gdb says "Unexpected size of section `.reg-xstate/...' in core file"

gdb says "Unexpected size of section `.reg-xstate/...' in core file"

[Zbigniew Jędrzejewski-Szmek]

Hi,

I'm running gdb (via coredumpctl) on a core file from a program
crashing in Fedora Rawhide. One of the gdb maintainers in Fedora, Jan
Kratochvil, directed me to this mailing list. bt and other commands
work fine, but gdb shows the warning in $subject (and the core file
doesn't seem to be truncated):

$ coredumpctl gdb
...
Using host libthread_db library "/lib64/libthread_db.so.1".
Core was generated by `/usr/lib/systemd/systemd-oomd'.
Program terminated with signal SIGABRT, Aborted.

warning: Unexpected size of section `.reg-xstate/59286' in core file.
#0  0x00007f552f8b3b95 in raise () from /lib64/libc.so.6
(gdb)

It's a VM (libvirt, kvm, uefi). /proc/cpuinfo shows xsave is present:

vendor_id  : GenuineIntel
cpu family : 6
model        : 94
model name   : Intel Core Processor (Skylake, IBRS)
stepping     : 3
microcode    : 0x1
cpu MHz        : 2591.998
cache size     : 16384 KB
physical id    : 0
siblings : 1
core id    : 0
cpu cores  : 1
apicid       : 0
initial apicid : 0
fpu            : yes
fpu_exception  : yes
cpuid level    : 13
wp             : yes
flags            : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx
fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology cpuid tsc_known_freq
pni pclmulqdq vmx ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx
f16c rdrand hypervisor lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb stibp
tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx
rdseed adx smap clflushopt xsaveopt xsavec xgetbv1 xsaves arat umip md_clear arch_capabilities
vmx flags        : vnmi preemption_timer invvpid ept_x_only ept_ad ept_1gb flexpriority tsc_offset vtpr
mtf vapic ept vpid unrestricted_guest shadow_vmcs pml
bugs               : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit
srbds
bogomips           : 5183.99
clflush size       : 64
cache_alignment    : 64
address sizes      : 40 bits physical, 48 bits virtual

The guest has kernel 5.8.0-0.rc2.20200622git625d3449788f.1.fc33.x86_64, and
gdb-9.2-2.fc33.x86_64 which is the latest rawhide build... Does gdb need updating?

Zbyszek

Re: gdb says "Unexpected size of section `.reg-xstate/...' in core file"

[Kevin Buettner]

On Tue, 14 Jul 2020 07:20:43 +0000
Zbigniew J__drzejewski-Szmek <zbyszek@in.waw.pl> wrote:

> I'm running gdb (via coredumpctl) on a core file from a program
> crashing in Fedora Rawhide. One of the gdb maintainers in Fedora, Jan
> Kratochvil, directed me to this mailing list. bt and other commands
> work fine, but gdb shows the warning in $subject (and the core file
> doesn't seem to be truncated):
> 
> $ coredumpctl gdb
> ...
> Using host libthread_db library "/lib64/libthread_db.so.1".
> Core was generated by `/usr/lib/systemd/systemd-oomd'.
> Program terminated with signal SIGABRT, Aborted.
> 
> warning: Unexpected size of section `.reg-xstate/59286' in core file.
> #0  0x00007f552f8b3b95 in raise () from /lib64/libc.so.6
> (gdb)

This looks like the same bug that I investigated and fixed last week. 
It turned out to be a kernel bug.  I sent a patch to the kernel
maintainers; it's been accepted into several development trees.

Here's a link to the Fedora bug report that I filed:

https://bugzilla.redhat.com/show_bug.cgi?id=1858645

Kevin