RFR: 8247351: [aarch64] NullPointerException during stack walking (clhsdb "where -a")

[Nick Gasson]

On Tue, 13 Jul 2021 17:49:40 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> Running the jtreg test serviceability/sa/ClhsdbWhere.java with -Xcomp
>> -XX:-TieredCompilation fails with the following exception:
>> 
>>   Error: java.lang.NullPointerException: Cannot invoke "sun.jvm.hotspot.debugger.Address.getJLongAt(long)" because "valueAddr" is null
>>   java.lang.NullPointerException: Cannot invoke "sun.jvm.hotspot.debugger.Address.getJLongAt(long)" because "valueAddr" is null
>>           at jdk.hotspot.agent/sun.jvm.hotspot.runtime.CompiledVFrame.createStackValue(CompiledVFrame.java:270)
>>           at jdk.hotspot.agent/sun.jvm.hotspot.runtime.CompiledVFrame.getLocals(CompiledVFrame.java:107)
>>           at jdk.hotspot.agent/sun.jvm.hotspot.ui.classbrowser.HTMLGenerator.genHTMLForJavaStackTrace(HTMLGenerator.java:1937)
>>           at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor$43.doit(CommandProcessor.java:1573)
>>           at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:2090)
>>           at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:2060)
>> 
>> The oop map for the frame being inspected is:
>> 
>>    ScopeDesc(pc=0x0000ffff8957e000 offset=140):
>>    jdk.test.lib.apps.LingeredApp::steadyState at 7 (line 536)
>>    Locals
>>     - l0: empty
>>     - l1: reg rfp [58],oop
>>     - l2: empty
>>    Monitor stack
>>     - @0: monitor{reg rfp [58],oop,stack[16]}
>> 
>> But RegisterMap::getLocation() returns a null Address for register
>> 58 (=RFP).
>> 
>> This patch fixes two problems: the fp VMReg value used in
>> AARCH64Frame::updateMapWithSavedLink should be 29<<1 not 29 because a
>> VMReg has two slots in a 64-bit VM.  The other bug is that
>> RegisterMap::setLocation and getLocation calculate the long
>> locationValid mask using (1 << (i % locationValidTypeSize)) where i and
>> locationValidTypeSize are both int.  We need to do this calculation as a
>> long if i % locationValidTypeSize can be > 32.  There's no failure on
>> x86_64 because that only has 16 integer registers.
>
> This looks like a dup of [https://bugs.openjdk.java.net/browse/JDK-8247351](JDK-8247351). If so, please close this CR out as a dup and target this PR to JDK-8247351.

Thanks @plummercj . I think I did something wrong with the /issue commands and now I ended up with the JBS line in the commit message duplicated. Not sure how to fix that...

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PR: https://git.openjdk.java.net/jdk/pull/4737