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/*
* User address space access functions.
*
* For licencing details see kernel-base/COPYING
*/
#include <linux/uaccess.h>
#include <linux/export.h>
#include <linux/instrumented.h>
#include <asm/tlbflush.h>
/**
* copy_from_user_nmi - NMI safe copy from user
* @to: Pointer to the destination buffer
* @from: Pointer to a user space address of the current task
* @n: Number of bytes to copy
*
* Returns: The number of not copied bytes. 0 is success, i.e. all bytes copied
*
* Contrary to other copy_from_user() variants this function can be called
* from NMI context. Despite the name it is not restricted to be called
* from NMI context. It is safe to be called from any other context as
* well. It disables pagefaults across the copy which means a fault will
* abort the copy.
*
* For NMI context invocations this relies on the nested NMI work to allow
* atomic faults from the NMI path; the nested NMI paths are careful to
* preserve CR2.
*/
unsigned long
copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
{
unsigned long ret;
if (!__access_ok(from, n))
return n;
if (!nmi_uaccess_okay())
return n;
/*
* Even though this function is typically called from NMI/IRQ context
* disable pagefaults so that its behaviour is consistent even when
* called from other contexts.
*/
pagefault_disable();
instrument_copy_from_user_before(to, from, n);
ret = raw_copy_from_user(to, from, n);
instrument_copy_from_user_after(to, from, n, ret);
pagefault_enable();
return ret;
}
EXPORT_SYMBOL_GPL(copy_from_user_nmi);
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