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

Josh Poimboeuf
2015-02-09T17:31:37Z

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@redhat.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