[PATCH] kbuild: rust: remove now-unneeded `rusttest` custom sysroot handling

From: Miguel Ojeda
Date: Tue May 28 2024 - 12:35:27 EST

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Since we dropped our custom `alloc` in commit 9d0441bab775 ("rust: alloc:
remove our fork of the `alloc` crate"), there is no need anymore to keep
the custom sysroot hack.

Thus delete it, which makes the target way simpler and faster too.

This also means we are not using Cargo for anything at the moment,
and that no download is required anymore, so update the main `Makefile`
and the documentation accordingly.

Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
---
Documentation/rust/quick-start.rst | 14 ------
Documentation/rust/testing.rst | 5 +--
Makefile | 3 +-
rust/Makefile | 70 ++++--------------------------
4 files changed, 11 insertions(+), 81 deletions(-)

diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index cc3f11e0d441..5ca13be451f5 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -164,20 +164,6 @@ can be installed manually::
The standalone installers also come with ``clippy``.

-cargo
-*****
-
-``cargo`` is the Rust native build system. It is currently required to run
-the tests since it is used to build a custom standard library that contains
-the facilities provided by the custom ``alloc`` in the kernel. The tests can
-be run using the ``rusttest`` Make target.
-
-If ``rustup`` is being used, all the profiles already install the tool,
-thus nothing needs to be done.
-
-The standalone installers also come with ``cargo``.
-
-
rustdoc
*******

diff --git a/Documentation/rust/testing.rst b/Documentation/rust/testing.rst
index acfd0c2be48d..568b71b415a4 100644
--- a/Documentation/rust/testing.rst
+++ b/Documentation/rust/testing.rst
@@ -131,9 +131,8 @@ Additionally, there are the ``#[test]`` tests. These can be run using the

make LLVM=1 rusttest

-This requires the kernel ``.config`` and downloads external repositories. It
-runs the ``#[test]`` tests on the host (currently) and thus is fairly limited in
-what these tests can test.
+This requires the kernel ``.config``. It runs the ``#[test]`` tests on the host
+(currently) and thus is fairly limited in what these tests can test.

The Kselftests
--------------
diff --git a/Makefile b/Makefile
index f975b6396328..f368a9167de8 100644
--- a/Makefile
+++ b/Makefile
@@ -507,7 +507,6 @@ RUSTDOC = rustdoc
RUSTFMT = rustfmt
CLIPPY_DRIVER = clippy-driver
BINDGEN = bindgen
-CARGO = cargo
PAHOLE = pahole
RESOLVE_BTFIDS = $(objtree)/tools/bpf/resolve_btfids/resolve_btfids
LEX = flex
@@ -601,7 +600,7 @@ endif
export RUSTC_BOOTSTRAP := 1

export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC HOSTPKG_CONFIG
-export RUSTC RUSTDOC RUSTFMT RUSTC_OR_CLIPPY_QUIET RUSTC_OR_CLIPPY BINDGEN CARGO
+export RUSTC RUSTDOC RUSTFMT RUSTC_OR_CLIPPY_QUIET RUSTC_OR_CLIPPY BINDGEN
export HOSTRUSTC KBUILD_HOSTRUSTFLAGS
export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
diff --git a/rust/Makefile b/rust/Makefile
index f70d5e244fee..385378311322 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -44,17 +44,10 @@ rustc_sysroot := $(shell MAKEFLAGS= $(RUSTC) $(rust_flags) --print sysroot)
rustc_host_target := $(shell $(RUSTC) --version --verbose | grep -F 'host: ' | cut -d' ' -f2)
RUST_LIB_SRC ?= $(rustc_sysroot)/lib/rustlib/src/rust/library

-ifeq ($(quiet),silent_)
-cargo_quiet=-q
+ifneq ($(quiet),)
rust_test_quiet=-q
rustdoc_test_quiet=--test-args -q
rustdoc_test_kernel_quiet=>/dev/null
-else ifeq ($(quiet),quiet_)
-rust_test_quiet=-q
-rustdoc_test_quiet=--test-args -q
-rustdoc_test_kernel_quiet=>/dev/null
-else
-cargo_quiet=--verbose
endif

core-cfgs = \
@@ -135,22 +128,21 @@ quiet_cmd_rustc_test_library = RUSTC TL $<
@$(objtree)/include/generated/rustc_cfg $(rustc_target_flags) \
--crate-type $(if $(rustc_test_library_proc),proc-macro,rlib) \
--out-dir $(objtree)/$(obj)/test --cfg testlib \
- --sysroot $(objtree)/$(obj)/test/sysroot \
-L$(objtree)/$(obj)/test \
--crate-name $(subst rusttest-,,$(subst rusttestlib-,,$@)) $<

-rusttestlib-build_error: $(src)/build_error.rs rusttest-prepare FORCE
+rusttestlib-build_error: $(src)/build_error.rs FORCE
+$(call if_changed,rustc_test_library)

rusttestlib-macros: private rustc_target_flags = --extern proc_macro
rusttestlib-macros: private rustc_test_library_proc = yes
-rusttestlib-macros: $(src)/macros/lib.rs rusttest-prepare FORCE
+rusttestlib-macros: $(src)/macros/lib.rs FORCE
+$(call if_changed,rustc_test_library)

-rusttestlib-bindings: $(src)/bindings/lib.rs rusttest-prepare FORCE
+rusttestlib-bindings: $(src)/bindings/lib.rs FORCE
+$(call if_changed,rustc_test_library)

-rusttestlib-uapi: $(src)/uapi/lib.rs rusttest-prepare FORCE
+rusttestlib-uapi: $(src)/uapi/lib.rs FORCE
+$(call if_changed,rustc_test_library)

quiet_cmd_rustdoc_test = RUSTDOC T $<
@@ -159,7 +151,7 @@ quiet_cmd_rustdoc_test = RUSTDOC T $<
$(RUSTDOC) --test $(rust_common_flags) \
@$(objtree)/include/generated/rustc_cfg \
$(rustc_target_flags) $(rustdoc_test_target_flags) \
- --sysroot $(objtree)/$(obj)/test/sysroot $(rustdoc_test_quiet) \
+ $(rustdoc_test_quiet) \
-L$(objtree)/$(obj)/test --output $(rustdoc_output) \
--crate-name $(subst rusttest-,,$@) $<

@@ -192,7 +184,6 @@ quiet_cmd_rustc_test = RUSTC T $<
$(RUSTC) --test $(rust_common_flags) \
@$(objtree)/include/generated/rustc_cfg \
$(rustc_target_flags) --out-dir $(objtree)/$(obj)/test \
- --sysroot $(objtree)/$(obj)/test/sysroot \
-L$(objtree)/$(obj)/test \
--crate-name $(subst rusttest-,,$@) $<; \
$(objtree)/$(obj)/test/$(subst rusttest-,,$@) $(rust_test_quiet) \
@@ -200,60 +191,15 @@ quiet_cmd_rustc_test = RUSTC T $<

rusttest: rusttest-macros rusttest-kernel

-# This prepares a custom sysroot with our custom `alloc` instead of
-# the standard one.
-#
-# This requires several hacks:
-# - Unlike `core` and `alloc`, `std` depends on more than a dozen crates,
-# including third-party crates that need to be downloaded, plus custom
-# `build.rs` steps. Thus hardcoding things here is not maintainable.
-# - `cargo` knows how to build the standard library, but it is an unstable
-# feature so far (`-Zbuild-std`).
-# - `cargo` only considers the use case of building the standard library
-# to use it in a given package. Thus we need to create a dummy package
-# and pick the generated libraries from there.
-# - The usual ways of modifying the dependency graph in `cargo` do not seem
-# to apply for the `-Zbuild-std` steps, thus we have to mislead it
-# by modifying the sources in the sysroot.
-# - To avoid messing with the user's Rust installation, we create a clone
-# of the sysroot. However, `cargo` ignores `RUSTFLAGS` in the `-Zbuild-std`
-# steps, thus we use a wrapper binary passed via `RUSTC` to pass the flag.
-#
-# In the future, we hope to avoid the whole ordeal by either:
-# - Making the `test` crate not depend on `std` (either improving upstream
-# or having our own custom crate).
-# - Making the tests run in kernel space (requires the previous point).
-# - Making `std` and friends be more like a "normal" crate, so that
-# `-Zbuild-std` and related hacks are not needed.
-quiet_cmd_rustsysroot = RUSTSYSROOT
- cmd_rustsysroot = \
- rm -rf $(objtree)/$(obj)/test; \
- mkdir -p $(objtree)/$(obj)/test; \
- cp -a $(rustc_sysroot) $(objtree)/$(obj)/test/sysroot; \
- echo '\#!/bin/sh' > $(objtree)/$(obj)/test/rustc_sysroot; \
- echo "$(RUSTC) --sysroot=$(abspath $(objtree)/$(obj)/test/sysroot) \"\$$@\"" \
- >> $(objtree)/$(obj)/test/rustc_sysroot; \
- chmod u+x $(objtree)/$(obj)/test/rustc_sysroot; \
- $(CARGO) -q new $(objtree)/$(obj)/test/dummy; \
- RUSTC=$(objtree)/$(obj)/test/rustc_sysroot $(CARGO) $(cargo_quiet) \
- test -Zbuild-std --target $(rustc_host_target) \
- --manifest-path $(objtree)/$(obj)/test/dummy/Cargo.toml; \
- rm $(objtree)/$(obj)/test/sysroot/lib/rustlib/$(rustc_host_target)/lib/*; \
- cp $(objtree)/$(obj)/test/dummy/target/$(rustc_host_target)/debug/deps/* \
- $(objtree)/$(obj)/test/sysroot/lib/rustlib/$(rustc_host_target)/lib
-
-rusttest-prepare: FORCE
- +$(call if_changed,rustsysroot)
-
rusttest-macros: private rustc_target_flags = --extern proc_macro
rusttest-macros: private rustdoc_test_target_flags = --crate-type proc-macro
-rusttest-macros: $(src)/macros/lib.rs rusttest-prepare FORCE
+rusttest-macros: $(src)/macros/lib.rs FORCE
+$(call if_changed,rustc_test)
+$(call if_changed,rustdoc_test)

rusttest-kernel: private rustc_target_flags = --extern alloc \
--extern build_error --extern macros --extern bindings --extern uapi
-rusttest-kernel: $(src)/kernel/lib.rs rusttest-prepare \
+rusttest-kernel: $(src)/kernel/lib.rs \
rusttestlib-build_error rusttestlib-macros rusttestlib-bindings \
rusttestlib-uapi FORCE
+$(call if_changed,rustc_test)

base-commit: 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0
--
2.45.1

Next message: Marc Zyngier: "Re: [PATCH v4] of: property: Add fw_devlink support for interrupt-map property"
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