svn commit: r368789 - head/libexec/rtld-elf/rtld-libc

[John Baldwin]

On 12/19/20 8:27 PM, Ryan Libby wrote:
> On Sat, Dec 19, 2020 at 7:23 PM John Baldwin <jhb at freebsd.org> wrote:
>>
>> On 12/19/20 12:38 AM, Ryan Libby wrote:
>>> Author: rlibby
>>> Date: Sat Dec 19 08:38:31 2020
>>> New Revision: 368789
>>> URL: https://svnweb.freebsd.org/changeset/base/368789
>>>
>>> Log:
>>>   rtld-elf: link udivmoddi4 from compiler_rt
>>>
>>>   This fixes the gcc9 build of rtld-elf32 on amd64, which needed an
>>>   implementation of udivmoddi4.
>>>
>>>   rtld-elf uses certain functions normally found in libc, and so it
>>>   includes certain files from libc in its own build.  It has two
>>>   mechanisms to include files from libc: one that rebuilds source files in
>>>   the rtld-elf environment, and one that extracts object files from a
>>>   purpose-built no-SSP PIC archive.
>>>
>>>   In addition to libc functions, rtld-elf may need to link functions
>>>   normally found in libcompiler_rt (formerly libgcc).  Now, add an ability
>>>   to rebuild libcompiler_rt source files in the rtld-elf environment.  We
>>>   don't yet have a need for an object file extraction mechanism.
>>>
>>>   libcompiler_rt could also supply udivdi3 and umoddi3, but leave them
>>>   alone for now.
>>>
>>>   Reviewed by:        arichardson, kib
>>>   Sponsored by:       Dell EMC Isilon
>>>   Differential Revision:      https://reviews.freebsd.org/D27665
>>
>> Hmm, I had just linked against libcompiler_rt directly as we do on arm:
>>
>> https://reviews.freebsd.org/D26199
>>
>> It was stuck waiting for review feedback.
>>
>> Given libcompiler_rt is a static archive, we could probably safely link
>> against it directly unlike libc where we have to pick specific object
>> files.
>>
>> --
>> John Baldwin
> 
> Sorry, I wasn't aware of your review.  Do you want this backed out?

No.  I do have other patches you can see in that review stack that might
be relevant for GCC 9.  Some of them I should push as they've been
reviewed, but not all of them are ok'd I think.

> I did see the arm path.  I think it is not quite right, because
> libcompiler_rt is compiled with -fstack-protector-strong, which is not
> compatible with rtld.  However, it will work in practice if stack
> protection doesn't actually get used on any linked function.

Hmm, ok.  I think it's fine to use the current approach then, and perhaps
fix arm to match it and keep SSP out of rtld.

-- 
John Baldwin