On Tue, 12 Aug 2025 08:17:58 GMT, Volkan Yazici <vyaz...@openjdk.org> wrote:
>> Validate input in `java.lang.StringCoding` intrinsic Java wrappers, improve >> their documentation, enhance the checks in the associated IR or assembly >> code, and adapt them to cause VM crash on invalid input. >> >> ## Implementation notes >> >> The goal of the associated umbrella issue >> [JDK-8156534](https://bugs.openjdk.org/browse/JDK-8156534) is to, for >> `java.lang.String*` classes, >> >> 1. Move `@IntrinsicCandidate`-annotated `public` methods<sup>1</sup> (in >> Java code) to `private` ones, and wrap them with a `public` ["front door" >> method](https://github.com/openjdk/jdk/pull/24982#discussion_r2087493446) >> 2. Since we moved the `@IntrinsicCandidate` annotation to a new method, >> intrinsic mappings – i.e., associated `do_intrinsic()` calls in >> `vmIntrinsics.hpp` – need to be updated too >> 3. Add necessary input validation (range, null, etc.) checks to the newly >> created public front door method >> 4. Place all input validation checks in the intrinsic code (add if missing!) >> behind a `VerifyIntrinsicChecks` VM flag >> >> Following preliminary work needs to be carried out as well: >> >> 1. Add a new `VerifyIntrinsicChecks` VM flag >> 2. Update `generate_string_range_check` to produce a `HaltNode`. That is, >> crash the VM if `VerifyIntrinsicChecks` is set and a Java wrapper fails to >> spot an invalid input. >> >> <sup>1</sup> `@IntrinsicCandidate`-annotated constructors are not subject >> to this change, since they are a special case. >> >> ## Functional and performance tests >> >> - `tier1` (which includes `test/hotspot/jtreg/compiler/intrinsics/string`) >> passes on several platforms. Further tiers will be executed after >> integrating reviewer feedback. >> >> - Performance impact is still actively monitored using >> `test/micro/org/openjdk/bench/java/lang/String{En,De}code.java`, among other >> tests. If you have suggestions on benchmarks, please share in the comments. >> >> ## Verification of the VM crash >> >> I've tested the VM crash scenario as follows: >> >> 1. Created the following test program: >> >> public class StrIntri { >> public static void main(String[] args) { >> Exception lastException = null; >> for (int i = 0; i < 1_000_000; i++) { >> try { >> >> jdk.internal.access.SharedSecrets.getJavaLangAccess().countPositives(new >> byte[]{1,2,3}, 2, 5); >> } catch (Exception exception) { >> lastException = exception; >> } >> } >> if (lastException != null) { >> lastException.printStackTrace... > > Volkan Yazici has updated the pull request incrementally with one additional > commit since the last revision: > > Remove `@apiNote` in `encodeISOArray()` Javadoc > > Those who are touching to these methods should well be > aware of the details elaborated in the `@apiNote`, no > need to put it on a display. I've done some testing on linux-amd64 and verified that on microbenchmarks that exercise for example `StringCoding.hasNegatives` (a front door of one of the intrinsics this PR changes) the generated assembly is identical under ideal conditions. Spurious regressions seen in some setups could be inlining related: moving from a simple range check emitted by the intrinsic to a call to `Preconditions.checkFromIndexSize` may push us over some inlining threshold in some cases. I'll try to get my hands on a linux-aarch64 machine to do some diagnostic runs on. An idea for future investigation could be to make `Preconditions.checkFromIndexSize` an intrinsic similar to `Preconditions.checkIndex` - to help the compiler do the right thing with more ease and perhaps slightly faster. ------------- Marked as reviewed by redestad (Reviewer). PR Review: https://git.openjdk.org/jdk/pull/25998#pullrequestreview-3116268132
