Jim Klimov wrote:
[...]
OR...
+ parent struct:
* 4 single-bytes (they do remain single, right?..)
* 4-byte padding (...or the single-bytes should be 4*2-byte words)
++ Sub-structure in the union (8-aligned itself):
** 4-byte isl_len (starts at offset 8 from parent struct)
** 4-byte padding
** 8-byte pointer (8-aligned in both structures)
** 8-byte offset (starts at offset 24 from parent struct)
Does this layout fit the actual drivers? :)
Yes, that is correct. The alignment in inner struct
recursively forces both paddings.
Looking at it again, I see that I also had to #if
the attribute "__attribute__((packed))" at the end
of the structure. I did it for my compiler, but I
now think this is plain wrong and had to be deleted
for all 64-bit compilers (it must probably be kept
for 32-bit ones).
If so, some more #ifdef padding fields are needed, but I guess I can
craft them based on your offset numbers...
Does the first 4-byte padding belong in the child struct or in the
parent, prefixing all variations of the union sub-structures?
You need two paddings, the way you showed above. I suggest
the patch below (possibly damaged by the mailer), which
might be overkill :
--- include/ntoskrnl_var.h.ref 2013-04-26 17:20:58.881730000 +0200
+++ include/ntoskrnl_var.h 2013-04-26 17:59:49.473614000 +0200
@@ -848,10 +848,16 @@
* io_stack_location structure is opaque to drivers
* anyway, I'm not going to bother with the extra crap.
*/
+#ifdef __amd64__
+ uint32_t padding1; /* required for alignement */
+#endif
union {
struct {
uint32_t isl_len;
+#ifdef __amd64__
+ uint32_t padding1; /* for alignement */
+#endif
/* "POINTER_ALIGNMENT" according to msdn */
uint32_t *isl_key;
uint64_t isl_byteoff;
@@ -880,7 +886,7 @@
void *isl_arg3;
void *isl_arg4;
} isl_others;
-#if defined(SOZOBON)
+#ifdef __amd64__
} isl_parameters;
#else
} isl_parameters __attribute__((packed));
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