Add validation for page checksum version in pg_control.

This serves as an additional sanity check to be sure the pg_control format is as expected. The field is useful for being all the way at the end and being four bytes that can only have one of two values. Something more distinctive than 0 and 1 would be better, but this is what we have to work with.

Convert PgControl.pageChecksum to unsigned int and rename to PgControl.pageChecksumVersion and make all downstream changes required for the new datatype.

src/postgres/interface.c

@@ -276,6 +276,14 @@ pgControlFromBuffer(const Buffer *controlFile, const String *const pgVersionForc
     // Check the page size
     pgPageSizeCheck(result.pageSize);
 
+    // Check the checksum version
+    if (result.pageChecksumVersion != 0 && result.pageChecksumVersion != PG_DATA_CHECKSUM_VERSION)
+    {
+        THROW_FMT(
+            FormatError, "page checksum version is %u but only 0 and " STRINGIFY(PG_DATA_CHECKSUM_VERSION) " are valid",
+            result.pageChecksumVersion);
+    }
+
     FUNCTION_LOG_RETURN(PG_CONTROL, result);
 }
 
@@ -700,8 +708,8 @@ FN_EXTERN void
 pgControlToLog(const PgControl *const pgControl, StringStatic *const debugLog)
 {
     strStcFmt(
-        debugLog, "{version: %u, systemId: %" PRIu64 ", walSegmentSize: %u, pageChecksum: %s}", pgControl->version,
-        pgControl->systemId, pgControl->walSegmentSize, cvtBoolToConstZ(pgControl->pageChecksum));
+        debugLog, "{version: %u, systemId: %" PRIu64 ", walSegmentSize: %u, pageChecksumVersion: %u}", pgControl->version,
+        pgControl->systemId, pgControl->walSegmentSize, pgControl->pageChecksumVersion);
 }
 
 FN_EXTERN void

src/postgres/interface.h

@@ -109,7 +109,7 @@ typedef struct PgControl
     PgPageSize pageSize;
     unsigned int walSegmentSize;
 
-    bool pageChecksum;
+    unsigned int pageChecksumVersion;                               // Page checksum version (0 if no checksum, 1 if checksum)
 } PgControl;
 
 /***********************************************************************************************************************************

src/postgres/interface/static.vendor.h

@@ -124,6 +124,14 @@ typedef struct
 	uint32		xrecoff;		/* low bits */
 } PageXLogRecPtr;
 
+// PG_DATA_CHECKSUM_VERSION define
+// ---------------------------------------------------------------------------------------------------------------------------------
+/*
+ * As of Release 9.3, the checksum version must also be considered when
+ * handling pages.
+ */
+#define PG_DATA_CHECKSUM_VERSION	1
+
 // PageHeaderData type
 // ---------------------------------------------------------------------------------------------------------------------------------
 /*

src/postgres/interface/version.intern.h

@@ -70,7 +70,7 @@ Read the version specific pg_control into a general data structure
             .timeline = ((ControlFileData *)controlFile)->checkPointCopy.ThisTimeLineID,                                           \
             .pageSize = ((ControlFileData *)controlFile)->blcksz,                                                                  \
             .walSegmentSize = ((ControlFileData *)controlFile)->xlog_seg_size,                                                     \
-            .pageChecksum = ((ControlFileData *)controlFile)->data_checksum_version != 0,                                          \
+            .pageChecksumVersion = ((ControlFileData *)controlFile)->data_checksum_version,                                        \
         };                                                                                                                         \
     }