On Wed, Mar 14, 2018 at 03:27:02PM -0400, Joe Lawrence wrote: > On Tue, Mar 13, 2018 at 04:54:47PM +0100, Petr Mladek wrote: > > The existing API allows to pass a sample data to initialize the shadow > > data. It works well when the data are position independent. But it fails > > miserably when we need to set a pointer to the shadow structure itself. > > > > Unfortunately, we might need to initialize the pointer surprisingly > > often because of struct list_head. It is even worse because the list > > might be hidden in other common structures, for example, struct mutex, > > struct wait_queue_head. > > > > This patch makes the API more safe. A custom init function and data > > are passed to klp_shadow_*alloc() functions instead of the sample data. > > Yup, this looks kinda familiar, I remember tinkering with the same idea > last year [1] before settling on the simpler API. > > [1] https://github.com/torvalds/linux/compare/master...joe-lawrence:shadow_variables_v2_c > > > Note that the init_data are not longer a template for the shadow->data. > > It might point to any data that might be necessary when the init > > function is called. > > I'm not opposed to changing the API, but I was wondering if you had > thought about expanding it as an alternative? > > When working on this last summer, I remember holding onto to some less > than intuitive naming conventions so that I could support a basic API > and an extended API with bells and whistles like this patchset > implements. It didn't seem too difficult to layer the basic API ontop > of one like this (see [1] for example), so maybe that's an option to > keep basic shadow variable usage a little simpler. /two cents I like Petr's new API. It's not a big deal to just pass a couple of NULLs if you don't need the callback. And I prefer fewer functions anyway -- maybe it's my functionitis allergies acting up again. > Perhaps shadow variables are another candidate for some kind of > kselftest? Indeed! -- Josh -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
