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uaccess.c

/*
 * 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 "asm/current.h"
#include "asm/page.h"
#include "asm/pgtable.h"
#include "kern_util.h"
#include "os.h"

extern void *um_virt_to_phys(struct task_struct *task, unsigned long addr,
                       pte_t *pte_out);

static unsigned long maybe_map(unsigned long virt, int is_write)
{
      pte_t pte;
      int err;

      void *phys = um_virt_to_phys(current, virt, &pte);
      int dummy_code;

      if (IS_ERR(phys) || (is_write && !pte_write(pte))) {
            err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
            if (err)
                  return -1UL;
            phys = um_virt_to_phys(current, virt, NULL);
      }
      if (IS_ERR(phys))
            phys = (void *) -1;

      return (unsigned long) phys;
}

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)
{
      struct page *page;
      int n;

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

      page = phys_to_page(addr);
      addr = (unsigned long) kmap_atomic(page, KM_UML_USERCOPY) +
            (addr & ~PAGE_MASK);

      n = (*op)(addr, len, arg);

      kunmap_atomic(page, KM_UML_USERCOPY);

      return n;
}

static void do_buffer_op(void *jmpbuf, void *arg_ptr)
{
      va_list args;
      unsigned long addr;
      int len, is_write, size, remain, n;
      int (*op)(unsigned long, int, void *);
      void *arg;
      int *res;

      va_copy(args, *(va_list *)arg_ptr);
      addr = va_arg(args, unsigned long);
      len = va_arg(args, int);
      is_write = va_arg(args, int);
      op = va_arg(args, void *);
      arg = va_arg(args, void *);
      res = va_arg(args, int *);
      va_end(args);
      size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
      remain = len;

      current->thread.fault_catcher = jmpbuf;
      n = do_op_one_page(addr, size, is_write, op, arg);
      if (n != 0) {
            *res = (n < 0 ? remain : 0);
            goto out;
      }

      addr += size;
      remain -= size;
      if (remain == 0) {
            *res = 0;
            goto out;
      }

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

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

      n = do_op_one_page(addr, remain, is_write, op, arg);
      if (n != 0)
            *res = (n < 0 ? remain : 0);
      else *res = 0;
 out:
      current->thread.fault_catcher = NULL;
}

static int buffer_op(unsigned long addr, int len, int is_write,
                 int (*op)(unsigned long addr, int len, void *arg),
                 void *arg)
{
      int faulted, res;

      faulted = setjmp_wrapper(do_buffer_op, addr, len, is_write, op, arg,
                         &res);
      if (!faulted)
            return res;

      return addr + len - (unsigned long) current->thread.fault_addr;
}

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;
}

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;
}

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);
}

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;
}

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;
}

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