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