Date: Mon, 21 Dec 2020 09:31:06 -0800 From: John Baldwin <jhb@FreeBSD.org> To: Ryan Libby <rlibby@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org>, Konstantin Belousov <kib@freebsd.org>, Alex Richardson <arichardson@freebsd.org> Subject: Re: svn commit: r368789 - head/libexec/rtld-elf/rtld-libc Message-ID: <a209cf2c-4950-66b4-2d81-f1b476951088@FreeBSD.org> In-Reply-To: <CAHgpiFz2ir10rbHWWF=oX%2BPkT%2Bb7nV99Wwzfj03oj6VkLV-5rg@mail.gmail.com> References: <202012190838.0BJ8cVJ3064816@repo.freebsd.org> <47e9db0f-14b4-0a0d-45c4-7e466e69711f@FreeBSD.org> <CAHgpiFz2ir10rbHWWF=oX%2BPkT%2Bb7nV99Wwzfj03oj6VkLV-5rg@mail.gmail.com>
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On 12/19/20 8:27 PM, Ryan Libby wrote: > On Sat, Dec 19, 2020 at 7:23 PM John Baldwin <jhb@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
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