diff mbox series

[v6,5/8] kernel: tracepoints: add support for relative references

Message ID 20171227085033.22389-6-ard.biesheuvel@linaro.org
State Superseded
Headers show
Series add support for relative references in special sections | expand

Commit Message

Ard Biesheuvel Dec. 27, 2017, 8:50 a.m. UTC
To avoid the need for relocating absolute references to tracepoint
structures at boot time when running relocatable kernels (which may
take a disproportionate amount of space), add the option to emit
these tables as relative references instead.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

---
 include/linux/tracepoint.h | 19 ++++++--
 kernel/tracepoint.c        | 50 +++++++++++---------
 2 files changed, 42 insertions(+), 27 deletions(-)

-- 
2.11.0

Comments

Steven Rostedt Dec. 28, 2017, 3:42 p.m. UTC | #1
On Wed, 27 Dec 2017 08:50:30 +0000
Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> To avoid the need for relocating absolute references to tracepoint

> structures at boot time when running relocatable kernels (which may

> take a disproportionate amount of space), add the option to emit

> these tables as relative references instead.

> 


I gave this patch a quick skim over. It appears to not modify anything
when CONFIG_HAVE_PREL32_RELOCATIONS is not defined. I haven't
thoroughly reviewed it or tested it. But if it doesn't break anything,
I'm fine giving you an ack.

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>


--  Steve
Ard Biesheuvel Dec. 28, 2017, 11:24 p.m. UTC | #2
On 28 December 2017 at 15:42, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Wed, 27 Dec 2017 08:50:30 +0000

> Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

>

>> To avoid the need for relocating absolute references to tracepoint

>> structures at boot time when running relocatable kernels (which may

>> take a disproportionate amount of space), add the option to emit

>> these tables as relative references instead.

>>

>

> I gave this patch a quick skim over. It appears to not modify anything

> when CONFIG_HAVE_PREL32_RELOCATIONS is not defined. I haven't

> thoroughly reviewed it or tested it. But if it doesn't break anything,

> I'm fine giving you an ack.

>

> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

>


Thank you Steven.

I should mention though (as you don't appear to recall) that an
earlier version of this patch triggered an issue for you

https://marc.info/?l=linux-arch&m=150584374820168&w=2

but I have never managed to reproduce it, neither at the time nor
currently with this v6.


ard@bezzzef:~/linux-2.6$ sudo tools/testing/selftests/ftrace/ftracetest
=== Ftrace unit tests ===
[1] Basic trace file check [PASS]
[2] Basic test for tracers [PASS]
[3] Basic trace clock test [PASS]
[4] Basic event tracing check [PASS]
[5] event tracing - enable/disable with event level files [PASS]
[6] event tracing - restricts events based on pid [PASS]
[7] event tracing - enable/disable with subsystem level files [PASS]
[8] event tracing - enable/disable with top level files [PASS]
[9] ftrace - function graph filters with stack tracer [PASS]
[10] ftrace - function graph filters [PASS]
[11] ftrace - test for function event triggers [PASS]
[12] ftrace - function glob filters [PASS]
[13] ftrace - function pid filters [PASS]
[14] ftrace - function profiler with function tracing [PASS]
[15] ftrace - test reading of set_ftrace_filter [PASS]
[16] ftrace - test for function traceon/off triggers [PASS]
[17] Test creation and deletion of trace instances while setting an event [PASS]
[18] Test creation and deletion of trace instances [PASS]
[19] Kprobe dynamic event - adding and removing [PASS]
[20] Kprobe dynamic event - busy event check [PASS]
[21] Kprobe dynamic event with arguments [PASS]
[22] Kprobes event arguments with types [PASS]
[23] Kprobe event auto/manual naming [PASS]
[24] Kprobe dynamic event with function tracer [PASS]
[25] Kprobe dynamic event - probing module [PASS]
[26] Kretprobe dynamic event with arguments [PASS]
[27] Kretprobe dynamic event with maxactive [PASS]
[28] Register/unregister many kprobe events [PASS]
[29] event trigger - test event enable/disable trigger [PASS]
[30] event trigger - test trigger filter [PASS]
[31] event trigger - test histogram modifiers [PASS]
[32] event trigger - test histogram trigger [PASS]
[33] event trigger - test multiple histogram triggers [PASS]
[34] event trigger - test snapshot-trigger [PASS]
[35] event trigger - test stacktrace-trigger [PASS]
[36] event trigger - test traceon/off trigger [PASS]
[37] (instance)  Basic test for tracers [PASS]
[38] (instance)  Basic trace clock test [PASS]
[39] (instance)  event tracing - enable/disable with event level files [PASS]
[40] (instance)  event tracing - restricts events based on pid [PASS]
[41] (instance)  event tracing - enable/disable with subsystem level
files [PASS]
[42] (instance)  ftrace - test for function event triggers [PASS]
[43] (instance)  ftrace - test for function traceon/off triggers [PASS]
[44] (instance)  event trigger - test event enable/disable trigger [PASS]
[45] (instance)  event trigger - test trigger filter [PASS]
[46] (instance)  event trigger - test histogram modifiers [PASS]
[47] (instance)  event trigger - test histogram trigger [PASS]
[48] (instance)  event trigger - test multiple histogram triggers [PASS]

# of passed:  48
# of failed:  0
# of unresolved:  0
# of untested:  0
# of unsupported:  0
# of xfailed:  0
# of undefined(test bug):  0
diff mbox series

Patch

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a26ffbe09e71..d02bf1a695e8 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -228,6 +228,19 @@  extern void syscall_unregfunc(void);
 		return static_key_false(&__tracepoint_##name.key);	\
 	}
 
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+#define __TRACEPOINT_ENTRY(name)					 \
+	asm("	.section \"__tracepoints_ptrs\", \"a\"		     \n" \
+	    "	.balign 4					     \n" \
+	    "	.long " VMLINUX_SYMBOL_STR(__tracepoint_##name) " - .\n" \
+	    "	.previous					     \n")
+#else
+#define __TRACEPOINT_ENTRY(name)					 \
+	static struct tracepoint * const __tracepoint_ptr_##name __used	 \
+	__attribute__((section("__tracepoints_ptrs"))) =		 \
+		&__tracepoint_##name
+#endif
+
 /*
  * We have no guarantee that gcc and the linker won't up-align the tracepoint
  * structures, so we create an array of pointers that will be used for iteration
@@ -237,11 +250,9 @@  extern void syscall_unregfunc(void);
 	static const char __tpstrtab_##name[]				 \
 	__attribute__((section("__tracepoints_strings"))) = #name;	 \
 	struct tracepoint __tracepoint_##name				 \
-	__attribute__((section("__tracepoints"))) =			 \
+	__attribute__((section("__tracepoints"), used)) =		 \
 		{ __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
-	static struct tracepoint * const __tracepoint_ptr_##name __used	 \
-	__attribute__((section("__tracepoints_ptrs"))) =		 \
-		&__tracepoint_##name;
+	__TRACEPOINT_ENTRY(name);
 
 #define DEFINE_TRACE(name)						\
 	DEFINE_TRACE_FN(name, NULL, NULL);
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 685c50ae6300..05649fef106c 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -327,6 +327,28 @@  int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
 }
 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
 
+static void for_each_tracepoint_range(struct tracepoint * const *begin,
+		struct tracepoint * const *end,
+		void (*fct)(struct tracepoint *tp, void *priv),
+		void *priv)
+{
+	if (!begin)
+		return;
+
+	if (IS_ENABLED(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)) {
+		const int *iter;
+
+		for (iter = (const int *)begin; iter < (const int *)end; iter++)
+			fct((struct tracepoint *)((unsigned long)iter + *iter),
+			    priv);
+	} else {
+		struct tracepoint * const *iter;
+
+		for (iter = begin; iter < end; iter++)
+			fct(*iter, priv);
+	}
+}
+
 #ifdef CONFIG_MODULES
 bool trace_module_has_bad_taint(struct module *mod)
 {
@@ -391,15 +413,9 @@  EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
  * Ensure the tracer unregistered the module's probes before the module
  * teardown is performed. Prevents leaks of probe and data pointers.
  */
-static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
-		struct tracepoint * const *end)
+static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
 {
-	struct tracepoint * const *iter;
-
-	if (!begin)
-		return;
-	for (iter = begin; iter < end; iter++)
-		WARN_ON_ONCE((*iter)->funcs);
+	WARN_ON_ONCE(tp->funcs);
 }
 
 static int tracepoint_module_coming(struct module *mod)
@@ -450,8 +466,9 @@  static void tracepoint_module_going(struct module *mod)
 			 * Called the going notifier before checking for
 			 * quiescence.
 			 */
-			tp_module_going_check_quiescent(mod->tracepoints_ptrs,
-				mod->tracepoints_ptrs + mod->num_tracepoints);
+			for_each_tracepoint_range(mod->tracepoints_ptrs,
+				mod->tracepoints_ptrs + mod->num_tracepoints,
+				tp_module_going_check_quiescent, NULL);
 			break;
 		}
 	}
@@ -503,19 +520,6 @@  static __init int init_tracepoints(void)
 __initcall(init_tracepoints);
 #endif /* CONFIG_MODULES */
 
-static void for_each_tracepoint_range(struct tracepoint * const *begin,
-		struct tracepoint * const *end,
-		void (*fct)(struct tracepoint *tp, void *priv),
-		void *priv)
-{
-	struct tracepoint * const *iter;
-
-	if (!begin)
-		return;
-	for (iter = begin; iter < end; iter++)
-		fct(*iter, priv);
-}
-
 /**
  * for_each_kernel_tracepoint - iteration on all kernel tracepoints
  * @fct: callback