| Message ID | 20240102190055.1602698-1-andrii@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | Libbpf-side __arg_ctx fallback support | expand |
On Tue, Jan 2, 2024 at 11:01 AM Andrii Nakryiko <andrii@kernel.org> 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. > Oops, I forgot to add version history. It's basically: v1->v2: - do internal functions renaming in patch #1 (Alexei); - extract cloning of FUNC -> FUNC_PROTO information into separate function (Alexei); > Andrii Nakryiko (9): > libbpf: name internal functions consistently > libbpf: make uniform use of btf__fd() accessor inside libbpf > libbpf: use explicit map reuse flag to skip map creation steps > libbpf: don't rely on map->fd as an indicator of map being created > libbpf: use stable map placeholder FDs > libbpf: move exception callbacks assignment logic into relocation step > libbpf: move BTF loading step after relocation step > libbpf: implement __arg_ctx fallback logic > selftests/bpf: add arg:ctx cases to test_global_funcs tests > > tools/lib/bpf/libbpf.c | 1055 ++++++++++------- > tools/lib/bpf/libbpf_internal.h | 24 + > .../bpf/progs/test_global_func_ctx_args.c | 49 + > 3 files changed, 725 insertions(+), 403 deletions(-) > > -- > 2.34.1 >
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. [...]
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. Andrii Nakryiko (9): libbpf: name internal functions consistently libbpf: make uniform use of btf__fd() accessor inside libbpf libbpf: use explicit map reuse flag to skip map creation steps libbpf: don't rely on map->fd as an indicator of map being created libbpf: use stable map placeholder FDs libbpf: move exception callbacks assignment logic into relocation step libbpf: move BTF loading step after relocation step libbpf: implement __arg_ctx fallback logic selftests/bpf: add arg:ctx cases to test_global_funcs tests tools/lib/bpf/libbpf.c | 1055 ++++++++++------- tools/lib/bpf/libbpf_internal.h | 24 + .../bpf/progs/test_global_func_ctx_args.c | 49 + 3 files changed, 725 insertions(+), 403 deletions(-)