Quelle usercopy.c Sprache: C

// SPDX-License-Identifier: GPL-2.0
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/fault-inject-usercopy.h>
#include <linux/instrumented.h>
#include <linux/kernel.h>
#include <linux/nospec.h>
#include <linux/string.h>
#include <linux/uaccess.h>
#include <linux/wordpart.h>

/* out-of-line parts */

#if !defined(INLINE_COPY_FROM_USER) || defined(CONFIG_RUST)
unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
{
return _inline_copy_from_user(to, from, n);
}
EXPORT_SYMBOL(_copy_from_user);
#endif

#if !defined(INLINE_COPY_TO_USER) || defined(CONFIG_RUST)
unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
{
return _inline_copy_to_user(to, from, n);
}
EXPORT_SYMBOL(_copy_to_user);
#endif

/**
* check_zeroed_user: check if a userspace buffer only contains zero bytes
* @from: Source address, in userspace.
* @size: Size of buffer.
*
* This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
* userspace addresses (and is more efficient because we don't care where the
* first non-zero byte is).
*
* Returns:
*  * 0: There were non-zero bytes present in the buffer.
*  * 1: The buffer was full of zero bytes.
*  * -EFAULT: access to userspace failed.
*/
int check_zeroed_user(const void __user *from, size_t size)
{
unsigned long val;
uintptr_t align = (uintptr_t) from % sizeof(unsigned long);

if (unlikely(size == 0))
  return 1;

from -= align;
size += align;

if (!user_read_access_begin(from, size))
  return -EFAULT;

unsafe_get_user(val, (unsigned long __user *) from, err_fault);
if (align)
  val &= ~aligned_byte_mask(align);

while (size > sizeof(unsigned long)) {
  if (unlikely(val))
   goto done;

  from += sizeof(unsigned long);
  size -= sizeof(unsigned long);

  unsafe_get_user(val, (unsigned long __user *) from, err_fault);
}

if (size < sizeof(unsigned long))
  val &= aligned_byte_mask(size);

done:
user_read_access_end();
return (val == 0);
err_fault:
user_read_access_end();
return -EFAULT;
}
EXPORT_SYMBOL(check_zeroed_user);

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