Per feedback, here is an updated version. As was pointed out, the prior version was checking stuff that either changed too often to be useful or was never going to change at all. The error reporting is cleaned up too, it now releases the module before throwing the error. It now only checks four things:
Major version number (7.4 or 8.1 for example) NAMEDATALEN FUNC_MAX_ARGS INDEX_MAX_KEYS The three constants were chosen because: 1. We document them in the config page in the docs 2. We mark them as changable in pg_config_manual.h 3. Changing any of these will break some of the more popular modules: FUNC_MAX_ARGS changes fmgr interface, every module uses this NAMEDATALEN changes syscache interface, every PL as well as tsearch uses this INDEX_MAX_KEYS breaks tsearch and anything using GiST. I considered others but ultimatly rejected them. For example, HAVE_INT64_TIMESTAMP, while changing the way timestamps are stored and being configurable by a configure option, doesn't actually break anything important (only the btree_gist example in contrib). Any more comments? Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to > litigate.
Index: doc/src/sgml/xfunc.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/xfunc.sgml,v
retrieving revision 1.112
diff -c -r1.112 xfunc.sgml
*** doc/src/sgml/xfunc.sgml 23 Apr 2006 03:39:52 -0000 1.112
--- doc/src/sgml/xfunc.sgml 8 May 2006 17:41:33 -0000
***************
*** 1149,1154 ****
--- 1149,1161 ----
</para>
<para>
+ After the module has been found, PostgreSQL looks for its magic block.
+ This block contains information about the environment a module was
+ compiled in. The server uses this to verify the module was compiled
+ under the same assumptions and environment as the backend.
+ </para>
+
+ <para>
The user ID the <productname>PostgreSQL</productname> server runs
as must be able to traverse the path to the file you intend to
load. Making the file or a higher-level directory not readable
***************
*** 1953,1958 ****
--- 1960,1985 ----
<listitem>
<para>
+ To ensure your module is not loaded into an incompatible backend, it
+ is recommended to include a magic block. To do this you must include
+ the header <filename>pgmagic.h</filename> and declare the block as
+ follows:
+ </para>
+
+ <programlisting>
+ #include "pgmagic.h"
+
+ PG_MODULE_MAGIC;
+ </programlisting>
+
+ <para>
+ If the module consists of multiple source files, this only needs to
+ be done in one of them.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
Symbol names defined within object files must not conflict
with each other or with symbols defined in the
<productname>PostgreSQL</productname> server executable. You
Index: src/backend/utils/fmgr/dfmgr.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/fmgr/dfmgr.c,v
retrieving revision 1.82
diff -c -r1.82 dfmgr.c
*** src/backend/utils/fmgr/dfmgr.c 5 Mar 2006 15:58:46 -0000 1.82
--- src/backend/utils/fmgr/dfmgr.c 8 May 2006 17:41:33 -0000
***************
*** 20,26 ****
#include "dynloader.h"
#include "miscadmin.h"
#include "utils/dynamic_loader.h"
!
/*
* List of dynamically loaded files (kept in malloc'd memory).
--- 20,26 ----
#include "dynloader.h"
#include "miscadmin.h"
#include "utils/dynamic_loader.h"
! #include "pgmagic.h"
/*
* List of dynamically loaded files (kept in malloc'd memory).
***************
*** 60,65 ****
--- 60,68 ----
static char *expand_dynamic_library_name(const char *name);
static char *substitute_libpath_macro(const char *name);
+ /* Magic structure that module needs to match to be accepted */
+ static Pg_magic_struct magic_data = PG_MODULE_MAGIC_DATA;
+
/*
* Load the specified dynamic-link library file, and look for a function
* named funcname in it. (funcname can be NULL to just load the file.)
***************
*** 116,121 ****
--- 119,125 ----
if (file_scanner == NULL)
{
+ PGModuleMagicFunction magic_func;
/*
* File not loaded yet.
*/
***************
*** 146,151 ****
--- 150,194 ----
fullname, load_error)));
}
+ /* Check the magic function to determine compatability */
+ magic_func = pg_dlsym( file_scanner->handle,
PG_MAGIC_FUNCTION_NAME_STRING );
+ if( magic_func )
+ {
+ Pg_magic_struct *module_magic_data = magic_func();
+ if( module_magic_data->len != magic_data.len ||
+ memcmp( module_magic_data, &magic_data,
magic_data.len ) != 0 )
+ {
+ pg_dlclose( file_scanner->handle );
+
+ if( module_magic_data->len != magic_data.len )
+ ereport(ERROR,
+ (errmsg("incompatible library
\"%s\": Magic block length mismatch",
+ fullname)));
+ if( module_magic_data->version !=
magic_data.version )
+ ereport(ERROR,
+ (errmsg("incompatible library
\"%s\": Version mismatch",
+ fullname),
+ errdetail("Expected %d.%d, got
%d.%d",
+ magic_data.version/100,
magic_data.version % 100,
+
module_magic_data->version/100, module_magic_data->version % 100)));
+
+ if( module_magic_data->magic !=
magic_data.magic )
+ ereport(ERROR,
+ (errmsg("incompatible library
\"%s\": Magic constant mismatch",
+ fullname),
+ errdetail("Expected 0x%08X, got
0x%08X",
+ magic_data.magic,
magic_data.magic)));
+ /* Should never get here */
+ ereport(ERROR,(errmsg("incompatible library
\"%s\": Reason unknown",
+ fullname)));
+ }
+ }
+ else
+ /* Currently we do not penalize modules for not having a
+ magic block, it would break every external module in
+ existance. At some point though... */
+ ereport(LOG, (errmsg("external library \"%s\" did not
have magic block", fullname )));
+
/* OK to link it into list */
if (file_list == NULL)
file_list = file_scanner;
Index: src/test/regress/regress.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/test/regress/regress.c,v
retrieving revision 1.65
diff -c -r1.65 regress.c
*** src/test/regress/regress.c 11 Jan 2006 20:12:43 -0000 1.65
--- src/test/regress/regress.c 8 May 2006 17:41:34 -0000
***************
*** 9,14 ****
--- 9,15 ----
#include "utils/geo_decls.h" /* includes <math.h> */
#include "executor/executor.h" /* For GetAttributeByName */
#include "commands/sequence.h" /* for nextval() */
+ #include "pgmagic.h"
#define P_MAXDIG 12
#define LDELIM '('
***************
*** 27,33 ****
extern Datum int44in(PG_FUNCTION_ARGS);
extern Datum int44out(PG_FUNCTION_ARGS);
!
/*
* Distance from a point to a path
*/
--- 28,34 ----
extern Datum int44in(PG_FUNCTION_ARGS);
extern Datum int44out(PG_FUNCTION_ARGS);
! PG_MODULE_MAGIC;
/*
* Distance from a point to a path
*/
Index: src/include/pgmagic.h
=========================================================================
*** src/include/pgmagic.h.orig Mon May 8 19:41:36 2006
--- src/include/pgmagic.h Mon May 8 19:41:18 2006
***************
*** 0 ****
--- 1,73 ----
+ /*-------------------------------------------------------------------------
+ *
+ * pgmagic.h
+ * Defines a magic block that can mark a module in a way so show that
+ * it is compatible with the server it is being loaded into.
+ *
+ * This file is intended to be included into modules that wish to load
+ * themselves into the backend. All they need to do is include this header
+ * into one of the source files and include the line:
+ *
+ * PG_MODULE_MAGIC;
+ *
+ * The trailing semi-colon is optional. To work with versions of PostgreSQL
+ * that do not support this, you may put an #ifdef/endif block around it.
+ *
+ * Note, there is space available, particularly in the bitfield part. If it
+ * turns out that a change has happened within a major release that would
+ * require all modules to be recompiled, just setting one unused bit there
+ * will do the trick.
+ *
+ * Originally written by Martijn van Oosterhout <kleptog@svana.org>
+ *
+ * $PostgreSQL: $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+ #ifndef PGMAGIC_H
+ #define PGMAGIC_H
+
+ #include "c.h"
+
+ /* The main structure in which the magic is stored. the length field is used
+ * to detect major changes */
+
+ typedef struct {
+ int len;
+ int version;
+ int magic;
+ } Pg_magic_struct;
+
+ /* Declare the module magic function. It needs to be a function as the dlsym
+ * in the backend is only guarenteed to work on functions, not data */
+
+ typedef Pg_magic_struct *(*PGModuleMagicFunction) (void);
+
+ #define PG_MAGIC_FUNCTION_NAME Pg_magic_func
+ #define PG_MAGIC_FUNCTION_NAME_STRING "Pg_magic_func"
+
+ #define PG_MODULE_MAGIC \
+ extern DLLIMPORT Pg_magic_struct *PG_MAGIC_FUNCTION_NAME(void); \
+ Pg_magic_struct * \
+ PG_MAGIC_FUNCTION_NAME(void) \
+ { \
+ static Pg_magic_struct Pg_magic_data = PG_MODULE_MAGIC_DATA; \
+ return &Pg_magic_data; \
+ }
+
+ /* Common user adjustable constants */
+ #define PG_MODULE_MAGIC_CONST \
+ ((INDEX_MAX_KEYS << 0) + \
+ (FUNC_MAX_ARGS << 8) + \
+ (NAMEDATALEN << 16))
+
+ /* Finally, the actual data block */
+ #define PG_MODULE_MAGIC_DATA \
+ { \
+ sizeof(Pg_magic_struct), \
+ PG_VERSION_NUM / 100, /* Major version of postgres */ \
+ PG_MODULE_MAGIC_CONST, /* Constants users can configure */ \
+ }
+
+ #endif /* PGMAGIC_H */
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