On Mon, 21 Oct 2024 13:53:58 GMT, Roman Kennke <rken...@openjdk.org> wrote:
>> Roman Kennke has updated the pull request incrementally with one additional >> commit since the last revision: >> >> Compact header riscv (#3) >> >> Implement compact headers on RISCV >> --------- >> >> Co-authored-by: hamlin <ham...@rivosinc.com> > >> I've managed to reproduce the ECoreIndexOf crash locally by running with >> -XX:+UseSerialGC -XX:+UnlockExperimentalVMOptions >> -XX:+UseCompactObjectHeaders. The crash happens on line 773 when reading >> past the needle. >> >> ``` >> │ 762 __ movq(index, needle_len); >> │ >> │ 763 __ andq(index, 0xf); // nLen % 16 >> │ 764 __ movq(offset, 0x10); >> │ 765 __ subq(offset, index); // 16 - (nLen % 16) >> │ 766 __ movq(index, offset); >> │ 767 __ shlq(offset, 1); // * 2 >> │ 768 __ negq(index); // -(16 - (nLen % 16)) >> │ >> │ 769 __ xorq(wr_index, wr_index); >> │ 770 >> │ 771 __ bind(L_top); >> │ 772 // load needle and expand >> │ 773 __ vpmovzxbw(xmm0, Address(needle, index, Address::times_1), >> Assembler::AVX_256bit); >> ``` >> >> We're reading this address: >> >> ``` >> (SEGV_MAPERR), si_addr: 0x00000007cffffffe >> ``` >> >> which is just before the start of the heap: >> >> ``` >> Heap address: 0x00000007d0000000, size: 768 MB, Compressed Oops mode: Zero >> based, Oop shift amount: 3 >> ``` >> >> When this crashed I had: >> >> ``` >> needle: 0x00000007d000000c >> needle_len = 0x12 >> index = 0xfffffffffffffffe >> ``` >> >> There has been previous fix to not read past the haystack: Fix header < 16 >> bytes in indexOf intrinsic, by @sviswa7 >> [f65ef5d](https://github.com/openjdk/jdk/commit/f65ef5dc325212155a50a2fc3a7f4aad18b8d9d0) >> >> maybe we need something similar for the needle. > > @sviswa7 @vpaprotsk could you have a look? If we can have a reasonable fix > for this soon, we could ship it in this PR, otherwise I'd defer it to a > follow-up issue and disable indexOf intrinsic when running with > +UseCompactObjectHeaders. > @rkennke Could you post the full command you used please? And perhaps also > the seed that gets printed.. having trouble getting it to fail.. > > So far I added a few options and perrmitations of: > `./build/linux-x86_64-server-fastdebug/images/jdk/bin/java -Xcomp > -XX:-TieredCompilation -XX:+UnlockDiagnosticVMOptions -XX:+EnableX86ECoreOpts > -XX:+UseSerialGC -XX:+UnlockExperimentalVMOptions > -XX:+UseCompactObjectHeaders > test/jdk/java/lang/StringBuffer/ECoreIndexOf.java` and lo luck.. IndexOf.java > test checks "all interesting" lengths of haystack and needle and can't get it > to fail either. I could reproduce on 3rd try with a fastdebug build with: make test TEST=java/lang/StringBuffer/ECoreIndexOf.java TEST_VM_OPTS="-XX:+UnlockExperimentalVMOptions -XX:+UseCompactObjectHeaders -XX:+UseSerialGC" It prints: Seed set to 636754923980405411 It probably depends on GC operation: It would only fail when the array happens to be the very first object in the heap. The relevant GC/heap configs would be: InitialHeapSize = 805306368 MaxHeapSize = 805306368 MaxNewSize = 268435456 So you should probably also add `-Xmx805306368 -Xms805306368 -Xmn268435456` ------------- PR Comment: https://git.openjdk.org/jdk/pull/20677#issuecomment-2427375886
