From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Mark Rutland , Laura Abbott , Shanker Donthineni , Will Deacon , Greg Hackmann , Alex Shi Subject: [PATCH 4.9 061/102] arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks Date: Fri, 6 Apr 2018 15:23:42 +0200 Message-Id: <20180406084340.132540841@linuxfoundation.org> In-Reply-To: <20180406084331.507038179@linuxfoundation.org> References: <20180406084331.507038179@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon commit 18011eac28c7 upstream. When unmapping the kernel at EL0, we use tpidrro_el0 as a scratch register during exception entry from native tasks and subsequently zero it in the kernel_ventry macro. We can therefore avoid zeroing tpidrro_el0 in the context-switch path for native tasks using the entry trampoline. Reviewed-by: Mark Rutland Tested-by: Laura Abbott Tested-by: Shanker Donthineni Signed-off-by: Will Deacon Signed-off-by: Alex Shi [v4.9 backport] Signed-off-by: Mark Rutland [v4.9 backport] Tested-by: Will Deacon Tested-by: Greg Hackmann Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/process.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -306,17 +306,17 @@ int copy_thread(unsigned long clone_flag static void tls_thread_switch(struct task_struct *next) { - unsigned long tpidr, tpidrro; + unsigned long tpidr; tpidr = read_sysreg(tpidr_el0); *task_user_tls(current) = tpidr; - tpidr = *task_user_tls(next); - tpidrro = is_compat_thread(task_thread_info(next)) ? - next->thread.tp_value : 0; + if (is_compat_thread(task_thread_info(next))) + write_sysreg(next->thread.tp_value, tpidrro_el0); + else if (!arm64_kernel_unmapped_at_el0()) + write_sysreg(0, tpidrro_el0); - write_sysreg(tpidr, tpidr_el0); - write_sysreg(tpidrro, tpidrro_el0); + write_sysreg(*task_user_tls(next), tpidr_el0); } /* Restore the UAO state depending on next's addr_limit */