8338731: MemoryLayout::offsetHandle can return a negative offset

[mcimadamore]

When working on startup improvements, I noticed that the method handle returned by MemoryLayout::offsetHandle can overflow if the client calls the handle with a base offset that is too big.

In other similar situations, the layout API always fails with ArithmeticException (see MemoryLayout::scale), so we should do the same here.

The fix is to use a Math::addExact(long, long) for the outermost add operation in the computation of the offset method handle. That outermost computation in fact is the only one that can overflow: it is an addition between a user-provided base offset B and a layout offset L. L is guaranteed not to overflow, by construction (as L is derived from a layout path). But B + L might overflow, so the new logic checks for that.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue
• Change requires CSR request JDK-8338742 to be approved

Issues

• JDK-8338731: MemoryLayout::offsetHandle can return a negative offset (Enhancement - P3)
• JDK-8338742: MemoryLayout::offsetHandle can return a negative offset (CSR)

Reviewers

• Per Minborg (@minborg - Reviewer)
• Paul Sandoz (@PaulSandoz - Reviewer) Review applies to 8ac9d262

Reviewing

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[mcimadamore]

/csr needed

[bridgekeeper]

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[openjdk]

@mcimadamore This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8338731: MemoryLayout::offsetHandle can return a negative offset

Reviewed-by: pminborg, psandoz

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At the time when this comment was updated there had been 10 new commits pushed to the master branch:

• 8e88da0: 8338041: Keyboard Navigation of JTable, Ctrl Shift RIGHT/LEFT doesn't follow native action in GTK L&F
• 449ca2c: 8337832: Optimize datetime toString
• b1b4cd4: 8332158: [XWayland] test/jdk/java/awt/Mouse/EnterExitEvents/ResizingFrameTest.java
• 284c3cd: 8336299: Improve GCLocker stall diagnostics
• 2e96f15: 8338489: Typo in MemorySegment doc
• 44d3a68: 8314124: RISC-V: implement Base64 intrinsic - decoding
• daf2617: 8338929: Make Metaspace::deallocate space-aware
• fa4ff78: 8338690: CompactNumberInstance.format incorrectly formats some numbers (few vs many)
• 1ff5f8d: 8338440: Parallel: Improve fragmentation mitigation in Full GC
• 0f66710: 8338939: Simplify processing of hidden class names

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[openjdk]

@mcimadamore has indicated that a compatibility and specification (CSR) request is needed for this pull request.

@mcimadamore please create a CSR request for issue JDK-8338731 with the correct fix version. This pull request cannot be integrated until the CSR request is approved.

[openjdk]

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[mlbridge]

Webrevs

• 01: Full (fb1682e5)
• 00: Full (8ac9d262)

[minborg]

Nice catch.

[openjdk]

@mcimadamore this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout offset_overflow
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[minborg]

Unrelated: I wonder if the performance of:

MH_ADD = lookup.findStatic(Long.class, "sum",
                    MethodType.methodType(long.class, long.class, long.class));
                    

and

MH_ADD = MethodHandles.publicLookup().findStatic(Long.class, "sum",
                    MethodType.methodType(long.class, long.class, long.class));

Differ?

[liach]

They should have the same performance characteristics. They have different permissions for access checks, and since Long is exported public API and sum is public both will pass.

[minborg]

Merge ok ;-)

[mcimadamore]

/integrate

[openjdk]

Going to push as commit 1ff9ac7.
Since your change was applied there have been 11 commits pushed to the master branch:

• 2e174c6: 8338445: jdk.internal.loader.URLClassPath may leak JarFile instance when dealing with unexpected Class-Path entry in manifest
• 8e88da0: 8338041: Keyboard Navigation of JTable, Ctrl Shift RIGHT/LEFT doesn't follow native action in GTK L&F
• 449ca2c: 8337832: Optimize datetime toString
• b1b4cd4: 8332158: [XWayland] test/jdk/java/awt/Mouse/EnterExitEvents/ResizingFrameTest.java
• 284c3cd: 8336299: Improve GCLocker stall diagnostics
• 2e96f15: 8338489: Typo in MemorySegment doc
• 44d3a68: 8314124: RISC-V: implement Base64 intrinsic - decoding
• daf2617: 8338929: Make Metaspace::deallocate space-aware
• fa4ff78: 8338690: CompactNumberInstance.format incorrectly formats some numbers (few vs many)
• 1ff5f8d: 8338440: Parallel: Improve fragmentation mitigation in Full GC
• ... and 1 more: https://git.openjdk.org/jdk/compare/b25095b08e4d21b95177a5fa3fff3807b2cf81e0...master

Your commit was automatically rebased without conflicts.

[openjdk]

@mcimadamore Pushed as commit 1ff9ac7.

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