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Commit f25a3f9a authored by Austin Clements's avatar Austin Clements
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Rearrange vm.c so it's in logical order and prints nicely. Shorten a few... 

Rearrange vm.c so it's in logical order and prints nicely.  Shorten a few functions in uninteresting ways to make them fit.
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runoff.spec
+ 8
− 2
View file @ f25a3f9a
......@@ -42,8 +42,14 @@ odd: proc.h
left: proc.c # VERY important
odd: proc.c # VERY important
# setjmp.S either
# vm.c either
# A few more action packed spreads
# page table creation and process loading
# walkpgdir mappages setupkvm vmenable switch[ku]vm inituvm loaduvm
# process memory management
# allocuvm deallocuvm freevm
right: vm.c
odd: vm.c
# kalloc.c either
# syscall.h either
......
vm.c
+ 129
− 135
View file @ f25a3f9a
......@@ -6,33 +6,38 @@
#include "proc.h"
#include "elf.h"
// The mappings from logical to linear are one to one (i.e.,
// segmentation doesn't do anything).
// 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..end : mapped direct (for the kernel's text and data)
// end..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
// 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).
#define USERTOP 0xA0000
static pde_t *kpgdir; // for use in scheduler()
// Set up CPU's kernel segment descriptors.
// Run once at boot time on each CPU.
void
ksegment(void)
{
struct cpu *c;
// 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, 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);
lgdt(c->gdt, sizeof(c->gdt));
loadgs(SEG_KCPU << 3);
// Initialize cpu-local storage.
cpu = c;
proc = 0;
}
// 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.
......@@ -50,10 +55,8 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
return 0;
else {
pgtab = (pte_t*) r;
// Make sure all those PTE_P bits are zero.
memset(pgtab, 0, PGSIZE);
// The permissions here are overly generous, but they can
// be further restricted by the permissions in the page table
// entries, if necessary.
......@@ -68,9 +71,9 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
static int
mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
{
char *first = PGROUNDDOWN(la);
char *a = PGROUNDDOWN(la);
char *last = PGROUNDDOWN(la + size - 1);
char *a = first;
while(1){
pte_t *pte = walkpgdir(pgdir, a, 1);
if(pte == 0)
......@@ -86,32 +89,75 @@ mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
return 1;
}
// Set up CPU's kernel segment descriptors.
// Run once at boot time on each CPU.
// The mappings from logical to linear are one to one (i.e.,
// segmentation doesn't do anything).
// 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..end : mapped direct (for the kernel's text and data)
// end..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
// 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).
// Allocate one page table for the machine for the kernel address
// space for scheduler processes.
void
ksegment(void)
kvmalloc(void)
{
struct cpu *c;
kpgdir = setupkvm();
}
// 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, 0, 0xffffffff, DPL_USER);
c->gdt[SEG_UDATA] = SEG(STA_W, 0, 0xffffffff, DPL_USER);
// Set up kernel part of a page table.
pde_t*
setupkvm(void)
{
pde_t *pgdir;
// map cpu, and curproc
c->gdt[SEG_KCPU] = SEG(STA_W, &c->cpu, 8, 0);
// Allocate page directory
if(!(pgdir = (pde_t *) kalloc()))
return 0;
memset(pgdir, 0, PGSIZE);
if(// Map IO space from 640K to 1Mbyte
!mappages(pgdir, (void *)USERTOP, 0x60000, USERTOP, PTE_W) ||
// Map kernel and free memory pool
!mappages(pgdir, (void *)0x100000, PHYSTOP-0x100000, 0x100000, PTE_W) ||
// Map devices such as ioapic, lapic, ...
!mappages(pgdir, (void *)0xFE000000, 0x2000000, 0xFE000000, PTE_W))
return 0;
return pgdir;
}
lgdt(c->gdt, sizeof(c->gdt));
loadgs(SEG_KCPU << 3);
// Initialize cpu-local storage.
cpu = c;
proc = 0;
// Turn on paging.
void
vmenable(void)
{
uint cr0;
switchkvm(); // load kpgdir into cr3
cr0 = rcr0();
cr0 |= CR0_PG;
lcr0(cr0);
}
// 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
}
// Switch h/w page table and TSS registers to point to process p.
......@@ -134,36 +180,6 @@ switchuvm(struct proc *p)
popcli();
}
// 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)
{
pde_t *pgdir;
// Allocate page directory
if(!(pgdir = (pde_t *) kalloc()))
return 0;
memset(pgdir, 0, PGSIZE);
// Map IO space from 640K to 1Mbyte
if(!mappages(pgdir, (void *)USERTOP, 0x60000, USERTOP, PTE_W))
return 0;
// Map kernel and free memory pool
if(!mappages(pgdir, (void *)0x100000, PHYSTOP-0x100000, 0x100000, PTE_W))
return 0;
// Map devices such as ioapic, lapic, ...
if(!mappages(pgdir, (void *)0xFE000000, 0x2000000, 0xFE000000, PTE_W))
return 0;
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
......@@ -177,6 +193,37 @@ uva2ka(pde_t *pgdir, char *uva)
return (char *)pa;
}
void
inituvm(pde_t *pgdir, char *init, uint sz)
{
char *mem = kalloc();
if (sz >= PGSIZE)
panic("inituvm: more than a page");
memset(mem, 0, PGSIZE);
mappages(pgdir, 0, PGSIZE, PADDR(mem), PTE_W|PTE_U);
memmove(mem, init, sz);
}
int
loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
{
uint i, pa, n;
pte_t *pte;
if((uint)addr % PGSIZE != 0)
panic("loaduvm: addr must be page aligned\n");
for(i = 0; i < sz; i += PGSIZE){
if(!(pte = walkpgdir(pgdir, addr+i, 0)))
panic("loaduvm: address should exist\n");
pa = PTE_ADDR(*pte);
if(sz - i < PGSIZE) n = sz - i;
else n = PGSIZE;
if(readi(ip, (char *)pa, offset+i, n) != n)
return 0;
}
return 1;
}
// 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.
......@@ -187,10 +234,9 @@ allocuvm(pde_t *pgdir, char *addr, uint sz)
{
if(addr + sz > (char*)USERTOP)
return 0;
char *first = PGROUNDDOWN(addr);
char *a = PGROUNDDOWN(addr);
char *last = PGROUNDDOWN(addr + sz - 1);
char *a;
for(a = first; a <= last; a += PGSIZE){
for(; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte == 0 || (*pte & PTE_P) == 0){
char *mem = kalloc();
......@@ -213,10 +259,9 @@ deallocuvm(pde_t *pgdir, char *addr, uint sz)
{
if(addr + sz > (char*)USERTOP)
return 0;
char *first = (char*) PGROUNDUP((uint)addr);
char *a = (char *)PGROUNDUP((uint)addr);
char *last = PGROUNDDOWN(addr + sz - 1);
char *a;
for(a = first; a <= last; a += PGSIZE){
for(; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte && (*pte & PTE_P) != 0){
uint pa = PTE_ADDR(*pte);
......@@ -246,37 +291,6 @@ freevm(pde_t *pgdir)
kfree((void *) pgdir);
}
int
loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
{
uint i, pa, n;
pte_t *pte;
if((uint)addr % PGSIZE != 0)
panic("loaduvm: addr must be page aligned\n");
for(i = 0; i < sz; i += PGSIZE){
if(!(pte = walkpgdir(pgdir, addr+i, 0)))
panic("loaduvm: address should exist\n");
pa = PTE_ADDR(*pte);
if(sz - i < PGSIZE) n = sz - i;
else n = PGSIZE;
if(readi(ip, (char *)pa, offset+i, n) != n)
return 0;
}
return 1;
}
void
inituvm(pde_t *pgdir, char *init, uint sz)
{
char *mem = kalloc();
if (sz >= PGSIZE)
panic("inituvm: more than a page");
memset(mem, 0, PGSIZE);
mappages(pgdir, 0, PGSIZE, PADDR(mem), PTE_W|PTE_U);
memmove(mem, init, sz);
}
// given a parent process's page table, create a copy
// of it for a child.
pde_t*
......@@ -307,23 +321,3 @@ bad:
return 0;
}
// Allocate one page table for the machine for the kernel address
// space for scheduler processes.
void
kvmalloc(void)
{
kpgdir = setupkvm();
}
// Turn on paging.
void
vmenable(void)
{
uint cr0;
switchkvm(); // load kpgdir into cr3
cr0 = rcr0();
cr0 |= CR0_PG;
lcr0(cr0);
}
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