RFR: 8332894: ubsan: vmError.cpp:2090:26: runtime error: division by zero

[Kim Barrett]

On Fri, 24 May 2024 13:30:41 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> When running with ubsan enabled on Linux x86_64, I get in the HS :tier1 tests this error :
> 
> runtime/ErrorHandling/TestDwarf_dontCheckDecoder.jtr
> 
> /jdk/src/hotspot/share/utilities/vmError.cpp:2090:26: runtime error: division by zero
>     #0 0x7f16bc531f32 in crash_with_sigfpe /jdk/src/hotspot/share/utilities/vmError.cpp:2090
>     #1 0x7f16bc531f32 in VMError::controlled_crash(int) /jdk/src/hotspot/share/utilities/vmError.cpp:2137
>     #2 0x7f16bea2d8fd in JNI_CreateJavaVM_inner /jdk/src/hotspot/share/prims/jni.cpp:3621
>     #3 0x7f16bea2d8fd in JNI_CreateJavaVM /jdk/src/hotspot/share/prims/jni.cpp:3672
>     #4 0x7f16c5dbd0e5 in InitializeJVM /jdk/src/java.base/share/native/libjli/java.c:1550
>     #5 0x7f16c5dbd0e5 in JavaMain /jdk/src/java.base/share/native/libjli/java.c:491
>     #6 0x7f16c5dc6748 in ThreadJavaMain /jdk/src/java.base/unix/native/libjli/java_md.c:642
>     #7 0x7f16c5d756e9 in start_thread (/lib64/libpthread.so.0+0xa6e9) (BuildId: 2f8d3c2d0f4d7888c2598d2ff6356537f5708a73)
>     #8 0x7f16c531550e in clone (/lib64/libc.so.6+0x11850e) (BuildId: f732026552f6adff988b338e92d466bc81a01c37)
> 
> Reason is that we do a float division by zero to get a signal . This is desired by us so not really an error but ubsan cannot know this.
> So add an attribute to this function that it has undefined behavior.
> See https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html   (division by zero) . "Floating point division by zero. This is undefined per the C and C++ standards"

src/hotspot/share/utilities/vmError.cpp line 2093:

> 2091: static void ALWAYSINLINE crash_with_sigfpe() {
> 2092: 
> 2093:   // generate a native synchronous SIGFPE where possible;

Maybe simpler would be to change the definition to only use the divide-by-zero
approach for _WIN32 and always use the currently conditional fallback to
pthread_kill on non-_WIN32.  Especially in light of the fact that the
divide-by-zero approach doesn't work on some platforms.

I also wonder if the comment about OSX incorrectly implementing raise is
correct? Maybe that's been fixed?  Or maybe it's not a bug, but a BSD-ism?

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PR Review Comment: https://git.openjdk.org/jdk/pull/19394#discussion_r1614725794