RFR(S) 8193318: ELF decoder should be able to use external debug info file

Mikael Vidstedt mikael.vidstedt at oracle.com
Wed Mar 14 16:42:08 UTC 2018


> On Mar 14, 2018, at 4:52 AM, coleen.phillimore at oracle.com wrote:
> 
> 
> Hi, I looked at this and I really wasn't happy with all this extra code going into the JVM.  And I don't know this code.  There's a large hex table in this file:
> 
> http://cr.openjdk.java.net/~zgu/8193318/webrev.00/src/hotspot/os/linux/decoder_linux.cpp.udiff.html <http://cr.openjdk.java.net/~zgu/8193318/webrev.00/src/hotspot/os/linux/decoder_linux.cpp.udiff.html>

I’m also curious - what is that code actually doing? Why is that hex table needed?

Cheers,
Mikael

> 
> This seems like something that will be painful to maintain.  Can the SA be used for the cases where the binary is stripped?  I believe that Oracle ships with minimal stripping so that we have these symbols, why don't all suppliers?   I don't really like this change.
> 
> Thanks,
> Coleen
> 
> On 3/8/18 11:12 AM, Zhengyu Gu wrote:
>> Ping! I can get formal review?
>> 
>> Thanks,
>> 
>> -Zhengyu
>> 
>> 
>> On 02/23/2018 12:26 PM, Zhengyu Gu wrote:
>>> Thanks, Aleksey.
>>> 
>>> On 02/23/2018 12:01 PM, Aleksey Shipilev wrote:
>>>> On 02/15/2018 06:59 PM, Zhengyu Gu wrote:
>>>>> This Linux only patch allows OpenJDK Linux distributions, which strip out debug symbols in
>>>>> production bundles, to use external debuginfo bundles, if present, to decode stacks.
>>>>> 
>>>>> The implementation mirrors SA implementation [1][2]. It has minimal impact to Oracle's JDK, which
>>>>> always contains symbol tables.
>>>>> 
>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8193318
>>>>> Webrev: http://cr.openjdk.java.net/~zgu/8193318/webrev.00/
>>>> 
>>>> Looks OK on my untrained eye.
>>>> 
>>>> *) I am wondering if we can merge the existing implementation in
>>>> src/jdk.hotspot.agent/linux/native/libsaproc/symtab.c and this mirror implementation in
>>>> src/hotspot/os/linux/decoder_linux.cpp? Notably, moving gnu_debuglink_crc32 to some shared file
>>>> would trim down the change.
>>> 
>>> Yes, but I don't know if there is a way.
>>> 
>>>> 
>>>> Andrew Haley knows this better, as he is the author of the related change.
>>> 
>>> Cc'ed Andrew Haley.
>>> 
>>> -Zhengyu
>>> 
>>> 
>>> 
>>>> 
>>>> Thanks,
>>>> -Aleksey
>>>> 
> 



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