RFR: JDK-8296906: VMError::controlled_crash crashes with wrong code and address

[David Holmes]

On Sun, 13 Nov 2022 09:01:09 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> We have VMError::controlled_crash() in debug builds, whose job is to trigger clearly defined faults to test VM error reporting. VMError::controlled_crash(14) (the numbers don't mean anything and probably should be replaced with clear enums) is to crash with a SIGSEGV + SEGV_MAPERR mapping error at a well-known crash address. But this does not work on Linux, where it generates a SIGSEGV with SI_KERNEL instead. We never noticed since it had not been used in tests so far.
> 
> The reason for SI_KERNEL was that the crash address we use (0xABC0000000000ABC) was outside the user-space address range on Linux. This patch redefines the crash address to a value that really generates a SIGSEGV + SEGV_MAPERR on all our platforms. That's one line; the rest is a new regression test that checks that signal info is printed correctly in hs-err files.

Did we not notice or was that exactly what was expected? When JDK-8065895 added that code it was known to generate SEGV _because_ it was outside the allowable range (otherwise there would have been no guarantee). Maybe the SI_KERNEL behaviour has changed since then? It doesn't seem an issue to change it to a low address (other than that doesn't work on AIX) but it seems odd to now consider it a bug - seems more like you now consider it too limited because the true address is not given in the sig info?

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PR: https://git.openjdk.org/jdk/pull/11122