tools: merge several bitop functions into xc_bitops.h

Bitmaps are used in save/restore, xenpaging and blktap2.  Merge the code into a
private xc_bitops.h file. All users are single threaded, so locking is not an
issue. The array of bits is handled as volatile because the x86 save/restore
code passes the bitmap to the hypervisor which in turn modifies the bitmap.

blktap2 uses a private bitmap. There was a possible overflow in the
bitmap_size() function, the remainder was not considered.

ia64 save/restore uses a bitmap to send the number of vcpus to the host.

x86 save/restore uses a bitmap to track dirty pages. This bitmap is shared with
the hypervisor. An unused function count_bits() was removed and a new
bitmap_size() function is now used.

xenpaging uses 3 private bitmaps to track the gfns which are in paged-out
state.  It had a copy of some Linux bitops.h, which is now obsolete. Also the
BITS_PER_LONG macro was hardcoded to 64 which made it impossible to run 32bit
tools on a 64bit host. Wether this works at all has to be tested, yet.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/tools/libxc/xc_bitops.h b/tools/libxc/xc_bitops.h
new file mode 100644
index 0000000000..8ee2aab95f
--- /dev/null
+++ b/tools/libxc/xc_bitops.h
@@ -0,0 +1,57 @@
+#ifndef XC_BITOPS_H
+#define XC_BITOPS_H 1
+
+/* bitmap operations for single threaded access */
+
+#include <stdlib.h>
+
+#define BITS_PER_LONG (sizeof(unsigned long) * 8)
+#define ORDER_LONG (sizeof(unsigned long) == 4 ? 5 : 6)
+
+#define BITMAP_ENTRY(_nr,_bmap) ((_bmap))[(_nr)/BITS_PER_LONG]
+#define BITMAP_SHIFT(_nr) ((_nr) % BITS_PER_LONG)
+
+/* calculate required space for number of longs needed to hold nr_bits */
+static inline int bitmap_size(int nr_bits)
+{
+    int nr_long, nr_bytes;
+    nr_long = (nr_bits + BITS_PER_LONG - 1) >> ORDER_LONG;
+    nr_bytes = nr_long * sizeof(unsigned long);
+    return nr_bytes;
+}
+
+static inline unsigned long *bitmap_alloc(int nr_bits)
+{
+    return calloc(1, bitmap_size(nr_bits));
+}
+
+static inline int test_bit(int nr, volatile unsigned long *addr)
+{
+    return (BITMAP_ENTRY(nr, addr) >> BITMAP_SHIFT(nr)) & 1;
+}
+
+static inline void clear_bit(int nr, volatile unsigned long *addr)
+{
+    BITMAP_ENTRY(nr, addr) &= ~(1UL << BITMAP_SHIFT(nr));
+}
+
+static inline void set_bit(int nr, volatile unsigned long *addr)
+{
+    BITMAP_ENTRY(nr, addr) |= (1UL << BITMAP_SHIFT(nr));
+}
+
+static inline int test_and_clear_bit(int nr, volatile unsigned long *addr)
+{
+    int oldbit = test_bit(nr, addr);
+    clear_bit(nr, addr);
+    return oldbit;
+}
+
+static inline int test_and_set_bit(int nr, volatile unsigned long *addr)
+{
+    int oldbit = test_bit(nr, addr);
+    set_bit(nr, addr);
+    return oldbit;
+}
+
+#endif  /* XC_BITOPS_H */