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.
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.
Arnd
