This has several advantages:
1) We don't need to resize mach_msg_header_t, it is just a copy.
2) Mig won't require any changes because it statically computes the size
of mach_msg_header_t, otherwise we would need two sizes (28 vs 32 bytes).
---
include/mach/message.h | 15 +++++++++++++--
x86_64/copy_user.c | 35 +++++++++++++----------------------
2 files changed, 26 insertions(+), 24 deletions(-)
diff --git a/include/mach/message.h b/include/mach/message.h
index 63341e6f..eb3b34c0 100644
--- a/include/mach/message.h
+++ b/include/mach/message.h
@@ -139,7 +139,15 @@ typedef integer_t mach_msg_id_t;
typedef struct mach_msg_header {
mach_msg_bits_t msgh_bits;
mach_msg_size_t msgh_size;
- mach_port_t msgh_remote_port;
+ union {
+ mach_port_t msgh_remote_port;
+ /*
+ * Ensure msgh_remote_port is wide enough to hold a kernel pointer
+ * to avoid message resizing for the 64 bits case. This field should
+ * not be used since it is here just for padding purposes.
+ */
+ rpc_uintptr_t msgh_remote_port_do_not_use;
+ };
union {
mach_port_t msgh_local_port;
rpc_uintptr_t msgh_protected_payload;
@@ -153,7 +161,10 @@ typedef struct mach_msg_header {
typedef struct {
mach_msg_bits_t msgh_bits;
mach_msg_size_t msgh_size;
- mach_port_name_t msgh_remote_port;
+ union {
+ mach_port_name_t msgh_remote_port;
+ rpc_uintptr_t msgh_remote_port_do_not_use;
+ };
union {
mach_port_name_t msgh_local_port;
rpc_uintptr_t msgh_protected_payload;
diff --git a/x86_64/copy_user.c b/x86_64/copy_user.c
index ae062645..dd9fe2d7 100644
--- a/x86_64/copy_user.c
+++ b/x86_64/copy_user.c
@@ -177,29 +177,24 @@ int copyinmsg (const void *userbuf, void *kernelbuf,
const size_t usize)
const mach_msg_user_header_t *umsg = userbuf;
mach_msg_header_t *kmsg = kernelbuf;
+#ifdef USER32
if (copyin(&umsg->msgh_bits, &kmsg->msgh_bits, sizeof(kmsg->msgh_bits)))
return 1;
/* kmsg->msgh_size is filled in later */
if (copyin_port(&umsg->msgh_remote_port, &kmsg->msgh_remote_port))
return 1;
-#ifdef USER32
- /* This could contain a payload, but for 32 bits it will be the same size as
a mach_port_name_t */
- _Static_assert(sizeof(rpc_uintptr_t) == sizeof(mach_port_name_t),
- "rpc_uintptr_t and mach_port_name_t expected to have the same
size");
if (copyin_port(&umsg->msgh_local_port, &kmsg->msgh_local_port))
return 1;
-#else
- /* For pure 64 bits, the protected payload is as large as a port pointer. */
- _Static_assert(sizeof(rpc_uintptr_t) == sizeof(mach_port_t),
- "rpc_uintptr_t and mach_port_t expected to have the same
size");
- if (copyin((char*)umsg + offsetof(mach_msg_user_header_t, msgh_local_port),
- (char*)kmsg + offsetof(mach_msg_header_t, msgh_local_port),
- sizeof(rpc_uintptr_t)))
- return 1;
-#endif
if (copyin(&umsg->msgh_seqno, &kmsg->msgh_seqno,
sizeof(kmsg->msgh_seqno) + sizeof(kmsg->msgh_id)))
return 1;
+#else
+ /* The 64 bit interface ensures the header is the same size, so it does not
need any resizing. */
+ _Static_assert(sizeof(mach_msg_header_t) == sizeof(mach_msg_user_header_t),
+ "mach_msg_header_t and mach_msg_user_header_t expected to be
of the same size");
+ if (copyin(&umsg, &kmsg, sizeof(mach_msg_header_t)))
+ return 1;
+#endif
vm_offset_t usaddr, ueaddr, ksaddr;
ksaddr = (vm_offset_t)(kmsg + 1);
@@ -283,25 +278,21 @@ int copyoutmsg (const void *kernelbuf, void *userbuf,
const size_t ksize)
{
const mach_msg_header_t *kmsg = kernelbuf;
mach_msg_user_header_t *umsg = userbuf;
-
+#ifdef USER32
if (copyout(&kmsg->msgh_bits, &umsg->msgh_bits, sizeof(kmsg->msgh_bits)))
return 1;
/* umsg->msgh_size is filled in later */
if (copyout_port(&kmsg->msgh_remote_port, &umsg->msgh_remote_port))
return 1;
-#ifdef USER32
if (copyout_port(&kmsg->msgh_local_port, &umsg->msgh_local_port))
return 1;
-#else
- /* Handle protected payloads correctly, same as copyinmsg. */
- if (copyout((char*)kmsg + offsetof(mach_msg_header_t, msgh_local_port),
- (char*)umsg + offsetof(mach_msg_user_header_t, msgh_local_port),
- sizeof(rpc_uintptr_t)))
- return 1;
-#endif
if (copyout(&kmsg->msgh_seqno, &umsg->msgh_seqno,
sizeof(kmsg->msgh_seqno) + sizeof(kmsg->msgh_id)))
return 1;
+#else
+ if (copyout(&kmsg, &umsg, sizeof(mach_msg_header_t)))
+ return 1;
+#endif /* USER32 */
vm_offset_t ksaddr, keaddr, usaddr;
ksaddr = (vm_offset_t)(kmsg + 1);
--
2.39.1
