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Message-ID: <6c03d212-775c-cddb-b0d0-d7b00571694b@ghiti.fr> Date: Wed, 15 Jan 2020 15:48:18 -0500 From: Alexandre Ghiti <alexandre@...ti.fr> To: Alexei Starovoitov <alexei.starovoitov@...il.com>, Zong Li <zong.li@...ive.com> Cc: Palmer Dabbelt <palmerdabbelt@...gle.com>, Stephen Rothwell <sfr@...b.auug.org.au>, Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov <ast@...nel.org>, Network Development <netdev@...r.kernel.org>, Linux-Next Mailing List <linux-next@...r.kernel.org>, "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>, ppc-dev <linuxppc-dev@...ts.ozlabs.org>, linux-arm-kernel <linux-arm-kernel@...ts.infradead.org> Subject: Re: linux-next: build warning after merge of the bpf-next tree On 1/14/20 6:23 AM, Alexei Starovoitov wrote: > On Sun, Jan 12, 2020 at 8:33 PM Zong Li<zong.li@...ive.com> wrote: >> I'm not quite familiar with btf, so I have no idea why there are two >> weak symbols be added in 8580ac9404f6 ("bpf: Process in-kernel BTF") > I can explain what these weak symbols are for, but that won't change > the fact that compiler or linker are buggy. The weak symbols should work > in all cases and compiler should pick correct relocation. > In this case it sounds that compiler picked relative relocation and failed > to reach zero from that address. Sorry for the response delay: I now agree that there is nothing weird about those relocations. All compiler/linker I took a look at (arm64, ppc64 and riscv64) correctly emit an absolute relocation to the address 0 in case of a weak unresolved symbol, so there's no buggy compiler/linker. And regarding ppc warning, the kernel being compiled as -pie, the scripts looks for absolute relocations which it considers as "bad", except for one that is known to be weak and that is ignored: I have just sent a patch to fix this script so that weak undefined symbol relocations are not considered as bad. Thanks, Alex
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