Re: livepatch: reuse module loader code to write relocations

[Jessica Yu]

+++ Petr Mladek [17/12/15 16:45 +0100]:
> On Wed 2015-12-16 00:40:48, Jessica Yu wrote:
> > Turns out the string parsing stuff, even with the help of lib/string.c, doesn't
> > look very pretty. As I'm working on v3, I'm starting to think having
> > klp_write_object_relocations() loop simply through all the elf sections might
> > not be a good idea. Let me explain.
> >
> > I don't like the amount of string manipulation code that would potentially come
> > with this change. Even with a string as simple as ".klp.rela.objname", we'll
> > end up with a bunch of kstrdup's/kmalloc's and kfree's (unless we modify and
> > chop the section name string in place, which I don't think we should do) that
> > are going to be required at every iteration of the loop, all just to be able to
> > call strcmp() and see if we're dealing with a klp rela section that belongs to
> > the object in question. This also leads to more complicated error handling.
>
> I do not think that we need to allocate and free buffers every time
> we compare a substring.
>
> One possibility is to find the position of the substring using
> strchr(). Then you could compare it using strncmp() and pass there
> the pointer where the substring begins.

Hm, yes you're right. Specifically, it looks like strcspn() would also
be useful for this situation (i.e. calculate the length of a substring
that does not contain certain characters); combined with strncmp(),
this should make the string code much simpler, and no more buffer
allocating/freeing. :-)

Jessica
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