Compile error ppc64le: Cannot find symbol for section 11: .text.unlikely.
Veronika Kabatova
vkabatov at redhat.com
Wed Mar 2 02:52:12 PST 2022
On Wed, Mar 2, 2022 at 8:50 AM Coiby Xu <coxu at redhat.com> wrote:
>
> On Fri, Feb 25, 2022 at 11:46:41AM +0800, Coiby Xu wrote:
> >On Fri, Dec 03, 2021 at 04:54:19PM +0100, Veronika Kabatova wrote:
> >>On Wed, Dec 1, 2021 at 3:20 AM Coiby Xu <coxu at redhat.com> wrote:
> >>>
> >>>On Wed, Nov 24, 2021 at 09:47:43PM +0800, Baoquan He wrote:
> >>>>On 11/24/21 at 01:47pm, Veronika Kabatova wrote:
> >>>>> Hi,
> >>>>>
> >>>>> for a while we've been seen the following error when compiling
> >>>>> the mainline kernel with gcc 11.2 and binutils 2.37:
> >>>>>
> >>>>> 00:02:32 Cannot find symbol for section 11: .text.unlikely.
> >>>>> 00:02:32 kernel/kexec_file.o: failed
> >>>>> 00:02:32 make[3]: *** [scripts/Makefile.build:287: kernel/kexec_file.o] Error 1
> >>>>> 00:02:32 make[3]: *** Deleting file 'kernel/kexec_file.o'
> >>>>> 00:02:32 make[2]: *** [Makefile:1846: kernel] Error 2
> >>>>> 00:02:32 make[2]: *** Waiting for unfinished jobs....
> >>>>>
> >>>>> The error only happens with ppc64le. I've tested this with cross
> >>>>> compilation, but the only reference to the error I found suggests
> >>>>> the same happens with the native compiles as well:
> >>>>>
> >>>>> https://github.com/groeck/linux-build-test/commit/142cbefbc0d37962c9a6c7f28ee415ecd5fd1e98
> >>>>>
> >>>>> In case it matters, the config used is the Fedora config with
> >>>>> kselftest options enabled, which you can grab from
> >>>>>
> >>>>> https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-trusted-contributors/-/jobs/1760752896/artifacts/raw/artifacts/kernel-mainline.kernel.org-ppc64le-e4e737bb5c170df6135a127739a9e6148ee3da82.config
> >>>>>
> >>>>>
> >>>>> I've reached out to the Fedora compiler folks and Nick Clifton
> >>>>> suggested this is a problem with the kernel:
> >>>>>
> >>>>> This message comes from the recordmcount tool, which is part of the kernel
> >>>>> sources:
> >>>>>
> >>>>> linux/scripts/recordmcount.[ch]
> >>>>>
> >>>>> It appears to be triggered when a compiler update causes code to be
> >>>>> rearranged. The problem has been reported before in various forums,
> >>>>> but in particular I found this reference:
> >>>>>
> >>>>> https://lore.kernel.org/lkml/20201204165742.3815221-2-arnd@kernel.org/
> >>>>>
> >>>>> The point of which to me at least is that this is a kernel issue rather than
> >>>>> a compiler issue. Ie there must be some weak symbols in kexec_file.o file
> >>>>> which need to be moved elsewhere.
> >>>>
> >>>>It could be arch_kexec_kernel_verify_sig() in kernel/kexec_file.c which
> >>>>is __weak, but not implemented in any ARCH. If true, this has been
> >>>>pointed out by Eric in one patch thread from Coiby.
> >>>>
> >>>>[PATCH v3 1/3] kexec: clean up arch_kexec_kernel_verify_sig
> >>>>http://lkml.kernel.org/r/20211018083137.338757-2-coxu@redhat.com
> >>>>
> >>>>Maybe Coiby can fetch above config file and run the test to check.
> >>>
> >>>"[PATCH v3 1/3] kexec: clean up arch_kexec_kernel_verify_sig" alone
> >>>would fix the error. If I turn arch_kexec_apply_relocations{_add,} into
> >
> >Sorry I meant "alone won't fix the error".
> >
> >>>static function, the error would be gone. As attached is the patch would
> >>>make this error disappear.
> >>>
> >>
> >>Thank you! I can confirm the attached patch fixes the problem.
> >>
> >>
> >>Veronika
> >>
> >>>However, s390 and x86 have its own implementation of
> >>>arch_kexec_apply_relocations_add. This makes it looks like to be gcc's
> >>>issue.
> >
> >Based on the above point and further investigation, I think the root cause is
> >find_secsym_ndx in linux/scripts/recordmcount.h,
> > /*
> > * Find a symbol in the given section, to be used as the base for relocating
> > * the table of offsets of calls to mcount. A local or global symbol suffices,
> > * but avoid a Weak symbol because it may be overridden; the change in value
> > * would invalidate the relocations of the offsets of the calls to mcount.
> > * Often the found symbol will be the unnamed local symbol generated by
> > * GNU 'as' for the start of each section. For example:
> > * Num: Value Size Type Bind Vis Ndx Name
> > * 2: 00000000 0 SECTION LOCAL DEFAULT 1
> > */
> > static int find_secsym_ndx(unsigned const txtndx,
> > char const *const txtname,
> > uint_t *const recvalp,
> > unsigned int *sym_index,
> > Elf_Shdr const *const symhdr,
> > Elf32_Word const *symtab,
> > Elf32_Word const *symtab_shndx,
> > Elf_Ehdr const *const ehdr)
> > {
> > ...
> > if (txtndx == get_symindex(symp, symtab, symtab_shndx)
> > /* avoid STB_WEAK */
> >
> > fprintf(stderr, "Cannot find symbol for section %u: %s.\n",
> > txtndx, txtname);
> >
> >This function prints the above warning after failing to find
> >arch_kexec_kernel_verify_sig or arch_kexec_apply_relocations{_add,} in
> >section 11: .text.unlikely. because it ignores the weak symbol and ppc64le
> >doesn't its arch implementations of these functions. I'll see if I can fix
> >it in linux/scripts/recordmcount.h.
>
> After digging deeper into linux/scripts/recordmcount.h, I think this
> issue can be either fixed in the compiler or recordmcount. So I fild two bugs
> - gcc: https://bugzilla.redhat.com/show_bug.cgi?id=2059838
Hi,
I have also opened a BZ for gcc some time ago and that is where I
was redirected to this mailing list, linking it here if it helps:
https://bugzilla.redhat.com/show_bug.cgi?id=2022470
Veronika
> - linux/scripts/recordmcount.h: https://bugzilla.redhat.com/show_bug.cgi?id=2059842
>
> >
> >>>
> >>>
> >>>>
> >>>>Thanks
> >>>>Baoquan
> >>>>
> >>>
> >>>--
> >>>Best regards,
> >>>Coiby
> >>
> >
> >--
> >Best regards,
> >Coiby
>
> --
> Best regards,
> Coiby
>
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