The following commit has been merged into the x86/cleanups branch of tip: Commit-ID: 907f8eb8e0eb2b3312b292e67dc4dbc493424747 Gitweb: https://git.kernel.org/tip/907f8eb8e0eb2b3312b292e67dc4dbc493424747 Author: Thomas Gleixner <t...@linutronix.de> AuthorDate: Tue, 17 Nov 2020 21:23:35 +01:00 Committer: Borislav Petkov <b...@suse.de> CommitterDate: Wed, 18 Nov 2020 13:19:01 +01:00
x86/uaccess: Document copy_from_user_nmi() Document the functionality of copy_from_user_nmi() to avoid further confusion. Fix the typo in the existing comment while at it. Requested-by: Borislav Petkov <b...@alien8.de> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Borislav Petkov <b...@suse.de> Link: https://lkml.kernel.org/r/20201117202753.806376...@linutronix.de --- arch/x86/lib/usercopy.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c index 3f435d7..c3e8a62 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);
