linux-kernel - [PATCH -tip 2/4]Text Edit Lock - kprobes architecture independent support (v3)

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Date:	Fri, 06 Mar 2009 10:36:38 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH -tip 2/4]Text Edit Lock - kprobes architecture independent
 support (v3)

From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>

Use the mutual exclusion provided by the text edit lock in the kprobes code. It
allows coherent manipulation of the kernel code by other subsystems.

Changelog:

Move the kernel_text_lock/unlock out of the for loops.
Use text_mutex directly instead of a function.
Remove whitespace modifications.

(note : kprobes_mutex is always taken outside of text_mutex)

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Acked-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@...hat.com>
CC: ananth@...ibm.com
CC: anil.s.keshavamurthy@...el.com
CC: davem@...emloft.net
CC: Roel Kluin <12o3l@...cali.nl>
---
 kernel/kprobes.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

Index: 2.6.29-rc7/kernel/kprobes.c
===================================================================
--- 2.6.29-rc7.orig/kernel/kprobes.c
+++ 2.6.29-rc7/kernel/kprobes.c
@@ -43,6 +43,7 @@
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
 #include <linux/kdebug.h>
+#include <linux/memory.h>

 #include <asm-generic/sections.h>
 #include <asm/cacheflush.h>
@@ -699,9 +700,10 @@ int __kprobes register_kprobe(struct kpr
 		goto out;
 	}

+	mutex_lock(&text_mutex);
 	ret = arch_prepare_kprobe(p);
 	if (ret)
-		goto out;
+		goto out_unlock_text;

 	INIT_HLIST_NODE(&p->hlist);
 	hlist_add_head_rcu(&p->hlist,
@@ -710,6 +712,8 @@ int __kprobes register_kprobe(struct kpr
 	if (kprobe_enabled)
 		arch_arm_kprobe(p);

+out_unlock_text:
+	mutex_unlock(&text_mutex);
 out:
 	mutex_unlock(&kprobe_mutex);

@@ -746,8 +750,11 @@ valid_p:
 		 * enabled and not gone - otherwise, the breakpoint would
 		 * already have been removed. We save on flushing icache.
 		 */
-		if (kprobe_enabled && !kprobe_gone(old_p))
+		if (kprobe_enabled && !kprobe_gone(old_p)) {
+			mutex_lock(&text_mutex);
 			arch_disarm_kprobe(p);
+			mutex_unlock(&text_mutex);
+		}
 		hlist_del_rcu(&old_p->hlist);
 	} else {
 		if (p->break_handler && !kprobe_gone(p))
@@ -1280,12 +1287,14 @@ static void __kprobes enable_all_kprobes
 	if (kprobe_enabled)
 		goto already_enabled;

+	mutex_lock(&text_mutex);
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
 		hlist_for_each_entry_rcu(p, node, head, hlist)
 			if (!kprobe_gone(p))
 				arch_arm_kprobe(p);
 	}
+	mutex_unlock(&text_mutex);

 	kprobe_enabled = true;
 	printk(KERN_INFO "Kprobes globally enabled\n");
@@ -1310,6 +1319,7 @@ static void __kprobes disable_all_kprobe

 	kprobe_enabled = false;
 	printk(KERN_INFO "Kprobes globally disabled\n");
+	mutex_lock(&text_mutex);
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
 		hlist_for_each_entry_rcu(p, node, head, hlist) {
@@ -1318,6 +1328,7 @@ static void __kprobes disable_all_kprobe
 		}
 	}

+	mutex_unlock(&text_mutex);
 	mutex_unlock(&kprobe_mutex);
 	/* Allow all currently running kprobes to complete */
 	synchronize_sched();
-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com


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