Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756268Ab3JIV35 (ORCPT ); Wed, 9 Oct 2013 17:29:57 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:45732 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752090Ab3JIV3z (ORCPT ); Wed, 9 Oct 2013 17:29:55 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, "Paul E. McKenney" Subject: [PATCH v2 tip/core/rcu 01/13] rcu: Make rcu_assign_pointer's assignment volatile and type-safe Date: Wed, 9 Oct 2013 14:29:34 -0700 Message-Id: <1381354186-16285-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <20131009212920.GA15413@linux.vnet.ibm.com> References: <20131009212920.GA15413@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13100921-1344-0000-0000-0000024E81CF Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2473 Lines: 64 From: Josh Triplett rcu_assign_pointer needs to use ACCESS_ONCE to make the assignment to the destination pointer volatile, to protect against compilers too clever for their own good. In addition, since rcu_assign_pointer force-casts the source pointer to add the __rcu address space (overriding any existing address space), add an explicit check that the source pointer has the __kernel address space to start with. This new check produces warnings like this, when attempting to assign from a __user pointer: test.c:25:9: warning: incorrect type in argument 2 (different address spaces) test.c:25:9: expected struct foo * test.c:25:9: got struct foo [noderef] *badsrc Signed-off-by: Josh Triplett Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index f1f1bc39346b..5b444e0596a6 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -506,8 +506,17 @@ static inline void rcu_preempt_sleep_check(void) #ifdef __CHECKER__ #define rcu_dereference_sparse(p, space) \ ((void)(((typeof(*p) space *)p) == p)) +/* The dummy first argument in __rcu_assign_pointer_typecheck makes the + * typechecked pointer the second argument, matching rcu_assign_pointer itself; + * this avoids confusion about argument numbers in warning messages. */ +#define __rcu_assign_pointer_check_kernel(v) \ + do { \ + extern void __rcu_assign_pointer_typecheck(int, typeof(*(v)) __kernel *); \ + __rcu_assign_pointer_typecheck(0, v); \ + } while (0) #else /* #ifdef __CHECKER__ */ #define rcu_dereference_sparse(p, space) +#define __rcu_assign_pointer_check_kernel(v) do { } while (0) #endif /* #else #ifdef __CHECKER__ */ #define __rcu_access_pointer(p, space) \ @@ -551,7 +560,8 @@ static inline void rcu_preempt_sleep_check(void) #define __rcu_assign_pointer(p, v, space) \ do { \ smp_wmb(); \ - (p) = (typeof(*v) __force space *)(v); \ + __rcu_assign_pointer_check_kernel(v); \ + ACCESS_ONCE(p) = (typeof(*(v)) __force space *)(v); \ } while (0) -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/