* Rename __attribute_pure__ to just __pure before it gains users.
* Identify the areas of xen/bitops.h which are a mess.
* Create common/bitops.c for compile and runtime testing. This provides a
statement of the ABI, and a confirmation that arch-specific implementations
behave as expected.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Roger Pau Monné <roger....@citrix.com>
CC: Wei Liu <w...@xen.org>
CC: Stefano Stabellini <sstabell...@kernel.org>
CC: Julien Grall <jul...@xen.org>
CC: Volodymyr Babchuk <volodymyr_babc...@epam.com>
CC: Bertrand Marquis <bertrand.marq...@arm.com>
CC: Michal Orzel <michal.or...@amd.com>
CC: Oleksii Kurochko <oleksii.kuroc...@gmail.com>
CC: Shawn Anastasio <sanasta...@raptorengineering.com>
CC: consult...@bugseng.com <consult...@bugseng.com>
CC: Simone Ballarin <simone.balla...@bugseng.com>
CC: Federico Serafini <federico.seraf...@bugseng.com>
CC: Nicola Vetrini <nicola.vetr...@bugseng.com>
I expect MISRA will have something to say about the macros here, but they are
in aid of better testing.
---
xen/common/Makefile | 1 +
xen/common/bitops.c | 41 ++++++++++++++++++++++++++++++++++++++
xen/include/xen/bitops.h | 13 +++++++++---
xen/include/xen/compiler.h | 3 ++-
4 files changed, 54 insertions(+), 4 deletions(-)
create mode 100644 xen/common/bitops.c
diff --git a/xen/common/Makefile b/xen/common/Makefile
index e5eee19a8537..1f8ca9a2f4f8 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -1,5 +1,6 @@
obj-$(CONFIG_ARGO) += argo.o
obj-y += bitmap.o
+obj-y += bitops.o
obj-$(CONFIG_GENERIC_BUG_FRAME) += bug.o
obj-$(CONFIG_HYPFS_CONFIG) += config_data.o
obj-$(CONFIG_CORE_PARKING) += core_parking.o
diff --git a/xen/common/bitops.c b/xen/common/bitops.c
new file mode 100644
index 000000000000..4c07191b4030
--- /dev/null
+++ b/xen/common/bitops.c
@@ -0,0 +1,41 @@
+#include <xen/bitops.h>
+#include <xen/bug.h>
+#include <xen/init.h>
+
+/* Hide a value from the optimiser. */
+#define HIDE(x) ({ typeof(x) _x = x; asm volatile ( "" : "+r" (_x) ); _x; })
+
+/*
+ * Check that fn(val) can be calcuated by the compiler, and that it gives the
+ * expected answer.
+ */
+#define COMPILE_CHECK(fn, val, res) \
+ do { \
+ if ( fn(val) != res ) \
+ asm (".error \"Compile time check '" STR(fn(val) == res) "'
failed\""); \
+ } while ( 0 )
+
+/*
+ * Check that Xen's runtime logic for fn(val) gives the expected answer. This
+ * requires using HIDE() to prevent the optimiser from emitting the full
+ * calculation.
+ */
+#define RUNTIME_CHECK(fn, val, res) \
+ do { \
+ BUG_ON(fn(HIDE(val)) != res); \
+ } while ( 0 )
+
+/*
+ * Perform compiletime and runtime checks for fn(val) == res.
+ */
+#define CHECK(fn, val, res) \
+ do { \
+ COMPILE_CHECK(fn, val, res); \
+ RUNTIME_CHECK(fn, val, res); \
+ } while ( 0 )
+
+static int __init cf_check test_bitops(void)
+{
+ return 0;
+}
+__initcall(test_bitops);
diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index e3c5a4ccf321..9b40f20381a2 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -1,5 +1,7 @@
-#ifndef _LINUX_BITOPS_H
-#define _LINUX_BITOPS_H
+#ifndef XEN_BITOPS_H
+#define XEN_BITOPS_H
+
+#include <xen/compiler.h>
#include <xen/types.h>
/*
@@ -103,8 +105,13 @@ static inline int generic_flsl(unsigned long x)
* Include this here because some architectures need generic_ffs/fls in
* scope
*/
+
+/* --------------------- Please tidy above here --------------------- */
+
#include <asm/bitops.h>
+/* --------------------- Please tidy below here --------------------- */
+
#ifndef find_next_bit
/**
* find_next_bit - find the next set bit in a memory region
@@ -294,4 +301,4 @@ static inline __u32 ror32(__u32 word, unsigned int shift)
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
-#endif
+#endif /* XEN_BITOPS_H */
diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
index 16d554f2a593..972719df55b3 100644
--- a/xen/include/xen/compiler.h
+++ b/xen/include/xen/compiler.h
@@ -85,7 +85,8 @@
#define inline inline __init
#endif
-#define __attribute_pure__ __attribute__((__pure__))
+#define __pure __attribute__((__pure__))
+
#define __attribute_const__ __attribute__((__const__))
#define __transparent__ __attribute__((__transparent_union__))
--
2.30.2
