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@xxxxxxxxxx> 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@xxxxxxxxxx/
>>
>> 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@xxxxxxxxxx
>
>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.
>
>Thanks
>Baoquan
>
--
Best regards,
Coiby
--
Best regards,
Coiby
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