diff options
Diffstat (limited to 'arch/i386/mm/mprotect.c')
| -rw-r--r-- | arch/i386/mm/mprotect.c | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/arch/i386/mm/mprotect.c b/arch/i386/mm/mprotect.c new file mode 100644 index 000000000..99252183b --- /dev/null +++ b/arch/i386/mm/mprotect.c @@ -0,0 +1,230 @@ +/* + * linux/mm/mprotect.c + * + * (C) Copyright 1994 Linus Torvalds + */ +#include <linux/stat.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/shm.h> +#include <linux/errno.h> +#include <linux/mman.h> +#include <linux/string.h> +#include <linux/malloc.h> + +#include <asm/segment.h> +#include <asm/system.h> + +#define CHG_MASK (PAGE_MASK | PAGE_ACCESSED | PAGE_DIRTY | PAGE_PWT | PAGE_PCD) + +static void change_protection(unsigned long start, unsigned long end, int prot) +{ + unsigned long *page_table, *dir; + unsigned long page, offset; + int nr; + + dir = PAGE_DIR_OFFSET(current->tss.cr3, start); + offset = (start >> PAGE_SHIFT) & (PTRS_PER_PAGE-1); + nr = (end - start) >> PAGE_SHIFT; + while (nr > 0) { + page = *dir; + dir++; + if (!(page & PAGE_PRESENT)) { + nr = nr - PTRS_PER_PAGE + offset; + offset = 0; + continue; + } + page_table = offset + (unsigned long *) (page & PAGE_MASK); + offset = PTRS_PER_PAGE - offset; + if (offset > nr) + offset = nr; + nr = nr - offset; + do { + page = *page_table; + if (page & PAGE_PRESENT) + *page_table = (page & CHG_MASK) | prot; + ++page_table; + } while (--offset); + } + return; +} + +static inline int mprotect_fixup_all(struct vm_area_struct * vma, + int newflags, int prot) +{ + vma->vm_flags = newflags; + vma->vm_page_prot = prot; + return 0; +} + +static inline int mprotect_fixup_start(struct vm_area_struct * vma, + unsigned long end, + int newflags, int prot) +{ + struct vm_area_struct * n; + + n = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); + if (!n) + return -ENOMEM; + *n = *vma; + vma->vm_start = end; + n->vm_end = end; + vma->vm_offset += vma->vm_start - n->vm_start; + n->vm_flags = newflags; + n->vm_page_prot = prot; + if (n->vm_inode) + n->vm_inode->i_count++; + if (n->vm_ops && n->vm_ops->open) + n->vm_ops->open(n); + insert_vm_struct(current, n); + return 0; +} + +static inline int mprotect_fixup_end(struct vm_area_struct * vma, + unsigned long start, + int newflags, int prot) +{ + struct vm_area_struct * n; + + n = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); + if (!n) + return -ENOMEM; + *n = *vma; + vma->vm_end = start; + n->vm_start = start; + n->vm_offset += n->vm_start - vma->vm_start; + n->vm_flags = newflags; + n->vm_page_prot = prot; + if (n->vm_inode) + n->vm_inode->i_count++; + if (n->vm_ops && n->vm_ops->open) + n->vm_ops->open(n); + insert_vm_struct(current, n); + return 0; +} + +static inline int mprotect_fixup_middle(struct vm_area_struct * vma, + unsigned long start, unsigned long end, + int newflags, int prot) +{ + struct vm_area_struct * left, * right; + + left = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); + if (!left) + return -ENOMEM; + right = (struct vm_area_struct *) kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL); + if (!right) { + kfree(left); + return -ENOMEM; + } + *left = *vma; + *right = *vma; + left->vm_end = start; + vma->vm_start = start; + vma->vm_end = end; + right->vm_start = end; + vma->vm_offset += vma->vm_start - left->vm_start; + right->vm_offset += right->vm_start - left->vm_start; + vma->vm_flags = newflags; + vma->vm_page_prot = prot; + if (vma->vm_inode) + vma->vm_inode->i_count += 2; + if (vma->vm_ops && vma->vm_ops->open) { + vma->vm_ops->open(left); + vma->vm_ops->open(right); + } + insert_vm_struct(current, left); + insert_vm_struct(current, right); + return 0; +} + +static int mprotect_fixup(struct vm_area_struct * vma, + unsigned long start, unsigned long end, unsigned int newflags) +{ + int prot, error; + + if (newflags == vma->vm_flags) + return 0; + prot = PAGE_PRESENT; + if (newflags & (VM_READ | VM_EXEC)) + prot |= PAGE_READONLY; + if (newflags & VM_WRITE) + if (newflags & VM_SHARED) + prot |= PAGE_SHARED; + else + prot |= PAGE_COPY; + + if (start == vma->vm_start) + if (end == vma->vm_end) + error = mprotect_fixup_all(vma, newflags, prot); + else + error = mprotect_fixup_start(vma, end, newflags, prot); + else if (end == vma->vm_end) + error = mprotect_fixup_end(vma, start, newflags, prot); + else + error = mprotect_fixup_middle(vma, start, end, newflags, prot); + + if (error) + return error; + + change_protection(start, end, prot); + return 0; +} + +asmlinkage int sys_mprotect(unsigned long start, size_t len, unsigned long prot) +{ + unsigned long end, tmp; + struct vm_area_struct * vma, * next; + int error; + + if (start & ~PAGE_MASK) + return -EINVAL; + len = (len + ~PAGE_MASK) & PAGE_MASK; + end = start + len; + if (end < start) + return -EINVAL; + if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC)) + return -EINVAL; + if (end == start) + return 0; + for (vma = current->mm->mmap ; ; vma = vma->vm_next) { + if (!vma) + return -EFAULT; + if (vma->vm_end > start) + break; + } + if (vma->vm_start > start) + return -EFAULT; + + for ( ; ; ) { + unsigned int newflags; + + /* Here we know that vma->vm_start <= start < vma->vm_end. */ + + newflags = prot | (vma->vm_flags & ~(PROT_READ | PROT_WRITE | PROT_EXEC)); + if ((newflags & ~(newflags >> 4)) & 0xf) { + error = -EACCES; + break; + } + + if (vma->vm_end >= end) { + error = mprotect_fixup(vma, start, end, newflags); + break; + } + + tmp = vma->vm_end; + next = vma->vm_next; + error = mprotect_fixup(vma, start, tmp, newflags); + if (error) + break; + start = tmp; + vma = next; + if (!vma || vma->vm_start != start) { + error = -EFAULT; + break; + } + } + merge_segments(current->mm->mmap); + return error; +} |