unexpected end of section

[nickdesaulniers]

via https://github.com/ClangBuiltLinux/continuous-integration2/runs/3927890481?check_suite_focus=true:

Warning: sound/pci/trident/snd-trident.lto.o: warning: objtool: .text.snd_trident_free_voice: unexpected end of section
Warning: drivers/video/fbdev/intelfb/intelfb.lto.o: warning: objtool: .text.intelfbhw_validate_mode: unexpected end of section
Warning: drivers/net/ethernet/wiznet/w5100.lto.o: warning: objtool: .text.w5100_tx_skb: unexpected end of section
Warning: drivers/net/ethernet/wiznet/w5100.lto.o: warning: objtool: .text.w5100_readbuf: unexpected end of section

I'm surprised to see .lto.o files as part of allmodconfig. Isn't LTO disabled for allmodconfig?

[nathanchance]

That is an allmodconfig + ThinLTO build.

[nickdesaulniers]

ah, right, the "kconfig" is printed from the build.json (otherwise the config/build name is cutoff in github UI for me).

[nathanchance]

Reported upstream: https://reviews.llvm.org/D105169#3116810

I believe current ToT should be fine, as it has a revert of that change: llvm/llvm-project@fd9b099

[nathanchance]

Closing as the problematic commit has been reverted and we have a reproducer so that it is fixed in the next revision.

[nathanchance]

This is likely going to come back so I am preemptively reopening this.

On Monday, I will try to distill down some of the warnings I see and start a thread with Josh and Peter upstream to see if there is any way to minimize the impact of this change in objtool.

[nathanchance]

llvm/llvm-project@1b1c8d8

[nickdesaulniers]

-Xclang -disable-noundef-analysis might be able to get us back to the previous state, for now.

[nathanchance]

I am pretty sure all of these were a result of CONFIG_UBSAN_DIV_ZERO (LTO enables -ffunction-sections so "fallthrough" warnings become "unexpected end of section" warnings), so I am going to dedup this for #1657, which has more information.