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)
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https://bugs.launchpad.net/bugs/1850258
Title:
First breakpoint at AVX instruction with memory operand causes SIGSEGV
when tring to continue execution
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