create-diff-object fails to find new static functions in some cases

[euspectre]

If a source patch adds a global function foo() that takes a callback as an argument, and a static function bar() that is used as such callback, create-diff-object may fail to find bar() in some cases. Namely, - if foo() is defined in one source file, but called in another source file where bar() is defined.

Example:
new-static-callback.patch

create-diff-object complains as follows:

base.o: new function: foo
meminfo.o: changed function: meminfo_proc_open
meminfo.o: new function: bar
/usr/libexec/kpatch/create-diff-object: ERROR: meminfo.o: kpatch_create_intermediate_sections: 2485: lookup_local_symbol bar needed for .text.meminfo_proc_open
ERROR: 1 error(s) encountered.

A workaround is simple: just make the callback bar() non-static. The binary patch is built successfully and works OK in that case, so this issue is not that critical.

I guess, I probably missed some special case when preparing the patch for #755, but I haven't dug into this yet.

x86_64, OS: Virtuozzo 7, kpatch 0.5.

[jpoimboe]

I'm in the middle of refactoring the dynrela code anyway, so I can take a look at this one.

[jpoimboe]

It's an easy fix, may_need_dynrela() just needs to add a check for new symbols in the function pointer check.

[jpoimboe]

A workaround is simple: just make the callback bar() non-static. The binary patch is built successfully and works OK in that case, so this issue is not that critical.

BTW, this indicates another bug related to #755. Function pointer references to existing global functions aren't getting converted to dynrelas. I'll open another issue for that one.

[euspectre]

Thanks for looking into this!