uaccess.c

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/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <linux/err.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <asm/current.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <kern_util.h>
#include <os.h>

pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
{
    pgd_t *pgd;
    pud_t *pud;
    pmd_t *pmd;

    if (mm == NULL)
        return NULL;

    pgd = pgd_offset(mm, addr);
    if (!pgd_present(*pgd))
        return NULL;

    pud = pud_offset(pgd, addr);
    if (!pud_present(*pud))
        return NULL;

    pmd = pmd_offset(pud, addr);
    if (!pmd_present(*pmd))
        return NULL;

    return pte_offset_kernel(pmd, addr);
}

static pte_t *maybe_map(unsigned long virt, int is_write)
{
    pte_t *pte = virt_to_pte(current->mm, virt);
    int err, dummy_code;

    if ((pte == NULL) || !pte_present(*pte) ||
        (is_write && !pte_write(*pte))) {
        err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
        if (err)
            return NULL;
        pte = virt_to_pte(current->mm, virt);
    }
    if (!pte_present(*pte))
        pte = NULL;

    return pte;
}

static int do_op_one_page(unsigned long addr, int len, int is_write,
         int (*op)(unsigned long addr, int len, void *arg), void *arg)
{
    jmp_buf buf;
    struct page *page;
    pte_t *pte;
    int n, faulted;

    pte = maybe_map(addr, is_write);
    if (pte == NULL)
        return -1;

    page = pte_page(*pte);
    addr = (unsigned long) kmap_atomic(page) +
        (addr & ~PAGE_MASK);

    current->thread.fault_catcher = &buf;

    faulted = UML_SETJMP(&buf);
    if (faulted == 0)
        n = (*op)(addr, len, arg);
    else
        n = -1;

    current->thread.fault_catcher = NULL;

    kunmap_atomic((void *)addr);

    return n;
}

static int buffer_op(unsigned long addr, int len, int is_write,
             int (*op)(unsigned long, int, void *), void *arg)
{
    int size, remain, n;

    size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
    remain = len;

    n = do_op_one_page(addr, size, is_write, op, arg);
    if (n != 0) {
        remain = (n < 0 ? remain : 0);
        goto out;
    }

    addr += size;
    remain -= size;
    if (remain == 0)
        goto out;

    while (addr < ((addr + remain) & PAGE_MASK)) {
        n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
        if (n != 0) {
            remain = (n < 0 ? remain : 0);
            goto out;
        }

        addr += PAGE_SIZE;
        remain -= PAGE_SIZE;
    }
    if (remain == 0)
        goto out;

    n = do_op_one_page(addr, remain, is_write, op, arg);
    if (n != 0) {
        remain = (n < 0 ? remain : 0);
        goto out;
    }

    return 0;
 out:
    return remain;
}

static int copy_chunk_from_user(unsigned long from, int len, void *arg)
{
    unsigned long *to_ptr = arg, to = *to_ptr;

    memcpy((void *) to, (void *) from, len);
    *to_ptr += len;
    return 0;
}

int copy_from_user(void *to, const void __user *from, int n)
{
    if (segment_eq(get_fs(), KERNEL_DS)) {
        memcpy(to, (__force void*)from, n);
        return 0;
    }

    return access_ok(VERIFY_READ, from, n) ?
           buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to):
           n;
}
EXPORT_SYMBOL(copy_from_user);

static int copy_chunk_to_user(unsigned long to, int len, void *arg)
{
    unsigned long *from_ptr = arg, from = *from_ptr;

    memcpy((void *) to, (void *) from, len);
    *from_ptr += len;
    return 0;
}

int copy_to_user(void __user *to, const void *from, int n)
{
    if (segment_eq(get_fs(), KERNEL_DS)) {
        memcpy((__force void *) to, from, n);
        return 0;
    }

    return access_ok(VERIFY_WRITE, to, n) ?
           buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from) :
           n;
}
EXPORT_SYMBOL(copy_to_user);

static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
{
    char **to_ptr = arg, *to = *to_ptr;
    int n;

    strncpy(to, (void *) from, len);
    n = strnlen(to, len);
    *to_ptr += n;

    if (n < len)
            return 1;
    return 0;
}

int strncpy_from_user(char *dst, const char __user *src, int count)
{
    int n;
    char *ptr = dst;

    if (segment_eq(get_fs(), KERNEL_DS)) {
        strncpy(dst, (__force void *) src, count);
        return strnlen(dst, count);
    }

    if (!access_ok(VERIFY_READ, src, 1))
        return -EFAULT;

    n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
              &ptr);
    if (n != 0)
        return -EFAULT;
    return strnlen(dst, count);
}
EXPORT_SYMBOL(strncpy_from_user);

static int clear_chunk(unsigned long addr, int len, void *unused)
{
    memset((void *) addr, 0, len);
    return 0;
}

int __clear_user(void __user *mem, int len)
{
    return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
}

int clear_user(void __user *mem, int len)
{
    if (segment_eq(get_fs(), KERNEL_DS)) {
        memset((__force void*)mem, 0, len);
        return 0;
    }

    return access_ok(VERIFY_WRITE, mem, len) ?
           buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL) : len;
}
EXPORT_SYMBOL(clear_user);

static int strnlen_chunk(unsigned long str, int len, void *arg)
{
    int *len_ptr = arg, n;

    n = strnlen((void *) str, len);
    *len_ptr += n;

    if (n < len)
        return 1;
    return 0;
}

int strnlen_user(const void __user *str, int len)
{
    int count = 0, n;

    if (segment_eq(get_fs(), KERNEL_DS))
        return strnlen((__force char*)str, len) + 1;

    n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
    if (n == 0)
        return count + 1;
    return -EFAULT;
}
EXPORT_SYMBOL(strnlen_user);