Re: [RFC PATCH 3/9] livepatch: move patching functions into patch.c

Miroslav Benes
2015-02-13T14:28:34Z

On Mon, 9 Feb 2015, Josh Poimboeuf wrote:

> Move functions related to the actual patching of functions and objects
> into a new patch.c file.

I am definitely for splitting the code to several different files.
Otherwise it would be soon unmanageable. However I don't know if this
patch is the best possible. Maybe it is just nitpicking so let's not spend
too much time on this :)

Without this patch there are several different groups of functions in
core.c:
1. infrastructure such as global variables, klp_init and some helper
functions
2. (un)registration and initialization of the patch
3. enable/disable with patching/unpatching, ftrace handler
4. sysfs code
5. module notifier
6. relocations

I would move sysfs code away to separate file.

If we decide to move patching code I think it would make sense to move
enable/disable functions along with it. Or perhaps __klp_enable_patch and
__klp_disable_patch only. It is possible though that the result would be
much worse.

Or we can move some other group of functions...

[...]

> diff --git a/kernel/livepatch/patch.h b/kernel/livepatch/patch.h
> new file mode 100644
> index 0000000..bb34bd3
> --- /dev/null
> +++ b/kernel/livepatch/patch.h
> @@ -0,0 +1,25 @@
> +#include <linux/livepatch.h>
> +
> +/**
> + * struct klp_ops - structure for tracking registered ftrace ops structs
> + *
> + * A single ftrace_ops is shared between all enabled replacement functions
> + * (klp_func structs) which have the same old_addr. This allows the switch
> + * between function versions to happen instantaneously by updating the klp_ops
> + * struct's func_stack list. The winner is the klp_func at the top of the
> + * func_stack (front of the list).
> + *
> + * @node: node for the global klp_ops list
> + * @func_stack: list head for the stack of klp_func's (active func is on top)
> + * @fops: registered ftrace ops struct
> + */
> +struct klp_ops {
> + struct list_head node;
> + struct list_head func_stack;
> + struct ftrace_ops fops;
> +};
> +
> +struct klp_ops *klp_find_ops(unsigned long old_addr);
> +
> +extern int klp_patch_object(struct klp_object *obj);
> +extern void klp_unpatch_object(struct klp_object *obj);

Is there a reason why klp_find_ops is not extern and the other two
functions are? I think it is redundant and it is better to be consistent.

Regards,
Miroslav