Hotspot symbol visibility

[Kevin Walls]

Hi -

I've observed it being problematic for customers have access to .debuginfo files, either to acquire the .debuginfo bundles or to get them in the relevant place/machine.  This has I'm sure been a sticking point for support many times.  It would be great to avoid that.

The SA needs the gHotSpotVM.... symbols, and the vtable symbols.  The symbols need to be in the binary, but not necessarily findable by "dlsym", as it does ELF symbol lookup work itself (notes in JDK-8017234).

We would need to test if there are SA failures if these symbols are not exported?...
(There are some issues mentioned in JDK-8017234, maybe they are still true.)



-----Original Message-----
From: serviceability-dev <serviceability-dev-retn at openjdk.org> On Behalf Of Magnus Ihse Bursie
Sent: 19 February 2024 10:56
To: Andrew Haley <aph-open at littlepinkcloud.com>; hotspot-dev at openjdk.org; serviceability-dev at openjdk.java.net
Subject: Re: Hotspot symbol visibility
Importance: High

On 2024-02-18 11:15, Andrew Haley wrote:

> On 2/14/24 10:06, Magnus Ihse Bursie wrote:
>> My takeaway from the discussions is that we are most likely exporting 
>> a way too broad set of symbols to SA. It seems likely that this set 
>> can be drastically cut down. Actually getting an understanding of 
>> exactly which symbols SA need seem like a very good first step.
>>
>> So, is this a journey anyone would be interested in embarkering on? I 
>> will help as much as I can from a build PoV, but I have no clue 
>> whatsoever about what SA needs.
>
> Alternatively, we have separate debuginfo. SA can use the debug 
> symbols, allowing us to strip all others. What's wrong with this reasoning?
>
I don't know if there is anything wrong with that reasoning. It seems reasonable. I also hope that we won't need to take the detour of first generating the symbols and then strip them, but instead can add them directly to the debuginfo, if we should choose to do things this way.

Can anyone from serviceability chip in? Would it be okay for SA to require a .debuginfo or .diz file to be able to extract all the internal hotspot symbols?

/Magnus