From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: [PATCH v4 24/27] x86/int3: Avoid atomic instrumentation Date: Fri, 21 Feb 2020 14:34:40 +0100 Message-ID: <20200221134216.690116768@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 arch_atomic_*() and READ_ONCE_NOCHECK() to ensure nothing untoward creeps in and ruins things. That is; this is the INT3 text poke handler, strictly limit the code that runs in it, lest we inadvertenly hit yet another INT3. Reported-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/alternative.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -960,9 +960,9 @@ static struct bp_patching_desc *bp_desc; static __always_inline struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp) { - struct bp_patching_desc *desc = READ_ONCE(*descp); /* rcu_dereference */ + struct bp_patching_desc *desc = READ_ONCE_NOCHECK(*descp); /* rcu_dereference */ - if (!desc || !atomic_inc_not_zero(&desc->refs)) + if (!desc || !arch_atomic_inc_not_zero(&desc->refs)) return NULL; return desc; @@ -971,7 +971,7 @@ struct bp_patching_desc *try_get_desc(st static __always_inline void put_desc(struct bp_patching_desc *desc) { smp_mb__before_atomic(); - atomic_dec(&desc->refs); + arch_atomic_dec(&desc->refs); } static __always_inline void *text_poke_addr(struct text_poke_loc *tp) From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:45540 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728841AbgBUNuk (ORCPT ); Fri, 21 Feb 2020 08:50:40 -0500 Message-ID: <20200221134216.690116768@infradead.org> Date: Fri, 21 Feb 2020 14:34:40 +0100 From: Peter Zijlstra Subject: [PATCH v4 24/27] x86/int3: Avoid atomic instrumentation 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: <20200221133440.0NbcY0ejkCbgBaVIQhkYU3lQ5dPoDdQqVlpK6UtQfk4@z> Use arch_atomic_*() and READ_ONCE_NOCHECK() to ensure nothing untoward creeps in and ruins things. That is; this is the INT3 text poke handler, strictly limit the code that runs in it, lest we inadvertenly hit yet another INT3. Reported-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/alternative.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -960,9 +960,9 @@ static struct bp_patching_desc *bp_desc; static __always_inline struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp) { - struct bp_patching_desc *desc = READ_ONCE(*descp); /* rcu_dereference */ + struct bp_patching_desc *desc = READ_ONCE_NOCHECK(*descp); /* rcu_dereference */ - if (!desc || !atomic_inc_not_zero(&desc->refs)) + if (!desc || !arch_atomic_inc_not_zero(&desc->refs)) return NULL; return desc; @@ -971,7 +971,7 @@ struct bp_patching_desc *try_get_desc(st static __always_inline void put_desc(struct bp_patching_desc *desc) { smp_mb__before_atomic(); - atomic_dec(&desc->refs); + arch_atomic_dec(&desc->refs); } static __always_inline void *text_poke_addr(struct text_poke_loc *tp)