: PING: RFR: 8234624: jstack mixed mode should refer DWARF
Yasumasa Suenaga
suenaga at oss.nttdata.com
Mon Feb 17 04:07:03 UTC 2020
PING: Could you review it?
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8234624
>> webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.03/
This change has been already reviewed by Serguei.
I need one more reviewer to push.
Thanks,
Yasumasa
On 2020/02/03 1:37, Yasumasa Suenaga wrote:
> PING: Could you reveiw this change?
>
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8234624
>> webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.03/
>
> I believe this change helps troubleshooter to fight to postmortem analysis.
>
>
> Thanks,
>
> Yasumasa
>
>
> On 2020/01/19 3:16, Yasumasa Suenaga wrote:
>> PING: Could you review it?
>>
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8234624
>> webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.03/
>>
>> I updated webrev. I discussed with Serguei in off list, and I refactored webrev.02 .
>> It has passed tests on submit repo (mach5-one-ysuenaga-JDK-8234624-4-20200118-1353-8149549).
>>
>>
>> Thanks,
>>
>> Yasumasa
>>
>>
>> On 2019/12/15 10:51, Yasumasa Suenaga wrote:
>>> Hi Serguei,
>>>
>>> Thanks for your comment!
>>> I refactored LinuxCDebugger and LinuxAMD64CFrame in new webrev.
>>> Also I fixed to free lib->eh_frame.data in libproc_impl.c as Dmitry said.
>>>
>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.02/
>>>
>>> This change has been passed all tests on submit repo (mach5-one-ysuenaga-JDK-8234624-3-20191214-1527-7538487).
>>>
>>>
>>> Thanks,
>>>
>>> Yasumasa
>>>
>>>
>>> On 2019/12/14 10:02, serguei.spitsyn at oracle.com wrote:
>>>> Hi Yasumasa,
>>>>
>>>> This is nice move in general.
>>>> Thank you for working on this!
>>>>
>>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.01/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/debugger/linux/LinuxCDebugger.java.frames.html
>>>>
>>>> 96 long libptr = dbg.findLibPtrByAddress(pc); 97 if (libptr == 0L) { // Java frame 98 Address rbp = context.getRegisterAsAddress(AMD64ThreadContext.RBP); 99 if (rbp == null) { 100 return null; 101 } 102 return new LinuxAMD64CFrame(dbg, rbp, pc, null); 103 } else { // Native frame 104 DwarfParser dwarf; 105 try { 106 dwarf = new DwarfParser(libptr); 107 } catch (DebuggerException e) { 108 Address rbp = context.getRegisterAsAddress(AMD64ThreadContext.RBP); 109 if (rbp == null) { 110 return null; 111 } 112 return new LinuxAMD64CFrame(dbg, rbp, pc, null); 113 } 114 dwarf.processDwarf(pc); 115 Address cfa = ((dwarf.getCFARegister() == AMD64ThreadContext.RBP) && 116 !dwarf.isBPOffsetAvailable()) 117 ? context.getRegisterAsAddress(AMD64ThreadContext.RBP) 118 : context.getRegisterAsAddress(dwarf.getCFARegister()) 119 .addOffsetTo(dwarf.getCFAOffset()); 120 if (cfa == null) { 121 return null; 122 } 123 return new LinuxAMD64CFrame(dbg, cfa, pc, dwarf); 124 }
>>>>
>>>>
>>>> I'd suggest to simplify the logic by refactoring to something like below:
>>>>
>>>> long libptr = dbg.findLibPtrByAddress(pc);
>>>> Address cfa = context.getRegisterAsAddress(AMD64ThreadContext.RBP); // Java frame
>>>> DwarfParser dwarf = null;
>>>>
>>>> if (libptr != 0L) { // Native frame
>>>> try {
>>>> dwarf = new DwarfParser(libptr);
>>>> dwarf.processDwarf(pc);
>>>> Address cfa = ((dwarf.getCFARegister() == AMD64ThreadContext.RBP) &&
>>>> !dwarf.isBPOffsetAvailable())
>>>> ? context.getRegisterAsAddress(AMD64ThreadContext.RBP)
>>>> : context.getRegisterAsAddress(dwarf.getCFARegister())
>>>> .addOffsetTo(dwarf.getCFAOffset());
>>>>
>>>> } catch (DebuggerException e) { // bail out to Java frame case
>>>> }
>>>> }
>>>> if (cfa == null) {
>>>> return null;
>>>> }
>>>> return new LinuxAMD64CFrame(dbg, cfa, pc, dwarf);
>>>>
>>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.01/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/debugger/linux/amd64/LinuxAMD64CFrame.java.frames.html
>>>>
>>>> 58 long ofs = useDwarf ? dwarf.getReturnAddressOffsetFromCFA()
>>>>
>>>> Better to rename 'ofs' => 'offs'.
>>>>
>>>> 77 nextCFA = nextCFA.addOffsetTo(- nextDwarf.getBasePointerOffsetFromCFA());
>>>>
>>>> Extra space after '-' sign.
>>>>
>>>> 71 private Address getNextCFA(DwarfParser nextDwarf, ThreadContext context) {
>>>>
>>>> It feels like the logic has to be somehow refactored/simplified as
>>>> several typical fragments appears in slightly different contexts.
>>>> But it is not easy to understand what it is.
>>>> Could you, please, add some comments to key places explaining this logic.
>>>> Then I'll check if it is possible to make it a little bit simpler.
>>>>
>>>> 109 private CFrame javaSender(ThreadContext context) { 110 Address nextCFA; 111 Address nextPC; 112 113 nextPC = getNextPC(false); 114 if (nextPC == null) { 115 return null; 116 } 117 118 DwarfParser nextDwarf = null; 119 long libptr = dbg.findLibPtrByAddress(nextPC); 120 if (libptr != 0L) { // Native frame 121 try { 122 nextDwarf = new DwarfParser(libptr); 123 } catch (DebuggerException e) { 124 nextCFA = getNextCFA(null, context); 125 return (nextCFA == null) ? null : new LinuxAMD64CFrame(dbg, nextCFA, nextPC, null); 126 } 127 nextDwarf.processDwarf(nextPC); 128 } 129 130 nextCFA = getNextCFA(nextDwarf, context); 131 return (nextCFA == null) ? null 132 : new LinuxAMD64CFrame(dbg, nextCFA, nextPC, nextDwarf); 133 }
>>>>
>>>> The above can be simplified if a DebuggerException can not be thrown from processDwarf(nextPC):
>>>> private CFrame javaSender(ThreadContext context) {
>>>> Address nextPC = getNextPC(false);
>>>> if (nextPC == null) {
>>>> return null;
>>>> }
>>>> long libptr = dbg.findLibPtrByAddress(nextPC);
>>>> DwarfParser nextDwarf = null;
>>>>
>>>> if (libptr != 0L) { // Native frame
>>>> try {
>>>> nextDwarf = new DwarfParser(libptr);
>>>> nextDwarf.processDwarf(nextPC);
>>>> } catch (DebuggerException e) { // Bail out to Java frame
>>>> }
>>>> }
>>>> Address nextCFA = getNextCFA(nextDwarf, context);
>>>> return (nextCFA == null) ? null : new LinuxAMD64CFrame(dbg, nextCFA, nextPC, nextDwarf);
>>>> }
>>>>
>>>> 135 public CFrame sender(ThreadProxy thread) { 136 ThreadContext context = thread.getContext(); 137 138 if (dwarf == null) { // Java frame 139 return javaSender(context); 140 } 141 142 Address nextPC = getNextPC(true); 143 if (nextPC == null) { 144 return null; 145 } 146 147 Address nextCFA; 148 DwarfParser nextDwarf = dwarf; 149 if (!dwarf.isIn(nextPC)) { 150 long libptr = dbg.findLibPtrByAddress(nextPC); 151 if (libptr == 0L) { 152 // Next frame might be Java frame 153 nextCFA = getNextCFA(null, context); 154 return (nextCFA == null) ? null : new LinuxAMD64CFrame(dbg, nextCFA, nextPC, null); 155 } 156 try { 157 nextDwarf = new DwarfParser(libptr); 158 } catch (DebuggerException e) { 159 nextCFA = getNextCFA(null, context); 160 return (nextCFA == null) ? null : new LinuxAMD64CFrame(dbg, nextCFA, nextPC, null); 161 } 162 } 163 164 nextDwarf.processDwarf(nextPC); 165 nextCFA = getNextCFA(nextDwarf, context); 166 return (nextCFA == null) ? null : new LinuxAMD64CFrame(dbg,
>>>> nextCFA, nextPC, nextDwarf); 167 }
>>>>
>>>> This one can be also simplified a little:
>>>>
>>>> public CFrame sender(ThreadProxy thread) {
>>>> ThreadContext context = thread.getContext();
>>>>
>>>> if (dwarf == null) { // Java frame
>>>> return javaSender(context);
>>>> }
>>>> Address nextPC = getNextPC(true);
>>>> if (nextPC == null) {
>>>> return null;
>>>> }
>>>> DwarfParser nextDwarf = null;
>>>> if (!dwarf.isIn(nextPC)) {
>>>> long libptr = dbg.findLibPtrByAddress(nextPC);
>>>> if (libptr != 0L) {
>>>> try {
>>>> nextDwarf = new DwarfParser(libptr);
>>>> nextDwarf.processDwarf(nextPC);
>>>> } catch (DebuggerException e) { // Bail out to Java frame
>>>> }
>>>> }
>>>> }
>>>> Address nextCFA = getNextCFA(nextDwarf, context);
>>>> return (nextCFA == null) ? null : new LinuxAMD64CFrame(dbg, nextCFA, nextPC, nextDwarf);
>>>> }
>>>>
>>>> Finally, it looks like just one method could replace both
>>>> sender(ThreadProxy thread) and javaSender(ThreadContext context):
>>>>
>>>> private CFrame commonSender(ThreadProxy thread) {
>>>> ThreadContext context = thread.getContext();
>>>> Address nextPC = getNextPC(false);
>>>> if (nextPC == null) {
>>>> return null;
>>>> }
>>>> DwarfParser nextDwarf = null;
>>>>
>>>> long libptr = dbg.findLibPtrByAddress(nextPC);
>>>> if (dwarf == null || !dwarf.isIn(nextPC)) {
>>>> long libptr = dbg.findLibPtrByAddress(nextPC);
>>>> if (libptr != 0L) {
>>>> try {
>>>> nextDwarf = new DwarfParser(libptr);
>>>> nextDwarf.processDwarf(nextPC);
>>>> } catch (DebuggerException e) { // Bail out to Java frame
>>>> }
>>>> }
>>>> }
>>>> Address nextCFA = getNextCFA(nextDwarf, context);
>>>> return (nextCFA == null) ? null : new LinuxAMD64CFrame(dbg, nextCFA, nextPC, nextDwarf);
>>>> }
>>>>
>>>> I'm still reviewing the dwarf parser files.
>>>>
>>>> Thanks,
>>>> Serguei
>>>>
>>>>
>>>> On 11/28/19 4:39 AM, Yasumasa Suenaga wrote:
>>>>> Hi,
>>>>>
>>>>> I refactored LinuxAMD64CFrame.java . It works fine in serviceability/sa tests and
>>>>> all tests on submit repo (mach5-one-ysuenaga-JDK-8234624-2-20191128-0928-7059923).
>>>>> Could you review new webrev?
>>>>>
>>>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.01/
>>>>>
>>>>> The diff from previous webrev is here:
>>>>> http://hg.openjdk.java.net/jdk/submit/rev/4bc47efbc90b
>>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Yasumasa
>>>>>
>>>>>
>>>>> On 2019/11/25 14:08, Yasumasa Suenaga wrote:
>>>>>> Hi all,
>>>>>>
>>>>>> Please review this change:
>>>>>>
>>>>>> JBS: https://bugs.openjdk.java.net/browse/JDK-8234624
>>>>>> webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8234624/webrev.00/
>>>>>>
>>>>>>
>>>>>> According to 2.7 Stack Unwind Algorithm in System V Application Binary Interface AMD64
>>>>>> Architecture Processor Supplement [1], we need to use DWARF in .eh_frame or .debug_frame
>>>>>> for stack unwinding.
>>>>>>
>>>>>> As JDK-8022183 said, omit-frame-pointer is enabled by default since GCC 4.6, so system
>>>>>> library (e.g. libc) might be compiled with this feature.
>>>>>>
>>>>>> However `jhsdb jstack --mixed` does not do so, it uses base pointer register (RBP).
>>>>>> So it might be lack of stack frames.
>>>>>>
>>>>>> I guess JDK-8219201 is caused by same issue.
>>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Yasumasa
>>>>>>
>>>>>>
>>>>>> [1] https://software.intel.com/sites/default/files/article/402129/mpx-linux64-abi.pdf
>>>>
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