PING: RFR: 8234624: jstack mixed mode should refer DWARF
Yasumasa Suenaga
suenaga at oss.nttdata.com
Sun Feb 2 16:37:10 UTC 2020
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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