Public bug reported: I noticed random looking SIGSEGV to application when trying to continue execution after first breakpoint. I now seem to have narrowed the issue to SIMD instruction with memory operand as first breakpoint location. I haven't managed to figure out why the SIGSEGV is delivered to the debugger application.
It is important have first breakpoint exactly at a problematic instructions. If I first break on a different instruction then later breakpoints won't reproduce that crash I haven't tested if this is a hardware specific issue. I managed to write a simple test case which reproduces the crash if breakpoint is set. I attached the test.cc which includes compilation and testing instructions. test.cc is supposed to generate a simple main function like: Dump of assembler code for function main(): => 0x0000555555554520 <+0>: vmovdqa 0x1af8(%rip),%xmm0 # 0x555555556020 <foo> 0x0000555555554528 <+8>: vmovd %xmm0,%eax 0x000055555555452c <+12>: retq I set breakpoint with: b main Then either continue or stepping causes SIGSEGV to the debugged application. This was happening already with disco. I only now figured out enough details to make a simple test case which is worth a bug report. ProblemType: Bug DistroRelease: Ubuntu 19.10 Package: gdb 8.3-0ubuntu1 ProcVersionSignature: Ubuntu 5.3.0-19.20-generic 5.3.1 Uname: Linux 5.3.0-19-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.20.11-0ubuntu8 Architecture: amd64 CurrentDesktop: GNOME Date: Tue Oct 29 09:44:52 2019 InstallationDate: Installed on 2037-12-25 (-6632 days ago) InstallationMedia: Lubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1) SourcePackage: gdb UpgradeStatus: Upgraded to eoan on 2019-10-27 (1 days ago) ** Affects: gdb (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug eoan ** Attachment added: "A simple test case which crashes if first breakpoint is in main" https://bugs.launchpad.net/bugs/1850258/+attachment/5301095/+files/test.cc ** Description changed: I noticed random looking SIGSEGV to application when trying to continue execution after first breakpoint. I now seem to have narrowed the issue to SIMD instruction with memory operand as first breakpoint location. I haven't managed to figure out why the SIGSEGV is delivered to the debugger application. It is important have first breakpoint exactly at a problematic instructions. If I first break on a different instruction then later breakpoints won't reproduce that crash I haven't tested if this is a hardware specific issue. I managed to write a simple test case which reproduces the crash if breakpoint is set. I attached the test.cc which includes compilation and testing instructions. test.cc is supposed to generate a simple main function like: Dump of assembler code for function main(): => 0x0000555555554520 <+0>: vmovdqa 0x1af8(%rip),%xmm0 # 0x555555556020 <foo> - 0x0000555555554528 <+8>: vmovd %xmm0,%eax - 0x000055555555452c <+12>: retq + 0x0000555555554528 <+8>: vmovd %xmm0,%eax + 0x000055555555452c <+12>: retq I set breakpoint with: b main Then either continue or stepping causes SIGSEGV to the debugged application. + + This was happening already with disco. I only now figured out enough + details to make a simple test case which is worth a bug report. ProblemType: Bug DistroRelease: Ubuntu 19.10 Package: gdb 8.3-0ubuntu1 ProcVersionSignature: Ubuntu 5.3.0-19.20-generic 5.3.1 Uname: Linux 5.3.0-19-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.20.11-0ubuntu8 Architecture: amd64 CurrentDesktop: GNOME Date: Tue Oct 29 09:44:52 2019 InstallationDate: Installed on 2037-12-25 (-6632 days ago) InstallationMedia: Lubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1) SourcePackage: gdb UpgradeStatus: Upgraded to eoan on 2019-10-27 (1 days ago) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1850258 Title: First breakpoint at AVX instruction with memory operand causes SIGSEGV when tring to continue execution To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdb/+bug/1850258/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs