Re: [kvm-unit-tests BUG] lib/ldiv32.c breaks arm compilation

[Alexandru Elisei <alexandru.elisei@arm.com>]

Hi Paolo,

On 5/11/21 5:43 PM, Paolo Bonzini wrote:
> On 11/05/21 17:43, Alexandru Elisei wrote:
>> Hello,
>>
>> Commit 0b2d3dafc0d3 ("libcflat: provide long division routines"), which added the
>> lib/ldiv32.c file, breaks compilation for the arm architecture; arm64 seems to be
>> working just fine.
>
> The Fedora one is fixed in the commit immediately after, which replaces
> inttypes.h with stdint.h.

$ git remote -v show new
* remote new
  Fetch URL: https://gitlab.com/kvm-unit-tests/kvm-unit-tests.git/
  Push  URL: https://gitlab.com/kvm-unit-tests/kvm-unit-tests.git/
  HEAD branch: master
  Remote branches:
    master  tracked
    staging tracked
  Local branch configured for 'git pull':
    master merges with remote master
  Local ref configured for 'git push':
    master pushes to master (up to date)
$ git pull new
Already up to date.
$ git show
commit 0b2d3dafc0d31025636201df923fa0dc8d2e380e (HEAD -> master, new/master)
Author: Paolo Bonzini <pbonzini@redhat.com>
Date:   Wed May 5 08:33:38 2021 -0400

    libcflat: provide long division routines
[..]

I guess the patch has not been merged yet, right?

>
> For Arch Linux I'm not sure what the compiler is complaining about (especially
> since there are no options such as -fno-null-pointer-checks) but perhaps we can
> just initialize rem to 0?  Any chance you can check if that affects the assembly
> output?  (It shouldn't).

I think it's because I'm using the *arm-none-eabi* toolchain for compilation
instead of arm-linux-gnu, that's the toolchain for cross compiling arm code that
is present in the official Arch Linux repositories. Is that unsupported? I don't
remember any mention of it not being supported, but it's entirely possible that I
just forgot.

With rem initialized to 0 I get this:

rm-none-eabi-ld -nostdlib -Ttext=40010000 -o arm/selftest.elf -T
/home/alex/data/repos/kvm-unit-tests/arm/flat.lds \
    arm/selftest.o arm/cstart.o lib/libcflat.a lib/libfdt/libfdt.a
lib/arm/libeabi.a arm/selftest.aux.o
arm-none-eabi-ld: lib/libcflat.a(printf.o): in function `print_int':
/home/alex/data/repos/kvm-unit-tests/lib/printf.c:72: undefined reference to
`__aeabi_ldivmod'
arm-none-eabi-ld: /home/alex/data/repos/kvm-unit-tests/lib/printf.c:73: undefined
reference to `__aeabi_ldivmod'
arm-none-eabi-ld: lib/libcflat.a(printf.o): in function `print_unsigned':
/home/alex/data/repos/kvm-unit-tests/lib/printf.c:102: undefined reference to
`__aeabi_uldivmod'
arm-none-eabi-ld: lib/libcflat.a(alloc_page.o): in function `_page_alloc_init_area':
/home/alex/data/repos/kvm-unit-tests/lib/alloc_page.c:482: undefined reference to
`__aeabi_uldivmod'
make: *** [/home/alex/data/repos/kvm-unit-tests/arm/Makefile.common:65:
arm/selftest.elf] Error 1

Thanks,

Alex
>
> Paolo
>
>> On Arch Linux:
>>
>> $ ./configure --arch=arm --cross-prefix=arm-none-eabi-
>> $ make clean && make
>> rm -f lib/arm/asm-offsets.h lib/arm/asm-offsets.s \
>>        lib/generated/asm-offsets.h
>> rm -f arm/*.{o,flat,elf} lib/arm/libeabi.a lib/arm/eabi_compat.o \
>>        arm/.*.d lib/arm/.*.d
>>    CLEAN (libfdt)
>> rm -f lib/libfdt/*.o lib/libfdt/.*.d
>> rm -f lib/libfdt/libfdt.so.1
>> rm -f lib/libfdt/libfdt.a
>> rm -f lib/.*.d lib/libcflat.a lib/argv.o lib/printf.o lib/string.o lib/abort.o
>> lib/report.o lib/stack.o lib/arm/spinlock.o lib/arm/processor.o lib/arm/stack.o
>> lib/ldiv32.o lib/util.o lib/getchar.o lib/alloc_phys.o lib/alloc_page.o
>> lib/vmalloc.o lib/alloc.o lib/devicetree.o lib/pci.o lib/pci-host-generic.o
>> lib/pci-testdev.o lib/virtio.o lib/virtio-mmio.o lib/chr-testdev.o lib/arm/io.o
>> lib/arm/setup.o lib/arm/mmu.o lib/arm/bitops.o lib/arm/psci.o lib/arm/smp.o
>> lib/arm/delay.o lib/arm/gic.o lib/arm/gic-v2.o lib/arm/gic-v3.o
>> [..]
>> arm-none-eabi-gcc -marm -mfpu=vfp -mcpu=cortex-a15 -mno-unaligned-access
>> -std=gnu99 -ffreestanding -O2 -I /home/alex/data/repos/kvm-unit-tests/lib -I
>> /home/alex/data/repos/kvm-unit-tests/lib/libfdt -I lib -g -MMD -MF lib/.ldiv32.d
>> -fno-strict-aliasing -fno-common -Wall -Wwrite-strings -Wempty-body
>> -Wuninitialized -Wignored-qualifiers -Werror  -fno-omit-frame-pointer
>> -fno-stack-protector    -Wno-frame-address -D__U32_LONG_FMT__  -fno-pic  -no-pie
>> -Wclobbered  -Wunused-but-set-parameter  -Wmissing-parameter-type
>> -Wold-style-declaration -Woverride-init -Wmissing-prototypes -Wstrict-prototypes
>> -c -o lib/ldiv32.o lib/ldiv32.c
>> lib/ldiv32.c: In function '__moddi3':
>> lib/ldiv32.c:73:11: error: 'rem' may be used uninitialized in this function
>> [-Werror=maybe-uninitialized]
>>     73 |  uint64_t rem;
>>        |           ^~~
>> lib/ldiv32.c: In function '__umoddi3':
>> lib/ldiv32.c:75:9: error: 'rem' may be used uninitialized in this function
>> [-Werror=maybe-uninitialized]
>>     75 |  return rem;
>>        |         ^~~
>> cc1: all warnings being treated as errors
>> make: *** [<builtin>: lib/ldiv32.o] Error 1
>> $ arm-none-eabi-gcc --version
>> arm-none-eabi-gcc (Arch Repository) 10.3.0
>> Copyright (C) 2020 Free Software Foundation, Inc.
>> This is free software; see the source for copying conditions.  There is NO
>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>>
>> On Fedora 33:
>>
>> $ ./configure --arch=arm --cross-prefix=arm-linux-gnu-
>> $ make clean && make
>> rm -f lib/arm/asm-offsets.h lib/arm/asm-offsets.s \
>>        lib/generated/asm-offsets.h
>> rm -f arm/*.{o,flat,elf} lib/arm/libeabi.a lib/arm/eabi_compat.o \
>>        arm/.*.d lib/arm/.*.d
>>    CLEAN (libfdt)
>> rm -f lib/libfdt/*.o lib/libfdt/.*.d
>> rm -f lib/libfdt/libfdt.so.1
>> rm -f lib/libfdt/libfdt.a
>> rm -f lib/.*.d lib/libcflat.a lib/argv.o lib/printf.o lib/string.o lib/abort.o
>> lib/report.o lib/stack.o lib/arm/spinlock.o lib/arm/processor.o lib/arm/stack.o
>> lib/ldiv32.o lib/util.o lib/getchar.o lib/alloc_phys.o lib/alloc_page.o
>> lib/vmalloc.o lib/alloc.o lib/devicetree.o lib/pci.o lib/pci-host-generic.o
>> lib/pci-testdev.o lib/virtio.o lib/virtio-mmio.o lib/chr-testdev.o lib/arm/io.o
>> lib/arm/setup.o lib/arm/mmu.o lib/arm/bitops.o lib/arm/psci.o lib/arm/smp.o
>> lib/arm/delay.o lib/arm/gic.o lib/arm/gic-v2.o lib/arm/gic-v3.o
>> [..]
>> arm-linux-gnu-gcc -marm -mfpu=vfp -mcpu=cortex-a15 -mno-unaligned-access
>> -std=gnu99 -ffreestanding -O2 -I /home/alex/data/repos/kvm-unit-tests/lib -I
>> /home/alex/data/repos/kvm-unit-tests/lib/libfdt -I lib -g -MMD -MF lib/.ldiv32.d
>> -fno-strict-aliasing -fno-common -Wall -Wwrite-strings -Wempty-body
>> -Wuninitialized -Wignored-qualifiers -Werror  -fno-omit-frame-pointer
>> -fno-stack-protector    -Wno-frame-address   -fno-pic  -no-pie  -Wclobbered
>> -Wunused-but-set-parameter  -Wmissing-parameter-type  -Wold-style-declaration
>> -Woverride-init -Wmissing-prototypes -Wstrict-prototypes   -c -o lib/ldiv32.o
>> lib/ldiv32.c
>> lib/ldiv32.c:1:10: fatal error: inttypes.h: No such file or directory
>>      1 | #include <inttypes.h>
>>        |          ^~~~~~~~~~~~
>> compilation terminated.
>> make: *** [<builtin>: lib/ldiv32.o] Error 1
>> $ arm-linux-gnu-gcc --version
>> arm-linux-gnu-gcc (GCC) 10.2.1 20200826 (Red Hat Cross 10.2.1-3)
>> Copyright (C) 2020 Free Software Foundation, Inc.
>> This is free software; see the source for copying conditions.  There is NO
>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>>
>> Reverting the commit makes arm build again. I am not familiar with toolchains, and
>> unfortunately I can't propose a fix.
>>
>> Thanks,
>>
>> Alex
>>
>