Commit 79ac6ef5 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Steven Rostedt
Browse files

tracing: Use kstrdup_const instead of private implementation 

The kernel now has kstrdup_const/kfree_const for reusing .rodata
(typically string literals) when possible; there's no reason to
duplicate that logic in the tracing system. Moreover, as the comment
above core_kernel_data states, it may not always return true for
.rodata - that is for example the case on x86_64, where we thus end up
kstrdup'ing all the passed-in strings.

Arguably, testing for .rodata explicitly (as kstrdup_const does) is
also more correct: I don't think one is supposed to be able to change
the name after creating the event_subsystem by passing the address of
a static char (but non-const) array.

Link: http://lkml.kernel.org/r/1441833841-12955-1-git-send-email-linux@rasmusvillemoes.dk



Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 37aea98b

kernel/trace/trace_events.c

+8 −16
Original line number Diff line number Diff line
@@ -38,21 +38,19 @@ static LIST_HEAD(ftrace_common_fields); 
static struct kmem_cache *field_cachep;

static struct kmem_cache *file_cachep;



#define SYSTEM_FL_FREE_NAME		(1 << 31)



static inline int system_refcount(struct event_subsystem *system)

{

	return system->ref_count & ~SYSTEM_FL_FREE_NAME;

	return system->ref_count;

}



static int system_refcount_inc(struct event_subsystem *system)

{

	return (system->ref_count++) & ~SYSTEM_FL_FREE_NAME;

	return system->ref_count++;

}



static int system_refcount_dec(struct event_subsystem *system)

{

	return (--system->ref_count) & ~SYSTEM_FL_FREE_NAME;

	return --system->ref_count;

}



/* Double loops, do not use break, only goto's work */
@@ -461,8 +459,7 @@ static void __put_system(struct event_subsystem *system) 
		kfree(filter->filter_string);

		kfree(filter);

	}

	if (system->ref_count & SYSTEM_FL_FREE_NAME)

		kfree(system->name);

	kfree_const(system->name);

	kfree(system);

}
@@ -1493,13 +1490,9 @@ create_new_subsystem(const char *name) 
	system->ref_count = 1;



	/* Only allocate if dynamic (kprobes and modules) */

	if (!core_kernel_data((unsigned long)name)) {

		system->ref_count |= SYSTEM_FL_FREE_NAME;

		system->name = kstrdup(name, GFP_KERNEL);

	system->name = kstrdup_const(name, GFP_KERNEL);

	if (!system->name)

		goto out_free;

	} else

		system->name = name;



	system->filter = NULL;
@@ -1512,8 +1505,7 @@ create_new_subsystem(const char *name) 
	return system;



 out_free:

	if (system->ref_count & SYSTEM_FL_FREE_NAME)

		kfree(system->name);

	kfree_const(system->name);

	kfree(system);

	return NULL;

}

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