On Fri, Sep 11, 2015 at 03:56:38PM +0100, Julien Grall wrote: > Well, we can't assume that the function will be called with uaccess > disabled.
Please explain your reasoning. The reason copy_from_user() et.al. need to save and restore the DACR is because the DACR may be in one of two states on older ARM architectures. It may have set the kernel domain to 'manager' mode, to allow these accessors to work on kernel memory, or the kernel domain may be in 'client' mode, thereby preventing the accessors from touching kernel memory. Unless the code path is reachable with the kernel domain in manager mode, (iow, a set_fs(KERNEL_DS) or set_fs(get_ds()) has been done) then it should be safe to use uaccess_disable/uaccess_enable. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/