lib/zlib: adjust offset calculation for dfltcc_state

Patch series "lib/zlib: Set of s390 DFLTCC related patches for kernel zlib".

Patches 1-7 represent a set of s390 zlib hardware support (DFLTCC) related
fixes and enhancements integrated from zlib-ng repo relevant to kernel
zlib (https://github.com/zlib-ng/zlib-ng).

Since the official zlib repository never got DFLTCC support code merged,
all the patches have been picked from zlib-ng fork (zlib data compression
library for the next generation systems).  This repo contains new
optimizations and fixes not getting implemented into the official zlib
repository and falls under the same zlib License.  All of the original
patches from zlib-ng were authored by Ilya Leoshkevich
<iii@linux.ibm.com>.  Coding style has been preserved for future
maintainability.

Patches 1-2 should have no effect for the kernel zlib but make the code
closer to zlib-ng for future maintainability.

Only Patch 3 touches common zlib_deflate code, other patches are relevant
to s390 tree only.

Patch 8 is separate and intends to resolve an issue with kernel PPP driver
which can use kernel zlib for packet compression.  Without this patch PPP
decompression can fail due to error code returned by hardware
(dfltcc_inflate) and PPP disables zlib compression for further packets.


This patch (of 8):

This commit is based on:
  https://github.com/zlib-ng/zlib-ng/commit/d8b67f5

Link: https://lkml.kernel.org/r/20230126131428.1222214-1-zaslonko@linux.ibm.com
Link: https://lkml.kernel.org/r/20230126131428.1222214-2-zaslonko@linux.ibm.com


Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com> (s390)
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/zlib_dfltcc/dfltcc.h

@@ -100,8 +100,9 @@ struct dfltcc_state {
     char msg[64];                      /* Buffer for strm->msg */
 };
 
+#define ALIGN_UP(p, size) (__typeof__(p))(((uintptr_t)(p) + ((size) - 1)) & ~((size) - 1))
 /* Resides right after inflate_state or deflate_state */
-#define GET_DFLTCC_STATE(state) ((struct dfltcc_state *)((state) + 1))
+#define GET_DFLTCC_STATE(state) ((struct dfltcc_state *)((char *)(state) + ALIGN_UP(sizeof(*state), 8)))
 
 /* External functions */
 int dfltcc_can_deflate(z_streamp strm);