On Tue, 2024-01-02 at 11:00 -0800, Andrii Nakryiko wrote:
> Support __arg_ctx global function argument tag semantics even on older kernels
> that don't natively support it through btf_decl_tag("arg:ctx").
>
> Patch #1 does a bunch of internal renaming to make internal function naming
> consistent. We were doing it lazily up until now, but mixing single and double
> underscored names are confusing, so let's bite a bullet and get it over the
> finish line in one go.
>
> Patches #3-#7 are preparatory work to allow to postpone BTF loading into the
> kernel until after all the BPF program relocations (including global func
> appending to main programs) are done. Patch #5 is perhaps the most important
> and establishes pre-created stable placeholder FDs, so that relocations can
> embed valid map FDs into ldimm64 instructions.
>
> Once BTF is done after relocation, what's left is to adjust BTF information to
> have each main program's copy of each used global subprog to point to its own
> adjusted FUNC -> FUNC_PROTO type chain (if they use __arg_ctx) in such a way
> as to satisfy type expectations of BPF verifier regarding the PTR_TO_CTX
> argument definition. See patch #8 for details.
>
> Patch #9 adds few more __arg_ctx use cases (edge cases like multiple arguments
> having __arg_ctx, etc) to test_global_func_ctx_args.c, to make it simple to
> validate that this logic indeed works on old kernels. It does.
I've read through the patch-set and it seems to be fine,
as far as my (limited) understanding of the code base goes.
Left a few nitpicks.
[...]
