13
proc.c
View file

@ -142,10 +142,15 @@ userinit(void)
int
growproc(int n)
{
if(n > 0){
if (!allocuvm(proc->pgdir, (char *)proc->sz, n))
return -1;
} else if(n < 0){
if (!deallocuvm(proc->pgdir, (char *)(proc->sz + n), 0 - n))
return -1;
}
proc->sz += n;
loadvm(proc);
switchuvm(proc);
return 0;
}
@ -214,9 +219,10 @@ scheduler(void)
// to release ptable.lock and then reacquire it
// before jumping back to us.
proc = p;
loadvm(p);
switchuvm(p);
p->state = RUNNING;
swtch(&cpu->scheduler, proc->context);
switchkvm();
// Process is done running for now.
// It should have changed its p->state before coming back.
@ -242,7 +248,6 @@ sched(void)
panic("sched running");
if(readeflags()&FL_IF)
panic("sched interruptible");
lcr3(PADDR(kpgdir)); // Switch to the kernel page table
intena = cpu->intena;
swtch(&proc->context, cpu->scheduler);
cpu->intena = intena;
@ -414,9 +419,9 @@ wait(void)
// Found one.
pid = p->pid;
kfree(p->kstack, KSTACKSIZE);
p->kstack = 0;
freevm(p->pgdir);
p->state = UNUSED;
p->kstack = 0;
p->pid = 0;
p->parent = 0;
p->name[0] = 0;

9
proc.h
View file

@ -3,8 +3,8 @@
#define SEG_KCODE 1 // kernel code
#define SEG_KDATA 2 // kernel data+stack
#define SEG_KCPU 3 // kernel per-cpu data
#define SEG_UCODE 4
#define SEG_UDATA 5
#define SEG_UCODE 4 // user code
#define SEG_UDATA 5 // user data+stack
#define SEG_TSS 6 // this process's task state
#define NSEGS 7
@ -16,7 +16,7 @@
// Contexts are stored at the bottom of the stack they
// describe; the stack pointer is the address of the context.
// The layout of the context matches the layout of the stack in swtch.S
// at "Switch stacks" comment. Switch itself doesn't save eip explicitly,
// at the "Switch stacks" comment. Switch doesn't save eip explicitly,
// but it is on the stack and allocproc() manipulates it.
struct context {
uint edi;
@ -31,7 +31,7 @@ enum procstate { UNUSED, EMBRYO, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };
// Per-process state
struct proc {
uint sz; // Size of process memory (bytes)
pde_t* pgdir; // linear address of proc's pgdir
pde_t* pgdir; // Linear address of proc's pgdir
char *kstack; // Bottom of kernel stack for this process
enum procstate state; // Process state
volatile int pid; // Process ID
@ -48,6 +48,7 @@ struct proc {
// Process memory is laid out contiguously, low addresses first:
// text
// original data and bss
// invalid page
// fixed-size stack
// expandable heap

1
runoff.list
View file

@ -23,6 +23,7 @@ proc.c
swtch.S
vm.c
kalloc.c
vm.c
# system calls
traps.h

1
sh.c
View file

@ -420,7 +420,6 @@ parseexec(char **ps, char *es)
int tok, argc;
struct execcmd *cmd;
struct cmd *ret;
int *x = (int *) peek;
if(peek(ps, es, "("))
return parseblock(ps, es);

8
swtch.S
View file

@ -26,11 +26,3 @@ swtch:
popl %ebx
popl %ebp
ret
# Jump on a new stack, fake C calling conventions
.globl jstack
jstack:
movl 4(%esp), %esp
subl $16, %esp # space for arguments
movl $0, %ebp # terminate functions that follow ebp's
call mainc # continue at mainc

2
syscall.c
View file

@ -100,6 +100,7 @@ extern int sys_sleep(void);
extern int sys_unlink(void);
extern int sys_wait(void);
extern int sys_write(void);
extern int sys_uptime(void);
static int (*syscalls[])(void) = {
[SYS_chdir] sys_chdir,
@ -122,6 +123,7 @@ static int (*syscalls[])(void) = {
[SYS_unlink] sys_unlink,
[SYS_wait] sys_wait,
[SYS_write] sys_write,
[SYS_uptime] sys_uptime,
};
void

1
syscall.h
View file

@ -19,3 +19,4 @@
#define SYS_getpid 18
#define SYS_sbrk 19
#define SYS_sleep 20
#define SYS_uptime 21

16
sysproc.c
View file

@ -57,7 +57,8 @@ sys_sbrk(void)
int
sys_sleep(void)
{
int n, ticks0;
int n;
uint ticks0;
if(argint(0, &n) < 0)
return -1;
@ -73,3 +74,16 @@ sys_sleep(void)
release(&tickslock);
return 0;
}
// return how many clock tick interrupts have occurred
// since boot.
int
sys_uptime(void)
{
uint xticks;
acquire(&tickslock);
xticks = ticks;
release(&tickslock);
return xticks;
}

2
trap.c
View file

@ -11,7 +11,7 @@
struct gatedesc idt[256];
extern uint vectors[]; // in vectors.S: array of 256 entry pointers
struct spinlock tickslock;
int ticks;
uint ticks;
void
tvinit(void)

137
usertests.c
View file

@ -322,8 +322,9 @@ void
mem(void)
{
void *m1, *m2;
int pid;
int pid, ppid;
ppid = getpid();
if((pid = fork()) == 0){
m1 = 0;
while((m2 = malloc(10001)) != 0) {
@ -338,6 +339,7 @@ mem(void)
m1 = malloc(1024*20);
if(m1 == 0) {
printf(1, "couldn't allocate mem?!!\n");
kill(ppid);
exit();
}
free(m1);
@ -1229,6 +1231,136 @@ forktest(void)
printf(1, "fork test OK\n");
}
void
sbrktest(void)
{
int pid;
char *oldbrk = sbrk(0);
printf(stdout, "sbrk test\n");
// can one sbrk() less than a page?
char *a = sbrk(0);
int i;
for(i = 0; i < 5000; i++){
char *b = sbrk(1);
if(b != a){
printf(stdout, "sbrk test failed %d %x %x\n", i, a, b);
exit();
}
*b = 1;
a = b + 1;
}
pid = fork();
if(pid < 0){
printf(stdout, "sbrk test fork failed\n");
exit();
}
char *c = sbrk(1);
c = sbrk(1);
if(c != a + 1){
printf(stdout, "sbrk test failed post-fork\n");
exit();
}
if(pid == 0)
exit();
wait();
// can one allocate the full 640K?
a = sbrk(0);
uint amt = (640 * 1024) - (uint) a;
char *p = sbrk(amt);
if(p != a){
printf(stdout, "sbrk test failed 640K test, p %x a %x\n", p, a);
exit();
}
char *lastaddr = (char *)(640 * 1024 - 1);
*lastaddr = 99;
// is one forbidden from allocating more than 640K?
c = sbrk(4096);
if(c != (char *) 0xffffffff){
printf(stdout, "sbrk allocated more than 640K, c %x\n", c);
exit();
}
// can one de-allocate?
a = sbrk(0);
c = sbrk(-4096);
if(c == (char *) 0xffffffff){
printf(stdout, "sbrk could not deallocate\n");
exit();
}
c = sbrk(0);
if(c != a - 4096){
printf(stdout, "sbrk deallocation produced wrong address, a %x c %x\n", a, c);
exit();
}
// can one re-allocate that page?
a = sbrk(0);
c = sbrk(4096);
if(c != a || sbrk(0) != a + 4096){
printf(stdout, "sbrk re-allocation failed, a %x c %x\n", a, c);
exit();
}
if(*lastaddr == 99){
// should be zero
printf(stdout, "sbrk de-allocation didn't really deallocate\n");
exit();
}
c = sbrk(4096);
if(c != (char *) 0xffffffff){
printf(stdout, "sbrk was able to re-allocate beyond 640K, c %x\n", c);
exit();
}
// can we read the kernel's memory?
for(a = (char*)(640*1024); a < (char *)2000000; a += 50000){
int ppid = getpid();
int pid = fork();
if(pid < 0){
printf(stdout, "fork failed\n");
exit();
}
if(pid == 0){
printf(stdout, "oops could read %x = %x\n", a, *a);
kill(ppid);
exit();
}
wait();
}
if(sbrk(0) > oldbrk)
sbrk(-(sbrk(0) - oldbrk));
printf(stdout, "sbrk test OK\n");
}
void
stacktest(void)
{
printf(stdout, "stack test\n");
char dummy = 1;
char *p = &dummy;
int ppid = getpid();
int pid = fork();
if(pid < 0){
printf(stdout, "fork failed\n");
exit();
}
if(pid == 0){
// should cause a trap:
p[-4096] = 'z';
kill(ppid);
printf(stdout, "stack test failed: page before stack was writeable\n");
exit();
}
wait();
printf(stdout, "stack test OK\n");
}
int
main(int argc, char *argv[])
{
@ -1240,6 +1372,9 @@ main(int argc, char *argv[])
}
close(open("usertests.ran", O_CREATE));
stacktest();
sbrktest();
opentest();
writetest();
writetest1();

1
usys.S
View file

@ -28,3 +28,4 @@ SYSCALL(dup)
SYSCALL(getpid)
SYSCALL(sbrk)
SYSCALL(sleep)
SYSCALL(uptime)

186
vm.c
View file

@ -8,13 +8,20 @@
// The mappings from logical to linear are one to one (i.e.,
// segmentation doesn't do anything).
// The mapping from linear to physical are one to one for the kernel.
// The mappings for the kernel include all of physical memory (until
// PHYSTOP), including the I/O hole, and the top of physical address
// space, where additional devices are located.
// The kernel itself is linked to be at 1MB, and its physical memory
// is also at 1MB.
// Physical memory for user programs is allocated from physical memory
// There is one page table per process, plus one that's used
// when a CPU is not running any process (kpgdir).
// A user process uses the same page table as the kernel; the
// 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..kernend : mapped direct (for the kernel's text and data)
// kernend..PHYSTOP : mapped direct (kernel heap and user pages)
// 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
@ -22,7 +29,7 @@
// (both in physical memory and in the kernel's virtual address
// space).
#define PHYSTOP 0x300000
#define PHYSTOP 0x1000000
#define USERTOP 0xA0000
static uint kerntext; // Linker starts kernel at 1MB
@ -31,29 +38,11 @@ static uint kerndata;
static uint kerndsz;
static uint kernend;
static uint freesz;
pde_t *kpgdir; // One kernel page table for scheduler procs
void
printpgdir(pde_t *pgdir)
{
uint i;
uint j;
cprintf("printpgdir 0x%x\n", pgdir);
for (i = 0; i < NPDENTRIES; i++) {
if (pgdir[i] != 0 && i < 100) {
cprintf("pgdir %d, v=0x%x\n", i, pgdir[i]);
pte_t *pgtab = (pte_t*) PTE_ADDR(pgdir[i]);
for (j = 0; j < NPTENTRIES; j++) {
if (pgtab[j] != 0)
cprintf("pgtab %d, v=0x%x, addr=0x%x\n", j, PGADDR(i, j, 0),
PTE_ADDR(pgtab[j]));
}
}
}
cprintf("printpgdir done\n", pgdir);
}
static pde_t *kpgdir; // for use in scheduler()
// return the address of the PTE in page table pgdir
// that corresponds to linear address va. if create!=0,
// create any required page table pages.
static pte_t *
walkpgdir(pde_t *pgdir, const void *va, int create)
{
@ -80,16 +69,26 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
return &pgtab[PTX(va)];
}
// create PTEs for linear addresses starting at la that refer to
// physical addresses starting at pa. la and size might not
// be page-aligned.
static int
mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
{
uint i;
pte_t *pte;
for (i = 0; i < size; i += PGSIZE) {
if (!(pte = walkpgdir(pgdir, (void*)(la + i), 1)))
char *first = PGROUNDDOWN(la);
char *last = PGROUNDDOWN(la + size - 1);
char *a = first;
while(1){
pte_t *pte = walkpgdir(pgdir, a, 1);
if(pte == 0)
return 0;
*pte = (pa + i) | perm | PTE_P;
if(*pte & PTE_P)
panic("remap");
*pte = pa | perm | PTE_P;
if(a == last)
break;
a += PGSIZE;
pa += PGSIZE;
}
return 1;
}
@ -101,12 +100,15 @@ ksegment(void)
{
struct cpu *c;
// Map once virtual addresses to linear addresses using identity map
// Map virtual addresses to linear addresses using identity map.
// Cannot share a CODE descriptor for both kernel and user
// because it would have to have DPL_USR, but the CPU forbids
// an interrupt from CPL=0 to DPL=3.
c = &cpus[cpunum()];
c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, 0);
c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, 0x0, 0xffffffff, DPL_USER);
c->gdt[SEG_UDATA] = SEG(STA_W, 0x0, 0xffffffff, DPL_USER);
c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, DPL_USER);
c->gdt[SEG_UDATA] = SEG(STA_W, 0, 0xffffffff, DPL_USER);
// map cpu, and curproc
c->gdt[SEG_KCPU] = SEG(STA_W, &c->cpu, 8, 0);
@ -119,9 +121,9 @@ ksegment(void)
proc = 0;
}
// Setup address space and current process task state.
// Switch h/w page table and TSS registers to point to process p.
void
loadvm(struct proc *p)
switchuvm(struct proc *p)
{
pushcli();
@ -133,14 +135,21 @@ loadvm(struct proc *p)
ltr(SEG_TSS << 3);
if (p->pgdir == 0)
panic("loadvm: no pgdir\n");
panic("switchuvm: no pgdir\n");
lcr3(PADDR(p->pgdir)); // switch to new address space
popcli();
}
// Setup kernel part of a page table. Linear adresses map one-to-one
// on physical addresses.
// Switch h/w page table register to the kernel-only page table, for when
// no process is running.
void
switchkvm()
{
lcr3(PADDR(kpgdir)); // Switch to the kernel page table
}
// Set up kernel part of a page table.
pde_t*
setupkvm(void)
{
@ -153,10 +162,10 @@ setupkvm(void)
// Map IO space from 640K to 1Mbyte
if (!mappages(pgdir, (void *)USERTOP, 0x60000, USERTOP, PTE_W))
return 0;
// Map kernel text from kern text addr read-only
// Map kernel text read-only
if (!mappages(pgdir, (void *) kerntext, kerntsz, kerntext, 0))
return 0;
// Map kernel data form kern data addr R/W
// Map kernel data read/write
if (!mappages(pgdir, (void *) kerndata, kerndsz, kerndata, PTE_W))
return 0;
// Map dynamically-allocated memory read/write (kernel stacks, user mem)
@ -168,6 +177,10 @@ setupkvm(void)
return pgdir;
}
// return the physical address that a given user address
// maps to. the result is also a kernel logical address,
// since the kernel maps the physical memory allocated to user
// processes directly.
char*
uva2ka(pde_t *pgdir, char *uva)
{
@ -177,25 +190,60 @@ uva2ka(pde_t *pgdir, char *uva)
return (char *)pa;
}
// allocate sz bytes more memory for a process starting at the
// given user address; allocates physical memory and page
// table entries. addr and sz need not be page-aligned.
// it is a no-op for any parts of the requested memory
// that are already allocated.
int
allocuvm(pde_t *pgdir, char *addr, uint sz)
{
uint i, n;
char *mem;
n = PGROUNDUP(sz);
if (addr + n >= USERTOP)
if (addr + sz > (char*)USERTOP)
return 0;
for (i = 0; i < n; i += PGSIZE) {
if (!(mem = kalloc(PGSIZE))) { // XXX cleanup what we did?
char *first = PGROUNDDOWN(addr);
char *last = PGROUNDDOWN(addr + sz - 1);
char *a;
for(a = first; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte == 0 || (*pte & PTE_P) == 0){
char *mem = kalloc(PGSIZE);
if(mem == 0){
// XXX clean up?
return 0;
}
memset(mem, 0, PGSIZE);
mappages(pgdir, addr + i, PGSIZE, PADDR(mem), PTE_W|PTE_U);
mappages(pgdir, a, PGSIZE, PADDR(mem), PTE_W|PTE_U);
}
}
return 1;
}
// deallocate some of the user pages, in response to sbrk()
// with a negative argument. if addr is not page-aligned,
// then only deallocates starting at the next page boundary.
int
deallocuvm(pde_t *pgdir, char *addr, uint sz)
{
if (addr + sz > (char*)USERTOP)
return 0;
char *first = (char*) PGROUNDUP((uint)addr);
char *last = PGROUNDDOWN(addr + sz - 1);
char *a;
for(a = first; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte && (*pte & PTE_P) != 0){
uint pa = PTE_ADDR(*pte);
if(pa == 0)
panic("deallocuvm");
kfree((void *) pa, PGSIZE);
*pte = 0;
}
}
return 1;
}
// free a page table and all the physical memory pages
// in the user part.
void
freevm(pde_t *pgdir)
{
@ -211,8 +259,7 @@ freevm(pde_t *pgdir)
if (pgtab[j] != 0) {
uint pa = PTE_ADDR(pgtab[j]);
uint va = PGADDR(i, j, 0);
if (va >= USERTOP) // done with user part?
break;
if (va < USERTOP) // user memory
kfree((void *) pa, PGSIZE);
pgtab[j] = 0;
}
@ -261,6 +308,8 @@ inituvm(pde_t *pgdir, char *addr, char *init, uint sz)
}
}
// given a parent process's page table, create a copy
// of it for a child.
pde_t*
copyuvm(pde_t *pgdir, uint sz)
{
@ -273,6 +322,7 @@ copyuvm(pde_t *pgdir, uint sz)
for (i = 0; i < sz; i += PGSIZE) {
if (!(pte = walkpgdir(pgdir, (void *)i, 0)))
panic("copyuvm: pte should exist\n");
if(*pte & PTE_P){
pa = PTE_ADDR(*pte);
if (!(mem = kalloc(PGSIZE)))
return 0;
@ -280,10 +330,14 @@ copyuvm(pde_t *pgdir, uint sz)
if (!mappages(d, (void *)i, PGSIZE, PADDR(mem), PTE_W|PTE_U))
return 0;
}
}
return d;
}
// Gather about physical memory layout. Called once during boot.
// Gather information about physical memory layout.
// Called once during boot.
// Really should find out how much physical memory
// there is rather than assuming PHYSTOP.
void
pminit(void)
{
@ -298,27 +352,13 @@ pminit(void)
kernend = ((uint)end + PGSIZE) & ~(PGSIZE-1);
kerntext = ph[0].va;
kerndata = ph[1].va;
kerntsz = kerndata - kerntext;
kerndsz = kernend - kerndata;
kerntsz = ph[0].memsz;
kerndsz = ph[1].memsz;
freesz = PHYSTOP - kernend;
cprintf("kerntext@0x%x(sz=0x%x), kerndata@0x%x(sz=0x%x), kernend 0x%x freesz = 0x%x\n",
kerntext, kerntsz, kerndata, kerndsz, kernend, freesz);
kinit((char *)kernend, freesz);
}
// Jump to mainc on a properly-allocated kernel stack
void
jkstack(void)
{
char *kstack = kalloc(PGSIZE);
if (!kstack)
panic("jkstack\n");
char *top = kstack + PGSIZE;
jstack((uint) top);
}
// Allocate one page table for the machine for the kernel address
// space for scheduler processes.
void