[lldb-dev] strange issues on linux
Ryan Brown
ribrdb at google.com
Mon Jun 1 13:18:21 PDT 2015
The codes is at http://reviews.llvm.org/D5871
But I don't think that will help. OperatingSystemGo::UpdateThreadList is
getting called with the wrong real_thread_list the first time lldb stops.
This seems to fix it:
diff --git a/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
b/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
index 3ab8c18..174d3e7 100644
--- a/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
+++ b/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
@@ -790,6 +790,8 @@ ProcessGDBRemote::DoConnectRemote (Stream *strm, const
char *remote_url)
}
const StateType state = SetThreadStopInfo (response);
+ m_stop_packet_stack.clear();
+
if (state == eStateStopped)
{
SetPrivateState (state);
@@ -1080,6 +1082,7 @@ ProcessGDBRemote::DoLaunch (Module *exe_module,
ProcessLaunchInfo &launch_info)
}
SetPrivateState (SetThreadStopInfo (response));
+ m_stop_packet_stack.clear();
if (!disable_stdio)
{
-- Ryan Brown
On Mon, Jun 1, 2015 at 12:53 PM, Greg Clayton <gclayton at apple.com> wrote:
> One question for you:
>
> Are you associating your real threads with Go threads? Or are you letting
> the real threads show and also showing the go threads? Any ThreadMemory
> that has had ThreadMemory::SetBackingThread() called with a real thread
> will be just a thread that is in memory. Any that have had this function
> called with answer all thread related questions using the
> ThreadMemory::m_backing_thread_sp. For any threads that aren't backed by a
> real thread the thread registers will be created by calling
> OperatingSystemGo::CreateRegisterContextForThread(...) so you should be
> able to debug what is going wrong by stepping through this. For any threads
> that are backed by a real thread, it will just get the register context
> from the real thread via ThreadGDBRemote.
>
> If you can send me a copy of your OperatingSystemGo.cpp and .h file I
> might be able to help out.
>
> Greg
>
> > On May 28, 2015, at 5:43 PM, Ryan Brown <ribrdb at google.com> wrote:
> >
> > I'm running into some issues trying to debug with lldb on linux.
> > It started with errors that debugserver aborted. I ran lldb-server
> manually and then used process connect, and got this error:
> >
> > lldb-server:
> ../tools/lldb/source/Plugins/Process/Linux/NativeThreadLinux.cpp:227:
> virtual NativeRegisterContextSP
> lldb_private::process_linux::NativeThreadLinux::GetRegisterContext():
> Assertion `reg_interface && "OS or CPU not supported!"' failed.
> >
> > I synced lldb and llvm to head and rebuilt, and this error went away.
> But then later it showed up again on a different machine when debugging the
> same binary with the newly built lldb.
> >
> > Once I get the binary running under lldb I'm seeing strange things on my
> OperatingSystem plugin. Sometimes things work normally, sometimes the OS
> plugin seems to see incorrect register values but they're correct at the
> lldb prompt, and sometimes the registers just seem completely wrong.
> > The behaviour is pretty consistent when I set a breakpoint at the same
> line, but if I move it to a different line or move to a different machine
> I'll get a different behavior.
> >
> > Here's an example where the plugin sees invalid registers:
> > (lldb) run
> > OperatingSystemGo::UpdateThreadList(0, 1, 1) fetching thread data from
> Go for pid 678
> > Process 678 launched: 'vc.test' (x86_64)
> > I0528 17:09:01.105108 678 rand.go:86] Seeding pseudo-random number
> generator with 1432858141105104474
> > OperatingSystemGo::UpdateThreadList(1, 1, 1) fetching thread data from
> Go for pid 678
> > OperatingSystemGo: RealThread 0 has sp 7fffffffd430
> > Process 678 stopped
> > * thread #1: tid = 0x02a6, 0x000000000049f379
> vc.test`vc.createVCs(~r0=stream.XVC at 0x000000c208030668, ~r1=stream.XVC
> at 0x000000c208030678) + 73 at xvc_test.go:23, name =
> > 'vc.test', stop reason = breakpoint 1.1
> > frame #0: 0x000000000049f379 vc.test`vc.createVCs(~r0=stream.XVC at
> 0x000000c208030668, ~r1=stream.XVC at 0x000000c208030678) + 73 at
> xvc_test.go:23
> > (lldb) register read
> > General Purpose Registers:
> > rax = 0x000000c208030580
> > rbx = 0x0000000000000000
> > rcx = 0x000000c208001a40
> > rdx = 0x000000000095e678 vc.test`vc.TestXVC.f
> > rdi = 0x0000000000000000
> > rsi = 0x000000c208030768
> > rbp = 0x0000000000abe578 main.statictmp_0002 + 312
> > rsp = 0x000000c208030500
> > r8 = 0x000000005567ae1d
> > r9 = 0x0000000000000007
> > r10 = 0x000000000300c146
> > r11 = 0x000000000000007b
> > r12 = 0x0000000000000025
> > r13 = 0x000000000095d840 vc.test`runtime.gcbits.3082880518
> > r14 = 0x0000000000000008
> > r15 = 0x0000000000000000
> > rip = 0x000000000049f379 vc.test`vc.createVCs + 73 at
> xvc_test.go:23
> > rflags = 0x0000000000000246
> > cs = 0x0000000000000033
> > fs = 0x0000000000000000
> > gs = 0x0000000000000000
> > ss = 0x000000000000002b
> > ds = 0x0000000000000000
> > es = 0x0000000000000000
> >
> > So my plugin sees one real thread, but the SP is bogus: 7fffffffd430
> > When I print registers at the prompt i get the correct value:
> 0x000000c208030500
> >
> > Then I run stepi:
> >
> > (lldb) stepi
> > OperatingSystemGo::UpdateThreadList(8, 3, 3) fetching thread data from
> Go for pid 678
> > OperatingSystemGo: RealThread 0 has sp c2080304f8
> > OperatingSystemGo: RealThread 1 has sp 7ffff77f5df8
> > OperatingSystemGo: RealThread 2 has sp 7ffff6fb4d70
> >
> > Now my plugin is getting three threads. But we've only gone one
> instruction, so where are these other threads coming from? Thread 0 has the
> correct SP this time, but not the other threads.
> > Now that we've got the right SP value, the OS plugin is able to find the
> memory thread which confuses the threadplan so it keeps running till it
> hits a breakpoint:
> >
> > OperatingSystemGo::UpdateThreadList(9, 3, 3) fetching thread data from
> Go for pid 678
> > OperatingSystemGo: RealThread 0 has sp c208030500
> > OperatingSystemGo: RealThread 1 has sp 7ffff77f5df8
> > OperatingSystemGo: RealThread 2 has sp 7ffff6fb4d70
> > Process 678 stopped
> > * thread #8: tid = 0x0006, 0x000000000049f3b1
> vc.test`vc.createVCs(~r0=stream.XVC at 0x000000c208030668, ~r1=stream.XVC
> at 0x000000c208030678) + 129 at xvc_test.go:24, stop reason = breakpoint 2.1
> > frame #0: 0x000000000049f3b1 vc.test`vc.createVCs(~r0=stream.XVC at
> 0x000000c208030668, ~r1=stream.XVC at 0x000000c208030678) + 129 at
> xvc_test.go:24
> > (lldb)
> >
> > Debugging the same binary on a different machine with the same lldb
> binary, I get different behavior:
> >
> > (lldb) r
> > There is a running process, kill it and restart?: [Y/n] y
> > Process 127429 exited with status = 9 (0x00000009)
> > OperatingSystemGo::UpdateThreadList(0, 1, 1) fetching thread data from
> Go for pid 127449
> > Process 127449 launched: 'vc.test' (x86_64)
> > I0528 17:10:43.950815 127449 rand.go:86] Seeding pseudo-random number
> generator with 1432858243950810731
> > OperatingSystemGo::UpdateThreadList(1, 1, 1) fetching thread data from
> Go for pid 127449
> > OperatingSystemGo: RealThread 0 has sp 7fffffffde50
> > Process 127449 stopped
> > * thread #1: tid = 0x1f1d9, 0x00007ffff7ddb2d0, name = 'vc.test', stop
> reason = signal SIGSTOP
> > frame #0: 0x00007ffff7ddb2d0
> > -> 0x7ffff7ddb2d0: movq %rsp, %rdi
> > 0x7ffff7ddb2d3: callq 0x7ffff7ddea70
> > 0x7ffff7ddb2d8: movq %rax, %r12
> > 0x7ffff7ddb2db: movl 0x221b17(%rip), %eax
> > (lldb) register read
> > General Purpose Registers:
> > rax = 0x0000000000000000
> > rbx = 0x0000000000000000
> > rcx = 0x0000000000000000
> > rdx = 0x0000000000000000
> > rdi = 0x0000000000000000
> > rsi = 0x0000000000000000
> > rbp = 0x0000000000000000
> > rsp = 0x00007fffffffde50
> > r8 = 0x0000000000000000
> > r9 = 0x0000000000000000
> > r10 = 0x0000000000000000
> > r11 = 0x0000000000000000
> > r12 = 0x0000000000000000
> > r13 = 0x0000000000000000
> > r14 = 0x0000000000000000
> > r15 = 0x0000000000000000
> > rip = 0x00007ffff7ddb2d0
> > rflags = 0x0000000000000200
> > cs = 0x0000000000000033
> > fs = 0x0000000000000000
> > gs = 0x0000000000000000
> > ss = 0x000000000000002b
> > ds = 0x0000000000000000
> > es = 0x0000000000000000
> >
> > (lldb) bt
> > * thread #1: tid = 0x1f1d9, 0x00007ffff7ddb2d0, name = 'vc.test', stop
> reason = signal SIGSTOP
> > * frame #0: 0x00007ffff7ddb2d0
> >
> >
> > This time the plugin gets the invalid register values, but when lldb
> stops at the prompt things are still invalid. The rip is garbage, so lldb
> doesn't recognize that it's hit a breakpoint and the backtrace is wrong.
> >
> > Any ideas what could be going on here, or how I can debug this?
> >
> > -- Ryan Brown
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>
>
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