linux-kernel - [PATCH 2/2] livepatch: disable/enable_patch manners for interdependent patches

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Date:	Wed, 21 Jan 2015 17:07:42 +0800
From:	Li Bin <huawei.libin@...wei.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>, Jiri Slaby <jslaby@...e.cz>,
	Miroslav Benes <mbenes@...e.cz>
CC:	<live-patching@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lizefan@...wei.com>, <guohanjun@...wei.com>,
	<zhangdianfang@...wei.com>, <xiexiuqi@...wei.com>
Subject: [PATCH 2/2] livepatch: disable/enable_patch manners for interdependent patches

for disable_patch:
The patch is unallowed to be disabled if one patch after has
dependencies with it and has been enabled.

for enable_patch:
The patch is unallowed to be enabled if one patch before has
dependencies with it and has been disabled.

Signed-off-by: Li Bin <huawei.libin@...wei.com>
---
 kernel/livepatch/core.c |   60 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 7861ed2..a12a31c 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -114,6 +114,21 @@ static bool klp_is_patch_registered(struct klp_patch *patch)
 	return false;
 }
 
+static bool klp_func_in_patch(struct klp_func *kfunc, struct klp_patch *patch)
+{
+	struct klp_object *obj;
+	struct klp_func *func;
+
+	for (obj = patch->objs; obj->funcs; obj++) {
+		for (func = obj->funcs; func->old_name; func++) {
+			if (kfunc->old_addr == func->old_addr) {
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
 static bool klp_initialized(void)
 {
 	return klp_root_kobj;
@@ -466,8 +481,31 @@ unregister:
 static int __klp_disable_patch(struct klp_patch *patch)
 {
 	struct klp_object *obj;
+	struct klp_patch *temp;
+	struct klp_func *func;
 	int ret;
 
+	/*
+	 * the patch is unallowed to be disabled if one patch
+	 * after has dependencies with it and has been enabled.
+	 */
+	for (temp = list_next_entry(patch, list);
+			&temp->list != &klp_patches;
+			temp = list_next_entry(temp, list)) {
+		if (temp->state != KLP_ENABLED)
+			continue;
+
+		for (obj = patch->objs; obj->funcs; obj++) {
+			for (func = obj->funcs; func->old_name; func++) {
+				if (klp_func_in_patch(func, temp)) {
+					pr_err("this patch depends on '%s', please disable it firstly\n",
+						   temp->mod->name);
+					return -EBUSY;
+				}
+			}
+		}
+	}
+
 	pr_notice("disabling patch '%s'\n", patch->mod->name);
 
 	for (obj = patch->objs; obj->funcs; obj++) {
@@ -519,11 +557,33 @@ EXPORT_SYMBOL_GPL(klp_disable_patch);
 static int __klp_enable_patch(struct klp_patch *patch)
 {
 	struct klp_object *obj;
+	struct klp_patch *temp;
+	struct klp_func *func;
 	int ret;
 
 	if (WARN_ON(patch->state != KLP_DISABLED))
 		return -EINVAL;
 
+	/*
+	 * the patch is unallowed to be enabled if one patch
+	 * before has dependencies with it and has been disabled.
+	 */
+	for (temp = list_first_entry(&klp_patches, struct klp_patch, list);
+			temp != patch; temp = list_next_entry(temp, list)) {
+		if (temp->state != KLP_DISABLED)
+			continue;
+
+		for (obj = patch->objs; obj->funcs; obj++) {
+			for (func = obj->funcs; func->old_name; func++) {
+				if (klp_func_in_patch(func, temp)) {
+					pr_err("this patch depends on '%s', please enable it firstly\n",
+						   temp->mod->name);
+					return -EBUSY;
+				}
+			}
+		}
+	}
+
 	pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
 	add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
 
-- 
1.7.1

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