[Buildroot] Segfault on init (gcc-11, glibc-2.32-37, linux-5.13)

[Romain Naour]

Hello Maxim,

Le 08/07/2021 à 10:48, Maxim Kochetkov a écrit :
> Hi, all!
> 
> I found such a problem on x86 (gcc-11, glibc-2.32-37, linux-5.13):
> -------------------------------------------------------------------
>         0.0731111 Spectre  2: Spectre mitigation: kernel not compiled with retpoli
>                 auailablet
>         0.28786g atio21    segfault at 10 ip 00007f5f9a8d6e10 sp
> 00007fffa751f5c8 error 9 in Id-2.32.sof7f5f9a8cd000.200001
>         0.2882001 Code: 97 01 00 e8 12 60 00 00 98 86 9c 29 00 e9 e8 fb ff ff Of
> lf 89 00 00 00 00 00 91 57 91 56 91 55 91 54 99 89
> fc 55 98 89 d5 53 <69> 98 rtb 09 25 10 00 00 00 98 81 ec a0 00 00 00 98 89 79 29
> 10 98
>         0.2887921 Eernel paGame:ic - not syncing: Attempted to kill init.,
> exitcode=0x00000006
>         0.2890261 CPU: 9       I Comm: init Mot tainted 5.13.0.3 El
>         0 2892091 Hardware      Supermicro Super SeruerAllSSH-III9F, BIOS 2.5
> 11,26,020
>         0 2899931 Call Trace:
>         0 2895211 dump_stackt0x6,0x88
>         0 2896231 panictOxfdt0x287
>         0 2897161 doexit.coldt0x21,0x60
>         0 2898251 do_groupexittOx36,0xa0
>         0 2899371 get signaltOxe3t0x6f0
>         0 2900951 arch_do_sigoal or restarttOrd6t0x6c0
>         2901921 7 _rou_spin_unlock_irgrestoretOrlarOx20
>         0 2903981 7 force sig_ info to tasktOrcOtOxf0
>         0 2909891 exit to user mode preparetrd,Ox18
>         0 2906371 irgentryexit to user modetO0x9t0x300
>         0 2907811 irgentryexitt0x33,0x90
>         0 2908991 exc_page_faultt0x2c0Ax630
>         0 2910161 7 exit_to user mode preparet0x3,0x180
>         0 2911691 7 asmexc_page faulttOx8t0x30
>         0 2912981 asmexc_page_faulttOxlet0x30
>                 BIP: 0033:0x7f5f9a8d6e10
>         0.2915351 Code: 97 01 00 e8 12 60 00 00 98 86 9c 29 00 e9 e8 fb ff ff Of
> lf 89 00 00 00 00 00 91 57 91 56 91 55 91 54 99 89
> fc 55 98 89 d5 53 <69> 98 rtb 09 25 10 00 00 00 98 81 ec a0 00 00 00 98 89 79 29
> 10 98
>         0.2921211•
>         0.2922851 BAX: 00007fffa751f690 BBX: 00007fffa751f6b0 BCX: 00007f5f9a8f8ae8
>         0 2925091 BOX: 00007fffa751f688 BSI: 00007f5f9a8f8750 EDI: 00007f5f9a8ee191
>         0 2927311 BBP: 00007fffa751f688 B08: 00007fffa751f6b0 B09: 0000000000000000
>         0 2929551 B10: 0000000070000022 Ell: 0000000000000032 B12: 00007f5f9a8ee191
>         0 2931771 B13: 00007f5f9a8f8750 B19: 00007fffa751f688 B15: 000000006fffff91
>         0 2939091 Eernel Offset: Oxl6c00000 from Oxffffffff81000000 (relocation
> range: Oxffffffff80000000-Oxffffffffbfffffff7
>         0 2937901 -I end Eeroel panic - not syncing: Attempted to kill init,
> exitcode=0x00000006 1---
> 
> -------------------------------------------------------------------
> I did some additional test with different gcc/libc variants:
>      gcc |                  libc |         result |
> ---------|-----------------------|----------------|
>   11.1.0 |   2.32-37-g760e1d2878 |       SEGFAULT |
>   10.3.0 |   2.32-37-g760e1d2878 |             OK |
>   10.3.0 |      uClibc-ng-1.0.38 |             OK |
>   11.1.0 |      uClibc-ng-1.0.38 |             OK |
>   11.1.0 |      uClibc-ng-1.0.38 |             OK |
>   11.1.0 |   2.32-49-g27e892f660 |       SEGFAULT |
>   11.1.0 |   2.33-46-gedfd11197e |             OK |
> ---------------------------------------------------------
> It seems like we need to bump glibc version to 2.33-46-gedfd11197e for gcc 11 on
> x86.

Thanks for the report, the investigation and the version bump!

Indeed, Buildroot internal toolchains are only tested with uclibc-ng thanks to
the Qemu defconfigs runtime testing in Gitlab.

The toolchain-builder project can complete this testing on musl and glibc but it
take longer time to run.

Best regards,
Romain