In the UAPI header files, __BIG_ENDIAN and __LITTLE_ENDIAN must be compared
against __BYTE_ORDER in preprocessor conditionals where these are exposed to
userspace (that is they're not inside __KERNEL__ conditionals).
However, in the main kernel the norm is to check for "defined(__XXX_ENDIAN)"
rather than comparing against __BYTE_ORDER and this has incorrectly leaked
into the userspace headers.
The definition of struct mdp_superblock_s in linux/raid/md_p.h is wrong in this
way. Note that userspace will likely interpret the ordering of the fields
incorrectly as the big-endian variant on a little-endian machines - depending
on header inclusion order.
[!!!] NOTE [!!!] This patch may adversely change the userspace API. It might
be better to fix the ordering of events_hi, events_lo, cp_events_hi and
cp_events_lo in struct mdp_superblock_s / typedef mdp_super_t.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Neil Brown <neilb@xxxxxxx>
cc: linux-raid@xxxxxxxxxxxxxxx
---
include/uapi/linux/raid/md_p.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/raid/md_p.h b/include/uapi/linux/raid/md_p.h
index ee75353..fe1a540 100644
--- a/include/uapi/linux/raid/md_p.h
+++ b/include/uapi/linux/raid/md_p.h
@@ -145,16 +145,18 @@ typedef struct mdp_superblock_s {
__u32 failed_disks; /* 4 Number of failed disks */
__u32 spare_disks; /* 5 Number of spare disks */
__u32 sb_csum; /* 6 checksum of the whole superblock */
-#ifdef __BIG_ENDIAN
+#if defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : defined(__BIG_ENDIAN)
__u32 events_hi; /* 7 high-order of superblock update count */
__u32 events_lo; /* 8 low-order of superblock update count */
__u32 cp_events_hi; /* 9 high-order of checkpoint update count */
__u32 cp_events_lo; /* 10 low-order of checkpoint update count */
-#else
+#elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : defined(__LITTLE_ENDIAN)
__u32 events_lo; /* 7 low-order of superblock update count */
__u32 events_hi; /* 8 high-order of superblock update count */
__u32 cp_events_lo; /* 9 low-order of checkpoint update count */
__u32 cp_events_hi; /* 10 high-order of checkpoint update count */
+#else
+#error unspecified endianness
#endif
__u32 recovery_cp; /* 11 recovery checkpoint sector count */
/* There are only valid for minor_version > 90 */
--
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