Messages in this thread |  | | Date | Fri, 26 Jan 2018 16:55:54 -0800 | From | Andi Kleen <> | Subject | Re: [PATCH 20/21] Kbuild, lto: Add Link Time Optimization support |
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On Sat, Jan 27, 2018 at 01:15:49AM +0100, Arnd Bergmann wrote: > On Mon, Nov 27, 2017 at 10:34 PM, Andi Kleen <andi@firstfloor.org> wrote: > > From: Andi Kleen <ak@linux.intel.com> > > - Add a new LDFINAL variable that controls the final link > > for vmlinux or module. In this case we call gcc-ld instead > > of ld, to run the LTO step. > > When I tried this out on allmodconfig (following the lwn article), I ran into > a number of warnings:
Thanks for testing. Yes it's a known issue: during one module build when modpost looks at the file it is still in LTO format, and modpost doesn't understand the LTO symbol table. I had a patch to teach it to it at some point, but it got lost somewhere. The LLVM LTO patchkit has a different solution that actually fixes the sequence to run modpost only after a LTO final link, but I haven't gotten around to port that one.
It seems to work already for the single file modules.
-Andi
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