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Commit 46e0c9be authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Linus Torvalds
Browse files

kernel: tracepoints: add support for relative references 

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.

Link: http://lkml.kernel.org/r/20180704083651.24360-7-ard.biesheuvel@linaro.org


Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Acked-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morris <james.morris@microsoft.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Nicolas Pitre <nico@linaro.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c9d8b55f

include/linux/tracepoint.h

+15 −4
Original line number Diff line number Diff line
@@ -249,6 +249,19 @@ 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 	__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
@@ -258,11 +271,9 @@ 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);

kernel/tracepoint.c

+26 −23
Original line number Diff line number Diff line
@@ -371,6 +371,27 @@ 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(offset_to_ptr(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)

{
@@ -435,15 +456,9 @@ 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)
@@ -494,8 +509,9 @@ 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;

		}

	}
@@ -547,19 +563,6 @@ 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