From 6a320e76cb8080a6aa81b246190620f93f721df6 Mon Sep 17 00:00:00 2001
From: "Enrico Weigelt, metux IT consult" <info@metux.net>
Date: Tue, 2 Jul 2024 14:10:00 +0200
Subject: [PATCH] dix: add macros for request handlers and swapping

add some macros for making request handlers and byte swapping easier:

    * X_REQUEST_HEAD_STRUCT(type) and X_REQUEST_HEAD_AT_LEAST(type)
      declare header struct pointers and check size
    * X_REQUEST_FIELD_CARD16(field)
      swaps a CARD16 (word) header field (if neccessary)
    * X_REQUEST_FIELD_CARD32(field)
      swaps a CARD32 (dword) header field (if neccessary)
    * X_REQUEST_REST_CARD16()
      swaps remaining CARD16 array payload (if necessary)
    * X_REQUEST_REST_CARD32()
      swaps remaining CARD32 array payload (if necessary)
    * X_REQUEST_REST_COUNT_CARD16(count)
      check swaps `count` CARD16 payload fields and checks size
    * X_REQUEST_REST_COUNT_CARD32(count)
      check swaps `count` CARD32 payload fields and checks size

How to use them:

    1. put X_REQUEST_HEAD_STRUCT() or X_REQUEST_HEAD_AT_LEAST() ontop of each Proc*()
    2. add X_REQUEST_FIELD_*() et al below, for all fields to be swapped and
       drop the corresponding SProc*()'s
    3. let the dispatchers call Proc*() instead of SProc*()

Notes:

    * the length field is already swapped before request handlers called

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
---
 dix/request_priv.h | 56 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/dix/request_priv.h b/dix/request_priv.h
index 73ac303454..d17f780d15 100644
--- a/dix/request_priv.h
+++ b/dix/request_priv.h
@@ -101,4 +101,60 @@ static inline int __write_reply_hdr_simple(
 #define X_SEND_REPLY_SIMPLE(client, hdrstruct) \
     __write_reply_hdr_simple(client, &(hdrstruct), sizeof(hdrstruct));
 
+/*
+ * macros for request handlers
+ *
+ * these are handling request packet checking and swapping of multi-byte
+ * values, if necessary. (length field is already swapped earlier)
+ */
+
+/* declare request struct and check size */
+#define X_REQUEST_HEAD_STRUCT(type) \
+    REQUEST(type); \
+    if (stuff == NULL) return (BadLength); \
+    REQUEST_SIZE_MATCH(type);
+
+/* declare request struct and check size (at least as big) */
+#define X_REQUEST_HEAD_AT_LEAST(type) \
+    REQUEST(type); \
+    if (stuff == NULL) return (BadLength); \
+    REQUEST_AT_LEAST_SIZE(type); \
+
+/* declare request struct, do NOT check size !*/
+#define X_REQUEST_HEAD_NO_CHECK(type) \
+    REQUEST(type); \
+    if (stuff == NULL) return (BadLength); \
+
+/* swap a CARD16 request struct field if necessary */
+#define X_REQUEST_FIELD_CARD16(field) \
+    do { if (client->swapped) swaps(&stuff->field); } while (0)
+
+/* swap a CARD32 request struct field if necessary */
+#define X_REQUEST_FIELD_CARD32(field) \
+    do { if (client->swapped) swapl(&stuff->field); } while (0)
+
+/* swap a CARD64 request struct field if necessary */
+#define X_REQUEST_FIELD_CARD64(field) \
+    do { if (client->swapped) swapll(&stuff->field); } while (0)
+
+/* swap CARD16 rest of request (after the struct) */
+#define X_REQUEST_REST_CARD16() \
+    do { if (client->swapped) SwapRestS(stuff); } while (0)
+
+/* swap CARD32 rest of request (after the struct) */
+#define X_REQUEST_REST_CARD32() \
+    do { if (client->swapped) SwapRestL(stuff); } while (0)
+
+/* swap CARD16 rest of request (after the struct) - check fixed count */
+#define X_REQUEST_REST_COUNT_CARD16(count) \
+    REQUEST_FIXED_SIZE(*stuff, count * sizeof(CARD16)); \
+    CARD32 *request_rest = (CARD16 *) (&stuff[1]); \
+    do { if (client->swapped) SwapShorts(request_rest, count); } while (0)
+
+/* swap CARD32 rest of request (after the struct) - check fixed count */
+#define X_REQUEST_REST_COUNT_CARD32(count) \
+    REQUEST_FIXED_SIZE(*stuff, count * sizeof(CARD32)); \
+    CARD32 *request_rest = (CARD32 *) (&stuff[1]); \
+    do { if (client->swapped) SwapLongs(request_rest, count); } while (0) \
+
 #endif /* _XSERVER_DIX_REQUEST_PRIV_H */