cmd/compile: illegal Instruction on POWER8 with go 1.13

[trdyer]

What version of Go are you using (go version)?

$ go version
1.13

Does this issue reproduce with the latest release?

Yes, it occurs when built with go 1.14 as well.

What operating system and processor architecture are you using (go env)?

go env Output

[user@redacted ~]# uname -a
Linux redacted 3.10.0-327.4.4.el7.ppc64 #1 SMP Thu Dec 17 15:52:21 EST 2015 ppc64 ppc64 ppc64 GNU/Linux
[user@redacted ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.2 (Maipo)
[user@redacted ~]# lscpu
Architecture:          ppc64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Big Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    4
Core(s) per socket:    1
Socket(s):             2
NUMA node(s):          1
Model:                 IBM,8231-E1C
L1d cache:             32K
L1i cache:             32K
NUMA node0 CPU(s):     0-7
[root@pbul-rhel7-ppc64-01 ~]#

What did you do?

I built a minimal go binary on macOS Catalina cross-compiling to linux-ppc64 using https://github.com/trdyer/go-test-ppc64

My test platforms are: linux/amd64 solaris/amd64 darwin/amd64 linux/s390x aix/ppc64 linux/ppc64 linux/ppc64le

I scp'd the binary to the remote rhel7/ppc64 server and executed the program.

What did you expect to see?

The output should have said "whats going on!"

What did you see instead?

Illegal Instruction

As far as I can tell this is a POWER8 CPU that should be supported.

[trdyer]

I also ran it on a POWER8 server with a slightly different CPU and it executed.

0 user@redacted /tmp # ./bt-test_linux_ppc64
whats going on!
0 user@redacted /tmp # uname -a
Linux redacted 3.10.0-327.10.1.el7.ppc64 #1 SMP Sat Jan 23 04:57:27 EST 2016 ppc64 ppc64 ppc64 GNU/Linux
0 user@redacted /tmp # cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.2 (Maipo)
0 user@redacted /tmp # lscpu
Architecture:          ppc64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Big Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    8
Core(s) per socket:    1
Socket(s):             1
NUMA node(s):          2
Model:                 IBM,8284-22A
L1d cache:             64K
L1i cache:             32K
NUMA node0 CPU(s):     0-7
NUMA node2 CPU(s):
0 user@redacted /tmp #

[randall77]

@laboger
If you try it with tip, it should print the bytes for the instruction that caused the SIGILL. That might help.

[trdyer]

@randall77 @laboger in my reproductions it seems to be related to the CPU model. but maybe also kernel version.

For instance this rhel6 box with the same CPU model as my working rhel7 example does not work

[user@redacted ~]# lscpu
Architecture:          ppc64
Byte Order:            Big Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    4
Core(s) per socket:    1
Socket(s):             1
NUMA node(s):          1
Model:                 IBM,8284-22A
L1d cache:             64K
L1i cache:             32K
NUMA node0 CPU(s):     0-3
[user@redacted ~]# uname -a
Linux redacted 2.6.32-573.18.1.el6.ppc64 #1 SMP Wed Jan 6 11:15:06 EST 2016 ppc64 ppc64 ppc64 GNU/Linux

[laboger]

This does not fail for me on the linux/ppc64 systems I have. I even tried doing a cross compile with latest go1.13 and moving it over to a power8 and it worked fine. I am not familiar with the model you are using and don't have access to such a system.

Can you use gdb to find the bad instruction?
gdb ./bt-test_linux_ppc64
run
When it hits the SIGILL do:
x/i $pc

[laboger]

The model you display in your go env output is:
Model: IBM,8231-E1C
And this is a power7.

[laboger]

What RHEL 6 do you have on your 8284-22A? It should be at least RHEL 6.5 or RHEL 7 according to this https://www.ibm.com/support/knowledgecenter/linuxonibm/liaam/liaamdistros.html#liaamdistros__supportedpower8.

[trdyer]

@laboger
I have rhel 6.7 on the 8284-22A.

[user@rhel6-ppc64-01 tmp]# lscpu
Architecture:          ppc64
Byte Order:            Big Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    4
Core(s) per socket:    1
Socket(s):             1
NUMA node(s):          1
Model:                 IBM,8284-22A
L1d cache:             64K
L1i cache:             32K
NUMA node0 CPU(s):     0-3
[user@rhel6-ppc64-01 tmp]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.7 (Santiago)

with go 1.13

(gdb) run
Starting program: /tmp/bt-test_linux_ppc64

Program received signal SIGILL, Illegal instruction.
0x000000000004995c in runtime.check () at /usr/local/go/src/runtime/runtime1.go:238
238	/usr/local/go/src/runtime/runtime1.go: No such file or directory.
	in /usr/local/go/src/runtime/runtime1.go
(gdb) x/i $pc
=> 0x4995c :	lbarx   r31,0,r5
(gdb)

and go 1.14

(gdb) run
Starting program: /tmp/bt-test_linux_ppc64

Program received signal SIGILL, Illegal instruction.
0x000000000005007c in runtime.check () at /usr/local/go/src/runtime/runtime1.go:238
238	/usr/local/go/src/runtime/runtime1.go: No such file or directory.
	in /usr/local/go/src/runtime/runtime1.go
(gdb) x/i $pc
=> 0x5007c :	lbarx   r31,0,r5
(gdb)

[laboger]

Can you provide the full output when it gets the SIGILL (not using gdb)?

[laboger]

Or in gdb after you hit the SIGILL:
p $_siginfo.si_code

[trdyer]

[user@rhel6-ppc64-01 tmp]# ./bt-test_linux_ppc64
Illegal instruction
[user@rhel6-ppc64-01 tmp]# gdb ./bt-test_linux_ppc64
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-83.el6)
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "ppc64-redhat-linux-gnu".
For bug reporting instructions, please see:
...
Reading symbols from /tmp/bt-test_linux_ppc64...done.
warning: Missing auto-load scripts referenced in section .debug_gdb_scripts
of file /tmp/bt-test_linux_ppc64
Use `info auto-load python [REGEXP]' to list them.
(gdb) run
Starting program: /tmp/bt-test_linux_ppc64

Program received signal SIGILL, Illegal instruction.
0x000000000004995c in runtime.check () at /usr/local/go/src/runtime/runtime1.go:238
238	/usr/local/go/src/runtime/runtime1.go: No such file or directory.
	in /usr/local/go/src/runtime/runtime1.go
(gdb) p $_siginfo.si_code
Attempt to extract a component of a value that is not a structure.
(gdb)

[laboger]

Can you display /proc/cpuinfo on your RHEL6.

[laboger]

The suspicion is that your RHEL6.7 kernel is set up to run in power7 compat mode. Also run:
LD_SHOW_AUXV=1 /bin/true | grep _PLATFORM