On Wed, Apr 12, 2023 at 01:29:49PM -0700, Nick Desaulniers wrote: > On Fri, Apr 07, 2023 at 05:09:55PM -0700, Josh Poimboeuf wrote: > > Fixes the following warning: > > > > vmlinux.o: warning: objtool: x86_64_start_reservations+0x28: unreachable instruction > > > > Reported-by: kernel test robot <lkp@xxxxxxxxx> > > Link: https://lore.kernel.org/r/202302161142.K3ziREaj-lkp@xxxxxxxxx/ > > Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > > Ah, I just realized that my series will conflict with this. > https://lore.kernel.org/llvm/20230412-no_stackp-v1-1-46a69b507a4b@xxxxxxxxxx/ > Perhaps if my series gets positive feedback; I can rebase it on top of > this and it can become part of your series? Sure, I can take these on top. > For this patch, > Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Thanks! > Though I'm curious, it does look like it's necessary because of 01/11 in > the series? Any idea how the 0day bot report happened before 1/11 > existed? > > > (Surely gcc isn't assuming a weak function is implicitly noreturn and > make optimizations based on that (that's one hazard I'm worried about)?) As far as I can tell, GCC has been doing the right thing here, and it's instead been objtool getting confused by weak noreturns. That gets fixed later in patch 9. > It looks like perhaps the link to > https://lore.kernel.org/all/202302161142.K3ziREaj-lkp@xxxxxxxxx/ > on 2/11 was 0day testing the arch-cpu-idle-dead-noreturn branch of your > kernel tree > https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/log/?h=arch-cpu-idle-dead-noreturn > , which had 1/11 in it, IIUC? Perhaps this link should go on 1/11 > rather than 2/11? Good catch, patch 1 does introduce the warning. I think I'll just squash patches 1 and 2 so as not to break bisection. > Looking back at 1/11, 3/11, 8/11 I noticed not all patches have links to 0day > reports. Are you able to flesh out more info how/what/when such objtool > warnings are observed? Are the warnings ever results of patches earlier > in the series? Hopefully not, it's best to not introduce warnings even temporarily. I was doing a lot of build testing at the time with various branches, so it's possible. I'll see if I can figure out how I triggered those warnings and document that in the commit logs if possible. -- Josh
