| 1 | |
| 2 | * User address space access functions.
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| 3 | *
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| 4 | * For licencing details see kernel-base/COPYING
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| 5 |
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| 6 |
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| 7 | #include <linux/uaccess.h>
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| 8 | #include <linux/export.h>
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| 9 | #include <linux/instrumented.h>
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| 10 |
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| 11 | #include <asm/tlbflush.h>
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| 12 |
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| 13 | |
| 14 | * copy_from_user_nmi - NMI safe copy from user
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| 15 | * @to: Pointer to the destination buffer
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| 16 | * @from: Pointer to a user space address of the current task
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| 17 | * @n: Number of bytes to copy
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| 18 | *
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| 19 | * Returns: The number of not copied bytes. 0 is success, i.e. all bytes copied
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| 20 | *
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| 21 | * Contrary to other copy_from_user() variants this function can be called
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| 22 | * from NMI context. Despite the name it is not restricted to be called
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| 23 | * from NMI context. It is safe to be called from any other context as
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| 24 | * well. It disables pagefaults across the copy which means a fault will
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| 25 | * abort the copy.
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| 26 | *
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| 27 | * For NMI context invocations this relies on the nested NMI work to allow
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| 28 | * atomic faults from the NMI path; the nested NMI paths are careful to
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| 29 | * preserve CR2.
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| 30 |
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| 31 | unsigned long
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| 32 | copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
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| 33 | {
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| 34 | unsigned long ret;
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| 35 |
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| 36 | if (!__access_ok(from, n))
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| 37 | return n;
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| 38 |
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| 39 | if (!nmi_uaccess_okay())
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| 40 | return n;
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| 41 |
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| 42 | |
| 43 | * Even though this function is typically called from NMI/IRQ context
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| 44 | * disable pagefaults so that its behaviour is consistent even when
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| 45 | * called from other contexts.
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| 46 |
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| 47 | pagefault_disable();
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| 48 | instrument_copy_from_user_before(to, from, n);
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| 49 | ret = raw_copy_from_user(to, from, n);
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| 50 | instrument_copy_from_user_after(to, from, n, ret);
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| 51 | pagefault_enable();
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| 52 |
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| 53 | return ret;
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| 54 | }
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| 55 | EXPORT_SYMBOL_GPL(copy_from_user_nmi);
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