On Wed, Apr 28, 2021 at 1:53 PM Grant Seltzer Richman
<grantseltzer@xxxxxxxxx> wrote:
>
> Hi all,
>
> I'm working on enabling CO:RE in a project I work on, tracee, and am
> running into the dilemma of missing macros that we previously were
> able to import from their various header files. I understand that
> macros don't make their way into BTF and therefore the generated
> vmlinux.h won't have them. However I can't import the various header
> files because of multiple-definition issues.
Sadly, copy/pasting has been the only way so far.
>
> Do people typically redefine each of these macros for their project?
> If so is there anything I should be careful of, such as architectural
> differences. Does anyone have creative ideas, even if not developed
> fully yet that I can possibly contribute to libbpf?
We've discussed adding Clang built-in to detect if a specific type is
already defined and doing something like this in vmlinux.h:
#if !__builtin_is_type_defined(struct task_struct)
struct task_struct {
...
}
#endif
And just do that for every struct, union, typedef. That would allow
vmlinux.h to co-exist (somewhat) with other types.
Another alternative is to not use vmlinux.h and use just linux
headers, but mark necessary types with
__attribute__((preserve_access_index)) to make them CO-RE relocatable.
You can add that to existing types with the same pragma that vmlinux.h
uses.
>
> Thanks so much,
> Grant Seltzer
