On Tue, Jan 23, 2024 at 12:08:17PM +0900, Michael Paquier wrote: > That was on my TODO list of things to tackle and propose, but perhaps > there is no point in waiting more so I've applied your patch.
Slightly off topic and while I don't forget about it.. Please find
attached a copy of the patch posted around [1] to be able to define
injection points with input arguments, so as it is possible to execute
callbacks with values coming from the code path where the point is
attached.
For example, a backend could use this kind of macro to have a callback
attached to this point use some runtime value:
INJECTION_POINT_1ARG("InjectionPointBoo", &some_value);
[1]: https://www.postgresql.org/message-id/Za8TLyD9HIjzFlhJ%40paquier.xyz
--
Michael
From 1ebcd3c50c9db555b3d2078db931e8c8bdb87472 Mon Sep 17 00:00:00 2001
From: Michael Paquier <mich...@paquier.xyz>
Date: Tue, 23 Jan 2024 12:30:52 +0900
Subject: [PATCH] Extend injection points with optional runtime arguments
This extends injections points with a 1-argument flavor, so as it
becomes possible for callbacks to perform runtime checks.
---
src/include/utils/injection_point.h | 7 +-
src/backend/utils/misc/injection_point.c | 75 +++++++++++++++----
.../expected/injection_points.out | 25 +++++++
.../injection_points--1.0.sql | 10 +++
.../injection_points/injection_points.c | 31 +++++++-
.../injection_points/sql/injection_points.sql | 7 ++
doc/src/sgml/xfunc.sgml | 10 ++-
7 files changed, 146 insertions(+), 19 deletions(-)
diff --git a/src/include/utils/injection_point.h b/src/include/utils/injection_point.h
index 55524b568f..8e1527bb4a 100644
--- a/src/include/utils/injection_point.h
+++ b/src/include/utils/injection_point.h
@@ -16,22 +16,27 @@
*/
#ifdef USE_INJECTION_POINTS
#define INJECTION_POINT(name) InjectionPointRun(name)
+#define INJECTION_POINT_1ARG(name, arg1) InjectionPointRun1Arg(name, arg1)
#else
#define INJECTION_POINT(name) ((void) name)
+#define INJECTION_POINT_1ARG(name) ((void) name, (void) arg1)
#endif
/*
* Typedef for callback function launched by an injection point.
*/
typedef void (*InjectionPointCallback) (const char *name);
+typedef void (*InjectionPointCallback1Arg) (const char *name, void *arg1);
extern Size InjectionPointShmemSize(void);
extern void InjectionPointShmemInit(void);
extern void InjectionPointAttach(const char *name,
const char *library,
- const char *function);
+ const char *function,
+ int num_args);
extern void InjectionPointRun(const char *name);
+extern void InjectionPointRun1Arg(const char *name, void *arg1);
extern void InjectionPointDetach(const char *name);
#endif /* INJECTION_POINT_H */
diff --git a/src/backend/utils/misc/injection_point.c b/src/backend/utils/misc/injection_point.c
index 0cf4d51cac..468085e963 100644
--- a/src/backend/utils/misc/injection_point.c
+++ b/src/backend/utils/misc/injection_point.c
@@ -49,6 +49,7 @@ typedef struct InjectionPointEntry
char name[INJ_NAME_MAXLEN]; /* hash key */
char library[INJ_LIB_MAXLEN]; /* library */
char function[INJ_FUNC_MAXLEN]; /* function */
+ int num_args; /* number of arguments */
} InjectionPointEntry;
#define INJECTION_POINT_HASH_INIT_SIZE 16
@@ -61,7 +62,12 @@ typedef struct InjectionPointEntry
typedef struct InjectionPointCacheEntry
{
char name[INJ_NAME_MAXLEN];
- InjectionPointCallback callback;
+ int num_args;
+ union
+ {
+ InjectionPointCallback callback;
+ InjectionPointCallback1Arg callback_1arg;
+ };
} InjectionPointCacheEntry;
static HTAB *InjectionPointCache = NULL;
@@ -73,7 +79,8 @@ static HTAB *InjectionPointCache = NULL;
*/
static void
injection_point_cache_add(const char *name,
- InjectionPointCallback callback)
+ void *callback,
+ int num_args)
{
InjectionPointCacheEntry *entry;
bool found;
@@ -99,6 +106,13 @@ injection_point_cache_add(const char *name,
Assert(!found);
strlcpy(entry->name, name, sizeof(entry->name));
entry->callback = callback;
+ entry->num_args = num_args;
+ if (num_args == 0)
+ entry->callback = (InjectionPointCallback) callback;
+ else if (num_args == 1)
+ entry->callback_1arg = (InjectionPointCallback1Arg) callback;
+ else
+ elog(ERROR, "unsupported number of arguments"); /* not reachable */
}
/*
@@ -123,7 +137,7 @@ injection_point_cache_remove(const char *name)
*
* Retrieve an injection point from the local cache, if any.
*/
-static InjectionPointCallback
+static InjectionPointCacheEntry *
injection_point_cache_get(const char *name)
{
bool found;
@@ -137,7 +151,7 @@ injection_point_cache_get(const char *name)
hash_search(InjectionPointCache, name, HASH_FIND, &found);
if (found)
- return entry->callback;
+ return entry;
return NULL;
}
@@ -186,7 +200,8 @@ InjectionPointShmemInit(void)
void
InjectionPointAttach(const char *name,
const char *library,
- const char *function)
+ const char *function,
+ int num_args)
{
#ifdef USE_INJECTION_POINTS
InjectionPointEntry *entry_by_name;
@@ -223,6 +238,7 @@ InjectionPointAttach(const char *name,
entry_by_name->library[INJ_LIB_MAXLEN - 1] = '\0';
strlcpy(entry_by_name->function, function, sizeof(entry_by_name->function));
entry_by_name->function[INJ_FUNC_MAXLEN - 1] = '\0';
+ entry_by_name->num_args = num_args;
LWLockRelease(InjectionPointLock);
@@ -253,18 +269,18 @@ InjectionPointDetach(const char *name)
}
/*
- * Execute an injection point, if defined.
+ * Workhorse for execution of an injection point, if defined.
*
* Check first the shared hash table, and adapt the local cache depending
* on that as it could be possible that an entry to run has been removed.
*/
-void
-InjectionPointRun(const char *name)
+static inline void
+InjectionPointRunInternal(const char *name, int num_args, void *arg1)
{
#ifdef USE_INJECTION_POINTS
InjectionPointEntry *entry_by_name;
bool found;
- InjectionPointCallback injection_callback;
+ InjectionPointCacheEntry *cache_entry;
LWLockAcquire(InjectionPointLock, LW_SHARED);
entry_by_name = (InjectionPointEntry *)
@@ -282,14 +298,20 @@ InjectionPointRun(const char *name)
return;
}
+ if (entry_by_name->num_args != num_args)
+ elog(ERROR, "incorrect number of arguments in function \"%s\" for injection point \"%s\": defined %d but expected %d",
+ entry_by_name->function, name,
+ entry_by_name->num_args, num_args);
+
/*
* Check if the callback exists in the local cache, to avoid unnecessary
* external loads.
*/
- injection_callback = injection_point_cache_get(name);
- if (injection_callback == NULL)
+ cache_entry = injection_point_cache_get(name);
+ if (cache_entry == NULL)
{
char path[MAXPGPATH];
+ void *injection_callback;
/* not found in local cache, so load and register */
snprintf(path, MAXPGPATH, "%s/%s%s", pkglib_path,
@@ -299,7 +321,7 @@ InjectionPointRun(const char *name)
elog(ERROR, "could not find library \"%s\" for injection point \"%s\"",
path, name);
- injection_callback = (InjectionPointCallback)
+ injection_callback = (void *)
load_external_function(path, entry_by_name->function, false, NULL);
if (injection_callback == NULL)
@@ -307,11 +329,36 @@ InjectionPointRun(const char *name)
entry_by_name->function, path, name);
/* add it to the local cache when found */
- injection_point_cache_add(name, injection_callback);
+ injection_point_cache_add(name, injection_callback, num_args);
+
+ /* and fetch it */
+ cache_entry = injection_point_cache_get(name);
}
- injection_callback(name);
+ if (cache_entry->num_args == 0)
+ cache_entry->callback(name);
+ else if (cache_entry->num_args == 1)
+ cache_entry->callback_1arg(name, arg1);
+ else
+ {
+ Assert(false); /* cannot be reached */
+ }
#else
elog(ERROR, "Injection points are not supported by this build");
#endif
}
+
+/*
+ * Execute an injection point, with no arguments.
+ */
+void
+InjectionPointRun(const char *name)
+{
+ InjectionPointRunInternal(name, 0, NULL);
+}
+/* 1-argument version */
+void
+InjectionPointRun1Arg(const char *name, void *arg1)
+{
+ InjectionPointRunInternal(name, 1, arg1);
+}
diff --git a/src/test/modules/injection_points/expected/injection_points.out b/src/test/modules/injection_points/expected/injection_points.out
index 827456ccc5..7f50ba726d 100644
--- a/src/test/modules/injection_points/expected/injection_points.out
+++ b/src/test/modules/injection_points/expected/injection_points.out
@@ -115,4 +115,29 @@ NOTICE: notice triggered for injection point TestInjectionLog2
(1 row)
+-- 1-argument runs
+SELECT injection_points_run_1arg('TestInjectionLog2', 'blah'); -- error
+ERROR: incorrect number of arguments in function "injection_notice" for injection point "TestInjectionLog2": defined 0 but expected 1
+SELECT injection_points_attach('TestInjectionLogArg1', 'notice_1arg');
+ injection_points_attach
+-------------------------
+
+(1 row)
+
+SELECT injection_points_run('TestInjectionLogArg1'); -- error
+ERROR: incorrect number of arguments in function "injection_notice_1arg" for injection point "TestInjectionLogArg1": defined 1 but expected 0
+SELECT injection_points_run_1arg('TestInjectionLogArg1', 'blah'); -- notice
+NOTICE: notice triggered for injection point TestInjectionLogArg1: blah
+ injection_points_run_1arg
+---------------------------
+
+(1 row)
+
+SELECT injection_points_run_1arg('TestInjectionLogArg1', 'foobar'); -- notice
+NOTICE: notice triggered for injection point TestInjectionLogArg1: foobar
+ injection_points_run_1arg
+---------------------------
+
+(1 row)
+
DROP EXTENSION injection_points;
diff --git a/src/test/modules/injection_points/injection_points--1.0.sql b/src/test/modules/injection_points/injection_points--1.0.sql
index 5944c41716..9b99c17199 100644
--- a/src/test/modules/injection_points/injection_points--1.0.sql
+++ b/src/test/modules/injection_points/injection_points--1.0.sql
@@ -24,6 +24,16 @@ RETURNS void
AS 'MODULE_PATHNAME', 'injection_points_run'
LANGUAGE C STRICT PARALLEL UNSAFE;
+--
+-- injection_points_run_1arg()
+--
+-- Executes the action attached to the injection point.
+--
+CREATE FUNCTION injection_points_run_1arg(IN point_name TEXT, IN arg1 TEXT)
+RETURNS void
+AS 'MODULE_PATHNAME', 'injection_points_run_1arg'
+LANGUAGE C STRICT PARALLEL UNSAFE;
+
--
-- injection_points_detach()
--
diff --git a/src/test/modules/injection_points/injection_points.c b/src/test/modules/injection_points/injection_points.c
index e843e6594f..862f904a75 100644
--- a/src/test/modules/injection_points/injection_points.c
+++ b/src/test/modules/injection_points/injection_points.c
@@ -28,6 +28,7 @@ PG_MODULE_MAGIC;
extern PGDLLEXPORT void injection_error(const char *name);
extern PGDLLEXPORT void injection_notice(const char *name);
+extern PGDLLEXPORT void injection_notice_1arg(const char *name, void *arg1);
/* Set of callbacks available to be attached to an injection point. */
@@ -43,6 +44,13 @@ injection_notice(const char *name)
elog(NOTICE, "notice triggered for injection point %s", name);
}
+void
+injection_notice_1arg(const char *name, void *arg1)
+{
+ const char *str = (const char *) arg1;
+ elog(NOTICE, "notice triggered for injection point %s: %s", name, str);
+}
+
/*
* SQL function for creating an injection point.
*/
@@ -53,15 +61,21 @@ injection_points_attach(PG_FUNCTION_ARGS)
char *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
char *action = text_to_cstring(PG_GETARG_TEXT_PP(1));
char *function;
+ int num_args = 0;
if (strcmp(action, "error") == 0)
function = "injection_error";
else if (strcmp(action, "notice") == 0)
function = "injection_notice";
+ else if (strcmp(action, "notice_1arg") == 0)
+ {
+ function = "injection_notice_1arg";
+ num_args = 1;
+ }
else
elog(ERROR, "incorrect action \"%s\" for injection point creation", action);
- InjectionPointAttach(name, "injection_points", function);
+ InjectionPointAttach(name, "injection_points", function, num_args);
PG_RETURN_VOID();
}
@@ -80,6 +94,21 @@ injection_points_run(PG_FUNCTION_ARGS)
PG_RETURN_VOID();
}
+/*
+ * SQL function for triggering an injection point, 1-argument flavor.
+ */
+PG_FUNCTION_INFO_V1(injection_points_run_1arg);
+Datum
+injection_points_run_1arg(PG_FUNCTION_ARGS)
+{
+ char *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
+ char *arg1 = text_to_cstring(PG_GETARG_TEXT_PP(1));
+
+ INJECTION_POINT_1ARG(name, (void *) arg1);
+
+ PG_RETURN_VOID();
+}
+
/*
* SQL function for dropping an injection point.
*/
diff --git a/src/test/modules/injection_points/sql/injection_points.sql b/src/test/modules/injection_points/sql/injection_points.sql
index 23c7e435ad..eca528508b 100644
--- a/src/test/modules/injection_points/sql/injection_points.sql
+++ b/src/test/modules/injection_points/sql/injection_points.sql
@@ -31,4 +31,11 @@ SELECT injection_points_detach('TestInjectionLog'); -- fails
SELECT injection_points_run('TestInjectionLog2'); -- notice
+-- 1-argument runs
+SELECT injection_points_run_1arg('TestInjectionLog2', 'blah'); -- error
+SELECT injection_points_attach('TestInjectionLogArg1', 'notice_1arg');
+SELECT injection_points_run('TestInjectionLogArg1'); -- error
+SELECT injection_points_run_1arg('TestInjectionLogArg1', 'blah'); -- notice
+SELECT injection_points_run_1arg('TestInjectionLogArg1', 'foobar'); -- notice
+
DROP EXTENSION injection_points;
diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index 8a79ad0943..7659c81c09 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -3607,13 +3607,15 @@ uint32 WaitEventExtensionNew(const char *wait_event_name)
macro:
<programlisting>
INJECTION_POINT(name);
+INJECTION_POINT_1ARG(name, arg1);
</programlisting>
There are a few injection points already declared at strategic points
within the server code. After adding a new injection point the code needs
to be compiled in order for that injection point to be available in the
binary. Add-ins written in C-language can declare injection points in
- their own code using the same macro.
+ their own code using the same macro. It is possible to pass down arguments
+ to callbacks for runtime checks.
</para>
<para>
@@ -3622,12 +3624,14 @@ INJECTION_POINT(name);
<programlisting>
extern void InjectionPointAttach(const char *name,
const char *library,
- const char *function);
+ const char *function,
+ int num_args);
</programlisting>
<literal>name</literal> is the name of the injection point, which when
reached during execution will execute the <literal>function</literal>
- loaded from <literal>library</literal>.
+ loaded from <literal>library</literal>. <literal>num_args</literal> is
+ the number of arguments that are used by the callback.
</para>
<para>
--
2.43.0
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