1 files changed, 154 insertions, 0 deletions
diff --git a/results/classifier/105/network/1883984 b/results/classifier/105/network/1883984
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--- /dev/null
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@@ -0,0 +1,154 @@
+semantic: 0.931
+network: 0.925
+other: 0.924
+device: 0.915
+instruction: 0.906
+boot: 0.902
+graphic: 0.902
+vnc: 0.900
+assembly: 0.881
+KVM: 0.877
+mistranslation: 0.867
+socket: 0.826
+
+QEMU S/390x sqxbr (128-bit IEEE 754 square root) crashes qemu-system-s390x
+
+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.
+
+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.
+
+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.
+
+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!
+
+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 <email address hidden>  Mon, 03 Aug 2020 07:15:28 +0200
+
+Note: final upstream commit link https://git.qemu.org/?p=qemu.git;a=commit;h=9bf728a09bf7509b27543664f9cca6f4f337f608
+
+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.
+
+All autopkgtests for the newly accepted qemu (1:4.2-3ubuntu6.5) for focal have finished running.
+The following regressions have been reported in tests triggered by the package:
+
+ubuntu-image/1.9+20.04ubuntu1 (amd64)
+systemd/245.4-4ubuntu3.2 (amd64, armhf, s390x, ppc64el)
+livecd-rootfs/2.664.4 (amd64, arm64, s390x, ppc64el)
+
+
+Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].
+
+https://people.canonical.com/~ubuntu-archive/proposed-migration/focal/update_excuses.html#qemu
+
+[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions
+
+Thank you!
+
+
+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
+
+The verification of the Stable Release Update for qemu has completed successfully and the package is now being released to -updates.  Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report.  In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.
+
+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 <email address hidden>  Wed, 19 Aug 2020 13:40:49 +0200
+