diff options
| -rw-r--r-- | arch/x86/lib/usercopy.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c index 3f435d7fca5e..c3e8a62ca561 100644 --- a/arch/x86/lib/usercopy.c +++ b/arch/x86/lib/usercopy.c @@ -9,9 +9,23 @@ #include <asm/tlbflush.h> -/* - * We rely on the nested NMI work to allow atomic faults from the NMI path; the - * nested NMI paths are careful to preserve CR2. +/** + * 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) @@ -27,7 +41,7 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n) /* * Even though this function is typically called from NMI/IRQ context * disable pagefaults so that its behaviour is consistent even when - * called form other contexts. + * called from other contexts. */ pagefault_disable(); ret = __copy_from_user_inatomic(to, from, n); |