Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Masahiro Yamada <> | Subject | [PATCH v2] kbuild: do not export LDFLAGS_vmlinux to decompressor Makefiles | Date | Sun, 8 Jan 2023 18:53:42 +0900 |
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Nathan Chancellor reports an error message from $(NM) if GNU Make 4.4 is used to build the ARM decompressor.
$ 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 it works fine.
GNU Make 4.4 expands KBSS_SZ in the parse stage, where the directory arm/arm/boot/compressed does not exit yet. When compiled O= option, 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> ---
Changes in v2: - Postpone the change for arch/arm/boot/compressed/Makefile - Update the commit description
Makefile | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile index dfba294ae790..658fc0e602c9 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 +1248,11 @@ vmlinux.o modules.builtin.modinfo modules.builtin: vmlinux_o @: PHONY += vmlinux +# LDFLAGS_vmlinux flags from the top Makefile and arch/*/Makefile should be +# exported for building the top vmlinux, but not for building decompressors. +# They happen to have the same base name (arch/*/boot/compressed/vmlinux). +# The decompressor Makefiles should not inherit LDFLAGS_vmlinux. +vmlinux: export LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) vmlinux: vmlinux.o $(KBUILD_LDS) modpost $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux -- 2.34.1
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