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

[Aleksey Shipilev]

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.

Andrew Haley knows this better, as he is the author of the related change.

Thanks,
-Aleksey