Messages in this thread | | | Date | Wed, 17 May 2023 18:42:06 -0700 | Subject | Re: [PATCH bpf-next] bpf: btf: restore resolve_mode when popping the resolve stack | From | Martin KaFai Lau <> |
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On 5/17/23 2:01 AM, Lorenz Bauer wrote: > On Wed, May 17, 2023 at 7:26 AM Martin KaFai Lau <martin.lau@linux.dev> wrote: >> >> On 5/15/23 5:15 AM, Lorenz Bauer wrote: >>> In commit 9b459804ff99 ("btf: fix resolving BTF_KIND_VAR after ARRAY, STRUCT, UNION, PTR") >>> I fixed a bug that occurred during resolving of a DATASEC by strategically resetting >>> resolve_mode. This fixes the immediate bug but leaves us open to future bugs where >>> nested types have to be resolved. >> >> hmm... future bugs like when adding new BTF_KIND in the future? > > It could just be refactoring of the codebase? What is the downside of > restoring the mode when popping the item? It also makes push and pop > symmetrical.
I can see your point to refactor it to make it work for all different BTF_KIND.
Other than BTF_KIND_DATASEC, env->resolve_mode stays the same for all other kinds once it is decided. It is why resolve_mode is in the "env" instead of "v". My concern is this will hide some bugs (existing or future) that accidentally changed the resolve_mode in the middle. If there is another legit case that could be found other than BTF_KIND_DATASEC, that will be a better time to do this refactoring with a proper test case considering most bpf progs need btf to load nowadays and probably need to veristat test also. If it came to that, might as well consider moving resolve_mode from "env" to "v".
btf_datasec_resolve() is acting as a very top level resolver like btf_resolve(), so it reset env->resolve_mode before resolving its var member like how btf_resolve() does. imo, together with env->resolve_mode stays the same for others, it is more straight forward to reason. I understand that it is personal preference and could argue either way.
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