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Add pgmagic header block to store compile-time constants:

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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.

Martijn van Oosterhout
This commit is contained in:
Bruce Momjian 2006-05-30 14:09:32 +00:00
parent 87bd07d979
commit 01b2168c90
4 changed files with 149 additions and 5 deletions
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29
doc/src/sgml/xfunc.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.112 2006/04/23 03:39:52 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.113 2006/05/30 14:09:32 momjian Exp $ -->
<sect1 id="xfunc">
<title>User-Defined Functions</title>
@ -1148,6 +1148,13 @@ CREATE FUNCTION square_root(double precision) RETURNS double precision
that fails as well, the load will fail.
</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
@ -1951,6 +1958,26 @@ concat_text(PG_FUNCTION_ARGS)
</para>
</listitem>
<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

47
src/backend/utils/fmgr/dfmgr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.82 2006/03/05 15:58:46 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.83 2006/05/30 14:09:32 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -20,7 +20,7 @@
#include "dynloader.h"
#include "miscadmin.h"
#include "utils/dynamic_loader.h"
#include "pgmagic.h"
/*
* List of dynamically loaded files (kept in malloc'd memory).
@ -60,6 +60,9 @@ static char *find_in_dynamic_libpath(const char *basename);
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.)
@ -116,6 +119,7 @@ load_external_function(char *filename, char *funcname,
if (file_scanner == NULL)
{
PGModuleMagicFunction magic_func;
/*
* File not loaded yet.
*/
@ -146,6 +150,45 @@ load_external_function(char *filename, char *funcname,
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;

73
src/include/pgmagic.h Normal file
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@ -0,0 +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: pgsql/src/include/pgmagic.h,v 1.1 2006/05/30 14:09:32 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#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 */

5
src/test/regress/regress.c
View File

@ -1,5 +1,5 @@
/*
* $PostgreSQL: pgsql/src/test/regress/regress.c,v 1.65 2006/01/11 20:12:43 tgl Exp $
* $PostgreSQL: pgsql/src/test/regress/regress.c,v 1.66 2006/05/30 14:09:32 momjian Exp $
*/
#include "postgres.h"
@ -9,6 +9,7 @@
#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 '('
@ -27,7 +28,7 @@ extern int oldstyle_length(int n, text *t);
extern Datum int44in(PG_FUNCTION_ARGS);
extern Datum int44out(PG_FUNCTION_ARGS);
PG_MODULE_MAGIC;
/*
* Distance from a point to a path
*/