2010-07-23 18:52:35 +02:00
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#include "param.h"
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#include "types.h"
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#include "defs.h"
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#include "x86.h"
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#include "mmu.h"
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#include "proc.h"
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#include "elf.h"
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2010-07-26 02:30:21 +02:00
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#define USERTOP 0xA0000
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2010-08-06 17:12:18 +02:00
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static pde_t *kpgdir; // for use in scheduler()
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2010-07-23 18:52:35 +02:00
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2010-09-02 22:23:15 +02:00
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// Set up CPU's kernel segment descriptors.
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// Run once at boot time on each CPU.
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void
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ksegment(void)
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{
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struct cpu *c;
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// Map virtual addresses to linear addresses using identity map.
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// Cannot share a CODE descriptor for both kernel and user
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// because it would have to have DPL_USR, but the CPU forbids
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// an interrupt from CPL=0 to DPL=3.
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c = &cpus[cpunum()];
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c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, 0);
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c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
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c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, DPL_USER);
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c->gdt[SEG_UDATA] = SEG(STA_W, 0, 0xffffffff, DPL_USER);
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2010-09-02 22:36:38 +02:00
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// Map cpu, and curproc
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2010-09-02 22:23:15 +02:00
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c->gdt[SEG_KCPU] = SEG(STA_W, &c->cpu, 8, 0);
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lgdt(c->gdt, sizeof(c->gdt));
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loadgs(SEG_KCPU << 3);
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// Initialize cpu-local storage.
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cpu = c;
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proc = 0;
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}
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2010-09-02 22:36:38 +02:00
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// Return the address of the PTE in page table pgdir
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// that corresponds to linear address va. If create!=0,
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2010-08-05 18:10:54 +02:00
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// create any required page table pages.
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2010-07-23 18:52:35 +02:00
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static pte_t *
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walkpgdir(pde_t *pgdir, const void *va, int create)
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{
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uint r;
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pde_t *pde;
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pte_t *pgtab;
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pde = &pgdir[PDX(va)];
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2010-09-01 06:41:25 +02:00
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if(*pde & PTE_P){
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2010-07-23 18:52:35 +02:00
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pgtab = (pte_t*) PTE_ADDR(*pde);
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2010-09-01 06:41:25 +02:00
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} else if(!create || !(r = (uint) kalloc()))
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2010-07-23 18:52:35 +02:00
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return 0;
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else {
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pgtab = (pte_t*) r;
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// Make sure all those PTE_P bits are zero.
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memset(pgtab, 0, PGSIZE);
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// The permissions here are overly generous, but they can
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// be further restricted by the permissions in the page table
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// entries, if necessary.
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*pde = PADDR(r) | PTE_P | PTE_W | PTE_U;
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}
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return &pgtab[PTX(va)];
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}
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2010-09-02 22:36:38 +02:00
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// Create PTEs for linear addresses starting at la that refer to
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2010-08-05 22:00:59 +02:00
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// physical addresses starting at pa. la and size might not
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// be page-aligned.
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2010-07-23 18:52:35 +02:00
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static int
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2010-07-26 14:10:02 +02:00
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mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
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2010-07-23 18:52:35 +02:00
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{
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2010-09-02 22:23:15 +02:00
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char *a = PGROUNDDOWN(la);
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2010-08-05 22:00:59 +02:00
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char *last = PGROUNDDOWN(la + size - 1);
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2010-09-02 22:23:15 +02:00
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2010-08-05 22:00:59 +02:00
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while(1){
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pte_t *pte = walkpgdir(pgdir, a, 1);
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if(pte == 0)
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2010-07-23 18:52:35 +02:00
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return 0;
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2010-08-05 18:10:54 +02:00
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if(*pte & PTE_P)
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panic("remap");
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2010-08-05 22:00:59 +02:00
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*pte = pa | perm | PTE_P;
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if(a == last)
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break;
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a += PGSIZE;
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pa += PGSIZE;
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2010-07-23 18:52:35 +02:00
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}
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return 1;
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}
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2010-09-02 22:23:15 +02:00
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// The mappings from logical to linear are one to one (i.e.,
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// segmentation doesn't do anything).
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// There is one page table per process, plus one that's used
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// when a CPU is not running any process (kpgdir).
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// A user process uses the same page table as the kernel; the
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// page protection bits prevent it from using anything other
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// than its memory.
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//
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// setupkvm() and exec() set up every page table like this:
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// 0..640K : user memory (text, data, stack, heap)
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// 640K..1M : mapped direct (for IO space)
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// 1M..end : mapped direct (for the kernel's text and data)
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// end..PHYSTOP : mapped direct (kernel heap and user pages)
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// 0xfe000000..0 : mapped direct (devices such as ioapic)
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//
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// The kernel allocates memory for its heap and for user memory
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// between kernend and the end of physical memory (PHYSTOP).
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// The virtual address space of each user program includes the kernel
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// (which is inaccessible in user mode). The user program addresses
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// range from 0 till 640KB (USERTOP), which where the I/O hole starts
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// (both in physical memory and in the kernel's virtual address
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// space).
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// Allocate one page table for the machine for the kernel address
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// space for scheduler processes.
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2010-07-23 18:52:35 +02:00
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void
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2010-09-02 22:23:15 +02:00
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kvmalloc(void)
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2010-07-23 18:52:35 +02:00
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{
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2010-09-02 22:23:15 +02:00
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kpgdir = setupkvm();
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}
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2010-07-23 18:52:35 +02:00
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2010-09-02 22:23:15 +02:00
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// Set up kernel part of a page table.
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pde_t*
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setupkvm(void)
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{
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pde_t *pgdir;
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2010-07-23 18:52:35 +02:00
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2010-09-02 22:23:15 +02:00
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// Allocate page directory
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if(!(pgdir = (pde_t *) kalloc()))
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return 0;
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memset(pgdir, 0, PGSIZE);
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if(// Map IO space from 640K to 1Mbyte
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!mappages(pgdir, (void *)USERTOP, 0x60000, USERTOP, PTE_W) ||
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// Map kernel and free memory pool
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!mappages(pgdir, (void *)0x100000, PHYSTOP-0x100000, 0x100000, PTE_W) ||
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// Map devices such as ioapic, lapic, ...
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!mappages(pgdir, (void *)0xFE000000, 0x2000000, 0xFE000000, PTE_W))
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return 0;
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return pgdir;
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}
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2010-07-23 18:52:35 +02:00
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2010-09-02 22:23:15 +02:00
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// Turn on paging.
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void
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vmenable(void)
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{
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uint cr0;
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switchkvm(); // load kpgdir into cr3
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cr0 = rcr0();
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cr0 |= CR0_PG;
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lcr0(cr0);
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}
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2010-09-02 22:36:38 +02:00
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// Switch h/w page table register to the kernel-only page table,
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// for when no process is running.
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2010-09-02 22:23:15 +02:00
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void
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switchkvm()
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{
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2010-09-02 22:36:38 +02:00
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lcr3(PADDR(kpgdir)); // switch to the kernel page table
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2010-07-23 18:52:35 +02:00
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}
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2010-08-06 17:12:18 +02:00
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// Switch h/w page table and TSS registers to point to process p.
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2010-07-23 18:52:35 +02:00
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void
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2010-08-06 17:12:18 +02:00
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switchuvm(struct proc *p)
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2010-07-23 18:52:35 +02:00
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{
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pushcli();
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// Setup TSS
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cpu->gdt[SEG_TSS] = SEG16(STS_T32A, &cpu->ts, sizeof(cpu->ts)-1, 0);
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cpu->gdt[SEG_TSS].s = 0;
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cpu->ts.ss0 = SEG_KDATA << 3;
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cpu->ts.esp0 = (uint)proc->kstack + KSTACKSIZE;
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ltr(SEG_TSS << 3);
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2010-09-01 06:41:25 +02:00
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if(p->pgdir == 0)
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2010-08-06 17:12:18 +02:00
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panic("switchuvm: no pgdir\n");
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2010-07-23 18:52:35 +02:00
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lcr3(PADDR(p->pgdir)); // switch to new address space
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popcli();
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}
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2010-09-02 22:36:38 +02:00
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// Return the physical address that a given user address
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// maps to. The result is also a kernel logical address,
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2010-08-06 17:12:18 +02:00
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// since the kernel maps the physical memory allocated to user
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// processes directly.
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2010-07-23 18:52:35 +02:00
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char*
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uva2ka(pde_t *pgdir, char *uva)
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{
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pte_t *pte = walkpgdir(pgdir, uva, 0);
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2010-09-01 06:41:25 +02:00
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if(pte == 0) return 0;
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2010-07-23 18:52:35 +02:00
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uint pa = PTE_ADDR(*pte);
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return (char *)pa;
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}
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2010-09-02 22:39:55 +02:00
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// Load the initcode into address 0 of pgdir.
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// sz must be less than a page.
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2010-09-02 22:23:15 +02:00
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void
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inituvm(pde_t *pgdir, char *init, uint sz)
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{
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char *mem = kalloc();
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if (sz >= PGSIZE)
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panic("inituvm: more than a page");
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memset(mem, 0, PGSIZE);
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mappages(pgdir, 0, PGSIZE, PADDR(mem), PTE_W|PTE_U);
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memmove(mem, init, sz);
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}
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2010-09-02 22:39:55 +02:00
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// Load a program segment into pgdir. addr must be page-aligned
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// and the pages from addr to addr+sz must already be mapped.
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2010-09-02 22:23:15 +02:00
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int
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loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
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{
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uint i, pa, n;
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pte_t *pte;
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if((uint)addr % PGSIZE != 0)
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panic("loaduvm: addr must be page aligned\n");
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for(i = 0; i < sz; i += PGSIZE){
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if(!(pte = walkpgdir(pgdir, addr+i, 0)))
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panic("loaduvm: address should exist\n");
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pa = PTE_ADDR(*pte);
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if(sz - i < PGSIZE) n = sz - i;
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else n = PGSIZE;
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if(readi(ip, (char *)pa, offset+i, n) != n)
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return 0;
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}
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return 1;
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}
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2010-09-03 00:28:36 +02:00
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// Allocate memory to the process to bring its size from oldsz to
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// newsz. Allocates physical memory and page table entries. oldsz and
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// newsz need not be page-aligned, nor does newsz have to be larger
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// than oldsz. Returns the new process size or 0 on error.
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2010-07-23 18:52:35 +02:00
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int
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2010-09-03 00:28:36 +02:00
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allocuvm(pde_t *pgdir, uint oldsz, uint newsz)
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2010-07-23 18:52:35 +02:00
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{
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2010-09-03 00:28:36 +02:00
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if(newsz > USERTOP)
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2010-07-23 18:52:35 +02:00
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return 0;
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2010-09-03 00:28:36 +02:00
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char *a = (char *)PGROUNDUP(oldsz);
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char *last = PGROUNDDOWN(newsz - 1);
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for (; a <= last; a += PGSIZE){
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char *mem = kalloc();
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if(mem == 0){
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cprintf("allocuvm out of memory\n");
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deallocuvm(pgdir, newsz, oldsz);
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return 0;
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2010-07-23 18:52:35 +02:00
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}
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2010-09-03 00:28:36 +02:00
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memset(mem, 0, PGSIZE);
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mappages(pgdir, a, PGSIZE, PADDR(mem), PTE_W|PTE_U);
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2010-07-23 18:52:35 +02:00
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}
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2010-09-03 00:28:36 +02:00
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return newsz > oldsz ? newsz : oldsz;
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2010-07-23 18:52:35 +02:00
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}
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2010-09-03 00:28:36 +02:00
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// Deallocate user pages to bring the process size from oldsz to
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// newsz. oldsz and newsz need not be page-aligned, nor does newsz
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// need to be less than oldsz. oldsz can be larger than the actual
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// process size. Returns the new process size.
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2010-08-10 23:08:41 +02:00
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int
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2010-09-03 00:28:36 +02:00
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deallocuvm(pde_t *pgdir, uint oldsz, uint newsz)
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2010-08-10 23:08:41 +02:00
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{
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2010-09-03 00:28:36 +02:00
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char *a = (char *)PGROUNDUP(newsz);
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char *last = PGROUNDDOWN(oldsz - 1);
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2010-09-02 22:23:15 +02:00
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for(; a <= last; a += PGSIZE){
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2010-08-10 23:08:41 +02:00
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pte_t *pte = walkpgdir(pgdir, a, 0);
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if(pte && (*pte & PTE_P) != 0){
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uint pa = PTE_ADDR(*pte);
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if(pa == 0)
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2010-09-03 00:28:36 +02:00
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panic("kfree");
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2010-08-31 18:54:47 +02:00
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kfree((void *) pa);
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2010-08-10 23:08:41 +02:00
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*pte = 0;
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}
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}
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2010-09-03 00:28:36 +02:00
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return newsz < oldsz ? newsz : oldsz;
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2010-08-10 23:08:41 +02:00
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}
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2010-09-02 22:36:38 +02:00
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// Free a page table and all the physical memory pages
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2010-08-05 22:00:59 +02:00
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// in the user part.
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2010-07-23 18:52:35 +02:00
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void
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freevm(pde_t *pgdir)
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{
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2010-09-02 21:18:19 +02:00
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uint i;
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2010-07-23 18:52:35 +02:00
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2010-09-01 06:41:25 +02:00
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if(!pgdir)
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2010-09-02 21:18:19 +02:00
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panic("freevm: no pgdir");
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2010-09-03 00:28:36 +02:00
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deallocuvm(pgdir, USERTOP, 0);
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2010-09-01 06:41:25 +02:00
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for(i = 0; i < NPDENTRIES; i++){
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2010-09-02 21:18:19 +02:00
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if(pgdir[i] & PTE_P)
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kfree((void *) PTE_ADDR(pgdir[i]));
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2010-07-23 18:52:35 +02:00
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}
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2010-08-31 18:54:47 +02:00
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kfree((void *) pgdir);
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2010-07-23 18:52:35 +02:00
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}
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2010-09-02 22:36:38 +02:00
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// Given a parent process's page table, create a copy
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2010-08-06 17:12:18 +02:00
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// of it for a child.
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2010-07-23 18:52:35 +02:00
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pde_t*
|
|
|
|
copyuvm(pde_t *pgdir, uint sz)
|
|
|
|
{
|
|
|
|
pde_t *d = setupkvm();
|
|
|
|
pte_t *pte;
|
|
|
|
uint pa, i;
|
|
|
|
char *mem;
|
|
|
|
|
2010-09-01 06:41:25 +02:00
|
|
|
if(!d) return 0;
|
|
|
|
for(i = 0; i < sz; i += PGSIZE){
|
|
|
|
if(!(pte = walkpgdir(pgdir, (void *)i, 0)))
|
2010-07-23 18:52:35 +02:00
|
|
|
panic("copyuvm: pte should exist\n");
|
2010-09-01 23:14:58 +02:00
|
|
|
if(!(*pte & PTE_P))
|
|
|
|
panic("copyuvm: page not present\n");
|
|
|
|
pa = PTE_ADDR(*pte);
|
|
|
|
if(!(mem = kalloc()))
|
|
|
|
goto bad;
|
|
|
|
memmove(mem, (char *)pa, PGSIZE);
|
|
|
|
if(!mappages(d, (void *)i, PGSIZE, PADDR(mem), PTE_W|PTE_U))
|
|
|
|
goto bad;
|
2010-07-23 18:52:35 +02:00
|
|
|
}
|
|
|
|
return d;
|
2010-09-01 06:27:12 +02:00
|
|
|
|
|
|
|
bad:
|
|
|
|
freevm(d);
|
|
|
|
return 0;
|
2010-07-23 18:52:35 +02:00
|
|
|
}
|
|
|
|
|