replace build.rs with bindgen

Co-authored-by: Matthias Beyer <mail@beyermatthias.de>
Signed-off-by: Finn Behrens <me@kloenk.de>

Makefile

@@ -450,6 +450,7 @@ STRIP		= $(CROSS_COMPILE)strip
 endif
 RUSTC		= rustc
 CARGO		= cargo
+BINDGEN		= bindgen
 PAHOLE		= pahole
 RESOLVE_BTFIDS	= $(objtree)/tools/bpf/resolve_btfids/resolve_btfids
 LEX		= flex
@@ -513,8 +514,9 @@ KBUILD_RUSTCFLAGS :=
 # TODO: another option is using explicit target specs, e.g.
 # `--target=$(srctree)/arch/$(SRCARCH)/rust-target-spec.json`
 KBUILD_CARGOFLAGS := $(CARGO_VERBOSE) --locked \
-		    -Z build-std=core,alloc -Z unstable-options \
-		    --out-dir=out --target=x86_64-linux-kernel
+			-Z build-std=core,alloc \
+			-Z unstable-options \
+			--target=x86_64-linux-kernel
 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
 KBUILD_RUSTCFLAGS_KERNEL :=
@@ -528,7 +530,7 @@ export KBUILD_LDS_MODULE := $(srctree)/scripts/module-common.lds
 KBUILD_LDFLAGS :=
 CLANG_FLAGS :=
 
-export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC RUSTC CARGO
+export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC RUSTC CARGO BINDGEN
 export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
 export PERL PYTHON PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
 export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
@@ -728,7 +730,7 @@ $(KCONFIG_CONFIG):
 # This exploits the 'multi-target pattern rule' trick.
 # The syncconfig should be executed only once to make all the targets.
 # (Note: use the grouped target '&:' when we bump to GNU Make 4.3)
-%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h: $(KCONFIG_CONFIG)
+%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h %/generated/rust_cfg: $(KCONFIG_CONFIG)
 	$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
 else # !may-sync-config
 # External modules and some install targets need include/generated/autoconf.h

rust/kernel/src/bindings.rs

@@ -9,7 +9,7 @@
 )]
 mod bindings_raw {
     use crate::c_types;
-    include!("bindings_gen.rs");
+    include!(env!("RUST_BINDGEN_FILE"));
 }
 pub use bindings_raw::*;
 

scripts/Makefile.build

@@ -307,14 +307,18 @@ $(obj)/%.lst: $(src)/%.c FORCE
 # ---------------------------------------------------------------------------
 
 quiet_cmd_cargo = CARGO $(quiet_modtag) $@
-      cmd_cargo = cd $(src) && $(CARGO) build $(cargo_flags)
+      cmd_cargo = export RUST_BINDGEN_FILE=$(shell readlink -f rust_bindings.rs) && $(CARGO) build $(cargo_flags) -p $(shell basename $(basename $(src))) --out-dir $(src)
+
+rust_bindings.rs: FORCE
+	$(Q)$(BINDGEN) $(srctree)/rust/kernel/src/bindings_helper.h --opaque-type xregs_state --opaque-type desc_struct --use-core --ctypes-prefix c_types -o rust_bindings.rs --size_t-is-usize -- $(c_flags)
 
 # The .o from the Rust staticlib
-$(obj)/%.o: $(src)/out/lib%.a
+#$(obj)/%.o: $(src)/out/lib%.a
+$(obj)/%.o: $(obj)/lib%.a
 	$(Q)$(LD) -r -o $@ --whole-archive $<
 
 # The Rust staticlib from cargo
-$(obj)/out/lib%.a: FORCE
+$(obj)/lib%.a: FORCE rust_bindings.rs
 	$(call cmd,cargo)
 
 # Compile assembler sources (.S)

scripts/Makefile.lib

@@ -229,9 +229,11 @@ c_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 RUST_BINDGEN_CFLAGS = $(c_flags) $(KBUILD_CFLAGS_MODULE)
 export RUST_BINDGEN_CFLAGS
 
-rustc_cfg_flags = $(shell sed -nE 's/^(CONFIG_[^=]+)=(y|m)$$/--cfg \1/p' $(srctree)/include/config/auto.conf | xargs)
+KCONFIG_RUSTCONFIG ?= include/generated/rust_cfg
 
-rustc_flags     = $(_rustc_flags) $(modkern_rustcflags) $(rustc_cfg_flags)
+rustconfig_path = $(shell readlink -f $(KCONFIG_RUSTCONFIG))
+
+rustc_flags     = $(_rustc_flags) $(modkern_rustcflags) @$(rustconfig_path)
 
 # Passed by cargo
 RUSTFLAGS = $(rustc_flags)