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// SPDX-License-Identifier: GPL-2.0-only
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <asm/vsyscall.h>
#ifdef CONFIG_X86_64
bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
{
unsigned long vaddr = (unsigned long)unsafe_src;
/*
* Do not allow userspace addresses. This disallows
* normal userspace and the userspace guard page:
*/
if (vaddr < TASK_SIZE_MAX + PAGE_SIZE)
return false;
/*
* Reading from the vsyscall page may cause an unhandled fault in
* certain cases. Though it is at an address above TASK_SIZE_MAX, it is
* usually considered as a user space address.
*/
if (is_vsyscall_vaddr(vaddr))
return false;
/*
* Allow everything during early boot before 'x86_virt_bits'
* is initialized. Needed for instruction decoding in early
* exception handlers.
*/
if (!boot_cpu_data.x86_virt_bits)
return true;
return __is_canonical_address(vaddr, boot_cpu_data.x86_virt_bits);
}
#else
bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
{
return (unsigned long)unsafe_src >= TASK_SIZE_MAX;
}
#endif
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