8274527: Minimal VM build fails after JDK-8273459 #5764

DamonFool · 2021-09-29T23:41:06Z

Hi all,

The broken was observed when

(gdb) bt
#0  MacroAssembler::align (this=0x7ffff0025b98, modulus=32) at /home/jvm/jiefu/docker/jdk/src/hotspot/cpu/x86/macroAssembler_x86.cpp:1182
#1  0x00007ffff67fc6c5 in MacroAssembler::kernel_crc32 (this=0x7ffff0025b98, crc=0x7, buf=0x6, len=0x2, table=0x1, tmp=0xb)
    at /home/jvm/jiefu/docker/jdk/src/hotspot/cpu/x86/macroAssembler_x86.cpp:6911
#2  0x00007ffff69a3555 in StubGenerator::generate_updateBytesCRC32 (this=0x7ffff5e9c900) at /home/jvm/jiefu/docker/jdk/src/hotspot/cpu/x86/stubGenerator_x86_64.cpp:6532
#3  0x00007ffff69a589b in StubGenerator::generate_initial (this=0x7ffff5e9c900) at /home/jvm/jiefu/docker/jdk/src/hotspot/cpu/x86/stubGenerator_x86_64.cpp:7583
#4  0x00007ffff69a6801 in StubGenerator::StubGenerator (this=0x7ffff5e9c900, code=0x7ffff5e9c9c0, all=false)
    at /home/jvm/jiefu/docker/jdk/src/hotspot/cpu/x86/stubGenerator_x86_64.cpp:7909
#5  0x00007ffff697fa21 in StubGenerator_generate (code=0x7ffff5e9c9c0, all=false) at /home/jvm/jiefu/docker/jdk/src/hotspot/cpu/x86/stubGenerator_x86_64.cpp:7919
#6  0x00007ffff69a6c13 in StubRoutines::initialize1 () at /home/jvm/jiefu/docker/jdk/src/hotspot/share/runtime/stubRoutines.cpp:223
#7  0x00007ffff69a790d in stubRoutines_init1 () at /home/jvm/jiefu/docker/jdk/src/hotspot/share/runtime/stubRoutines.cpp:366
#8  0x00007ffff672044d in init_globals () at /home/jvm/jiefu/docker/jdk/src/hotspot/share/runtime/init.cpp:119
#9  0x00007ffff69fb39f in Threads::create_vm (args=0x7ffff5e9ce10, canTryAgain=0x7ffff5e9cd33) at /home/jvm/jiefu/docker/jdk/src/hotspot/share/runtime/thread.cpp:2827
#10 0x00007ffff6787879 in JNI_CreateJavaVM_inner (vm=0x7ffff5e9ce68, penv=0x7ffff5e9ce70, args=0x7ffff5e9ce10)
    at /home/jvm/jiefu/docker/jdk/src/hotspot/share/prims/jni.cpp:3616
#11 0x00007ffff6787a72 in JNI_CreateJavaVM (vm=0x7ffff5e9ce68, penv=0x7ffff5e9ce70, args=0x7ffff5e9ce10)
    at /home/jvm/jiefu/docker/jdk/src/hotspot/share/prims/jni.cpp:3704
#12 0x00007ffff79b8141 in InitializeJVM (pvm=0x7ffff5e9ce68, penv=0x7ffff5e9ce70, ifn=0x7ffff5e9cec0)
    at /home/jvm/jiefu/docker/jdk/src/java.base/share/native/libjli/java.c:1459
#13 0x00007ffff79b4f39 in JavaMain (_args=0x7fffffffb1a0) at /home/jvm/jiefu/docker/jdk/src/java.base/share/native/libjli/java.c:411
#14 0x00007ffff79bba79 in ThreadJavaMain (args=0x7fffffffb1a0) at /home/jvm/jiefu/docker/jdk/src/java.base/unix/native/libjli/java_md.c:651
#15 0x00007ffff779cea5 in start_thread () from /lib64/libpthread.so.0
#16 0x00007ffff72c19fd in clone () from /lib64/libc.so.6

In this case, modulus=32 and CodeEntryAlignment=16.

So this assert shouldn't be added in align since we may use it (modulus > CodeEntryAlignment) in highly optimized hand-crafted assembly code.

Thanks.
Best regards,
Jie

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Issue

JDK-8274527: Minimal VM build fails after JDK-8273459

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bridgekeeper · 2021-09-29T23:42:13Z

👋 Welcome back jiefu! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2021-09-29T23:52:07Z

@DamonFool The following label will be automatically applied to this pull request:

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mlbridge · 2021-09-29T23:57:21Z

Webrevs

01: Full - Incremental (cdd8743b)
00: Full (63d635bf)

asgibbons · 2021-09-30T01:26:45Z

Hi, Jie. With a value of 16 for CodeEntryAlignment, there is no way to ensure that the address of the byte following the align(32) is, in fact, 32-byte aligned. This is the exact case that I found that caused me to file the bug. I would suggest you verify this with an assert following your align(32) verifying that the alignment is correct. I think you'll discover that it will be unaligned ~50% of the time.

This is because align() uses the offset from the beginning of the segment to determine the number of nops to emit. If the segment has the starting address 0xXXXXXX10 (16-byte aligned), align(32) will calculate the offset() and align the pc to a multiple of 32 bytes from this starting address. This means that the address after the align(32) has the possibility of being 0xXXXXXX30 about half the time.

I would suggest that if you absolutely require 32-byte alignment, you take a similar path that I took for 64-byte alignment. That is, to create align32() and have it call align(32, pc()). This will ensure (for stub code) that the alignment is correct.

DamonFool · 2021-09-30T03:07:54Z

Hi, Jie. With a value of 16 for CodeEntryAlignment, there is no way to ensure that the address of the byte following the align(32) is, in fact, 32-byte aligned. This is the exact case that I found that caused me to file the bug. I would suggest you verify this with an assert following your align(32) verifying that the alignment is correct. I think you'll discover that it will be unaligned ~50% of the time.

This is because align() uses the offset from the beginning of the segment to determine the number of nops to emit. If the segment has the starting address 0xXXXXXX10 (16-byte aligned), align(32) will calculate the offset() and align the pc to a multiple of 32 bytes from this starting address. This means that the address after the align(32) has the possibility of being 0xXXXXXX30 about half the time.

I would suggest that if you absolutely require 32-byte alignment, you take a similar path that I took for 64-byte alignment. That is, to create align32() and have it call align(32, pc()). This will ensure (for stub code) that the alignment is correct.

Ah, you are right.
I missed that align is with the offset() not the pc().
So the assert should make sense.

Updated.
Thanks.

asgibbons · 2021-09-30T13:52:03Z

Looks good to me.

vnkozlov

Good.

openjdk · 2021-09-30T17:57:59Z

@DamonFool 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:

8274527: Minimal VM build fails after JDK-8273459

Reviewed-by: kvn

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 15 new commits pushed to the master branch:

7326481: 8274393: Suppress more warnings on non-serializable non-transient instance fields in security libs
8215b2e: 8274398: Suppress more warnings on non-serializable non-transient instance fields in management libs
9573022: 8253197: vmTestbase/nsk/jvmti/StopThread/stopthrd007/TestDescription.java fails with "ERROR: DebuggeeSleepingThread: ThreadDeath lost"
f08180f: 8274501: c2i entry barriers read int as long on AArch64
c57ed22: 8274528: Add comment to explain an HKDF optimization in SSLSecretDerivation
9180d9a: 8273216: JCMD does not work across container boundaries with Podman
3e0d7c3: 8270290: NTLM authentication fails if HEAD request is used
bfd6163: 8274196: Crashes in VM_HeapDumper::work after JDK-8252842
bb95dda: 8248001: javadoc generates invalid HTML pages whose ftp:// links are broken
2f955d6: 8273142: Remove dependancy of TestHttpServer, HttpTransaction, HttpCallback from open/test/jdk/sun/net/www/protocol/http/ tests
... and 5 more: https://git.openjdk.java.net/jdk/compare/355356c405adb9287b786b0b045c2eb974d2ffca...master

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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

DamonFool · 2021-09-30T23:10:20Z

Thanks @asgibbons and @vnkozlov for your review.
/integrate

openjdk · 2021-09-30T23:12:06Z

Going to push as commit a8edd1b.
Since your change was applied there have been 15 commits pushed to the master branch:

7326481: 8274393: Suppress more warnings on non-serializable non-transient instance fields in security libs
8215b2e: 8274398: Suppress more warnings on non-serializable non-transient instance fields in management libs
9573022: 8253197: vmTestbase/nsk/jvmti/StopThread/stopthrd007/TestDescription.java fails with "ERROR: DebuggeeSleepingThread: ThreadDeath lost"
f08180f: 8274501: c2i entry barriers read int as long on AArch64
c57ed22: 8274528: Add comment to explain an HKDF optimization in SSLSecretDerivation
9180d9a: 8273216: JCMD does not work across container boundaries with Podman
3e0d7c3: 8270290: NTLM authentication fails if HEAD request is used
bfd6163: 8274196: Crashes in VM_HeapDumper::work after JDK-8252842
bb95dda: 8248001: javadoc generates invalid HTML pages whose ftp:// links are broken
2f955d6: 8273142: Remove dependancy of TestHttpServer, HttpTransaction, HttpCallback from open/test/jdk/sun/net/www/protocol/http/ tests
... and 5 more: https://git.openjdk.java.net/jdk/compare/355356c405adb9287b786b0b045c2eb974d2ffca...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-09-30T23:12:18Z

@DamonFool Pushed as commit a8edd1b.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

8274527: Minimal VM build fails after JDK-8273459

63d635b

DamonFool mentioned this pull request Sep 29, 2021

8273459: Update code segment alignment to 64 bytes #5547

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Use align32

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8274527: Minimal VM build fails after JDK-8273459 #5764

8274527: Minimal VM build fails after JDK-8273459 #5764

DamonFool commented Sep 29, 2021 •

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openjdk bot commented Sep 30, 2021

8274527: Minimal VM build fails after JDK-8273459 #5764

8274527: Minimal VM build fails after JDK-8273459 #5764

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DamonFool commented Sep 29, 2021 • edited by openjdk[bot] bot

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DamonFool commented Sep 29, 2021 •

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