RFR: 8282828: CDS uncompressed oops archive is not deterministic
Ioi Lam
iklam at openjdk.java.net
Fri Apr 29 23:00:09 UTC 2022
During `java -Xshare:dump -XX:-UseCompressedOops`, the location of the Java heap is chosen by the OS. Due to Address Space Layout Randomization, the heap will always start at a different location. This causes the archive for uncompressed oops ($JAVA_HOME/lib/server/classes_nocoops.jsa) to be non-deterministic.
The fix is to patch the archived object pointers to make it look like the heap starts at a fixed address -- I chose 0x10000000, but the exact value doesn't really matter.
At runtime, the object pointers will be patched again according to the real location of the heap.
Tested with tiers 1-5. I am running builds-tier5 several times to test the xxx-cmp-baseline builds.
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Commit messages:
- 8282828: CDS uncompressed oops archive is not deterministic
Changes: https://git.openjdk.java.net/jdk/pull/8478/files
Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8478&range=00
Issue: https://bugs.openjdk.java.net/browse/JDK-8282828
Stats: 86 lines in 6 files changed: 62 ins; 2 del; 22 mod
Patch: https://git.openjdk.java.net/jdk/pull/8478.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/8478/head:pull/8478
PR: https://git.openjdk.java.net/jdk/pull/8478
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