kernel: add common infrastructure for unaligned access

Create a linux/unaligned directory similar in spirit to the linux/byteorder
folder to hold generic implementations collected from various arches.

Currently there are five implementations:
1) packed_struct.h: C-struct based, from asm-generic/unaligned.h
2) le_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
3) be_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
4) memmove.h: taken from multiple implementations in tree
5) access_ok.h: taken from x86 and others, unaligned access is ok.

All of the new implementations checks for sizes not equal to 1,2,4,8
and will fail to link.

API additions:

get_unaligned_{le16|le32|le64|be16|be32|be64}(p) which is meant to replace
code of the form:
le16_to_cpu(get_unaligned((__le16 *)p));

put_unaligned_{le16|le32|le64|be16|be32|be64}(val, pointer) which is meant to
replace code of the form:
put_unaligned(cpu_to_le16(val), (__le16 *)p);

The headers that arches should include from their asm/unaligned.h:

access_ok.h : Wrappers of the byteswapping functions in asm/byteorder

Choose a particular implementation for little-endian access:
le_byteshift.h
le_memmove.h (arch must be LE)
le_struct.h (arch must be LE)

Choose a particular implementation for big-endian access:
be_byteshift.h
be_memmove.h (arch must be BE)
be_struct.h (arch must be BE)

After including as needed from the above, include unaligned/generic.h and
define your arch's get/put_unaligned as (for LE):

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/include/linux/unaligned/memmove.h b/include/linux/unaligned/memmove.h
new file mode 100644
index 000000000000..eeb5a779a4fd
--- /dev/null
+++ b/include/linux/unaligned/memmove.h
@@ -0,0 +1,45 @@
+#ifndef _LINUX_UNALIGNED_MEMMOVE_H
+#define _LINUX_UNALIGNED_MEMMOVE_H
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+
+/* Use memmove here, so gcc does not insert a __builtin_memcpy. */
+
+static inline u16 __get_unaligned_memmove16(const void *p)
+{
+        u16 tmp;
+        memmove(&tmp, p, 2);
+        return tmp;
+}
+
+static inline u32 __get_unaligned_memmove32(const void *p)
+{
+        u32 tmp;
+        memmove(&tmp, p, 4);
+        return tmp;
+}
+
+static inline u64 __get_unaligned_memmove64(const void *p)
+{
+        u64 tmp;
+        memmove(&tmp, p, 8);
+        return tmp;
+}
+
+static inline void __put_unaligned_memmove16(u16 val, void *p)
+{
+        memmove(p, &val, 2);
+}
+
+static inline void __put_unaligned_memmove32(u32 val, void *p)
+{
+        memmove(p, &val, 4);
+}
+
+static inline void __put_unaligned_memmove64(u64 val, void *p)
+{
+        memmove(p, &val, 8);
+}
+
+#endif /* _LINUX_UNALIGNED_MEMMOVE_H */