linux-kernel - [RFC PATCH 4/9] livepatch: get function sizes

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Date:	Mon,  9 Feb 2015 11:31:16 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Seth Jennings <sjenning@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 4/9] livepatch: get function sizes

For the consistency model we'll need to know the sizes of the old and
new functions to determine if they're on any task stacks.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 include/linux/livepatch.h |  3 +++
 kernel/livepatch/core.c   | 19 ++++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 22a67d1..0e65b4d 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -37,6 +37,8 @@
  * @kobj:	kobject for sysfs resources
  * @state:	tracks function-level patch application state
  * @stack_node:	list node for klp_ops func_stack list
+ * @old_size:	size of the old function
+ * @new_size:	size of the new function
  * @patched:	the func has been added to the klp_ops list
  */
 struct klp_func {
@@ -56,6 +58,7 @@ struct klp_func {
 	/* internal */
 	struct kobject kobj;
 	struct list_head stack_node;
+	unsigned long old_size, new_size;
 	int patched;
 };
 
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 0c09eba..85d4ef7 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -197,8 +197,25 @@ static int klp_find_verify_func_addr(struct klp_object *obj,
 	else
 		ret = klp_verify_vmlinux_symbol(func->old_name,
 						func->old_addr);
+	if (ret)
+		return ret;
 
-	return ret;
+	ret = kallsyms_lookup_size_offset(func->old_addr, &func->old_size,
+					  NULL);
+	if (!ret) {
+		pr_err("kallsyms lookup failed for '%s'\n", func->old_name);
+		return -EINVAL;
+	}
+
+	ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
+					  &func->new_size, NULL);
+	if (!ret) {
+		pr_err("kallsyms lookup failed for '%s' replacement\n",
+		       func->old_name);
+		return -EINVAL;
+	}
+
+	return 0;
 }
 
 /*
-- 
2.1.0

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