From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935359AbcIPOrI (ORCPT ); Fri, 16 Sep 2016 10:47:08 -0400 Received: from mail-pa0-f66.google.com ([209.85.220.66]:36432 "EHLO mail-pa0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756293AbcIPOrB (ORCPT ); Fri, 16 Sep 2016 10:47:01 -0400 From: Stafford Horne To: Jonas Bonn , Stefan Kristiansson , Andrew Morton Cc: linux-kernel@vger.kernel.org, Stafford Horne Subject: [PATCH 3/7] openrisc: restore call-saved regs on sigreturn Date: Fri, 16 Sep 2016 23:43:01 +0900 Message-Id: <1474036985-20981-4-git-send-email-shorne@gmail.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1474036985-20981-1-git-send-email-shorne@gmail.com> References: <1474036985-20981-1-git-send-email-shorne@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jonas Bonn Return to userspace via _resume_userspace instead of via syscall return path for the rt_sigreturn syscall. I'll rework this comment more later, but this patch needs testing. Old comment from previous patch: The sigreturn syscall is more like a context switch than a function call; it entails a return from one context (the signal handler) to another (the process in question). For a context switch like this there are effectively no call-saved regs that remain constant across the transition. This patch restores the call-saved regs from pt_regs before returning from the syscall, effectively restoring the context that the process had before being interrupted by the signal handler. Restoring the call-saved regs in this way allows us to return to userspace via the usual syscall fast path. Reported-by: Sebastian Macke Signed-off-by: Jonas Bonn Signed-off-by: Stafford Horne --- arch/openrisc/kernel/entry.S | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S index fec8bf9..572d223 100644 --- a/arch/openrisc/kernel/entry.S +++ b/arch/openrisc/kernel/entry.S @@ -1101,8 +1101,16 @@ ENTRY(__sys_fork) l.addi r3,r1,0 ENTRY(sys_rt_sigreturn) - l.j _sys_rt_sigreturn + l.jal _sys_rt_sigreturn l.addi r3,r1,0 + l.sfne r30,r0 + l.bnf _no_syscall_trace + l.nop + l.jal do_syscall_trace_leave + l.addi r3,r1,0 +_no_syscall_trace: + l.j _resume_userspace + l.nop /* This is a catch-all syscall for atomic instructions for the OpenRISC 1000. * The functions takes a variable number of parameters depending on which -- 2.7.4