LXR linux/arch/x86/mm/maccess.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2
   3#include <linux/uaccess.h>
   4#include <linux/kernel.h>
   5
   6#ifdef CONFIG_X86_64
   7static __always_inline u64 canonical_address(u64 vaddr, u8 vaddr_bits)
   8{
   9        return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits);
  10}
  11
  12bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
  13{
  14        unsigned long vaddr = (unsigned long)unsafe_src;
  15
  16        /*
  17         * Range covering the highest possible canonical userspace address
  18         * as well as non-canonical address range. For the canonical range
  19         * we also need to include the userspace guard page.
  20         */
  21        return vaddr >= TASK_SIZE_MAX + PAGE_SIZE &&
  22               canonical_address(vaddr, boot_cpu_data.x86_virt_bits) == vaddr;
  23}
  24#else
  25bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
  26{
  27        return (unsigned long)unsafe_src >= TASK_SIZE_MAX;
  28}
  29#endif
  30