Commit a0060505 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jessica Yu
Browse files

module: use RCU to synchronize find_module 



Allow for a RCU-sched critical section around find_module, following
the lower level find_module_all helper, and switch the two callers
outside of module.c to use such a RCU-sched critical section instead
of module_mutex.

Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Acked-by: default avatarMiroslav Benes <mbenes@suse.cz>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJessica Yu <jeyu@kernel.org>
parent 089049f6

include/linux/module.h

+1 −1
Original line number Diff line number Diff line
@@ -586,7 +586,7 @@ static inline bool within_module(unsigned long addr, const struct module *mod) 
	return within_module_init(addr, mod) || within_module_core(addr, mod);

}



/* Search for module by name: must hold module_mutex. */

/* Search for module by name: must be in a RCU-sched critical section. */

struct module *find_module(const char *name);



struct symsearch {

kernel/livepatch/core.c

+3 −2
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/moduleloader.h>

#include <linux/completion.h>

#include <linux/memory.h>

#include <linux/rcupdate.h>

#include <asm/cacheflush.h>

#include "core.h"

#include "patch.h"
@@ -57,7 +58,7 @@ static void klp_find_object_module(struct klp_object *obj) 
	if (!klp_is_module(obj))

		return;



	mutex_lock(&module_mutex);

	rcu_read_lock_sched();

	/*

	 * We do not want to block removal of patched modules and therefore

	 * we do not take a reference here. The patches are removed by
@@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object *obj) 
	if (mod && mod->klp_alive)

		obj->mod = mod;



	mutex_unlock(&module_mutex);

	rcu_read_unlock_sched();

}



static bool klp_initialized(void)

kernel/module.c

+0 −1
Original line number Diff line number Diff line
@@ -668,7 +668,6 @@ static struct module *find_module_all(const char *name, size_t len, 


struct module *find_module(const char *name)

{

	module_assert_mutex();

	return find_module_all(name, strlen(name), false);

}

kernel/trace/trace_kprobe.c

+2 −2
Original line number Diff line number Diff line
@@ -124,9 +124,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) 
	if (!p)

		return true;

	*p = '\0';

	mutex_lock(&module_mutex);

	rcu_read_lock_sched();

	ret = !!find_module(tk->symbol);

	mutex_unlock(&module_mutex);

	rcu_read_unlock_sched();

	*p = ':';



	return ret;