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-rw-r--r--runoff.spec10
-rw-r--r--vm.c264
2 files changed, 137 insertions, 137 deletions
diff --git a/runoff.spec b/runoff.spec
index 9d87528..d5b5334 100644
--- a/runoff.spec
+++ b/runoff.spec
@@ -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
diff --git a/vm.c b/vm.c
index 9c0783d..f3436b7 100644
--- a/vm.c
+++ b/vm.c
@@ -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);
-}
-