[RFC v14-rc2][PATCH 24/29] c/r: Add CR_COPY() macro (v4)

[Oren Laadan]

From: Dan Smith <danms at us.ibm.com>

As suggested by Dave[1], this provides us a way to make the copy-in and
copy-out processes symmetric.  CR_COPY_ARRAY() provides us a way to do
the same thing but for arrays.  It's not critical, but it helps us unify
the checkpoint and restart paths for some things.

Changelog:
    Mar 04:
            . Removed semicolons
            . Added build-time check for __must_be_array in CR_COPY_ARRAY
    Feb 27:
            . Changed CR_COPY() to use assignment, eliminating the need
              for the CR_COPY_BIT() macro
            . Add CR_COPY_ARRAY() macro to help copying register arrays,
              etc
            . Move the macro definitions inside the CR #ifdef
    Feb 25:
            . Changed WARN_ON() to BUILD_BUG_ON()

Signed-off-by: Dan Smith <danms at us.ibm.com>
Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>

1: https://lists.linux-foundation.org/pipermail/containers/2009-February/015821.html (all the way at the bottom)
---
 include/linux/checkpoint.h |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 031e414..59ec563 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -120,6 +120,32 @@ extern int cr_read_mm(struct cr_ctx *ctx);
 extern int cr_read_fd_table(struct cr_ctx *ctx);
 extern int cr_read_file(struct cr_ctx *ctx, int objref);
 
+/* useful macros to copy fields and buffers to/from cr_hdr_xxx structures */
+#define CR_CPT 1
+#define CR_RST 2
+
+#define CR_COPY(op, SAVE, LIVE)				        \
+	do {							\
+		if (op == CR_CPT)				\
+			SAVE = LIVE;				\
+		else						\
+			LIVE = SAVE;				\
+	} while (0)
+
+/*
+ * Copy @count items from @LIVE to @SAVE if op is CR_CPT (otherwise,
+ * copy in the reverse direction)
+ */
+#define CR_COPY_ARRAY(op, SAVE, LIVE, count)				\
+	do {								\
+		BUILD_BUG_ON(sizeof(*SAVE) != sizeof(*LIVE));		\
+		if (op == CR_CPT)					\
+			memcpy(SAVE, LIVE, count * sizeof(*SAVE));	\
+		else							\
+			memcpy(LIVE, SAVE, count * sizeof(*SAVE));	\
+	} while (__must_be_array(SAVE) && __must_be_array(LIVE) && 0)
+
+
 #define cr_debug(fmt, args...)  \
 	pr_debug("[%d:c/r:%s] " fmt, task_pid_vnr(current), __func__, ## args)
 
-- 
1.5.4.3