On Sat, Dec 19, 2020 at 7:23 PM John Baldwin <j...@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? 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. We could build a special libcompiler_rt with no stack protection like we do just for rtld with libc, but since we'd only want this no-SSP library for rtld, that's not much different from just rebuilding its source files in rtld. In addition, by rebuilding specific files we avoid overlinking--although that may not be a big deal (?), and there may be other cleaner ways to avoid that (?). On a tangent, it might be neat to split out an rtld_bootstrap (everything through init_rtld()) so that only the bootstrap code needs to be compiled and linked with no-SSP. I looked at this some but I figured there might not be appetite for a bunch of reorganization of rtld just to enable SSP. Anyway the bootstrap code would still need these particular libcompiler_rt functions to be no-SSP, as they get used in the printf procedure, which I am guessing the bootstrap may need. Ryan _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
