Request for approval: Allow Java's ELF symtab reader to use separate debuginfo files

[Andrew Haley]

On 01/11/2010 08:36 PM, Tom Rodriguez wrote:
>
> On Jan 9, 2010, at 3:03 AM, Andrew Haley wrote:
>
>> On 01/08/2010 07:54 PM, Tom Rodriguez wrote:
>>
>>> I think a better fix is to add the required gHotSpot* symbols to the
>>> mapfile so that they are always exported.
>>
>> I'm not sure this will work on all GNU/Linux distros, since symtabs
>> are routinely removed in their entirety from DSOs.  Is there some
>> logic in the symtab handling to do a look-aside into the dynamic
>> symtab instead of the symtab?
>
> The solaris libproc does this and I assumed that the linux code we
> wrote would also do this but it looks to me like it doesn't.  I
> don't think it would be hard to add support for parsing the dynsym
> table in build_symtab and it would allow these tools to work if the
> libraries are commonly stripped.  The code could either be modified
> to look for SHT_DYNSYM if SHT_SYMTAB doesn't exist or it could
> always parse both of them.  Something limited like this works ok:
>
> ...
>
>> Also, are these the only symbols that are ever looked up by this
>> symtab reader?
>
> Those are the only ones needed by the core SA functionality.  The
> only thing other symbols are used for is the jstack -m mode that
> dumps mixed Java and native frames ala pstack and adding the
> external debug info reader to support this seems reasonable.

OK, right.  I'll make a new webrev that includes my patch for external
debug info and your patch for reading the dynsym table.  I'll test
with and without debuginfo and make sure that jmap works in both
cases.

Andrew.