From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: [PATCH v4 06/27] x86/doublefault: Remove memmove() call Date: Fri, 21 Feb 2020 14:34:22 +0100 Message-ID: <20200221134215.385886177@infradead.org> References: <20200221133416.777099322@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org Cc: peterz@infradead.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org List-Id: linux-arch.vger.kernel.org Use of memmove() in #DF is problematic when you consider tracing and other instrumentation. Remove the memmove() call and simply write out what need doing; Boris argues the ranges should not overlap. Survives selftests/x86, specifically sigreturn_64. (Andy ?!) Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200220121727.GB507@zn.tnic --- arch/x86/kernel/traps.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -278,6 +278,7 @@ dotraplinkage void do_double_fault(struc regs->ip == (unsigned long)native_irq_return_iret) { struct pt_regs *gpregs = (struct pt_regs *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1; + unsigned long *p = (unsigned long *)regs->sp; /* * regs->sp points to the failing IRET frame on the @@ -285,7 +286,11 @@ dotraplinkage void do_double_fault(struc * in gpregs->ss through gpregs->ip. * */ - memmove(&gpregs->ip, (void *)regs->sp, 5*8); + gpregs->ip = p[0]; + gpregs->cs = p[1]; + gpregs->flags = p[2]; + gpregs->sp = p[3]; + gpregs->ss = p[4]; gpregs->orig_ax = 0; /* Missing (lost) #GP error code */ /* From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:45512 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728829AbgBUNui (ORCPT ); Fri, 21 Feb 2020 08:50:38 -0500 Message-ID: <20200221134215.385886177@infradead.org> Date: Fri, 21 Feb 2020 14:34:22 +0100 From: Peter Zijlstra Subject: [PATCH v4 06/27] x86/doublefault: Remove memmove() call References: <20200221133416.777099322@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org Cc: peterz@infradead.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org Message-ID: <20200221133422.hsg9ivZFutXwMAXjN8q6iVeCDOZsTD6lp6zpl-VjI6k@z> Use of memmove() in #DF is problematic when you consider tracing and other instrumentation. Remove the memmove() call and simply write out what need doing; Boris argues the ranges should not overlap. Survives selftests/x86, specifically sigreturn_64. (Andy ?!) Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200220121727.GB507@zn.tnic --- arch/x86/kernel/traps.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -278,6 +278,7 @@ dotraplinkage void do_double_fault(struc regs->ip == (unsigned long)native_irq_return_iret) { struct pt_regs *gpregs = (struct pt_regs *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1; + unsigned long *p = (unsigned long *)regs->sp; /* * regs->sp points to the failing IRET frame on the @@ -285,7 +286,11 @@ dotraplinkage void do_double_fault(struc * in gpregs->ss through gpregs->ip. * */ - memmove(&gpregs->ip, (void *)regs->sp, 5*8); + gpregs->ip = p[0]; + gpregs->cs = p[1]; + gpregs->flags = p[2]; + gpregs->sp = p[3]; + gpregs->ss = p[4]; gpregs->orig_ax = 0; /* Missing (lost) #GP error code */ /*