* x86 - weird cross-compile build problem with try-run next-20210602
@ 2021-06-04 20:33 Valdis Klētnieks
2021-06-05 8:19 ` Masahiro Yamada
0 siblings, 1 reply; 3+ messages in thread
From: Valdis Klētnieks @ 2021-06-04 20:33 UTC (permalink / raw)
To: Masahiro Yamada, Thomas Gleixner, Ingo Molnar; +Cc: linux-kernel, x86
I built a gcc 11.1 cross-compiler targeting x86_64, and builds
were throwing an error message:
Makefile:149: CONFIG_X86_X32 enabled but no binutils support
so I added some debugging to arch/x86/Makefile:
ifdef CONFIG_X86_X32
x32_ld_ok := $(call try-run,\
/bin/echo -e '1: .quad 1b' | \
$(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \
$(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMP.o" && \
$(LD) -m elf32_x86_64 "$$TMP.o" -o "$$TMP",y,n)
$(warning x32_ld_ok is +$(x32_ld_ok)+ with CC=$(CC) $(KBUILD_AFLAGS) OBJ=$(OBJCOPY) LD=$(LD) )
ifeq ($(x32_ld_ok),y)
CONFIG_X86_X32_ABI := y
and that throws:
arch/x86/Makefile:143: x32_ld_ok is ++ with CC=x86_64-unknown-linux-gnu-gcc -D__ASSEMBLY__ -fno-PIE -m64 OBJ=x86_64-unknown-linux-gnu-objcopy LD=x86_64-unknown-linux-gnu-ld
Anybody have a clue why $(x32_ld_ok) is null rather than 'y' or 'n'?
(It's totally possible that my cross-compiler is broken, but I still don't see how
try-run would return null rather than 'n' in that case... I built a shell script that did the
test and that ended with $? == 0, but had a warning msg:
+ /bin/echo -e '1: .quad 1b'
+ x86_64-unknown-linux-gnu-gcc -D__ASSEMBLY__ -fno-PIE -m64 -c -x assembler -o /tmp/z97 -
+ x86_64-unknown-linux-gnu-objcopy -O elf32-x86-64 /tmp/z97 /tmp/z99.o
+ x86_64-unknown-linux-gnu-ld -m elf32_x86_64 /tmp/z99.o -o /tmp/z98
x86_64-unknown-linux-gnu-ld: warning: cannot find entry symbol _start; defaulting to 0000000000401000
echo $?
+ echo 0
0
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: x86 - weird cross-compile build problem with try-run next-20210602
2021-06-04 20:33 x86 - weird cross-compile build problem with try-run next-20210602 Valdis Klētnieks
@ 2021-06-05 8:19 ` Masahiro Yamada
2021-06-05 10:50 ` Valdis Klētnieks
0 siblings, 1 reply; 3+ messages in thread
From: Masahiro Yamada @ 2021-06-05 8:19 UTC (permalink / raw)
To: Valdis Klētnieks
Cc: Thomas Gleixner, Ingo Molnar, Linux Kernel Mailing List, X86 ML
On Sat, Jun 5, 2021 at 5:33 AM Valdis Klētnieks <valdis.kletnieks@vt.edu> wrote:
>
> I built a gcc 11.1 cross-compiler targeting x86_64, and builds
> were throwing an error message:
>
> Makefile:149: CONFIG_X86_X32 enabled but no binutils support
>
> so I added some debugging to arch/x86/Makefile:
>
> ifdef CONFIG_X86_X32
> x32_ld_ok := $(call try-run,\
> /bin/echo -e '1: .quad 1b' | \
> $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \
> $(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMP.o" && \
> $(LD) -m elf32_x86_64 "$$TMP.o" -o "$$TMP",y,n)
> $(warning x32_ld_ok is +$(x32_ld_ok)+ with CC=$(CC) $(KBUILD_AFLAGS) OBJ=$(OBJCOPY) LD=$(LD) )
> ifeq ($(x32_ld_ok),y)
> CONFIG_X86_X32_ABI := y
>
> and that throws:
>
> arch/x86/Makefile:143: x32_ld_ok is ++ with CC=x86_64-unknown-linux-gnu-gcc -D__ASSEMBLY__ -fno-PIE -m64 OBJ=x86_64-unknown-linux-gnu-objcopy LD=x86_64-unknown-linux-gnu-ld
>
> Anybody have a clue why $(x32_ld_ok) is null rather than 'y' or 'n'?
What command did you run?
I see this warning message for 'make install' for example.
$ make install
arch/x86/Makefile:148: CONFIG_X86_X32 enabled but no binutils support
Please add one more debug line:
$(warning need-compiler is +$(need-compiler)+)
and what will you get?
One quick fix is to change
ifeq ($(x32_ld_ok),y)
to
ifneq ($(x32_ld_ok),n)
But, I think moving this check to Kconfig
is a more proper fix.
> (It's totally possible that my cross-compiler is broken, but I still don't see how
> try-run would return null rather than 'n' in that case... I built a shell script that did the
> test and that ended with $? == 0, but had a warning msg:
>
> + /bin/echo -e '1: .quad 1b'
> + x86_64-unknown-linux-gnu-gcc -D__ASSEMBLY__ -fno-PIE -m64 -c -x assembler -o /tmp/z97 -
> + x86_64-unknown-linux-gnu-objcopy -O elf32-x86-64 /tmp/z97 /tmp/z99.o
> + x86_64-unknown-linux-gnu-ld -m elf32_x86_64 /tmp/z99.o -o /tmp/z98
> x86_64-unknown-linux-gnu-ld: warning: cannot find entry symbol _start; defaulting to 0000000000401000
> echo $?
> + echo 0
> 0
>
>
>
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: x86 - weird cross-compile build problem with try-run next-20210602
2021-06-05 8:19 ` Masahiro Yamada
@ 2021-06-05 10:50 ` Valdis Klētnieks
0 siblings, 0 replies; 3+ messages in thread
From: Valdis Klētnieks @ 2021-06-05 10:50 UTC (permalink / raw)
To: Masahiro Yamada
Cc: Thomas Gleixner, Ingo Molnar, Linux Kernel Mailing List, X86 ML
On Sat, 05 Jun 2021 17:19:30 +0900, Masahiro Yamada said:
> > Anybody have a clue why $(x32_ld_ok) is null rather than 'y' or 'n'?
>
>
> What command did you run?
>
> I see this warning message for 'make install' for example.
>
> $ make install
> arch/x86/Makefile:148: CONFIG_X86_X32 enabled but no binutils support
> Please add one more debug line:
> $(warning need-compiler is +$(need-compiler)+)
> and what will you get?
>
Bingo.
arch/x86/Makefile:143: need-compiler is ++ x32_ld_ok is ++ with CC=(.... same as before)
And it was hitting on a 'make kernelrelease'
805b2e1d427aa (Masahiro Yamada 2021-02-28 15:10:28 +0900 275) # is an exception where build artifacts may be updated. This must be fixed.
805b2e1d427aa (Masahiro Yamada 2021-02-28 15:10:28 +0900 276) no-compiler-targets := $(no-dot-config-targets) install dtbs_install \
805b2e1d427aa (Masahiro Yamada 2021-02-28 15:10:28 +0900 277) headers_install modules_install kernelrelease image_name
993bdde945478 (Masahiro Yamada 2021-02-28 15:10:25 +0900 278) no-sync-config-targets := $(no-dot-config-targets) %install kernelrelease \
I suspect it's this:
# Include this also for config targets because some architectures need
# cc-cross-prefix to determine CROSS_COMPILE.
+ifdef need-compiler
include $(srctree)/scripts/Makefile.compiler
+endif
and as a result, try-run isn't defined when we get into the ifdef CONFIG_X86_32
chunk in arch/x86/Makefile, which silently fails and returns a null. I added
more debugging to double-check...
ifdef CONFIG_X86_X32
x32_ld_ok := $(call try-run,\
/bin/echo -e '1: .quad 1b' | \
$(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \
$(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMP.o" && \
$(LD) -m elf32_x86_64 "$$TMP.o" -o "$$TMP",y,n)
$(warning need-compiler is +$(need-compiler)+ x32_ld_ok is +$(x32_ld_ok)+ with CC=$(CC) $(KBUILD_AFLAGS) OBJ=$(OBJCOPY) LD=$(LD) )
foo := $(call wombats-r-us )
$(warning foo is +$(foo)+ )
ifeq ($(x32_ld_ok),y)
and that gets:
/usr/src/linux-next/arch/x86/Makefile:143: need-compiler is ++ x32_ld_ok is ++ with CC=x86_64-unknown-linux-gnu-gcc -D__ASSEMBLY__ -fno-PIE -m64 OBJ=x86_64-unknown-linux-gnu-objcopy LD=x86_64-unknown-linux-gnu-ld
/usr/src/linux-next/arch/x86/Makefile:145: foo is ++
/usr/src/linux-next/arch/x86/Makefile:151: CONFIG_X86_X32 enabled but no binutils support
So the call to the undefined 'wombats-r-us' fails silently and returns a null..
and try-run is also failing silently the same way because it's not defined either.
There's only a few uses of try-run outside Makefile.compiler, and it looks like
x32_ld_ok is the only place where Makefile logic changes based on what try-run
returns (the rest just change compiler flags).
Havings said that, I'm not sure what the proper fix is. Move try-run out of Makefile.compiler?
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-06-05 10:52 UTC | newest]
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2021-06-04 20:33 x86 - weird cross-compile build problem with try-run next-20210602 Valdis Klētnieks
2021-06-05 8:19 ` Masahiro Yamada
2021-06-05 10:50 ` Valdis Klētnieks
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