[POC][RFC][PATCH 2/2 v2] tracepoints: Implement it with dynamic functions

From: Steven Rostedt
Date: Mon Oct 08 2018 - 20:54:18 EST

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From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
include/linux/tracepoint-defs.h | 3 ++
include/linux/tracepoint.h | 65 ++++++++++++++++++++++-----------
include/trace/define_trace.h | 14 +++----
kernel/tracepoint.c | 29 +++++++++++++--
4 files changed, 79 insertions(+), 32 deletions(-)

diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 22c5a46e9693..a9d267be98de 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -11,6 +11,8 @@
#include <linux/atomic.h>
#include <linux/static_key.h>

+struct dynfunc_struct;
+
struct trace_print_flags {
unsigned long mask;
const char *name;
@@ -30,6 +32,7 @@ struct tracepoint_func {
struct tracepoint {
const char *name; /* Tracepoint name */
struct static_key key;
+ struct dynfunc_struct *dynfunc;
int (*regfunc)(void);
void (*unregfunc)(void);
struct tracepoint_func __rcu *funcs;
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 041f7e56a289..800c1b025e1f 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -21,6 +21,7 @@
#include <linux/cpumask.h>
#include <linux/rcupdate.h>
#include <linux/tracepoint-defs.h>
+#include <linux/jump_function.h>

struct module;
struct tracepoint;
@@ -94,7 +95,9 @@ extern int syscall_regfunc(void);
extern void syscall_unregfunc(void);
#endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */

+#ifndef PARAMS
#define PARAMS(args...) args
+#endif

#define TRACE_DEFINE_ENUM(x)
#define TRACE_DEFINE_SIZEOF(x)
@@ -138,12 +141,11 @@ extern void syscall_unregfunc(void);
* as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
* "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
*/
-#define __DO_TRACE(tp, proto, args, cond, rcuidle) \
+#define __DO_TRACE(name, proto, args, cond, rcuidle) \
do { \
struct tracepoint_func *it_func_ptr; \
- void *it_func; \
- void *__data; \
int __maybe_unused idx = 0; \
+ void *__data; \
\
if (!(cond)) \
return; \
@@ -163,14 +165,11 @@ extern void syscall_unregfunc(void);
rcu_irq_enter_irqson(); \
} \
\
- it_func_ptr = rcu_dereference_raw((tp)->funcs); \
- \
+ it_func_ptr = \
+ rcu_dereference_raw((&__tracepoint_##name)->funcs); \
if (it_func_ptr) { \
- do { \
- it_func = (it_func_ptr)->func; \
- __data = (it_func_ptr)->data; \
- ((void(*)(proto))(it_func))(args); \
- } while ((++it_func_ptr)->func); \
+ __data = (it_func_ptr)->data; \
+ dynfunc_tp_func_##name(args); \
} \
\
if (rcuidle) { \
@@ -186,7 +185,7 @@ extern void syscall_unregfunc(void);
static inline void trace_##name##_rcuidle(proto) \
{ \
if (static_key_false(&__tracepoint_##name.key)) \
- __DO_TRACE(&__tracepoint_##name, \
+ __DO_TRACE(name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), 1); \
@@ -208,11 +207,13 @@ extern void syscall_unregfunc(void);
* poking RCU a bit.
*/
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
+ DECLARE_DYNAMIC_FUNCTION(tp_func_##name, PARAMS(data_proto), \
+ PARAMS(data_args)); \
extern struct tracepoint __tracepoint_##name; \
static inline void trace_##name(proto) \
{ \
if (static_key_false(&__tracepoint_##name.key)) \
- __DO_TRACE(&__tracepoint_##name, \
+ __DO_TRACE(name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), 0); \
@@ -271,21 +272,43 @@ extern void syscall_unregfunc(void);
* structures, so we create an array of pointers that will be used for iteration
* on the tracepoints.
*/
-#define DEFINE_TRACE_FN(name, reg, unreg) \
+#define DEFINE_TRACE_FN(name, reg, unreg, proto, args) \
static const char __tpstrtab_##name[] \
__attribute__((section("__tracepoints_strings"))) = #name; \
struct tracepoint __tracepoint_##name \
__attribute__((section("__tracepoints"), used)) = \
- { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
- __TRACEPOINT_ENTRY(name);
+ { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, \
+ &___dyn_func__tp_func_##name, reg, unreg, NULL }; \
+ __TRACEPOINT_ENTRY(name); \
+ int __tracepoint_iter_##name(void *__data, proto) \
+ { \
+ struct tracepoint_func *it_func_ptr; \
+ void *it_func; \
+ \
+ it_func_ptr = \
+ rcu_dereference_raw((&__tracepoint_##name)->funcs); \
+ do { \
+ it_func = (it_func_ptr)->func; \
+ __data = (it_func_ptr)->data; \
+ ((void(*)(void *, proto))(it_func))(__data, args); \
+ } while ((++it_func_ptr)->func); \
+ return 0; \
+ } \
+ DEFINE_DYNAMIC_FUNCTION(tp_func_##name, __tracepoint_iter_##name, \
+ PARAMS(void *__data, proto))

-#define DEFINE_TRACE(name) \
- DEFINE_TRACE_FN(name, NULL, NULL);
+#define DEFINE_TRACE(name, proto, args) \
+ DEFINE_TRACE_FN(name, NULL, NULL, PARAMS(proto), PARAMS(args));

#define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
- EXPORT_SYMBOL_GPL(__tracepoint_##name)
+ EXPORT_SYMBOL_GPL(__tracepoint_##name); \
+ EXPORT_SYMBOL_GPL(___dyn_func__tp_func_##name); \
+ EXPORT_SYMBOL_GPL(dynfunc_tp_func_##name)
#define EXPORT_TRACEPOINT_SYMBOL(name) \
- EXPORT_SYMBOL(__tracepoint_##name)
+ EXPORT_SYMBOL(__tracepoint_##name); \
+ EXPORT_SYMBOL(___dyn_func__tp_func_##name); \
+ EXPORT_SYMBOL(dynfunc_tp_func_##name)
+

#else /* !TRACEPOINTS_ENABLED */
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
@@ -314,8 +337,8 @@ extern void syscall_unregfunc(void);
return false; \
}

-#define DEFINE_TRACE_FN(name, reg, unreg)
-#define DEFINE_TRACE(name)
+#define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
+#define DEFINE_TRACE(name, proto, args)
#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
#define EXPORT_TRACEPOINT_SYMBOL(name)

diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index cb30c5532144..c19aea44efb2 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -25,7 +25,7 @@

#undef TRACE_EVENT
#define TRACE_EVENT(name, proto, args, tstruct, assign, print) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef TRACE_EVENT_CONDITION
#define TRACE_EVENT_CONDITION(name, proto, args, cond, tstruct, assign, print) \
@@ -39,24 +39,24 @@
#undef TRACE_EVENT_FN
#define TRACE_EVENT_FN(name, proto, args, tstruct, \
assign, print, reg, unreg) \
- DEFINE_TRACE_FN(name, reg, unreg)
+ DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))

#undef TRACE_EVENT_FN_COND
#define TRACE_EVENT_FN_COND(name, proto, args, cond, tstruct, \
assign, print, reg, unreg) \
- DEFINE_TRACE_FN(name, reg, unreg)
+ DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))

#undef DEFINE_EVENT
#define DEFINE_EVENT(template, name, proto, args) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef DEFINE_EVENT_FN
#define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg) \
- DEFINE_TRACE_FN(name, reg, unreg)
+ DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))

#undef DEFINE_EVENT_PRINT
#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef DEFINE_EVENT_CONDITION
#define DEFINE_EVENT_CONDITION(template, name, proto, args, cond) \
@@ -64,7 +64,7 @@

#undef DECLARE_TRACE
#define DECLARE_TRACE(name, proto, args) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef TRACE_INCLUDE
#undef __TRACE_INCLUDE
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index bf2c06ef9afc..b141f25d4b3a 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -140,7 +140,7 @@ static void debug_print_probes(struct tracepoint_func *funcs)

static struct tracepoint_func *
func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
- int prio)
+ int prio, int *tot_probes)
{
struct tracepoint_func *old, *new;
int nr_probes = 0;
@@ -183,11 +183,12 @@ func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
new[nr_probes + 1].func = NULL;
*funcs = new;
debug_print_probes(*funcs);
+ *tot_probes = nr_probes + 1;
return old;
}

static void *func_remove(struct tracepoint_func **funcs,
- struct tracepoint_func *tp_func)
+ struct tracepoint_func *tp_func, int *left)
{
int nr_probes = 0, nr_del = 0, i;
struct tracepoint_func *old, *new;
@@ -241,6 +242,7 @@ static int tracepoint_add_func(struct tracepoint *tp,
struct tracepoint_func *func, int prio)
{
struct tracepoint_func *old, *tp_funcs;
+ int probes = 0;
int ret;

if (tp->regfunc && !static_key_enabled(&tp->key)) {
@@ -251,7 +253,7 @@ static int tracepoint_add_func(struct tracepoint *tp,

tp_funcs = rcu_dereference_protected(tp->funcs,
lockdep_is_held(&tracepoints_mutex));
- old = func_add(&tp_funcs, func, prio);
+ old = func_add(&tp_funcs, func, prio, &probes);
if (IS_ERR(old)) {
WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
return PTR_ERR(old);
@@ -266,6 +268,15 @@ static int tracepoint_add_func(struct tracepoint *tp,
rcu_assign_pointer(tp->funcs, tp_funcs);
if (!static_key_enabled(&tp->key))
static_key_slow_inc(&tp->key);
+
+ if (probes == 1) {
+// printk("make direct call to %pS\n", tp_funcs->func);
+ assign_dynamic_function(tp->dynfunc, tp_funcs->func);
+ } else {
+// printk("[%d] make call to iterator %pS\n", probes, tp->dynfunc->func);
+ assign_dynamic_function(tp->dynfunc, tp->dynfunc->func);
+ }
+
release_probes(old);
return 0;
}
@@ -280,10 +291,11 @@ static int tracepoint_remove_func(struct tracepoint *tp,
struct tracepoint_func *func)
{
struct tracepoint_func *old, *tp_funcs;
+ int probes_left = 0;

tp_funcs = rcu_dereference_protected(tp->funcs,
lockdep_is_held(&tracepoints_mutex));
- old = func_remove(&tp_funcs, func);
+ old = func_remove(&tp_funcs, func, &probes_left);
if (IS_ERR(old)) {
WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
return PTR_ERR(old);
@@ -297,6 +309,15 @@ static int tracepoint_remove_func(struct tracepoint *tp,
if (static_key_enabled(&tp->key))
static_key_slow_dec(&tp->key);
}
+
+ if (probes_left == 1) {
+// printk("make direct call to %pS\n", tp_funcs->func);
+ assign_dynamic_function(tp->dynfunc, tp_funcs->func);
+ } else {
+// printk("[%d] make call to iterator %pS\n", probes_left, tp->dynfunc->func);
+ assign_dynamic_function(tp->dynfunc, tp->dynfunc->func);
+ }
+
rcu_assign_pointer(tp->funcs, tp_funcs);
release_probes(old);
return 0;
--
2.19.0

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