Merge tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Remove potentially incomplete targets when Kbuid is interrupted by
   SIGINT etc in case GNU Make may miss to do that when stderr is piped
   to another program.

 - Rewrite the single target build so it works more correctly.

 - Fix rpm-pkg builds with V=1.

 - List top-level subdirectories in ./Kbuild.

 - Ignore auto-generated __kstrtab_* and __kstrtabns_* symbols in
   kallsyms.

 - Avoid two different modules in lib/zstd/ having shared code, which
   potentially causes building the common code as build-in and modular
   back-and-forth.

 - Unify two modpost invocations to optimize the build process.

 - Remove head-y syntax in favor of linker scripts for placing
   particular sections in the head of vmlinux.

 - Bump the minimal GNU Make version to 3.82.

 - Clean up misc Makefiles and scripts.

* tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (41 commits)
  docs: bump minimal GNU Make version to 3.82
  ia64: simplify esi object addition in Makefile
  Revert "kbuild: Check if linker supports the -X option"
  kbuild: rebuild .vmlinux.export.o when its prerequisite is updated
  kbuild: move modules.builtin(.modinfo) rules to Makefile.vmlinux_o
  zstd: Fixing mixed module-builtin objects
  kallsyms: ignore __kstrtab_* and __kstrtabns_* symbols
  kallsyms: take the input file instead of reading stdin
  kallsyms: drop duplicated ignore patterns from kallsyms.c
  kbuild: reuse mksysmap output for kallsyms
  mksysmap: update comment about __crc_*
  kbuild: remove head-y syntax
  kbuild: use obj-y instead extra-y for objects placed at the head
  kbuild: hide error checker logs for V=1 builds
  kbuild: re-run modpost when it is updated
  kbuild: unify two modpost invocations
  kbuild: move vmlinux.o rule to the top Makefile
  kbuild: move .vmlinux.objs rule to Makefile.modpost
  kbuild: list sub-directories in ./Kbuild
  Makefile.compiler: replace cc-ifversion with compiler-specific macros
  ...

Author: torvalds

Documentation/kbuild/makefiles.rst

@@ -341,30 +341,14 @@ more details, with real examples.
 
 	Examples are:
 
-	1) head objects
-
-	    Some objects must be placed at the head of vmlinux. They are
-	    directly linked to vmlinux without going through built-in.a
-	    A typical use-case is an object that contains the entry point.
-
-	    arch/$(SRCARCH)/Makefile should specify such objects as head-y.
-
-	    Discussion:
-	      Given that we can control the section order in the linker script,
-	      why do we need head-y?
-
-	2) vmlinux linker script
+	1) vmlinux linker script
 
 	    The linker script for vmlinux is located at
 	    arch/$(SRCARCH)/kernel/vmlinux.lds
 
 	Example::
 
 		# arch/x86/kernel/Makefile
-		extra-y	:= head_$(BITS).o
-		extra-y	+= head$(BITS).o
-		extra-y	+= ebda.o
-		extra-y	+= platform-quirks.o
 		extra-y	+= vmlinux.lds
 
 	$(extra-y) should only contain targets needed for vmlinux.
@@ -683,22 +667,27 @@ more details, with real examples.
 	In the above example, -Wno-unused-but-set-variable will be added to
 	KBUILD_CFLAGS only if gcc really accepts it.
 
-    cc-ifversion
-	cc-ifversion tests the version of $(CC) and equals the fourth parameter
-	if version expression is true, or the fifth (if given) if the version
-	expression is false.
+    gcc-min-version
+	gcc-min-version tests if the value of $(CONFIG_GCC_VERSION) is greater than
+	or equal to the provided value and evaluates to y if so.
+
+	Example::
+
+		cflags-$(call gcc-min-version, 70100) := -foo
+
+	In this example, cflags-y will be assigned the value -foo if $(CC) is gcc and
+	$(CONFIG_GCC_VERSION) is >= 7.1.
+
+    clang-min-version
+	clang-min-version tests if the value of $(CONFIG_CLANG_VERSION) is greater
+	than or equal to the provided value and evaluates to y if so.
 
 	Example::
 
-		#fs/reiserfs/Makefile
-		ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
+		cflags-$(call clang-min-version, 110000) := -foo
 
-	In this example, ccflags-y will be assigned the value -O1 if the
-	$(CC) version is less than 4.2.
-	cc-ifversion takes all the shell operators:
-	-eq, -ne, -lt, -le, -gt, and -ge
-	The third parameter may be a text as in this example, but it may also
-	be an expanded variable or a macro.
+	In this example, cflags-y will be assigned the value -foo if $(CC) is clang
+	and $(CONFIG_CLANG_VERSION) is >= 11.0.0.
 
     cc-cross-prefix
 	cc-cross-prefix is used to check if there exists a $(CC) in path with
@@ -1099,8 +1088,7 @@ When kbuild executes, the following steps are followed (roughly):
    - The values of the above variables are expanded in arch/$(SRCARCH)/Makefile.
 5) All object files are then linked and the resulting file vmlinux is
    located at the root of the obj tree.
-   The very first objects linked are listed in head-y, assigned by
-   arch/$(SRCARCH)/Makefile.
+   The very first objects linked are listed in scripts/head-object-list.txt.
 6) Finally, the architecture-specific part does any required post processing
    and builds the final bootimage.
    - This includes building boot records
@@ -1272,6 +1260,9 @@ When kbuild executes, the following steps are followed (roughly):
 	All object files for vmlinux. They are linked to vmlinux in the same
 	order as listed in KBUILD_VMLINUX_OBJS.
 
+	The objects listed in scripts/head-object-list.txt are exceptions;
+	they are placed before the other objects.
+
     KBUILD_VMLINUX_LIBS
 
 	All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and
@@ -1315,8 +1306,7 @@ When kbuild executes, the following steps are followed (roughly):
 	machinery is all architecture-independent.
 
 
-	head-y, core-y, libs-y, drivers-y
-	    $(head-y) lists objects to be linked first in vmlinux.
+	core-y, libs-y, drivers-y
 
 	    $(libs-y) lists directories where a lib.a archive can be located.
 

Documentation/process/changes.rst

@@ -33,7 +33,7 @@ GNU C                  5.1              gcc --version
 Clang/LLVM (optional)  11.0.0           clang --version
 Rust (optional)        1.62.0           rustc --version
 bindgen (optional)     0.56.0           bindgen --version
-GNU make               3.81             make --version
+GNU make               3.82             make --version
 bash                   4.2              bash --version
 binutils               2.23             ld -v
 flex                   2.5.35           flex --version
@@ -108,7 +108,7 @@ It depends on ``libclang``.
 Make
 ----
 
-You will need GNU make 3.81 or later to build the kernel.
+You will need GNU make 3.82 or later to build the kernel.
 
 Bash
 ----

Kbuild

@@ -2,18 +2,18 @@
 #
 # Kbuild for top-level directory of the kernel
 
-#####
+# Prepare global headers and check sanity before descending into sub-directories
+# ---------------------------------------------------------------------------
+
 # Generate bounds.h
 
 bounds-file := include/generated/bounds.h
 
-always-y := $(bounds-file)
 targets := kernel/bounds.s
 
 $(bounds-file): kernel/bounds.s FORCE
 	$(call filechk,offsets,__LINUX_BOUNDS_H__)
 
-#####
 # Generate timeconst.h
 
 timeconst-file := include/generated/timeconst.h
@@ -23,37 +23,77 @@ filechk_gentimeconst = echo $(CONFIG_HZ) | bc -q $<
 $(timeconst-file): kernel/time/timeconst.bc FORCE
 	$(call filechk,gentimeconst)
 
-#####
 # Generate asm-offsets.h
 
 offsets-file := include/generated/asm-offsets.h
 
-always-y += $(offsets-file)
 targets += arch/$(SRCARCH)/kernel/asm-offsets.s
 
 arch/$(SRCARCH)/kernel/asm-offsets.s: $(timeconst-file) $(bounds-file)
 
 $(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
 	$(call filechk,offsets,__ASM_OFFSETS_H__)
 
-#####
 # Check for missing system calls
 
-always-y += missing-syscalls
-
 quiet_cmd_syscalls = CALL    $<
       cmd_syscalls = $(CONFIG_SHELL) $< $(CC) $(c_flags) $(missing_syscalls_flags)
 
-missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
+PHONY += missing-syscalls
+missing-syscalls: scripts/checksyscalls.sh $(offsets-file)
 	$(call cmd,syscalls)
 
-#####
-# Check atomic headers are up-to-date
-
-always-y += old-atomics
-
-quiet_cmd_atomics = CALL    $<
-      cmd_atomics = $(CONFIG_SHELL) $<
-
-old-atomics: scripts/atomic/check-atomics.sh FORCE
-	$(call cmd,atomics)
+# Check the manual modification of atomic headers
+
+quiet_cmd_check_sha1 = CHKSHA1 $<
+      cmd_check_sha1 = \
+	if ! command -v sha1sum >/dev/null; then \
+		echo "warning: cannot check the header due to sha1sum missing"; \
+		exit 0; \
+	fi; \
+	if [ "$$(sed -n '$$s:// ::p' $<)" != \
+	     "$$(sed '$$d' $< | sha1sum | sed 's/ .*//')" ]; then \
+		echo "error: $< has been modified." >&2; \
+		exit 1; \
+	fi; \
+	touch $@
+
+atomic-checks += $(addprefix $(obj)/.checked-, \
+	  atomic-arch-fallback.h \
+	  atomic-instrumented.h \
+	  atomic-long.h)
+
+targets += $(atomic-checks)
+$(atomic-checks): $(obj)/.checked-%: include/linux/atomic/%  FORCE
+	$(call if_changed,check_sha1)
+
+# A phony target that depends on all the preparation targets
+
+PHONY += prepare
+prepare: $(offsets-file) missing-syscalls $(atomic-checks)
+	@:
+
+# Ordinary directory descending
+# ---------------------------------------------------------------------------
+
+obj-y			+= init/
+obj-y			+= usr/
+obj-y			+= arch/$(SRCARCH)/
+obj-y			+= $(ARCH_CORE)
+obj-y			+= kernel/
+obj-y			+= certs/
+obj-y			+= mm/
+obj-y			+= fs/
+obj-y			+= ipc/
+obj-y			+= security/
+obj-y			+= crypto/
+obj-$(CONFIG_BLOCK)	+= block/
+obj-$(CONFIG_IO_URING)	+= io_uring/
+obj-$(CONFIG_RUST)	+= rust/
+obj-y			+= $(ARCH_LIB)
+obj-y			+= drivers/
+obj-y			+= sound/
+obj-$(CONFIG_SAMPLES)	+= samples/
+obj-$(CONFIG_NET)	+= net/
+obj-y			+= virt/
+obj-y			+= $(ARCH_DRIVERS)