From: "Alex Bennée" <alex.bennee@linaro.org>
To: qemu-devel@nongnu.org
Cc: pbonzini@redhat.com, sbruno@freebsd.org,
"Alex Bennée" <alex.bennee@linaro.org>,
peter.maydell@linaro.org
Subject: [Qemu-devel] [PATCH v1 2/2] include/qemu/atomic: add compile time asserts
Date: Mon, 21 Mar 2016 16:23:06 +0000 [thread overview]
Message-ID: <1458577386-9984-3-git-send-email-alex.bennee@linaro.org> (raw)
In-Reply-To: <1458577386-9984-1-git-send-email-alex.bennee@linaro.org>
To be safely portable no atomic access should be trying to do more than
the natural word width of the host. The most common abuse is trying to
atomically access 64 bit values on a 32 bit host.
This patch adds some QEMU_BUILD_BUG_ON to the __atomic instrinsic paths
to create a build failure if (sizeof(*ptr) > sizeof(void *)).
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
include/qemu/atomic.h | 58 ++++++++++++++++++++++++++++++---------------------
1 file changed, 34 insertions(+), 24 deletions(-)
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
index 8f1d8d9..5bc4d6c 100644
--- a/include/qemu/atomic.h
+++ b/include/qemu/atomic.h
@@ -42,30 +42,34 @@
* loads/stores past the atomic operation load/store. However there is
* no explicit memory barrier for the processor.
*/
-#define atomic_read(ptr) \
- ({ \
- typeof(*ptr) _val; \
- __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
- _val; \
+#define atomic_read(ptr) \
+ ({ \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
+ typeof(*ptr) _val; \
+ __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
+ _val; \
})
-#define atomic_set(ptr, i) do { \
- typeof(*ptr) _val = (i); \
- __atomic_store(ptr, &_val, __ATOMIC_RELAXED); \
+#define atomic_set(ptr, i) do { \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
+ typeof(*ptr) _val = (i); \
+ __atomic_store(ptr, &_val, __ATOMIC_RELAXED); \
} while(0)
/* Atomic RCU operations imply weak memory barriers */
-#define atomic_rcu_read(ptr) \
- ({ \
- typeof(*ptr) _val; \
- __atomic_load(ptr, &_val, __ATOMIC_CONSUME); \
- _val; \
+#define atomic_rcu_read(ptr) \
+ ({ \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
+ typeof(*ptr) _val; \
+ __atomic_load(ptr, &_val, __ATOMIC_CONSUME); \
+ _val; \
})
-#define atomic_rcu_set(ptr, i) do { \
- typeof(*ptr) _val = (i); \
- __atomic_store(ptr, &_val, __ATOMIC_RELEASE); \
+#define atomic_rcu_set(ptr, i) do { \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
+ typeof(*ptr) _val = (i); \
+ __atomic_store(ptr, &_val, __ATOMIC_RELEASE); \
} while(0)
/* atomic_mb_read/set semantics map Java volatile variables. They are
@@ -79,6 +83,7 @@
#if defined(_ARCH_PPC)
#define atomic_mb_read(ptr) \
({ \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
smp_rmb(); \
@@ -86,22 +91,25 @@
})
#define atomic_mb_set(ptr, i) do { \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val = (i); \
smp_wmb(); \
__atomic_store(ptr, &_val, __ATOMIC_RELAXED); \
smp_mb(); \
} while(0)
#else
-#define atomic_mb_read(ptr) \
- ({ \
- typeof(*ptr) _val; \
- __atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \
- _val; \
+#define atomic_mb_read(ptr) \
+ ({ \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
+ typeof(*ptr) _val; \
+ __atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \
+ _val; \
})
-#define atomic_mb_set(ptr, i) do { \
- typeof(*ptr) _val = (i); \
- __atomic_store(ptr, &_val, __ATOMIC_SEQ_CST); \
+#define atomic_mb_set(ptr, i) do { \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
+ typeof(*ptr) _val = (i); \
+ __atomic_store(ptr, &_val, __ATOMIC_SEQ_CST); \
} while(0)
#endif
@@ -109,6 +117,7 @@
/* All the remaining operations are fully sequentially consistent */
#define atomic_xchg(ptr, i) ({ \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _new = (i), _old; \
__atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \
_old; \
@@ -117,6 +126,7 @@
/* Returns the eventual value, failed or not */
#define atomic_cmpxchg(ptr, old, new) \
({ \
+ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _old = (old), _new = (new); \
__atomic_compare_exchange(ptr, &_old, &_new, false, \
__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \
--
2.7.3
next prev parent reply other threads:[~2016-03-21 16:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-21 16:23 [Qemu-devel] [PATCH v1 0/2] Fix for FreeBSD compile on i386 Alex Bennée
2016-03-21 16:23 ` [Qemu-devel] [PATCH v1 1/2] cpus: don't use atomic_read for vm_clock_warp_start Alex Bennée
2016-03-21 16:26 ` Paolo Bonzini
2016-03-21 17:45 ` Alex Bennée
2016-03-21 16:23 ` Alex Bennée [this message]
2016-04-01 15:03 ` [Qemu-devel] [PATCH v1 2/2] include/qemu/atomic: add compile time asserts Alex Bennée
2016-04-04 8:33 ` Paolo Bonzini
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