From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: [PATCH v3 04/22] x86/doublefault: Make memmove() notrace/NOKPROBE Date: Wed, 19 Feb 2020 15:47:28 +0100 Message-ID: <20200219150744.604459293@infradead.org> References: <20200219144724.800607165@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from merlin.infradead.org ([205.233.59.134]:52026 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727803AbgBSPOh (ORCPT ); Wed, 19 Feb 2020 10:14:37 -0500 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 Hitting the tracer or a kprobes from #DF is 'interesting', lets avoid that. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/traps.c | 3 ++- arch/x86/lib/memcpy_32.c | 7 ++++++- arch/x86/lib/memmove_64.S | 5 +++++ 3 files changed, 13 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -271,7 +271,8 @@ dotraplinkage void do_double_fault(struc * The net result is that our #GP handler will think that we * entered from usermode with the bad user context. * - * No need for nmi_enter() here because we don't use RCU. + * No need for nmi_enter() here because we don't call out to anything + * except memmove() and that is notrace/NOKPROBE. */ if (((long)regs->sp >> P4D_SHIFT) == ESPFIX_PGD_ENTRY && regs->cs == __KERNEL_CS && --- a/arch/x86/lib/memcpy_32.c +++ b/arch/x86/lib/memcpy_32.c @@ -21,7 +21,7 @@ __visible void *memset(void *s, int c, s } EXPORT_SYMBOL(memset); -__visible void *memmove(void *dest, const void *src, size_t n) +__visible notrace void *memmove(void *dest, const void *src, size_t n) { int d0,d1,d2,d3,d4,d5; char *ret = dest; @@ -207,3 +207,8 @@ __visible void *memmove(void *dest, cons } EXPORT_SYMBOL(memmove); +/* + * The double fault handler uses memmove(), do not mess with it or risk a + * tripple fault. + */ +NOKPROBE_SYMBOL(memmove); --- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -212,3 +212,8 @@ SYM_FUNC_END(__memmove) SYM_FUNC_END_ALIAS(memmove) EXPORT_SYMBOL(__memmove) EXPORT_SYMBOL(memmove) +/* + * The double fault handler uses memmove(), do not mess with it or risk a + * tripple fault. + */ +_ASM_NOKPROBE(__memmove)