scx: Aggregate build logic for rust schedulers

scx_rusty currently defines several build targets and recipes that would
have to be duplicated by any other rust scheduler we may add. Let's add
some build scaffolding to avoid people having to copy paste.

Note that we can't fully avoid running any make logic if we take the
same approach as with the C schedulers. The C schedulers add a layer of
indirection where the "base" target (e.g. scx_simple) do nothing but
take a dependency on the binary output file. This doesn't work with rust
schedulers, because we're relying on Cargo to tell us when it needs to
be rebuilt.

Signed-off-by: David Vernet <[email protected]>

tools/sched_ext/Makefile

@@ -195,29 +195,36 @@ $(addprefix $(BINDIR)/,$(c-sched-targets)): \
 	$(CC) -o $@ $(SCXOBJ_DIR)/$(sched).o $(HOST_BPFOBJ) $(LDFLAGS)
 $(c-sched-targets): %: $(BINDIR)/%
 
+
+###################
+# Rust schedulers #
+###################
+rust-sched-targets := scx_rusty
+
 # Separate build target that is available for build systems to use to fetch
 # dependencies in a separate step from building. This allows the scheduler
 # to be compiled without network access.
 #
-# If the scx_rusty Make target is invoked without CARGO_OFFLINE=1 (e.g. if
-# building locally), then cargo build will download all of the necessary
-# dependencies, and scx_rusty_deps can be skipped.
-scx_rusty_deps:
-	cargo fetch --manifest-path=scx_rusty/Cargo.toml
-
-scx_rusty: export RUSTFLAGS = -C link-args=-lzstd -C link-args=-lz -C link-args=-lelf -L $(BPFOBJ_DIR)
-scx_rusty: export SCX_RUSTY_CLANG = $(CLANG)
-scx_rusty: export SCX_RUSTY_BPF_CFLAGS = $(BPF_CFLAGS)
-scx_rusty: $(INCLUDE_DIR)/vmlinux.h $(SCX_COMMON_DEPS)
-	cargo build --manifest-path=$@/Cargo.toml $(CARGOFLAGS)
-	$(Q)cp $(OUTPUT_DIR)/release/$@ $(BINDIR)/$@
+# If the regular rust scheduler Make target (e.g. scx_rusty) is invoked without
+# CARGO_OFFLINE=1 (e.g. if building locally), then cargo build will download
+# all of the necessary dependencies, and the deps target can be skipped.
+$(addsuffix _deps,$(rust-sched-targets)):
+	$(Q)cargo fetch --manifest-path=scx_rusty/Cargo.toml
+
+$(rust-sched-targets): %: $(INCLUDE_DIR)/vmlinux.h $(SCX_COMMON_DEPS)
+	$(eval export RUSTFLAGS = -C link-args=-lzstd -C link-args=-lz -C link-args=-lelf -L $(BPFOBJ_DIR))
+	$(eval export SCX_RUST_CLANG = $(CLANG))
+	$(eval export SCX_RUST_BPF_CFLAGS= $(BPF_CFLAGS))
+	$(eval sched=$(notdir $@))
+	$(Q)cargo build --manifest-path=$(sched)/Cargo.toml $(CARGOFLAGS)
+	$(Q)cp $(OUTPUT_DIR)/release/$(sched) $(BINDIR)/$@
 
 install: all
 	$(Q)mkdir -p $(DESTDIR)/usr/bin/
 	$(Q)cp $(BINDIR)/* $(DESTDIR)/usr/bin/
 
 clean:
-	cargo clean --manifest-path=scx_rusty/Cargo.toml
+	$(foreach sched,$(rust-sched-targets),cargo clean --manifest-path=$(sched)/Cargo.toml;)
 	rm -rf $(OUTPUT_DIR) $(HOST_OUTPUT_DIR)
 	rm -f *.o *.bpf.o *.skel.h *.subskel.h
 	rm -f $(c-sched-targets)
@@ -284,7 +291,7 @@ help:
 	@echo  '                    rust files for rust schedulers, and also trigger a'
 	@echo  '                    clean of the kernel at the root of the whole repository.'
 
-.PHONY: all $(c-sched-targets) scx_rusty clean fullclean help
+.PHONY: all $(c-sched-targets) $(rust-sched-targets) clean fullclean help
 
 # delete failed targets
 .DELETE_ON_ERROR:

tools/sched_ext/scx_rusty/build.rs

@@ -40,8 +40,8 @@ fn bindgen_rusty() {
 }
 
 fn gen_bpf_sched(name: &str) {
-    let bpf_cflags = env::var("SCX_RUSTY_BPF_CFLAGS").unwrap();
-    let clang = env::var("SCX_RUSTY_CLANG").unwrap();
+    let bpf_cflags = env::var("SCX_RUST_BPF_CFLAGS").unwrap();
+    let clang = env::var("SCX_RUST_CLANG").unwrap();
     eprintln!("{}", clang);
     let outpath = format!("./src/bpf/.output/{}.skel.rs", name);
     let skel = Path::new(&outpath);