[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
This bug was fixed in the package qemu - 1:4.2-3ubuntu6.5
---
qemu (1:4.2-3ubuntu6.5) focal; urgency=medium
* further stabilize qemu by importing patches of qemu v4.2.1
Fixes (LP: #1891203) and (LP: #1891877)
- d/p/stable/lp-1891877-*
- as part of the stabilization this also fixes an
riscv emulation issue due to the CVE-2020-13754 fixes via
d/p/ubuntu/hw-riscv-Allow-64-bit-access-to-SiFive-CLINT.patch
* fix s390x SQXBR emulation (LP: #1883984)
- d/p/ubuntu/lp-1883984-target-s390x-Fix-SQXBR.patch
* fix -no-reboot for s390x protvirt guests (LP: #1890154)
- d/p/ubuntu/lp-1890154-s390x-protvirt-allow-to-IPL-secure-guests-with-*
-- Christian Ehrhardt Wed, 19 Aug
2020 13:40:49 +0200
** Changed in: qemu (Ubuntu Focal)
Status: Fix Committed => Fix Released
** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2020-13754
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Released
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Fix Released
Bug description:
[Impact]
* An instruction was described wrong so that on usage the program would
crash.
[Test Case]
* Run s390x in emulation and there use this program:
For simplicity and speed you can use KVM guest as usual on s390x, that
after prep of the test you run in qemu-tcg like:
$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
Obviously is you have no s390x access you need to use emulation right
away.
* Build and run failing program
$ sudo apt install clang
$ cat > bug-sqrtl-one-line.c << EOF
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
EOF
$ cc bug-sqrtl-one-line.c
$ ./a.out
Segmentation fault (core dumped)
qemu is dead by now as long as the bug is present
[Regression Potential]
* The change only modifies 128 bit square root on s390x so regressions
should be limited to exactly that - which formerly before this fix was
a broken instruction.
[Other Info]
* n/a
---
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
old version
sudo apt install qemu-system-s390x=1:4.2-3ubuntu6.4
...test as listed in the test instructions ...
ubuntu@focal-sqxbr:~$ ./a.out
Segmentation fault
(qemu is dead at this point)
$ sudo apt install qemu-system-s390x=1:4.2-3ubuntu6.5
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
qemu-system-s390x
1 upgraded, 0 newly installed, 0 to remove and 315 not upgraded.
Need to get 2334 kB of archives.
After this operation, 4096 B of additional disk space will be used.
Get:1 http://ports.ubuntu.com focal-proposed/main s390x qemu-system-s390x s390x
1:4.2-3ubuntu6.5 [2334 kB]
Fetched 2334 kB in 1s (3927 kB/s)
(Reading database ... 203254 files and directories currently installed.)
Preparing to unpack .../qemu-system-s390x_1%3a4.2-3ubuntu6.5_s390x.deb ...
Unpacking qemu-system-s390x (1:4.2-3ubuntu6.5) over (1:4.2-3ubuntu6.4) ...
Setting up qemu-system-s390x (1:4.2-3ubuntu6.5) ...
Processing triggers for man-db (2.9.3-2) ...
ubuntu@s1lp05:~$
ubuntu@focal-sqxbr:~$ ./a.out
(no crash)
Setting verified
** Tags removed: verification-needed verification-needed-focal
** Tags added: verification-done verification-done-focal
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Released
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Fix Committed
Bug description:
[Impact]
* An instruction was described wrong so that on usage the program would
crash.
[Test Case]
* Run s390x in emulation and there use this program:
For simplicity and speed you can use KVM guest as usual on s390x, that
after prep of the test you run in qemu-tcg like:
$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
Obviously is you have no s390x access you need to use emulation right
away.
* Build and run failing program
$ sudo apt install clang
$ cat > bug-sqrtl-one-line.c << EOF
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
EOF
$ cc bug-sqrtl-one-line.c
$ ./a.out
Segmentation fault (core dumped)
qemu is dead by now as long as the bug is present
[Regression Potential]
* The change only modifies 128 bit square root on s390x so regressions
should be limited to exactly that - which formerly before this fix was
a broken instruction.
[Other Info]
* n/a
---
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
Hello Nelson, or anyone else affected,
Accepted qemu into focal-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/qemu/1:4.2-3ubuntu6.5
in a few hours, and then in the -proposed repository.
Please help us by testing this new package. See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed. Your feedback will aid us getting this
update out to other Ubuntu users.
If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
focal to verification-done-focal. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-focal. In either case, without details of your testing we will
not be able to proceed.
Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in
advance for helping!
N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.
** Changed in: qemu (Ubuntu Focal)
Status: Triaged => Fix Committed
** Tags added: verification-needed verification-needed-focal
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Released
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Fix Committed
Bug description:
[Impact]
* An instruction was described wrong so that on usage the program would
crash.
[Test Case]
* Run s390x in emulation and there use this program:
For simplicity and speed you can use KVM guest as usual on s390x, that
after prep of the test you run in qemu-tcg like:
$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
Obviously is you have no s390x access you need to use emulation right
away.
* Build and run failing program
$ sudo apt install clang
$ cat > bug-sqrtl-one-line.c << EOF
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
EOF
$ cc bug-sqrtl-one-line.c
$ ./a.out
Segmentation fault (core dumped)
qemu is dead by now as long as the bug is present
[Regression Potential]
* The change only modifies 128 bit square root on s390x so regressions
should be limited to exactly that - which formerly before this fix was
a broken instruction.
[Other Info]
* n/a
---
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
** Changed in: qemu
Status: Fix Committed => Fix Released
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Released
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Triaged
Bug description:
[Impact]
* An instruction was described wrong so that on usage the program would
crash.
[Test Case]
* Run s390x in emulation and there use this program:
For simplicity and speed you can use KVM guest as usual on s390x, that
after prep of the test you run in qemu-tcg like:
$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
Obviously is you have no s390x access you need to use emulation right
away.
* Build and run failing program
$ sudo apt install clang
$ cat > bug-sqrtl-one-line.c << EOF
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
EOF
$ cc bug-sqrtl-one-line.c
$ ./a.out
Segmentation fault (core dumped)
qemu is dead by now as long as the bug is present
[Regression Potential]
* The change only modifies 128 bit square root on s390x so regressions
should be limited to exactly that - which formerly before this fix was
a broken instruction.
[Other Info]
* n/a
---
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
** Merge proposal linked:
https://code.launchpad.net/~paelzer/ubuntu/+source/qemu/+git/qemu/+merge/389527
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Triaged
Bug description:
[Impact]
* An instruction was described wrong so that on usage the program would
crash.
[Test Case]
* Run s390x in emulation and there use this program:
For simplicity and speed you can use KVM guest as usual on s390x, that
after prep of the test you run in qemu-tcg like:
$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
Obviously is you have no s390x access you need to use emulation right
away.
* Build and run failing program
$ sudo apt install clang
$ cat > bug-sqrtl-one-line.c << EOF
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
EOF
$ cc bug-sqrtl-one-line.c
$ ./a.out
Segmentation fault (core dumped)
qemu is dead by now as long as the bug is present
[Regression Potential]
* The change only modifies 128 bit square root on s390x so regressions
should be limited to exactly that - which formerly before this fix was
a broken instruction.
[Other Info]
* n/a
---
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
Note: final upstream commit link
https://git.qemu.org/?p=qemu.git;a=commit;h=9bf728a09bf7509b27543664f9cca6f4f337f608
** Changed in: qemu (Ubuntu)
Assignee: Christian Ehrhardt (paelzer) => (unassigned)
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Triaged
Bug description:
[Impact]
* An instruction was described wrong so that on usage the program would
crash.
[Test Case]
* Run s390x in emulation and there use this program:
For simplicity and speed you can use KVM guest as usual on s390x, that
after prep of the test you run in qemu-tcg like:
$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
Obviously is you have no s390x access you need to use emulation right
away.
* Build and run failing program
$ sudo apt install clang
$ cat > bug-sqrtl-one-line.c << EOF
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
EOF
$ cc bug-sqrtl-one-line.c
$ ./a.out
Segmentation fault (core dumped)
qemu is dead by now as long as the bug is present
[Regression Potential]
* The change only modifies 128 bit square root on s390x so regressions
should be limited to exactly that - which formerly before this fix was
a broken instruction.
[Other Info]
* n/a
---
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
** Description changed:
+ [Impact]
+
+ * An instruction was described wrong so that on usage the program would
+crash.
+
+ [Test Case]
+
+ * Run s390x in emulation and there use this program:
+For simplicity and speed you can use KVM guest as usual on s390x, that
+after prep of the test you run in qemu-tcg like:
+
+$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
+Obviously is you have no s390x access you need to use emulation right
+away.
+
+ * Build and run failing program
+$ sudo apt install clang
+$ cat > bug-sqrtl-one-line.c << EOF
+ int main(void) { volatile long double x, r; x = 4.0L; __asm__
+ __volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
+ EOF
+$ cc bug-sqrtl-one-line.c
+$ ./a.out
+Segmentation fault (core dumped)
+
+qemu is dead by now as long as the bug is present
+
+ [Regression Potential]
+
+ * The change only modifies 128 bit square root on s390x so regressions
+should be limited to exactly that - which formerly before this fix was
+a broken instruction.
+
+ [Other Info]
+
+ * n/a
+
+ ---
+
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
- that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
- (Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
- workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
+ that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
+ (Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
+ workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Triaged
Bug description:
[Impact]
* An instruction was described wrong so that on usage the program would
crash.
[Test Case]
* Run s390x in emulation and there use this program:
For simplicity and speed you can use KVM guest as usual on s390x, that
after prep of the test you run in qemu-tcg like:
$ sudo qemu-system-s390x -machine s390-ccw-virtio,accel=tcg -cpu
max,zpci=on -serial mon:stdio -display none -m 4096 -nic
user,model=virtio,hostfwd=tcp::-:22 -drive
file=/var/lib/uvtool/libvirt/images/focal-sqxbr.qcow,if=none,id=drive-virtio-disk0,format=qcow2,cache=none
-device
virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off
Obviously is you have no s390x access you need to use emulation right
away.
* Build and run failing program
$ sudo apt install clang
$ cat > bug-sqrtl-one-line.c << EOF
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
EOF
$ cc bug-sqrtl-one-line.c
$ ./a.out
Segmentation fault (core dumped)
qemu is dead by now as long as the bug is present
[Regression Potential]
* The change only modifies 128 bit square root on s390x so regressions
should be limited to exactly that - which formerly before this fix was
a broken instruction.
[Other Info]
* n/a
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
This bug was fixed in the package qemu - 1:5.0-5ubuntu4
---
qemu (1:5.0-5ubuntu4) groovy; urgency=medium
* xen: provide compat links to what libxen-dev reports where to find
the binaries (LP: #1890005)
* d/p/ubuntu/lp-1883984-target-s390x-Fix-SQXBR.patch: avoid crash on
SQXBR (LP: #1883984)
* d/p/lp-1890154-*: fix -no-reboot on s390x secure boot (LP: #1890154)
-- Christian Ehrhardt Mon, 03 Aug
2020 07:15:28 +0200
** Changed in: qemu (Ubuntu)
Status: In Progress => Fix Released
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Focal:
Triaged
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
** Also affects: qemu (Ubuntu Focal)
Importance: Undecided
Status: New
** Changed in: qemu (Ubuntu Focal)
Status: New => Triaged
** Changed in: qemu (Ubuntu Focal)
Importance: Undecided => Medium
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Status in qemu package in Ubuntu:
In Progress
Status in qemu source package in Focal:
Triaged
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
** Merge proposal linked:
https://code.launchpad.net/~paelzer/ubuntu/+source/qemu/+git/qemu/+merge/388545
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Status in qemu package in Ubuntu:
In Progress
Status in qemu source package in Focal:
Triaged
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
** Also affects: qemu (Ubuntu)
Importance: Undecided
Status: New
** Changed in: qemu (Ubuntu)
Status: New => In Progress
** Changed in: qemu (Ubuntu)
Assignee: (unassigned) => Christian Ehrhardt (paelzer)
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Status in qemu package in Ubuntu:
In Progress
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
** Changed in: qemu
Status: Confirmed => Fix Committed
--
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Fix Committed
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
I confirm that the patch https://lists.gnu.org/archive/html/qemu-
s390x/2020-06/msg00213.html fixes the issue, both for qemu-s390x and
qemu-system-s390x.
Thanks Richard!
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https://bugs.launchpad.net/bugs/1883984
Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Confirmed
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
With --enable-debug,
qemu-s390x: /home/rth/qemu/qemu/include/tcg/tcg.h:687: temp_idx:
Assertion `n >= 0 && n < tcg_ctx->nb_temps' failed.
which turns out to be related to a null-pointer temporary.
** Changed in: qemu
Status: New => Confirmed
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Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
Confirmed
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
[Bug 1883984] Re: QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
Another way to reproduce this bug is with qemu-s390x and a cross-
compiled binary:
$ s390x-linux-gnu-gcc-5 -static -o bug-sqrtl-one-line.s390x bug-sqrtl-one-line.c
$ qemu-s390x bug-sqrtl-one-line.s390x
Segmentation fault (core dumped)
Find attached the binary.
** Attachment added: "statically compiled binary"
https://bugs.launchpad.net/qemu/+bug/1883984/+attachment/5385168/+files/bug-sqrtl-one-line.s390x
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Title:
QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-
s390x
Status in QEMU:
New
Bug description:
In porting software to guest Ubuntu 18.04 and 20.04 VMs for S/390x, I
discovered
that some of my own numerical programs, and also a GNU configure script for at
least one package with CC=clang, would cause an instant crash of the VM,
sometimes
also destroying recently opened files, and producing long strings of NUL
characters
in /var/log/syslog in the S/390 guest O/S.
Further detective work narrowed the cause of the crash down to a single IBM
S/390
instruction: sqxbr (128-bit IEEE 754 square root). Here is a one-line program
that when compiled and run on a VM hosted on QEMUcc emulator version 4.2.0
(Debian 1:4.2-3ubuntu6.1) [hosted on Ubuntu 20.04 on a Dell Precision 7920
workstation with an Intel Xeon Platinum 8253 CPU], and also on QEMU emulator
version 5.0.0, reproducibly produces a VM crash under qemu-system-s390x.
% cat bug-sqrtl-one-line.c
int main(void) { volatile long double x, r; x = 4.0L; __asm__
__volatile__("sqxbr %0, %1" : "=f" (r) : "f" (x)); return (0);}
% cc bug-sqrtl-one-line.c && ./a.out
Segmentation fault (core dumped)
The problem code may be the function float128_sqrt() defined in
qemu-5.0.0/fpu/softfloat.c
starting at line 7619. I have NOT attempted to run the qemu-system-s390x
executable
under a debugger. However, I observe that S/390 is the only CPU family that
I know of,
except possibly for a Fujitsu SPARC-64, that has a 128-bit square root in
hardware.
Thus, this instruction bug may not have been seen before.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1883984/+subscriptions
