[RFC PATCH v1 0/3] tools: Add Rust library build infrastructure and prefer zlib-rs

[Ian Rogers <irogers@google.com>]

The zlib-rs project (https://github.com/trifectatechfoundation/zlib-rs)
provides a memory-safe, high-performance Rust implementation of the zlib
compression specification along with a C ABI layer (libz-rs-sys) that is a
drop-in replacement for the standard C zlib library.

On many Linux distributions (such as Debian and Ubuntu), Rust crates like
zlib-rs and libz-rs-sys are packaged as Cargo registry sources under
/usr/share/cargo/registry/ (e.g. librust-libz-rs-sys-dev) rather than as
prebuilt C shared libraries, while other environments may install prebuilt
libz_rs libraries via pkg-config or a custom prefix (LIBZ_RS_DIR).

This RFC series lays the groundwork for building and linking Rust crate
libraries in tools/ (without requiring network access or invoking cargo) and
integrates zlib-rs support into perf and bpftool, preferring zlib-rs over C
zlib when available:

1. **tools build: Add Rust library build infrastructure and zlib-rs feature test**:
   - Adds `tools/build/Makefile.rust` with helpers to locate Cargo crate
     sources in distro (`/usr/share/cargo/registry`) or local Cargo
     registries (`CARGO_HOME` / `~/.cargo`), map `.rlib` prerequisites to
     explicit `--extern <crate>=<path>` flags, and compile `.rlib` and `.a`
     targets directly with `rustc`.
   - Resolves `zlib-rs` compiler and linker flags via `LIBZ_RS_DIR`,
     `pkg-config` (`libz-rs-sys-cdylib`, `zlib-rs`, `z_rs`), or compiling
     `liblibc.rlib`, `libzlib_rs.rlib`, and `libz_rs.a` (with the
     `export-symbols`, `c-allocator`, `std`, and `gz` features) into
     `$(OUTPUT)libz_rs/`.
   - Adds `tools/build/feature/test-zlib-rs.c` checking
     `ZLIB_VER_SUBREVISION == 15` (`0xf`, which distinguishes
     `libz-rs-sys`'s `zlib.h` from standard C `zlib.h`) and linking against
     `inflateInit()`.
   - Extends `tools/build/Build.include`, `tools/build/Makefile.build`,
     `tools/scripts/Makefile.arch`, and `tools/scripts/Makefile.include`
     with reusable Rust build rules, cross-compilation target triples
     (`RUST_TARGET_FLAGS_<arch>`), and the `feature_rust_lib` macro.

2. **perf build: Prefer zlib-rs over zlib when available**:
   - Moves Rust detection ahead of zlib detection in
     `tools/perf/Makefile.config` and prefers `zlib-rs` over C `zlib` unless
     `NO_ZLIB_RS=1` (or `NO_ZLIB=1` / `NO_RUST=1`) is set.
   - Defines both `HAVE_ZLIB_SUPPORT` and `HAVE_ZLIB_RS_SUPPORT` when
     `zlib-rs` is used so existing zlib call sites in `perf` work unchanged
     while `perf version --build-options` and `perf check feature zlib-rs`
     report whether `zlib-rs` is active.
   - Shares `$(OUTPUT)libz_rs/` with the host bootstrap `bpftool` build in
     `tools/perf/bpf_skel.mak` and adds `NO_ZLIB` / `NO_ZLIB_RS` tests to
     `tools/perf/tests/make`.

3. **bpftool: Prefer zlib-rs over zlib when available**:
   - Adds `zlib-rs` and `zlib` to `FEATURE_TESTS` and `FEATURE_DISPLAY` in
     `tools/bpf/bpftool/Makefile` and configures `ZLIB_CFLAGS` and
     `ZLIB_LIBS` via `feature_rust_lib` when `zlib-rs` is detected.

AI Assistance Disclosure (per Documentation/process/coding-assistants.rst
and Documentation/process/generated-content.rst):
- Tools used: Antigravity coding assistant and Sashiko automated patch
  review using Gemini 4 LLMs.
- Summary of prompts and assistance: Interactive pair-programming session to
  identify distro packaging for zlib-rs/libz-rs-sys, implement the zlib-rs
  feature test and Makefile.rust crate build rules, integrate zlib-rs
  detection into perf and bpftool, separate Rust library outputs into
  $(OUTPUT)libz_rs/, and address automated review feedback on crate version
  sorting, cross-compilation flags, and libbpf EXTRA_CFLAGS handling.
- Testing performed: Built and tested perf and bpftool with zlib-rs
  (default), NO_ZLIB_RS=1 (fallback to C zlib), NO_ZLIB=1, and MINIMAL=1;
  verified `perf version --build-options`, `perf check feature`, and the
  `make_no_zlib` / `make_no_zlib_rs` tests in `tools/perf/tests/make`; and
  checked all commits with `scripts/checkpatch.pl`.

Assisted-by: Antigravity:gemini-4

Ian Rogers (3):
  tools build: Add Rust library build infrastructure and zlib-rs feature
    test
  perf build: Prefer zlib-rs over zlib when available
  bpftool: Prefer zlib-rs over zlib when available

 tools/bpf/bpftool/.gitignore             |   1 +
 tools/bpf/bpftool/Makefile               |  56 ++++++++-
 tools/build/Build.include                |  14 ++-
 tools/build/Makefile.build               |  13 +-
 tools/build/Makefile.feature             |   9 +-
 tools/build/Makefile.rust                | 149 +++++++++++++++++++++++
 tools/build/feature/.gitignore           |   1 +
 tools/build/feature/Makefile             |   9 +-
 tools/build/feature/test-zlib-rs.c       |  19 +++
 tools/perf/.gitignore                    |   1 +
 tools/perf/Documentation/perf-check.txt  |   1 +
 tools/perf/Makefile.config               |  89 ++++++++------
 tools/perf/Makefile.perf                 |  32 ++++-
 tools/perf/bpf_skel.mak                  |   8 +-
 tools/perf/builtin-check.c               |   1 +
 tools/perf/scripts/install-build-deps.sh |   6 +
 tools/perf/tests/make                    |   9 ++
 tools/scripts/Makefile.arch              |  14 +++
 tools/scripts/Makefile.include           |  10 ++
 19 files changed, 385 insertions(+), 57 deletions(-)
 create mode 100644 tools/build/Makefile.rust
 create mode 100644 tools/build/feature/test-zlib-rs.c

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2.56.0.313.g2479322e68-goog