Re: powerpc: userspace processes crash on abort() from libc.so.6

[Shivaprasad G Bhat <sbhat@linux.ibm.com>]

Hi Shrikanth,


On 8/27/26 5:08 PM, Shrikanth Hegde wrote:
> Hi Shivaprasad.
> 
> On 8/27/26 11:13 AM, Shivaprasad G Bhat wrote:
>>
>> Hi All, Thomas,
>>
>> On my PPC64 machine, I see the below systemd crash orginating from 
>> abort() during boot on top of the tree. Complete dmesg can be seen 
>> here [1]
>>        abort (libc.so.6 + 0x29484)
>>        __libc_message_impl (libc.so.6 + 0x9e00c)
>>        __libc_fatal (libc.so.6 + 0x9e06c)
>>        start_thread (libc.so.6 + 0xadffc)
>>        __clone (libc.so.6 + 0x152d68)
>>        __clone (libc.so.6 + 0x152d68)
>>        create_thread.constprop.0 (libc.so.6 + 0xad9c8)
>>
>> The git bisect pointed me to commit 3424d8c18a7da "(Merge tag 'core- 
>> entry-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/ 
>> tip/tip)"
>>
>> Please find the kernel config used to build the kernel at [2].
>>
>> I have tried applying the pending fixes from Mukesh [3] and Ritesh [4] 
>> for the currently outstanding issues and still see the problem.
>>
>> The system is running Fedora 42, with glibc-2.41-7.fc42.ppc64le. The
>> complete list of toolchain and packages can be found here [5]
>>
>> Thanks and Regards,
>> Shivaprasad
>>
>> References:
>> 1 - https://gist.github.com/ 
>> shivaprasadbhat/6f166374bab12b4f4c1cd4ac829e562c
>> 2 - https://gist.github.com/shivaprasadbhat/ 
>> aa499468e124015eec5932fb13e88e05
>> 3 - https://lore.kernel.org/linuxppc-dev/ 
>> lda1jyut.ritesh.list@gmail.com/#t
>> 4 - https://lore.kernel.org/linuxppc-dev/20260820134718.2176411-1- 
>> mkchauras@gmail.com/
>> 5 - https://gist.github.com/shivaprasadbhat/ 
>> ae56ca849c3009e8642a6313dc465ea7
>>
>> =========
>> Backtrace from dmesg:
>> [   22.039343][ T1833] systemd-coredump[1833]: Module libsystemd- 
>> shared-257.6-1.fc42.so from rpm systemd-257.6-1.fc42.ppc64le
>> [   22.039378][ T1833] systemd-coredump[1833]: Stack trace of thread 
>> 1828:
>> [   22.039378][ T1833] systemd-coredump[1833]: Stack trace of thread 
>> 1828:
>> [   22.039401][ T1833] systemd-coredump[1833]: #0  0x00007fffa4c29484 
>> abort (libc.so.6 + 0x29484)
>> [   22.039401][ T1833] systemd-coredump[1833]: #0  0x00007fffa4c29484 
>> abort (libc.so.6 + 0x29484)
>> [   22.039429][ T1833] systemd-coredump[1833]: #1  0x00007fffa4c9e00c 
>> __libc_message_impl (libc.so.6 + 0x9e00c)
>> [   22.039429][ T1833] systemd-coredump[1833]: #1  0x00007fffa4c9e00c 
>> __libc_message_impl (libc.so.6 + 0x9e00c)
>> [   22.039461][ T1833] systemd-coredump[1833]: #2  0x00007fffa4c9e06c 
>> __libc_fatal (libc.so.6 + 0x9e06c)
>> [   22.039461][ T1833] systemd-coredump[1833]: #2  0x00007fffa4c9e06c 
>> __libc_fatal (libc.so.6 + 0x9e06c)
>> [   22.039491][ T1833] systemd-coredump[1833]: #3  0x00007fffa4cadffc 
>> start_thread (libc.so.6 + 0xadffc)
>> [   22.039491][ T1833] systemd-coredump[1833]: #3  0x00007fffa4cadffc 
>> start_thread (libc.so.6 + 0xadffc)
>> [   22.039521][ T1833] systemd-coredump[1833]: #4  0x00007fffa4d52d68 
>> __clone (libc.so.6 + 0x152d68)
>> [   22.039521][ T1833] systemd-coredump[1833]: #4  0x00007fffa4d52d68 
>> __clone (libc.so.6 + 0x152d68)
>> [   22.039551][ T1833] systemd-coredump[1833]: #5  0x00007fffa4d52d68 
>> __clone (libc.so.6 + 0x152d68)
>> [   22.039551][ T1833] systemd-coredump[1833]: #5  0x00007fffa4d52d68 
>> __clone (libc.so.6 + 0x152d68)
>> [   22.039580][ T1833] systemd-coredump[1833]: #6  0x00007fffa4cad9c8 
>> create_thread.constprop.0 (libc.so.6 + 0xad9c8)
>> [   22.039580][ T1833] systemd-coredump[1833]: #6  0x00007fffa4cad9c8 
>> create_thread.constprop.0 (libc.so.6 + 0xad9c8)
>> [   22.039614][ T1833] systemd-coredump[1833]: #7  0x00000000003af858 
>> n/a (n/a + 0x0)
>> [   22.039614][ T1833] systemd-coredump[1833]: #7  0x00000000003af858 
>> n/a (n/a + 0x0)
>> [   22.039639][ T1833] systemd-coredump[1833]: ELF object binary 
>> architecture: PowerPC64
>> [   22.039639][ T1833] systemd-coredump[1833]: ELF object binary 
>> architecture: PowerPC64
>> [   22.042109][    T1] systemd[1]: systemd-journald.service: Scheduled 
>> restart job, restart counter is at 1.
> 
> I was looking at merge patch and It is possible that TIF_SYSCALL_RET is 
> still set when it is returned
> and maybe causing a mismatch.
> 
> Does below help?
> ---
> 
> --- a/arch/powerpc/kernel/syscall.c
> +++ b/arch/powerpc/kernel/syscall.c
> @@ -19,8 +19,10 @@ notrace long system_call_exception(struct pt_regs 
> *regs, unsigned long r0)
>       long ret;
>       syscall_fn f;
> 
> -    if (unlikely(!syscall_enter_from_user_mode_randomize_stack(regs, 
> &r0)))
> +    if (unlikely(!syscall_enter_from_user_mode_randomize_stack(regs, 
> &r0))) {
> +        clear_thread_flag(TIF_SYSCALL_RET);

Yes. This worked.

Thanks,
Shivaprasad>           return syscall_get_error(current, regs);
> +    }
> 
>       if (unlikely(test_and_clear_thread_flag(TIF_SYSCALL_RET)))
>           return syscall_get_error(current, regs);