| Message ID | 20230108192317.2988108-1-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] kbuild: export top-level LDFLAGS_vmlinux only to scripts/Makefile.vmlinux | expand |
On Mon, Jan 09, 2023 at 04:23:17AM +0900, Masahiro Yamada wrote: > Nathan Chancellor reports that $(NM) emits an error message when > GNU Make 4.4 is used to build the ARM zImage. > > $ make-4.4 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- O=build defconfig zImage > [snip] > LD vmlinux > NM System.map > SORTTAB vmlinux > OBJCOPY arch/arm/boot/Image > Kernel: arch/arm/boot/Image is ready > arm-linux-gnueabi-nm: 'arch/arm/boot/compressed/../../../../vmlinux': No such file > /bin/sh: 1: arithmetic expression: expecting primary: " " > LDS arch/arm/boot/compressed/vmlinux.lds > AS arch/arm/boot/compressed/head.o > GZIP arch/arm/boot/compressed/piggy_data > AS arch/arm/boot/compressed/piggy.o > CC arch/arm/boot/compressed/misc.o > > This occurs since GNU Make commit 98da874c4303 ("[SV 10593] Export > variables to $(shell ...) commands"), and the O= option is needed to > reproduce it. The generated zImage is correct despite the error message. > > As the commit description of 98da874c4303 [1] says, exported variables > are passed down to $(shell ) functions, which means exported recursive > variables might be expanded earlier than before, in the parse stage. > > The following test code demonstrates the change for GNU Make 4.4. > > [Test Makefile] > > $(shell echo hello > foo) > export foo = $(shell cat bar/../foo) > $(shell mkdir bar) > > all: > @echo $(foo) > > [GNU Make 4.3] > > $ rm -rf bar; make-4.3 > hello > > [GNU Make 4.4] > > $ rm -rf bar; make-4.4 > cat: bar/../foo: No such file or directory > hello > > The 'foo' is a resursively expanded (i.e. lazily expanded) variable. > > GNU Make 4.3 expands 'foo' just before running the recipe '@echo $(foo)', > at this point, the directory 'bar' exists. > > GNU Make 4.4 expands 'foo' to evaluate $(shell mkdir bar) because it is > exported. At this point, the directory 'bar' does not exit yet. The cat > command cannot resolve the bar/../foo path, hence the error message. > > Let's get back to the kernel Makefile. > > In arch/arm/boot/compressed/Makefile, KBSS_SZ is referenced by > LDFLAGS_vmlinux, which is recursive and also exported by the top > Makefile. > > GNU Make 4.3 expands KBSS_SZ just before running the recipes, so no > error message. > > GNU Make 4.4 expands KBSS_SZ in the parse stage, where the directory > arm/arm/boot/compressed does not exit yet. When compiled with O=, > the output directory is created by $(shell mkdir -p $(obj-dirs)) > in scripts/Makefile.build. > > There are two ways to fix this particular issue: > > - change "$(obj)/../../../../vmlinux" in KBSS_SZ to "vmlinux" > - unexport LDFLAGS_vmlinux > > This commit takes the latter course because it is what I originally > intended. > > Commit 3ec8a5b33dea ("kbuild: do not export LDFLAGS_vmlinux") > unexported LDFLAGS_vmlinux. > > Commit 5d4aeffbf709 ("kbuild: rebuild .vmlinux.export.o when its > prerequisite is updated") accidentally exported it again. > > We can clean up arch/arm/boot/compressed/Makefile later. > > [1]: https://git.savannah.gnu.org/cgit/make.git/commit/?id=98da874c43035a490cdca81331724f233a3d0c9a > > Link: https://lore.kernel.org/all/Y7i8+EjwdnhHtlrr@dev-arch.thelio-3990X/ > Fixes: 5d4aeffbf709 ("kbuild: rebuild .vmlinux.export.o when its prerequisite is updated") > Reported-by: Nathan Chancellor <nathan@kernel.org> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> Tested-by: Nathan Chancellor <nathan@kernel.org> Thank you again for digging into this! > --- > > Changes in v3: > - Minimize the scope of exporting. > LDFLAGS_vmlinux is only exported to scripts/Makefile.vmlinux > > Changes in v2: > - Postpone the change for arch/arm/boot/compressed/Makefile > - Update the commit description > > Makefile | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index dfba294ae790..9eed3e9b3657 100644 > --- a/Makefile > +++ b/Makefile > @@ -549,7 +549,7 @@ LDFLAGS_MODULE = > CFLAGS_KERNEL = > RUSTFLAGS_KERNEL = > AFLAGS_KERNEL = > -export LDFLAGS_vmlinux = > +LDFLAGS_vmlinux = > > # Use USERINCLUDE when you must reference the UAPI directories only. > USERINCLUDE := \ > @@ -1248,6 +1248,18 @@ vmlinux.o modules.builtin.modinfo modules.builtin: vmlinux_o > @: > > PHONY += vmlinux > +# LDFLAGS_vmlinux in the top Makefile defines linker flags for the top vmlinux, > +# not for decompressors. LDFLAGS_vmlinux in arch/*/boot/compressed/Makefile is > +# unrelated; the decompressors just happen to have the same base name, > +# arch/*/boot/compressed/vmlinux. > +# Export LDFLAGS_vmlinux only to scripts/Makefile.vmlinux. > +# > +# _LDFLAGS_vmlinux is an indirection to work around the bug: > +# https://savannah.gnu.org/bugs/?61463 > +# For Make > 4.4, the following simple code will work: > +# vmlinux: private export LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) > +vmlinux: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) > +vmlinux: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux) > vmlinux: vmlinux.o $(KBUILD_LDS) modpost > $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux > > -- > 2.34.1 >
diff --git a/Makefile b/Makefile index dfba294ae790..9eed3e9b3657 100644 --- a/Makefile +++ b/Makefile @@ -549,7 +549,7 @@ LDFLAGS_MODULE = CFLAGS_KERNEL = RUSTFLAGS_KERNEL = AFLAGS_KERNEL = -export LDFLAGS_vmlinux = +LDFLAGS_vmlinux = # Use USERINCLUDE when you must reference the UAPI directories only. USERINCLUDE := \ @@ -1248,6 +1248,18 @@ vmlinux.o modules.builtin.modinfo modules.builtin: vmlinux_o @: PHONY += vmlinux +# LDFLAGS_vmlinux in the top Makefile defines linker flags for the top vmlinux, +# not for decompressors. LDFLAGS_vmlinux in arch/*/boot/compressed/Makefile is +# unrelated; the decompressors just happen to have the same base name, +# arch/*/boot/compressed/vmlinux. +# Export LDFLAGS_vmlinux only to scripts/Makefile.vmlinux. +# +# _LDFLAGS_vmlinux is an indirection to work around the bug: +# https://savannah.gnu.org/bugs/?61463 +# For Make > 4.4, the following simple code will work: +# vmlinux: private export LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) +vmlinux: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) +vmlinux: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux) vmlinux: vmlinux.o $(KBUILD_LDS) modpost $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux
Nathan Chancellor reports that $(NM) emits an error message when GNU Make 4.4 is used to build the ARM zImage. $ make-4.4 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- O=build defconfig zImage [snip] LD vmlinux NM System.map SORTTAB vmlinux OBJCOPY arch/arm/boot/Image Kernel: arch/arm/boot/Image is ready arm-linux-gnueabi-nm: 'arch/arm/boot/compressed/../../../../vmlinux': No such file /bin/sh: 1: arithmetic expression: expecting primary: " " LDS arch/arm/boot/compressed/vmlinux.lds AS arch/arm/boot/compressed/head.o GZIP arch/arm/boot/compressed/piggy_data AS arch/arm/boot/compressed/piggy.o CC arch/arm/boot/compressed/misc.o This occurs since GNU Make commit 98da874c4303 ("[SV 10593] Export variables to $(shell ...) commands"), and the O= option is needed to reproduce it. The generated zImage is correct despite the error message. As the commit description of 98da874c4303 [1] says, exported variables are passed down to $(shell ) functions, which means exported recursive variables might be expanded earlier than before, in the parse stage. The following test code demonstrates the change for GNU Make 4.4. [Test Makefile] $(shell echo hello > foo) export foo = $(shell cat bar/../foo) $(shell mkdir bar) all: @echo $(foo) [GNU Make 4.3] $ rm -rf bar; make-4.3 hello [GNU Make 4.4] $ rm -rf bar; make-4.4 cat: bar/../foo: No such file or directory hello The 'foo' is a resursively expanded (i.e. lazily expanded) variable. GNU Make 4.3 expands 'foo' just before running the recipe '@echo $(foo)', at this point, the directory 'bar' exists. GNU Make 4.4 expands 'foo' to evaluate $(shell mkdir bar) because it is exported. At this point, the directory 'bar' does not exit yet. The cat command cannot resolve the bar/../foo path, hence the error message. Let's get back to the kernel Makefile. In arch/arm/boot/compressed/Makefile, KBSS_SZ is referenced by LDFLAGS_vmlinux, which is recursive and also exported by the top Makefile. GNU Make 4.3 expands KBSS_SZ just before running the recipes, so no error message. GNU Make 4.4 expands KBSS_SZ in the parse stage, where the directory arm/arm/boot/compressed does not exit yet. When compiled with O=, the output directory is created by $(shell mkdir -p $(obj-dirs)) in scripts/Makefile.build. There are two ways to fix this particular issue: - change "$(obj)/../../../../vmlinux" in KBSS_SZ to "vmlinux" - unexport LDFLAGS_vmlinux This commit takes the latter course because it is what I originally intended. Commit 3ec8a5b33dea ("kbuild: do not export LDFLAGS_vmlinux") unexported LDFLAGS_vmlinux. Commit 5d4aeffbf709 ("kbuild: rebuild .vmlinux.export.o when its prerequisite is updated") accidentally exported it again. We can clean up arch/arm/boot/compressed/Makefile later. [1]: https://git.savannah.gnu.org/cgit/make.git/commit/?id=98da874c43035a490cdca81331724f233a3d0c9a Link: https://lore.kernel.org/all/Y7i8+EjwdnhHtlrr@dev-arch.thelio-3990X/ Fixes: 5d4aeffbf709 ("kbuild: rebuild .vmlinux.export.o when its prerequisite is updated") Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> --- Changes in v3: - Minimize the scope of exporting. LDFLAGS_vmlinux is only exported to scripts/Makefile.vmlinux Changes in v2: - Postpone the change for arch/arm/boot/compressed/Makefile - Update the commit description Makefile | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)