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
canonical_address(u64 vaddr,u8 vaddr_bits)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 
copy_from_kernel_nofault_allowed(const void * unsafe_src,size_t size)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
copy_from_kernel_nofault_allowed(const void * unsafe_src,size_t size)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
30