[RFC PATCH v1 1/3] tools build: Add Rust library build infrastructure and zlib-rs feature test

[Ian Rogers <irogers@google.com>]

Add shared Rust library build and feature detection support across tools/
and implement the zlib-rs feature check:

- Add tools/build/Makefile.rust with helpers to locate Cargo crate
  sources in distro (/usr/share/cargo/registry) or user Cargo registries,
  compile .rlib and .a targets with rustc, and resolve C compiler/linker
  flags via %-cflags and %-libs targets.
- Support resolving zlib-rs via LIBZ_RS_DIR, pkg-config
  (libz-rs-sys-cdylib, zlib-rs, z_rs), or building libz_rs.a (along with
  libzlib_rs.rlib and liblibc.rlib) into $(OUTPUT)libz_rs/.
- Add tools/build/feature/test-zlib-rs.c verifying ZLIB_VER_SUBREVISION
  == 15 (0xf) and linking against inflateInit().
- Extend tools/build/Build.include and tools/build/Makefile.build with
  cfgs-to-flags, rlibs-to-externs, per-target RUST_FLAGS/RUST_ENVS, and
  $(OUTPUT)lib%.rlib: %.rs pattern rules.
- Add RUST_TARGET_FLAGS_<arch> cross-compilation triples to
  tools/scripts/Makefile.arch and the feature_rust_lib helper macro to
  tools/scripts/Makefile.include.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 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/scripts/Makefile.arch        |  14 +++
 tools/scripts/Makefile.include     |  10 ++
 9 files changed, 229 insertions(+), 9 deletions(-)
 create mode 100644 tools/build/Makefile.rust
 create mode 100644 tools/build/feature/test-zlib-rs.c

diff --git a/tools/build/Build.include b/tools/build/Build.include
index cd0baa7a168d..45b61c31fd4c 100644
--- a/tools/build/Build.include
+++ b/tools/build/Build.include
@@ -100,12 +100,18 @@ cxx_flags = -Wp,-MD,$(depfile) -Wp,-MT,$@ $(CXXFLAGS) -D"BUILD_STR(s)=\#s" $(CXX
 
 ###
 # Rust flags to be used on rule definition, includes:
+# - cfgs-to-flags helper to turn cfg tokens into --cfg='...' flags
+# - rlibs-to-externs helper to map .rlib prerequisites to --extern <crate>=<path>
 # - global $(RUST_FLAGS)
-# - per target Rust flags
-# - per object Rust flags
-rust_flags_1 = $(RUST_FLAGS) $(RUST_FLAGS_$(basetarget).o) $(RUST_FLAGS_$(obj))
-rust_flags_2 = $(filter-out $(RUST_FLAGS_REMOVE_$(basetarget).o), $(rust_flags_1))
+# - per target Rust flags ($(RUST_FLAGS_<target>)) and envs ($(RUST_ENVS_<target>))
+# - per object Rust flags ($(RUST_FLAGS_<obj>)) and envs ($(RUST_ENVS_<obj>))
+cfgs-to-flags = $(patsubst %,--cfg='%',$1)
+rlibs-to-externs = $(foreach rlib,$(filter %.rlib,$1),--extern $(patsubst lib%.rlib,%,$(notdir $(rlib)))=$(rlib))
+
+rust_flags_1 = $(RUST_FLAGS) $(RUST_FLAGS_$(basetarget).o) $(RUST_FLAGS_$(notdir $@)) $(RUST_FLAGS_$(obj))
+rust_flags_2 = $(filter-out $(RUST_FLAGS_REMOVE_$(basetarget).o) $(RUST_FLAGS_REMOVE_$(notdir $@)), $(rust_flags_1))
 rust_flags   = $(filter-out $(RUST_FLAGS_REMOVE_$(obj)), $(rust_flags_2))
+rust_envs    = $(RUST_ENVS_$(notdir $@)) $(RUST_ENVS_$(obj))
 
 ###
 ## HOSTCC C flags
diff --git a/tools/build/Makefile.build b/tools/build/Makefile.build
index ad69efdd4e85..50c3eb57d34b 100644
--- a/tools/build/Makefile.build
+++ b/tools/build/Makefile.build
@@ -79,12 +79,15 @@ quiet_cmd_host_ld_multi = HOSTLD  $@
                           xargs $(HOSTLD) -r -o $@,rm -f $@; $(HOSTAR) rcs $@)
 
 rust_common_cmd = \
-	$(RUSTC) $(rust_flags) \
-	--crate-type staticlib -L $(objtree)/rust/ \
+	$(rust_envs) $(RUSTC) $(rust_flags) \
+	-L $(objtree)/rust/ $(call rlibs-to-externs,$^) \
 	--emit=dep-info=$(depfile),link
 
+quiet_cmd_rustc_rlib_rs = $(RUSTC) $(quiet_modtag) $@
+      cmd_rustc_rlib_rs = $(rust_common_cmd) --crate-type rlib --crate-name $(patsubst lib%.rlib,%,$(notdir $@)) -o $@ $<
+
 quiet_cmd_rustc_a_rs = $(RUSTC) $(quiet_modtag) $@
-      cmd_rustc_a_rs = $(rust_common_cmd) -o $@ -g $< $(cmd_objtool)
+      cmd_rustc_a_rs = $(rust_common_cmd) --crate-type staticlib -o $@ -g $< $(cmd_objtool)
 
 ifneq ($(filter $(obj),$(hostprogs)),)
   host = host_
@@ -117,6 +120,10 @@ $(OUTPUT)%.s: %.c FORCE
 
 # it's recommended to build a static rust library, when a foreight (to rust)
 # linker is used.
+$(OUTPUT)lib%.rlib: %.rs FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,rustc_rlib_rs)
+
 $(OUTPUT)%.a: %.rs FORCE
 	$(call rule_mkdir)
 	$(call if_changed_dep,rustc_a_rs)
diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 4d37d11f674c..c372600ae9e4 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -5,10 +5,11 @@ ifneq ($(OUTPUT),)
   OUTPUT_FEATURES = $(OUTPUT)feature/
   $(shell mkdir -p $(OUTPUT_FEATURES))
 endif
+RUST_OUTPUT ?= $(abspath $(or $(OUTPUT),$(CURDIR)))/
 
 feature_check = $(eval $(feature_check_code))
 define feature_check_code
-  feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CC="$(CC)" CXX="$(CXX)" CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0)
+  feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) RUST_OUTPUT="$(RUST_OUTPUT)" CC="$(CC)" CXX="$(CXX)" RUSTC="$(RUSTC)" $(if $(PKG_CONFIG),PKG_CONFIG="$(PKG_CONFIG)") CFLAGS="$(CLANG_CROSS_FLAGS) $(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(CLANG_CROSS_FLAGS) $(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" RUST_FLAGS="$(RUST_FLAGS)" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0)
 endef
 
 feature_set = $(eval $(feature_set_code))
@@ -128,6 +129,8 @@ FEATURE_TESTS_EXTRA :=                  \
          libdebuginfod			\
          clang-bpf-co-re		\
          bpftool-skeletons		\
+         zlib-rs			\
+         rust				\
          libunwind			\
          libunwind-debug-frame		\
          $(foreach arch,$(LIBUNWIND_ARCHS),libunwind-$(arch) libunwind-debug-frame-$(arch))
@@ -149,6 +152,7 @@ FEATURE_DISPLAY ?=              \
          libcapstone            \
          llvm-perf              \
          zlib                   \
+         zlib-rs                \
          lzma                   \
          bpf			\
          libaio			\
@@ -216,6 +220,9 @@ ifeq ($(feature-all), 1)
   $(call feature_check,compile-x32)
   $(call feature_check,bionic)
   $(call feature_check,babeltrace2-ctf-writer)
+  ifneq ($(filter zlib-rs,$(FEATURE_TESTS)),)
+    $(call feature_check,zlib-rs)
+  endif
   $(call feature_check,libunwind)
   $(call feature_check,libunwind-debug-frame)
   $(foreach arch,$(LIBUNWIND_ARCHS),$(call feature_check,libunwind-$(arch)))
diff --git a/tools/build/Makefile.rust b/tools/build/Makefile.rust
new file mode 100644
index 000000000000..cd9e0915b929
--- /dev/null
+++ b/tools/build/Makefile.rust
@@ -0,0 +1,149 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Shared rules and helpers for discovering and building Rust libraries
+# (either from pre-installed packages/pkg-config or from local Cargo crate
+# sources) for tools/ builds and feature detection.
+
+ifeq ($(pound),)
+include $(dir $(lastword $(MAKEFILE_LIST)))../scripts/Makefile.include
+endif
+
+ifeq ($(PKG_CONFIG),)
+  ifneq (, $(shell which $(CROSS_COMPILE)pkg-config 2>/dev/null))
+    PKG_CONFIG := $(CROSS_COMPILE)pkg-config
+  else
+    PKG_CONFIG := pkg-config
+
+    ifdef CROSS_COMPILE
+      ifeq ($(PKG_CONFIG_LIBDIR)$(PKG_CONFIG_PATH)$(PKG_CONFIG_SYSROOT_DIR),)
+        CROSS_ARCH = $(notdir $(CROSS_COMPILE:%-=%))
+        PKG_CONFIG_LIBDIR := /usr/local/$(CROSS_ARCH)/lib/pkgconfig/
+        PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/lib/$(CROSS_ARCH)/pkgconfig/
+        PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/lib/$(CROSS_ARCH)/pkgconfig/
+        PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/share/pkgconfig/
+        PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/share/pkgconfig/
+        export PKG_CONFIG_LIBDIR
+      endif
+    endif
+  endif
+endif
+
+ifeq ($(findstring -static,${LDFLAGS}),-static)
+  ifeq ($(findstring --static,$(PKG_CONFIG)),)
+    PKG_CONFIG += --static
+  endif
+endif
+
+# Search both distro-packaged Cargo registries (e.g. Debian/Ubuntu
+# /usr/share/cargo/registry from librust-*-dev packages) and user Cargo
+# registries ($CARGO_HOME/registry/src/* or ~/.cargo/registry/src/*).
+# Require a digit after "<crate>-" so prefixes like "libc-" do not match
+# unrelated crates such as "libc-print-*", and use version sorting (sort -V)
+# on the "<crate>-<version>" directory basename when multiple versions exist.
+CARGO_REGISTRY_DIR ?= /usr/share/cargo/registry $(wildcard $(or $(CARGO_HOME),$(HOME)/.cargo)/registry/src/*)
+cargo_crate_dirs = $(strip $(foreach dir,$(CARGO_REGISTRY_DIR),$(wildcard $(dir)/$(1)-[0-9]*)))
+cargo_crate_dir = $(if $(word 2,$(call cargo_crate_dirs,$(1))),$(shell printf '%s\n' $(call cargo_crate_dirs,$(1)) | awk -F/ '{print $$NF, $$0}' | sort -k1,1V | tail -n1 | cut -d' ' -f2-),$(call cargo_crate_dirs,$(1)))
+
+# Extract CARGO_PKG_VERSION* environment variables expected by crates using
+# env!("CARGO_PKG_VERSION*") from the "<crate>-<version>" directory name.
+define cargo_pkg_envs
+CARGO_PKG_VERSION=$(patsubst $(1)-%,%,$(notdir $(2))) \
+CARGO_PKG_VERSION_MAJOR=$(word 1,$(subst ., ,$(patsubst $(1)-%,%,$(notdir $(2))))) \
+CARGO_PKG_VERSION_MINOR=$(word 2,$(subst ., ,$(patsubst $(1)-%,%,$(notdir $(2)))))
+endef
+
+# Convert a whitespace-separated list of cfg tokens into --cfg='...' flags.
+cfgs-to-flags = $(patsubst %,--cfg='%',$1)
+
+# Map .rlib prerequisites to explicit --extern <crate>=<path.rlib> flags.
+# Passing explicit paths avoids -L ambiguity with sysroot crates (e.g. E0464
+# when both sysroot and local liblibc.rlib exist).
+rlibs-to-externs = $(foreach rlib,$(filter %.rlib,$1),--extern $(patsubst lib%.rlib,%,$(notdir $(rlib)))=$(rlib))
+rustc_common_flags := -C opt-level=3 -C relocation-model=pic
+
+cmd_rustc_rlib = \
+	$(rustc_target_envs) $(RUSTC) $(RUST_FLAGS) $(rustc_common_flags) $(rustc_target_flags) \
+	$(call rlibs-to-externs,$^) --crate-type rlib --crate-name $(patsubst lib%.rlib,%,$(notdir $@)) \
+	-o $@ $(filter %.rs,$^) > $(@:.rlib=.make.output) 2>&1
+
+cmd_rustc_staticlib = \
+	$(rustc_target_envs) $(RUSTC) $(RUST_FLAGS) $(rustc_common_flags) $(rustc_target_flags) \
+	$(call rlibs-to-externs,$^) --crate-type staticlib --crate-name $(patsubst lib%.a,%,$(notdir $@)) \
+	-o $@ $(filter %.rs,$^) > $(@:.a=.make.output) 2>&1
+
+# Helper targets invoked by $(call feature_rust_lib,<name>) to query the
+# resolved compiler and linker flags for a Rust library feature.
+%-cflags:
+	@echo $(FEATURE_CFLAGS-$*)
+
+%-libs:
+	@echo $(FEATURE_LIBS-$*)
+
+# Place compiled Rust library artifacts in their own subdirectory under the
+# build output root (e.g. $(OUTPUT)libz_rs/, alongside libapi/, libbpf/, etc.)
+# rather than inside $(OUTPUT)feature/.
+RUST_OUTPUT ?= $(patsubst %/feature/,%/,$(OUTPUT))
+LIBZ_RS_OUTPUT ?= $(RUST_OUTPUT)libz_rs/
+
+$(LIBZ_RS_OUTPUT):
+	$(Q)mkdir -p $@
+
+# Build chain for libz_rs.a from Cargo crate sources:
+#   libc (liblibc.rlib) -> zlib-rs (libzlib_rs.rlib) -> libz-rs-sys (libz_rs.a)
+LIBC_RS_DIR ?= $(call cargo_crate_dir,libc)
+libc-cfgs := feature="default" feature="std"
+libc-flags := --edition=2021 $(call cfgs-to-flags,$(libc-cfgs))
+
+$(LIBZ_RS_OUTPUT)liblibc.rlib: private rustc_target_flags = $(libc-flags)
+$(LIBZ_RS_OUTPUT)liblibc.rlib: $(wildcard $(LIBC_RS_DIR)/src/lib.rs) | $(LIBZ_RS_OUTPUT)
+	@$(if $<,$(cmd_rustc_rlib),false)
+
+ZLIB_RS_DIR ?= $(call cargo_crate_dir,zlib-rs)
+zlib_rs-cfgs := feature="__internal-api" feature="c-allocator" feature="rust-allocator" feature="std"
+zlib_rs-flags := --edition=2021 $(call cfgs-to-flags,$(zlib_rs-cfgs))
+
+$(LIBZ_RS_OUTPUT)libzlib_rs.rlib: private rustc_target_flags = $(zlib_rs-flags)
+$(LIBZ_RS_OUTPUT)libzlib_rs.rlib: $(wildcard $(ZLIB_RS_DIR)/src/lib.rs) | $(LIBZ_RS_OUTPUT)
+	@$(if $<,$(cmd_rustc_rlib),false)
+
+# Enable export-symbols, c-allocator, std, and gz so libz_rs.a exports the
+# full standard zlib C ABI (inflate*, deflate*, gz*, etc.) without symbol
+# prefixing.
+LIBZ_RS_SYS_DIR ?= $(call cargo_crate_dir,libz-rs-sys)
+libz_rs_sys-cfgs := feature="export-symbols" feature="c-allocator" feature="std" feature="gz"
+libz_rs_sys-flags := --edition=2021 $(call cfgs-to-flags,$(libz_rs_sys-cfgs))
+libz_rs_sys-envs := $(call cargo_pkg_envs,libz-rs-sys,$(LIBZ_RS_SYS_DIR))
+
+$(LIBZ_RS_OUTPUT)libz_rs.a: private rustc_target_envs = $(libz_rs_sys-envs)
+$(LIBZ_RS_OUTPUT)libz_rs.a: private rustc_target_flags = $(libz_rs_sys-flags)
+$(LIBZ_RS_OUTPUT)libz_rs.a: $(wildcard $(LIBZ_RS_SYS_DIR)/src/lib.rs) $(LIBZ_RS_OUTPUT)libzlib_rs.rlib $(LIBZ_RS_OUTPUT)liblibc.rlib | $(LIBZ_RS_OUTPUT)
+	@$(if $(filter %.rs,$^),$(cmd_rustc_staticlib),false)
+
+# Resolve zlib-rs flags and libraries in priority order:
+#   1. Explicit LIBZ_RS_DIR=/path/to/prefix override
+#   2. pkg-config (libz-rs-sys-cdylib, zlib-rs, or z_rs)
+#   3. Local Cargo crate sources built into $(LIBZ_RS_OUTPUT)libz_rs.a
+ifdef LIBZ_RS_DIR
+  FEATURE_CFLAGS-zlib-rs := -I$(LIBZ_RS_DIR)/include
+  FEATURE_LIBS-zlib-rs := -L$(LIBZ_RS_DIR)/lib -lz_rs
+endif
+
+ifeq ($(FEATURE_LIBS-zlib-rs),)
+  ZLIB_RS_PC := $(shell $(PKG_CONFIG) --exists libz-rs-sys-cdylib 2>/dev/null && echo libz-rs-sys-cdylib || \
+                        ($(PKG_CONFIG) --exists zlib-rs 2>/dev/null && echo zlib-rs) || \
+                        ($(PKG_CONFIG) --exists z_rs 2>/dev/null && echo z_rs))
+  ifneq ($(ZLIB_RS_PC),)
+    FEATURE_CFLAGS-zlib-rs := $(shell $(PKG_CONFIG) --cflags $(ZLIB_RS_PC) 2>/dev/null)
+    FEATURE_LIBS-zlib-rs := $(shell $(PKG_CONFIG) --libs $(ZLIB_RS_PC) 2>/dev/null)
+  endif
+endif
+
+ifeq ($(FEATURE_LIBS-zlib-rs),)
+  ifneq ($(and $(ZLIB_RS_DIR),$(LIBZ_RS_SYS_DIR),$(LIBC_RS_DIR)),)
+    FEATURE_CFLAGS-zlib-rs := -I$(LIBZ_RS_SYS_DIR)/include
+    FEATURE_STATIC-zlib-rs := $(LIBZ_RS_OUTPUT)libz_rs.a
+    FEATURE_LIBS-zlib-rs := $(FEATURE_STATIC-zlib-rs)
+  endif
+endif
+
+zlib-rs-libs: $(FEATURE_STATIC-zlib-rs)
diff --git a/tools/build/feature/.gitignore b/tools/build/feature/.gitignore
index 15fcd34acdb9..2fb933f84bd0 100644
--- a/tools/build/feature/.gitignore
+++ b/tools/build/feature/.gitignore
@@ -2,3 +2,4 @@
 *.d
 *.bin
 *.output
+libz_rs/
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 10340a537224..ff41e3d3569a 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -50,6 +50,7 @@ FILES=                                          \
          test-compile-32.bin                    \
          test-compile-x32.bin                   \
          test-zlib.bin                          \
+         test-zlib-rs.bin                       \
          test-lzma.bin                          \
          test-bpf.bin                           \
          test-libbpf.bin                        \
@@ -301,6 +302,11 @@ $(OUTPUT)test-compile-x32.bin:
 $(OUTPUT)test-zlib.bin:
 	$(BUILD) -lz
 
+include ../Makefile.rust
+
+$(OUTPUT)test-zlib-rs.bin: $(FEATURE_STATIC-zlib-rs)
+	$(BUILD) $(FEATURE_CFLAGS-zlib-rs) $(FEATURE_LIBS-zlib-rs) -lpthread -ldl -lm
+
 $(OUTPUT)test-lzma.bin:
 	$(BUILD) -llzma
 
@@ -374,4 +380,5 @@ $(OUTPUT)test-rust.bin:
 ###############################
 
 clean:
-	rm -f $(FILES) $(OUTPUT)*.d $(FILES:.bin=.make.output)
+	rm -f $(FILES) $(OUTPUT)*.d $(OUTPUT)*.make.output
+	rm -rf $(LIBZ_RS_OUTPUT)
diff --git a/tools/build/feature/test-zlib-rs.c b/tools/build/feature/test-zlib-rs.c
new file mode 100644
index 000000000000..b8729c5135bb
--- /dev/null
+++ b/tools/build/feature/test-zlib-rs.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <zlib.h>
+
+/*
+ * libz-rs-sys's bundled zlib.h defines ZLIB_VER_SUBREVISION to 15 (0xf) to
+ * distinguish itself from standard C zlib (which defines it to 0). Verify
+ * we are including the zlib-rs header and can link against its zlib C ABI.
+ */
+#if !defined(ZLIB_VER_SUBREVISION) || ZLIB_VER_SUBREVISION != 15
+#error "Not zlib-rs header"
+#endif
+
+int main(void)
+{
+	z_stream zs;
+
+	inflateInit(&zs);
+	return 0;
+}
diff --git a/tools/scripts/Makefile.arch b/tools/scripts/Makefile.arch
index ed5f008d400e..d5f25f3be555 100644
--- a/tools/scripts/Makefile.arch
+++ b/tools/scripts/Makefile.arch
@@ -50,3 +50,17 @@ ifeq ($(LP64), 1)
 else
   IS_64_BIT := 0
 endif
+
+# Map kernel ARCH to rustc --target triples when cross-compiling tools/.
+ifneq ($(CROSS_COMPILE),)
+  RUST_TARGET_FLAGS_arm		:= arm-unknown-linux-gnueabi
+  RUST_TARGET_FLAGS_arm64	:= aarch64-unknown-linux-gnu
+  RUST_TARGET_FLAGS_loongarch	:= loongarch64-unknown-linux-gnu
+  RUST_TARGET_FLAGS_m68k	:= m68k-unknown-linux-gnu
+  RUST_TARGET_FLAGS_mips	:= mipsel-unknown-linux-gnu
+  RUST_TARGET_FLAGS_powerpc	:= powerpc64le-unknown-linux-gnu
+  RUST_TARGET_FLAGS_riscv	:= riscv64gc-unknown-linux-gnu
+  RUST_TARGET_FLAGS_s390	:= s390x-unknown-linux-gnu
+  RUST_TARGET_FLAGS_x86		:= x86_64-unknown-linux-gnu
+  RUST_TARGET_FLAGS_x86_64	:= x86_64-unknown-linux-gnu
+endif
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 378387f62960..72394d245d5d 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -111,6 +111,16 @@ SYSTEM_BPFTOOL	?= bpftool
 
 RUSTC		?= rustc
 
+# Query tools/build/Makefile.rust for a Rust library feature's CFLAGS and LIBS
+# (building any required staticlib such as libz_rs.a under $(RUST_OUTPUT)), and
+# populate FEATURE_CFLAGS-<feat> and FEATURE_LIBS-<feat>.
+define feature_rust_lib_code
+  FEATURE_RUST_OUTPUT := $$(if $$(RUST_OUTPUT),$$(RUST_OUTPUT),$$(abspath $$(or $$(OUTPUT),$$(CURDIR)))/)
+  FEATURE_CFLAGS-$(1) := $$(shell $$(MAKE) -s --no-print-directory -f $$(srctree)/tools/build/Makefile.rust $$(if $$(PKG_CONFIG),PKG_CONFIG="$$(PKG_CONFIG)") LDFLAGS="$$(LDFLAGS)" $(1)-cflags)
+  FEATURE_LIBS-$(1) := $$(shell $$(MAKE) -s --no-print-directory -f $$(srctree)/tools/build/Makefile.rust RUST_OUTPUT="$$(FEATURE_RUST_OUTPUT)" $$(if $$(PKG_CONFIG),PKG_CONFIG="$$(PKG_CONFIG)") RUSTC="$$(RUSTC)" RUST_FLAGS="$$(RUST_FLAGS)" LDFLAGS="$$(LDFLAGS)" $(1)-libs)
+endef
+feature_rust_lib = $(eval $(feature_rust_lib_code))
+
 ifeq ($(CC_NO_CLANG), 1)
 EXTRA_WARNINGS += -Wstrict-aliasing=3
 
-- 
2.56.0.313.g2479322e68-goog