fix message fields alignment for 64 bit

On x86_64 alignment of structures is different, as the pointer size is different.
For simplicity we keep the same 4-byte alignment as used on
32-bit. This simplifies the support for 32-bit rpc on 64-bit kernels,
and also it seems not worth as an optimization, as we would need to
add more code in the ipc_kmsg* routines.

* routine.c: align both short and long descriptors
* utils.c: use a fixed alignment for data fields in structures
  representing messages.

Signed-off-by: Luca Dariz <luca@orpolo.org>
Message-Id: <20220628094927.442907-2-luca@orpolo.org>

2 files changed, 4 insertions, 2 deletions

diff --git a/routine.c b/routine.c
index 0edc6b9..6972e14 100644
--- a/routine.c
+++ b/routine.c
@@ -321,9 +321,9 @@ rtFindSize(const argument_t *args, u_int mask)
 	{
 	    ipc_type_t *it = arg->argType;
 
+	    /* might need proper alignment on demanding 64bit archies */
+	    size = (size + word_size-1) & ~(word_size-1);
 	    if (arg->argLongForm) {
-		/* might need proper alignment on 64bit archies */
-		size = (size + word_size-1) & ~(word_size-1);
 		size += sizeof_mach_msg_type_long_t;
 	    } else {
 		size += sizeof_mach_msg_type_t;
diff --git a/utils.c b/utils.c
index bdc39b7..a8ebc6b 100644
--- a/utils.c
+++ b/utils.c
@@ -338,10 +338,12 @@ void
 WriteStructDecl(FILE *file, const argument_t *args, write_list_fn_t *func,
 		u_int mask, const char *name)
 {
+    fprintf(file, "#pragma pack(push,%d)\n", word_size);
     fprintf(file, "\ttypedef struct {\n");
     fprintf(file, "\t\tmach_msg_header_t Head;\n");
     WriteList(file, args, func, mask, "\n", "\n");
     fprintf(file, "\t} %s;\n", name);
+    fprintf(file, "#pragma pack(pop)\n");
     fprintf(file, "\n");
 }