mm/vmalloc.c

38567 /*
38568  *  linux/mm/vmalloc.c
38569  *
38570  *  Copyright (C) 1993  Linus Torvalds
38571  */
38572 
38573 #include <linux/malloc.h>
38574 #include <linux/vmalloc.h>
38575 
38576 #include <asm/uaccess.h>
38577 
38578 static struct vm_struct * vmlist = NULL;
38579 
38580 static inline void free_area_pte(pmd_t * pmd,
38581   unsigned long address, unsigned long size)
38582 {
38583   pte_t * pte;
38584   unsigned long end;
38585 
38586   if (pmd_none(*pmd))
38587     return;
38588   if (pmd_bad(*pmd)) {
38589     printk("free_area_pte: bad pmd (%08lx)\n",
38590            pmd_val(*pmd));
38591     pmd_clear(pmd);
38592     return;
38593   }
38594   pte = pte_offset(pmd, address);
38595   address &= ~PMD_MASK;
38596   end = address + size;
38597   if (end > PMD_SIZE)
38598     end = PMD_SIZE;
38599   while (address < end) {
38600     pte_t page = *pte;
38601     pte_clear(pte);
38602     address += PAGE_SIZE;
38603     pte++;
38604     if (pte_none(page))
38605       continue;
38606     if (pte_present(page)) {
38607       free_page(pte_page(page));
38608       continue;
38609     }
38610     printk("Whee.. Swapped out page in "
38611            "kernel page table\n");
38612   }
38613 }
38614 
38615 static inline void free_area_pmd(pgd_t * dir,
38616   unsigned long address, unsigned long size)
38617 {
38618   pmd_t * pmd;
38619   unsigned long end;
38620 
38621   if (pgd_none(*dir))
38622     return;
38623   if (pgd_bad(*dir)) {
38624     printk("free_area_pmd: bad pgd (%08lx)\n",
38625            pgd_val(*dir));
38626     pgd_clear(dir);
38627     return;
38628   }
38629   pmd = pmd_offset(dir, address);
38630   address &= ~PGDIR_MASK;
38631   end = address + size;
38632   if (end > PGDIR_SIZE)
38633     end = PGDIR_SIZE;
38634   while (address < end) {
38635     free_area_pte(pmd, address, end - address);
38636     address = (address + PMD_SIZE) & PMD_MASK;
38637     pmd++;
38638   }
38639 }
38640 
38641 void vmfree_area_pages(unsigned long address,
38642                        unsigned long size)
38643 {
38644   pgd_t * dir;
38645   unsigned long end = address + size;
38646 
38647   dir = pgd_offset_k(address);
38648   flush_cache_all();
38649   while (address < end) {
38650     free_area_pmd(dir, address, end - address);
38651     address = (address + PGDIR_SIZE) & PGDIR_MASK;
38652     dir++;
38653   }
38654   flush_tlb_all();
38655 }
38656 
38657 static inline int alloc_area_pte(pte_t * pte,
38658   unsigned long address, unsigned long size)
38659 {
38660   unsigned long end;
38661 
38662   address &= ~PMD_MASK;
38663   end = address + size;
38664   if (end > PMD_SIZE)
38665     end = PMD_SIZE;
38666   while (address < end) {
38667     unsigned long page;
38668     if (!pte_none(*pte))
38669       printk("alloc_area_pte: page already exists\n");
38670     page = __get_free_page(GFP_KERNEL);
38671     if (!page)
38672       return -ENOMEM;
38673     set_pte(pte, mk_pte(page, PAGE_KERNEL));
38674     address += PAGE_SIZE;
38675     pte++;
38676   }
38677   return 0;
38678 }
38679 
38680 static inline int alloc_area_pmd(pmd_t * pmd,
38681   unsigned long address, unsigned long size)
38682 {
38683   unsigned long end;
38684 
38685   address &= ~PGDIR_MASK;
38686   end = address + size;
38687   if (end > PGDIR_SIZE)
38688     end = PGDIR_SIZE;
38689   while (address < end) {
38690     pte_t * pte = pte_alloc_kernel(pmd, address);
38691     if (!pte)
38692       return -ENOMEM;
38693     if (alloc_area_pte(pte, address, end - address))
38694       return -ENOMEM;
38695     address = (address + PMD_SIZE) & PMD_MASK;
38696     pmd++;
38697   }
38698   return 0;
38699 }
38700 
38701 int vmalloc_area_pages(unsigned long address,
38702                        unsigned long size)
38703 {
38704   pgd_t * dir;
38705   unsigned long end = address + size;
38706 
38707   dir = pgd_offset_k(address);
38708   flush_cache_all();
38709   while (address < end) {
38710     pmd_t *pmd;
38711     pgd_t olddir = *dir;
38712 
38713     pmd = pmd_alloc_kernel(dir, address);
38714     if (!pmd)
38715       return -ENOMEM;
38716     if (alloc_area_pmd(pmd, address, end - address))
38717       return -ENOMEM;
38718     if (pgd_val(olddir) != pgd_val(*dir))
38719       set_pgdir(address, *dir);
38720     address = (address + PGDIR_SIZE) & PGDIR_MASK;
38721     dir++;
38722   }
38723   flush_tlb_all();
38724   return 0;
38725 }
38726 
 Комментарий
38727 struct vm_struct * get_vm_area(unsigned long size)
38728 {
38729   unsigned long addr;
38730   struct vm_struct **p, *tmp, *area;
38731 
 Комментарий
38732   area = (struct vm_struct *) kmalloc(sizeof(*area),
38733                                       GFP_KERNEL);
38734   if (!area)
38735     return NULL;
38736   addr = VMALLOC_START;
38737   for (p = &vmlist; (tmp = *p) ; p = &tmp->next) {
38738     if (size + addr < (unsigned long) tmp->addr)
38739       break;
38740     if (addr > VMALLOC_END-size) {
38741       kfree(area);
38742       return NULL;
38743     }
38744     addr = tmp->size + (unsigned long) tmp->addr;
38745   }
38746   area->addr = (void *)addr;
38747   area->size = size + PAGE_SIZE;
38748   area->next = *p;
38749   *p = area;
38750   return area;
38751 }
38752 
 Комментарий
38753 void vfree(void * addr)
38754 {
38755   struct vm_struct **p, *tmp;
38756 
38757   if (!addr)
38758     return;
38759   if ((PAGE_SIZE-1) & (unsigned long) addr) {
38760     printk("Trying to vfree() bad address (%p)\n", addr);
38761     return;
38762   }
38763   for (p = &vmlist ; (tmp = *p) ; p = &tmp->next) {
38764     if (tmp->addr == addr) {
38765       *p = tmp->next;
38766       vmfree_area_pages(VMALLOC_VMADDR(tmp->addr),
38767                         tmp->size);
38768       kfree(tmp);
38769       return;
38770     }
38771   }
38772   printk("Trying to vfree() nonexistent vm area (%p)\n",
38773          addr);
38774 }
38775 
 Комментарий
38776 void * vmalloc(unsigned long size)
38777 {
38778   void * addr;
38779   struct vm_struct *area;
38780 
38781   size = PAGE_ALIGN(size);
38782   if (!size || size > (max_mapnr << PAGE_SHIFT))
38783     return NULL;
38784   area = get_vm_area(size);
38785   if (!area)
38786     return NULL;
38787   addr = area->addr;
38788   if (vmalloc_area_pages(VMALLOC_VMADDR(addr), size)) {
38789     vfree(addr);
38790     return NULL;
38791   }
38792   return addr;
38793 }
38794 
38795 long vread(char *buf, char *addr, unsigned long count)
38796 {
38797   struct vm_struct *tmp;
38798   char *vaddr, *buf_start = buf;
38799   unsigned long n;
38800 
38801   /* Don't allow overflow */
38802   if ((unsigned long) addr + count < count)
38803     count = -(unsigned long) addr;
38804 
38805   for (tmp = vmlist; tmp; tmp = tmp->next) {
38806     vaddr = (char *) tmp->addr;
38807     if (addr >= vaddr + tmp->size - PAGE_SIZE)
38808       continue;
38809     while (addr < vaddr) {
38810       if (count == 0)
38811         goto finished;
38812       put_user('\0', buf);
38813       buf++;
38814       addr++;
38815       count--;
38816     }
38817     n = vaddr + tmp->size - PAGE_SIZE - addr;
38818     do {
38819       if (count == 0)
38820         goto finished;
38821       put_user(*addr, buf);
38822       buf++;
38823       addr++;
38824       count--;
38825     } while (--n > 0);
38826   }
38827 finished:
38828   return buf - buf_start;
38829 }