llvm dev - Oct 2019 - llvm-strip creates unloadable shared objects on linux-armv7hf

Hello,

Recently we tried to streamline our toolchain by removing some GNU
tools with LLVM tools to avoid having multiple copies of strip, nm, ar
and similar tools. Today we ran into a really strange issue where
shared objects where not loadable.

We where able to track this down to llvm-strip with default arguments
creating a shared object that doesn't load correctly. It works if we
switch from not passing args to llvm-strip to pass -strip-all-gnu

I built bzip2 and libbz2.so to show this case here:
https://1drv.ms/u/s!Amjta5FRkBbbkiz14aHTRJe03LlL?e=2mGvTN

This is the error we got by using the stripped shared object with
llvm-strip -strip-all:

admin at Netgear-RN212:~/b$ LD_PRELOAD=./libbz2.so.all ./bzip2
ERROR: ld.so: object './libbz2.so.all' from LD_PRELOAD cannot be
preloaded (cannot open shared object file): ignored.
./bzip2: error while loading shared libraries: libbz2.so: cannot open
shared object file: No such file or directory

And with strip-all-gnu it works:
admin at Netgear-RN212:~/b$ LD_PRELOAD=./libbz2.so.all_gnu ./bzip2
bzip2: I won't write compressed data to a terminal.
bzip2: For help, type: `bzip2 --help'.

This only seems to happen on Linux-armv7hf - we haven't seen this on
any of the intel platforms.

Thanks,
Tobias

One thing I noticed is that llvm-strip seemed to remove a .ARM.attributes
section. Can you try --keep-section=.ARM.attributes to tell to the command
to keep the section?

On Thu, Oct 17, 2019 at 5:37 PM Tobias Hieta via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hello,
>
> Recently we tried to streamline our toolchain by removing some GNU
> tools with LLVM tools to avoid having multiple copies of strip, nm, ar
> and similar tools. Today we ran into a really strange issue where
> shared objects where not loadable.
>
> We where able to track this down to llvm-strip with default arguments
> creating a shared object that doesn't load correctly. It works if we
> switch from not passing args to llvm-strip to pass -strip-all-gnu
>
> I built bzip2 and libbz2.so to show this case here:
> https://1drv.ms/u/s!Amjta5FRkBbbkiz14aHTRJe03LlL?e=2mGvTN
>
> This is the error we got by using the stripped shared object with
> llvm-strip -strip-all:
>
> admin at Netgear-RN212:~/b$ LD_PRELOAD=./libbz2.so.all ./bzip2
> ERROR: ld.so: object './libbz2.so.all' from LD_PRELOAD cannot be
> preloaded (cannot open shared object file): ignored.
> ./bzip2: error while loading shared libraries: libbz2.so: cannot open
> shared object file: No such file or directory
>
> And with strip-all-gnu it works:
> admin at Netgear-RN212:~/b$ LD_PRELOAD=./libbz2.so.all_gnu ./bzip2
> bzip2: I won't write compressed data to a terminal.
> bzip2: For help, type: `bzip2 --help'.
>
> This only seems to happen on Linux-armv7hf - we haven't seen this on
> any of the intel platforms.
>
> Thanks,
> Tobias
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Hello Rui,

Thanks for your reply. I tried with the keep-section argument and that
made the shared library work.

Should these sections be kept around by default maybe?

-- Tobias

On Thu, Oct 17, 2019 at 11:06 AM Rui Ueyama <ruiu at google.com>
wrote:
>
> One thing I noticed is that llvm-strip seemed to remove a .ARM.attributes
section. Can you try --keep-section=.ARM.attributes to tell to the command to
keep the section?
>
> On Thu, Oct 17, 2019 at 5:37 PM Tobias Hieta via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>>
>> Hello,
>>
>> Recently we tried to streamline our toolchain by removing some GNU
>> tools with LLVM tools to avoid having multiple copies of strip, nm, ar
>> and similar tools. Today we ran into a really strange issue where
>> shared objects where not loadable.
>>
>> We where able to track this down to llvm-strip with default arguments
>> creating a shared object that doesn't load correctly. It works if
we
>> switch from not passing args to llvm-strip to pass -strip-all-gnu
>>
>> I built bzip2 and libbz2.so to show this case here:
>> https://1drv.ms/u/s!Amjta5FRkBbbkiz14aHTRJe03LlL?e=2mGvTN
>>
>> This is the error we got by using the stripped shared object with
>> llvm-strip -strip-all:
>>
>> admin at Netgear-RN212:~/b$ LD_PRELOAD=./libbz2.so.all ./bzip2
>> ERROR: ld.so: object './libbz2.so.all' from LD_PRELOAD cannot
be
>> preloaded (cannot open shared object file): ignored.
>> ./bzip2: error while loading shared libraries: libbz2.so: cannot open
>> shared object file: No such file or directory
>>
>> And with strip-all-gnu it works:
>> admin at Netgear-RN212:~/b$ LD_PRELOAD=./libbz2.so.all_gnu ./bzip2
>> bzip2: I won't write compressed data to a terminal.
>> bzip2: For help, type: `bzip2 --help'.
>>
>> This only seems to happen on Linux-armv7hf - we haven't seen this
on
>> any of the intel platforms.
>>
>> Thanks,
>> Tobias
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev