Re: [RFC PATCH v2 2/3] perf build: Prefer zlib-rs over zlib when available

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] perf build: missing -lz in BUILD_NONDISTRO when NO_ZLIB=1
--

commit db3abd69d02d2d4c46341fce54f1b1da8d6457de
Author: Ian Rogers <irogers@google.com>

perf build: Prefer zlib-rs over zlib when available

This commit detects and prefers zlib-rs over C zlib in the perf build unless
disabled with NO_ZLIB_RS=1, NO_ZLIB=1, or NO_RUST=1. It also integrates
libz_rs.a into the perf and bootstrap bpftool build rules and exposes zlib-rs
in perf check feature and build tests.

> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index b4764f69f47f4..d447f4bd8f5b1 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config

[ ... ]

> @@ -532,13 +538,54 @@ ifdef CORESIGHT
>    endif
>  endif
>  
> +ifndef NO_RUST
> +  $(call feature_check,rust)
> +  ifneq ($(feature-rust), 1)
> +    $(warning Rust is not found. Test workloads with rust are disabled.)
> +    NO_RUST := 1
> +  else
> +    NO_RUST := 0
> +    CFLAGS += -DHAVE_RUST_SUPPORT
> +    $(call detected,CONFIG_RUST_SUPPORT)
> +  endif
> +
> +  ifneq ($(CROSS_COMPILE),)
> +    ifeq ($(RUST_TARGET_FLAGS_$(ARCH)),)
> +      $(error Unknown rust cross compilation architecture $(ARCH))
> +    endif
> +  endif
> +endif
> +
> +# Building zlib-rs from Cargo crate sources requires a working rustc.
> +ifneq ($(NO_RUST), 0)
> +  NO_ZLIB_RS := 1
> +endif
> +
> +# Prefer zlib-rs over C zlib when available, unless disabled via NO_ZLIB=1 or
> +# NO_ZLIB_RS=1. Both provide the standard zlib C API (HAVE_ZLIB_SUPPORT), while
> +# HAVE_ZLIB_RS_SUPPORT records that zlib-rs is the implementation in use.
>  ifndef NO_ZLIB
> -  ifeq ($(feature-zlib), 1)
> +  ifndef NO_ZLIB_RS
> +    $(call feature_check,zlib-rs)
> +    ifeq ($(feature-zlib-rs), 1)
> +      $(call feature_rust_lib,zlib-rs)
> +      ZLIB_CFLAGS := $(FEATURE_CFLAGS-zlib-rs)
> +      ZLIB_LIBS := $(FEATURE_LIBS-zlib-rs)
> +      CFLAGS += -DHAVE_ZLIB_RS_SUPPORT $(ZLIB_CFLAGS)
> +      $(call detected,CONFIG_ZLIB_RS)
> +    endif
> +  endif
> +  ifeq ($(ZLIB_LIBS),)
> +    ifeq ($(feature-zlib), 1)
> +      ZLIB_LIBS := -lz
> +    else
> +      NO_ZLIB := 1
> +    endif
> +  endif
> +  ifneq ($(ZLIB_LIBS),)
>      CFLAGS += -DHAVE_ZLIB_SUPPORT
> -    EXTLIBS += -lz
> +    EXTLIBS += $(ZLIB_LIBS)
>      $(call detected,CONFIG_ZLIB)
> -  else
> -    NO_ZLIB := 1
>    endif
>  endif
>  
> @@ -908,7 +955,7 @@ ifdef BUILD_NONDISTRO
>    else ifeq ($(feature-libbfd-liberty), 1)
>      EXTLIBS += -lbfd -lopcodes -liberty
>    else ifeq ($(feature-libbfd-liberty-z), 1)
> -    EXTLIBS += -lbfd -lopcodes -liberty -lz
> +    EXTLIBS += -lbfd -lopcodes -liberty $(ZLIB_LIBS)
>    endif

[Severity: Low]
In the BUILD_NONDISTRO block of tools/perf/Makefile.config, ZLIB_LIBS is only
populated inside the ifndef NO_ZLIB block above, where it is already appended
to EXTLIBS.

When building with BUILD_NONDISTRO=1 and NO_ZLIB=1 on a system where libbfd
requires -liberty and -lz (so feature-libbfd-liberty-z is 1), ZLIB_LIBS is
empty.

Will replacing -lz with $(ZLIB_LIBS) here cause the link against libbfd to
fail with unresolved zlib symbols when NO_ZLIB=1, and duplicate $(ZLIB_LIBS)
in EXTLIBS when NO_ZLIB is not set?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261030202710.3863806-1-irogers@google.com?part=2