[PW_SID:1160850] kbuild: significantly speed up kernel builds

.gitignore

@@ -38,6 +38,7 @@
 *.lzo
 *.mod
 *.mod.c
+*.mod.S
 *.o
 *.o.*
 *.patch

Documentation/kbuild/kbuild.rst

@@ -110,6 +110,19 @@ HOSTLDLIBS
 ----------
 Additional libraries to link against when building host programs.
 
+KGZIP
+-----
+The gzip compressor used for the compressed kernel image, compressed
+modules and packaging.
+
+If unset, it defaults to pigz (a parallel implementation of gzip) if available,
+otherwise gzip.
+
+KBZIP2, KLZOP, LZMA, LZ4, XZ, ZSTD
+----------------------------------
+The compressor programs for the other formats. Each defaults to the program
+of the same name.
+
 .. _userkbuildflags:
 
 USERCFLAGS

Documentation/kbuild/reproducible-builds.rst

@@ -76,6 +76,22 @@ include generated files.  You should ensure the source tree is
 pristine by running ``make mrproper`` or ``git clean -d -f -x`` before
 building a source package.
 
+Compression tools
+-----------------
+
+The compressed kernel image, compressed modules and packages are produced
+using the binary specified by the environment variable ``KGZIP`` (described
+in Documentation/kbuild/kbuild.rst).
+
+This variable defaults to ``pigz`` if installed (a parallel implementation
+of gzip), or ``gzip`` otherwise.
+
+The generated output between two invocations of identical builds with
+either of the default tools will be byte-for-byte equivalent.
+
+However, for reproducible builds, ensure the same tool is used on all build
+hosts, as different tools may generate different output from one another.
+
 Module signing
 --------------
 

Kbuild

@@ -115,3 +115,8 @@ obj-$(CONFIG_NET)	+= net/
 obj-y			+= virt/
 obj-y			+= $(ARCH_DRIVERS)
 obj-$(CONFIG_DRM_HEADER_TEST)	+= include/
+
+# Rust code elsewhere in the tree depends upon rust/.
+ifdef CONFIG_RUST
+$(KBUILD_RUST_DIRS): | rust
+endif

Makefile

@@ -561,7 +561,7 @@ PERL		= perl
 PYTHON3		= python3
 CHECK		= sparse
 BASH		= bash
-KGZIP		= gzip
+KGZIP		:= $(if $(shell command -v pigz 2>/dev/null),pigz,gzip)
 KBZIP2		= bzip2
 KLZOP		= lzop
 LZMA		= lzma
@@ -946,8 +946,8 @@ KBUILD_RUSTFLAGS += -Coverflow-checks=$(if $(CONFIG_RUST_OVERFLOW_CHECKS),y,n)
 ifdef CONFIG_CC_IS_GCC
 # gcc-10 renamed --param=allow-store-data-races=0 to
 # -fno-allow-store-data-races.
-KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
-KBUILD_CFLAGS	+= $(call cc-option,-fno-allow-store-data-races)
+KBUILD_CFLAGS	+= $(if $(CONFIG_CC_HAS_ALLOW_STORE_DATA_RACES_PARAM),--param=allow-store-data-races=0)
+KBUILD_CFLAGS	+= $(if $(CONFIG_CC_HAS_NO_ALLOW_STORE_DATA_RACES),-fno-allow-store-data-races)
 endif
 
 ifdef CONFIG_READABLE_ASM
@@ -1011,18 +1011,18 @@ endif
 endif
 
 # Explicitly clear padding bits during variable initialization
-KBUILD_CFLAGS += $(call cc-option,-fzero-init-padding-bits=all)
+KBUILD_CFLAGS += $(if $(CONFIG_CC_HAS_ZERO_INIT_PADDING_BITS),-fzero-init-padding-bits=all)
 
 # While VLAs have been removed, GCC produces unreachable stack probes
 # for the randomize_kstack_offset feature. Disable it for all compilers.
-KBUILD_CFLAGS	+= $(call cc-option, -fno-stack-clash-protection)
+KBUILD_CFLAGS	+= $(if $(CONFIG_CC_HAS_NO_STACK_CLASH_PROTECTION),-fno-stack-clash-protection)
 
 # Get details on warnings generated due to GCC value tracking.
-KBUILD_CFLAGS	+= $(call cc-option, -fdiagnostics-show-context=2)
+KBUILD_CFLAGS	+= $(if $(CONFIG_CC_HAS_DIAGNOSTICS_SHOW_CONTEXT),-fdiagnostics-show-context=2)
 
 # Show inlining notes for __attribute__((warning/error)) call chains.
 # GCC supports this unconditionally while Clang 23+ provides a flag.
-KBUILD_CFLAGS	+= $(call cc-option, -fdiagnostics-show-inlining-chain)
+KBUILD_CFLAGS	+= $(if $(CONFIG_CC_HAS_DIAGNOSTICS_SHOW_INLINING_CHAIN),-fdiagnostics-show-inlining-chain)
 
 # Clear used registers at func exit (to reduce data lifetime and ROP gadgets).
 ifdef CONFIG_ZERO_CALL_USED_REGS
@@ -1033,7 +1033,7 @@ ifdef CONFIG_FUNCTION_TRACER
 ifdef CONFIG_FTRACE_MCOUNT_USE_CC
   CC_FLAGS_FTRACE	+= -mrecord-mcount
   ifdef CONFIG_HAVE_NOP_MCOUNT
-    ifeq ($(call cc-option-yn, -mnop-mcount),y)
+    ifdef CONFIG_CC_HAS_MNOP_MCOUNT
       CC_FLAGS_FTRACE	+= -mnop-mcount
       CC_FLAGS_USING	+= -DCC_USING_NOP_MCOUNT
     endif
@@ -1051,8 +1051,7 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
   endif
 endif
 ifdef CONFIG_HAVE_FENTRY
-  # s390-linux-gnu-gcc did not support -mfentry until gcc-9.
-  ifeq ($(call cc-option-yn, -mfentry),y)
+  ifdef CONFIG_CC_HAS_MFENTRY
     CC_FLAGS_FTRACE	+= -mfentry
     CC_FLAGS_USING	+= -DCC_USING_FENTRY
   endif
@@ -1160,7 +1159,7 @@ NOSTDINC_FLAGS += -nostdinc
 # the kernel uses only C99 flexible arrays for dynamically sized trailing
 # arrays. Enforce this for everything that may examine structure sizes and
 # perform bounds checking.
-KBUILD_CFLAGS += $(call cc-option, -fstrict-flex-arrays=3)
+KBUILD_CFLAGS += $(if $(CONFIG_CC_HAS_STRICT_FLEX_ARRAYS),-fstrict-flex-arrays=3)
 
 # disable invalid "can't wrap" optimizations for signed / pointers
 KBUILD_CFLAGS	+= -fno-strict-overflow
@@ -1205,6 +1204,10 @@ KBUILD_RUSTFLAGS += --remap-path-prefix=$(srcroot)/= --remap-path-scope=macro
 endif
 endif
 
+ifdef CONFIG_RUST
+KBUILD_RUSTFLAGS += $(if $(CONFIG_RUSTC_HAS_JOBS),-j8,$(if $(CONFIG_RUSTC_HAS_ZTHREADS),-Zthreads=8))
+endif
+
 # include additional Makefiles when needed
 include-y			:= scripts/Makefile.warn
 include-$(CONFIG_DEBUG_INFO)	+= scripts/Makefile.debug
@@ -1240,11 +1243,11 @@ LDFLAGS_vmlinux += --build-id=sha1
 # COMDAT-deduplicated sections. Use --force-group-allocation to resolve these
 # groups when linking modules. The option is available from ld.bfd 2.29 and
 # ld.lld 19.1.0.
-KBUILD_LDFLAGS_MODULE += $(call ld-option,--force-group-allocation)
+KBUILD_LDFLAGS_MODULE += $(if $(CONFIG_LD_HAS_FORCE_GROUP_ALLOCATION),--force-group-allocation)
 
 KBUILD_LDFLAGS	+= -z noexecstack
 ifeq ($(CONFIG_LD_IS_BFD),y)
-KBUILD_LDFLAGS	+= $(call ld-option,--no-warn-rwx-segments)
+KBUILD_LDFLAGS	+= $(if $(CONFIG_LD_HAS_NO_WARN_RWX_SEGMENTS),--no-warn-rwx-segments)
 endif
 
 ifeq ($(CONFIG_STRIP_ASM_SYMS),y)
@@ -1263,8 +1266,10 @@ LDFLAGS_vmlinux += --orphan-handling=$(CONFIG_LD_ORPHAN_WARN_LEVEL)
 endif
 
 ifneq ($(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS),)
-LDFLAGS_vmlinux	+= --emit-relocs --discard-none
+LDFLAGS_vmlinux	+= --discard-none
+LDFLAGS_vmlinux_relocs := --emit-relocs
 endif
+export LDFLAGS_vmlinux_relocs
 
 # Align the architecture of userspace programs with the kernel
 USERFLAGS_FROM_KERNEL := --target=%
@@ -1421,14 +1426,17 @@ archprepare: outputmakefile archheaders archscripts scripts include/config/kerne
 	include/generated/rustc_cfg remove-stale-files
 
 prepare0: archprepare
-	$(Q)$(MAKE) $(build)=scripts/mod
 	$(Q)$(MAKE) $(build)=. prepare
+	$(Q)$(MAKE) $(build)=scripts/mod
+
+ifdef CONFIG_RUST
+export KBUILD_RUST_DIRS := drivers lib mm samples
+endif
 
 # All the preparing..
 prepare: prepare0
 ifdef CONFIG_RUST
 	+$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh
-	$(Q)$(MAKE) $(build)=rust
 endif
 
 PHONY += remove-stale-files
@@ -1755,6 +1763,12 @@ modules: modules_prepare
 # Target to prepare building external modules
 modules_prepare: prepare
 	$(Q)$(MAKE) $(build)=scripts scripts/module.lds
+ifdef CONFIG_RUST
+# Ensure rust/ is build before any external rust module which will rely upon it.
+ifeq ($(MAKECMDGOALS),modules_prepare)
+	$(Q)$(MAKE) $(build)=rust
+endif
+endif
 
 endif # CONFIG_MODULES
 
@@ -2237,13 +2251,14 @@ clean: $(clean-dirs)
 	$(call cmd,rmfiles)
 	@find . $(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
+		-o -name '.depcheck.mk' -o -name '.depcheck.mk.tmp' \
 		-o -name '*.ko.*' -o -name '*.o.thinlto.bc' \
 		-o -name '*.dtb' -o -name '*.dtbo' \
 		-o -name '*.dtb.S' -o -name '*.dtbo.S' \
 		-o -name '*.dt.yaml' -o -name 'dtbs-list' \
 		-o -name '*.dwo' -o -name '*.lst' \
 		-o -name '*.su' -o -name '*.mod' \
-		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
+		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' -o -name '*.mod.S' \
 		-o -name '*.lex.c' -o -name '*.tab.[ch]' \
 		-o -name '*.asn1.[ch]' \
 		-o -name '*.symtypes' -o -name 'modules.order' \

arch/arm64/kernel/pi/Makefile

@@ -9,7 +9,7 @@ KBUILD_CFLAGS	:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \
 		   -include $(srctree)/include/linux/hidden.h \
 		   -D__DISABLE_EXPORTS -ffreestanding -D__NO_FORTIFY \
 		   -fno-asynchronous-unwind-tables -fno-unwind-tables \
-		   $(call cc-option,-fno-addrsig)
+		   $(if $(CONFIG_CC_HAS_NO_ADDRSIG),-fno-addrsig)
 
 # this code may run with the MMU off so disable unaligned accesses
 CFLAGS_map_range.o += -mstrict-align

arch/riscv/kernel/pi/Makefile

@@ -8,7 +8,7 @@ KBUILD_CFLAGS	:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \
 		   -include $(srctree)/include/linux/hidden.h \
 		   -D__DISABLE_EXPORTS -ffreestanding \
 		   -fno-asynchronous-unwind-tables -fno-unwind-tables \
-		   $(call cc-option,-fno-addrsig)
+		   $(if $(CONFIG_CC_HAS_NO_ADDRSIG),-fno-addrsig)
 
 # Disable LTO
 KBUILD_CFLAGS	:= $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))

arch/x86/Kconfig

@@ -2364,6 +2364,23 @@ config CC_HAS_KCFI_ARITY
 	def_bool $(cc-option,-fsanitize=kcfi -fsanitize-kcfi-arity)
 	depends on CC_IS_CLANG && !RUST
 
+config CC_HAS_INDIRECT_BRANCH_CS_PREFIX
+	def_bool $(cc-option,-mindirect-branch-cs-prefix)
+
+config CC_HAS_CF_PROTECTION_NONE
+	def_bool $(cc-option,-fcf-protection=none)
+
+# with jump tables off: the compilers use NOTRACK for them, which kernel IBT
+# does not allow
+config CC_HAS_CF_PROTECTION_BRANCH
+	def_bool $(cc-option,-fcf-protection=branch -fno-jump-tables)
+
+config CC_HAS_FALIGN_JUMPS
+	def_bool $(cc-option,-falign-jumps=1)
+
+config CC_HAS_FALIGN_LOOPS
+	def_bool $(cc-option,-falign-loops=1)
+
 config FUNCTION_PADDING_CFI
 	int
 	default 59 if FUNCTION_ALIGNMENT_64B

arch/x86/Makefile

@@ -20,7 +20,7 @@ ifdef CONFIG_CC_IS_CLANG
 RETPOLINE_CFLAGS	:= -mretpoline-external-thunk
 RETPOLINE_VDSO_CFLAGS	:= -mretpoline
 endif
-RETPOLINE_CFLAGS	+= $(call cc-option,-mindirect-branch-cs-prefix)
+RETPOLINE_CFLAGS	+= $(if $(CONFIG_CC_HAS_INDIRECT_BRANCH_CS_PREFIX),-mindirect-branch-cs-prefix)
 
 ifdef CONFIG_MITIGATION_RETHUNK
 RETHUNK_CFLAGS		:= -mfunction-return=thunk-extern
@@ -52,7 +52,7 @@ REALMODE_CFLAGS	:= $(CC_FLAGS_DIALECT) -m16 -g -Os \
 		   -DDISABLE_BRANCH_PROFILING -D__DISABLE_EXPORTS \
 		   -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \
 		   -fno-strict-aliasing -fomit-frame-pointer -fno-pic \
-		   -mno-mmx -mno-sse $(call cc-option,-fcf-protection=none)
+		   -mno-mmx -mno-sse $(if $(CONFIG_CC_HAS_CF_PROTECTION_NONE),-fcf-protection=none)
 
 REALMODE_CFLAGS += -ffreestanding
 REALMODE_CFLAGS += -fno-stack-protector
@@ -99,10 +99,10 @@ ifeq ($(CONFIG_X86_KERNEL_IBT),y)
 #
 #   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104816
 #
-KBUILD_CFLAGS += $(call cc-option,-fcf-protection=branch -fno-jump-tables)
+KBUILD_CFLAGS += $(if $(CONFIG_CC_HAS_CF_PROTECTION_BRANCH),-fcf-protection=branch -fno-jump-tables)
 KBUILD_RUSTFLAGS += -Zcf-protection=branch $(if $(call rustc-min-version,109300),-Cjump-tables=n,-Zno-jump-tables)
 else
-KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
+KBUILD_CFLAGS += $(if $(CONFIG_CC_HAS_CF_PROTECTION_NONE),-fcf-protection=none)
 endif
 
 ifeq ($(CONFIG_X86_32),y)
@@ -138,10 +138,10 @@ else
         KBUILD_CFLAGS += -m64
 
         # Align jump targets to 1 byte, not the default 16 bytes:
-        KBUILD_CFLAGS += $(call cc-option,-falign-jumps=1)
+        KBUILD_CFLAGS += $(if $(CONFIG_CC_HAS_FALIGN_JUMPS),-falign-jumps=1)
 
         # Pack loops tightly as well:
-        KBUILD_CFLAGS += $(call cc-option,-falign-loops=1)
+        KBUILD_CFLAGS += $(if $(CONFIG_CC_HAS_FALIGN_LOOPS),-falign-loops=1)
 
         # Don't autogenerate traditional x87 instructions
         KBUILD_CFLAGS += -mno-80387

arch/x86/boot/Makefile

@@ -74,7 +74,7 @@ SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
 sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [a-zA-Z] \(startup_32\|efi.._stub_entry\|efi\(32\)\?_pe_entry\|input_data\|kernel_info\|_end\|_ehead\|_text\|_e\?data\|_e\?sbat\|z_.*\)$$/\#define ZO_\2 0x\1/p'
 
 quiet_cmd_zoffset = ZOFFSET $@
-      cmd_zoffset = $(NM) $< | sed -n $(sed-zoffset) > $@
+      cmd_zoffset = $(NM) -p $< | sed -n $(sed-zoffset) > $@
 
 targets += zoffset.h
 $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE

arch/x86/boot/compressed/Makefile

@@ -76,7 +76,7 @@ HOST_EXTRACFLAGS += -I$(srctree)/tools/include
 sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABbCDGRSTtVW] \(_text\|__start_rodata\|_sinittext\|__inittext_end\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
 
 quiet_cmd_voffset = VOFFSET $@
-      cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
+      cmd_voffset = $(NM) -p $< | sed -n $(sed-voffset) > $@
 
 targets += ../voffset.h
 

drivers/firmware/efi/libstub/Makefile

@@ -40,7 +40,7 @@ KBUILD_CFLAGS			:= $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \
 				   -D__NO_FORTIFY \
 				   -ffreestanding \
 				   -fno-stack-protector \
-				   $(call cc-option,-fno-addrsig) \
+				   $(if $(CONFIG_CC_HAS_NO_ADDRSIG),-fno-addrsig) \
 				   -D__DISABLE_EXPORTS
 
 #

include/asm-generic/vmlinux.lds.h

@@ -855,7 +855,7 @@
 		KLP_SYMID
 
 #define MODINFO								\
-		.modinfo : { *(.modinfo) . = ALIGN(8); }
+		.modinfo (INFO) : { *(.modinfo) . = ALIGN(8); }
 
 #ifdef CONFIG_GENERIC_BUG
 #define BUG_TABLE							\

include/linux/vermagic.h

@@ -3,7 +3,7 @@
 #define _LINUX_VERMAGIC_H
 
 #ifndef INCLUDE_VERMAGIC
-#error "This header can be included from kernel/module.c or *.mod.c only"
+#error "This header can be included from kernel/module.c or scripts/module-common.c only"
 #endif
 
 #include <generated/utsrelease.h>