linux-kernel - [RFC PATCH v2 16/18] livepatch: store function sizes

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Date:	Thu, 28 Apr 2016 15:44:47 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Jessica Yu <jeyu@...hat.com>, Jiri Kosina <jikos@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org, Vojtech Pavlik <vojtech@...e.com>,
	Jiri Slaby <jslaby@...e.cz>, Petr Mladek <pmladek@...e.com>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [RFC PATCH v2 16/18] livepatch: store 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 the stacks of any tasks.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 include/linux/livepatch.h |  3 +++
 kernel/livepatch/core.c   | 16 ++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 9ba26c5..c38c694 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -37,6 +37,8 @@
  * @old_addr:	the address of the function being patched
  * @kobj:	kobject for sysfs resources
  * @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 {
 	unsigned long old_addr;
 	struct kobject kobj;
 	struct list_head stack_node;
+	unsigned long old_size, new_size;
 	bool patched;
 };
 
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index f28504d..aa3dbdf 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -577,6 +577,22 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 					     &func->old_addr);
 		if (ret)
 			return ret;
+
+		ret = kallsyms_lookup_size_offset(func->old_addr,
+						  &func->old_size, NULL);
+		if (!ret) {
+			pr_err("kallsyms size lookup failed for '%s'\n",
+			       func->old_name);
+			return -ENOENT;
+		}
+
+		ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
+						  &func->new_size, NULL);
+		if (!ret) {
+			pr_err("kallsyms size lookup failed for '%s' replacement\n",
+			       func->old_name);
+			return -ENOENT;
+		}
 	}
 
 	return 0;
-- 
2.4.11