On Wed, Jun 09, 2021 at 08:16:11AM -0700, Guenter Roeck wrote: > On Wed, Jun 09, 2021 at 01:24:18PM +0200, Arnd Bergmann wrote: > > On Wed, Jun 9, 2021 at 1:05 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > > On Thu, Feb 04, 2021 at 04:29:47PM +0100, Arnd Bergmann wrote: > > > > From: Arnd Bergmann <arnd@xxxxxxxx> > > > > > > > > ARM randconfig builds with lld sometimes show a build failure > > > > from kallsyms: > > > > > > > > Inconsistent kallsyms data > > > > Try make KALLSYMS_EXTRA_PASS=1 as a workaround > > > > > > > > The problem is the veneers/thunks getting added by the linker extend > > > > the symbol table, which in turn leads to more veneers being needed, > > > > so it may take a few extra iterations to converge. > > > > > > > > This bug has been fixed multiple times before, but comes back every time > > > > a new symbol name is used. lld uses a different set of idenitifiers from > > > > ld.bfd, so the additional ones need to be added as well. > > > > > > > > I looked through the sources and found that arm64 and mips define similar > > > > prefixes, so I'm adding those as well, aside from the ones I observed. I'm > > > > not sure about powerpc64, which seems to already be handled through a > > > > section match, but if it comes back, the "__long_branch_" and "__plt_" > > > > prefixes would have to get added as well. > > > > > > > > > > This is such a whack-a-mole. The problem is hitting us yet again. I suspect > > > it may be due to a new version of lld using new symbols, but I didn't really > > > try to track it down. Is there an easy way to search for missed symbols ? > > > > The way I did it previously was to hack Kbuild to not remove the temporary > > files after a failure, and then compare the "objdump --syms" output of the > > last two stages. > > Problem with that is that we have a non-deterministic problem: The build > fails for us on some build servers, but we are unable to reproduce the > problem when building the same image manually on a development server. > That is similar to what I had observed before, where powerpc builds would > pass on one server, but the same kernel with the same configuration would > fail to build on a second almost identical server. It would really be great > if we can find a better solution. > > > > > I suppose we could improve the situation if scripts/link-vmlinux.sh was able > > to do that automatically, and compare the kallsyms output .S file between > > steps 1 and 2. > > Comparing the .S files doesn't result in useful data; turns out there are > always irrelevant differences. We'll try to run a diff on the output of > "objdump --syms". Hopefully that will generate something useful. > Turns out it wasn't that useful. chromeos-kernel-5_10-5.10.42-r406: Symbol file differences: chromeos-kernel-5_10-5.10.42-r406: 7c7 chromeos-kernel-5_10-5.10.42-r406: < 00000000000325c8 g .rodata 0000000000000000 kallsyms_relative_base chromeos-kernel-5_10-5.10.42-r406: --- chromeos-kernel-5_10-5.10.42-r406: > 00000000000325c0 g .rodata 0000000000000000 kallsyms_relative_base chromeos-kernel-5_10-5.10.42-r406: 9,13c9,13 chromeos-kernel-5_10-5.10.42-r406: < 00000000000325d0 g .rodata 0000000000000000 kallsyms_num_syms chromeos-kernel-5_10-5.10.42-r406: < 00000000000325d8 g .rodata 0000000000000000 kallsyms_names chromeos-kernel-5_10-5.10.42-r406: < 00000000000cd7f0 g .rodata 0000000000000000 kallsyms_markers chromeos-kernel-5_10-5.10.42-r406: < 00000000000cdb18 g .rodata 0000000000000000 kallsyms_token_table chromeos-kernel-5_10-5.10.42-r406: < 00000000000cde78 g .rodata 0000000000000000 kallsyms_token_index chromeos-kernel-5_10-5.10.42-r406: --- chromeos-kernel-5_10-5.10.42-r406: > 00000000000325c8 g .rodata 0000000000000000 kallsyms_num_syms chromeos-kernel-5_10-5.10.42-r406: > 00000000000325d0 g .rodata 0000000000000000 kallsyms_names chromeos-kernel-5_10-5.10.42-r406: > 00000000000cd7d8 g .rodata 0000000000000000 kallsyms_markers chromeos-kernel-5_10-5.10.42-r406: > 00000000000cdb00 g .rodata 0000000000000000 kallsyms_token_table chromeos-kernel-5_10-5.10.42-r406: > 00000000000cde60 g .rodata 0000000000000000 kallsyms_token_index I thought I'd see the added symbols, but it looks like the only difference between the two files is the addresses. What am I missing ? Thanks, Guenter
