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
   7 static __always_inline u64 canonical_address(u64 vaddr, u8 vaddr_bits)
   8 {
   9         return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits);
  10 }
  11
  12 bool 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
  25 bool 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