RFR: 8346971: [ubsan] psCardTable.cpp:131:24: runtime error: large index is out of bounds [v2]

[Albert Mingkun Yang]

On Mon, 13 Jan 2025 10:42:33 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Please review this change to PSStripeShadowCardTable to avoid several examples
>> of UB in it's internal calculations.  We avoid the UB by switching to the
>> integer domain (using uintptr_t) for all of the internal calculations, with
>> casts between pointers and uintptr_t as needed at the boundaries.
>> 
>> This applies not just to the various pointer adjustments, but also to pointer
>> comparisons. In particular, the prior range check assertions using pointer
>> comparisons could have been partially or even completely "optimized" away
>> based on the no-UB assumption.
>> 
>> Testing: mach5 tier1-5
>> local (linux-x64) tier1 with -XX:+UseParallelGC
>
> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
> 
>   typo: intptr_t => uintptr_t

src/hotspot/share/gc/parallel/psCardTable.cpp line 149:

> 147:     assert(iaddr(card) >= iaddr(_table), "out of bounds");
> 148:     assert(iaddr(card) <= (iaddr(_table) + sizeof(_table)), "out of bounds");
> 149:   }

The two impls look identical to me. Also, can you change `check` to `verify` to make it more explicit that they are for verification only?

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PR Review Comment: https://git.openjdk.org/jdk/pull/23032#discussion_r1913094129