RFR(S): 8221175: Fix bad function case for controlled JVM crash on PPC64 big-endian
gromero at linux.vnet.ibm.com
Fri Mar 22 16:15:14 UTC 2019
Please, could I get reviews for the following change?
bug : https://bugs.openjdk.java.net/browse/JDK-8221175
It fixes the way a function pointer is defined in order to call a bad function
at address 0xF (controlled crash case 13) on PPC64 big-endian machines.
On PPC64 big-endian compiler defaults to ABI ELFv1 which mandates function
pointers to part of a function descriptor, at offset 0 .
Currently the SIGISEGV being generated by case 13 is incorrect because if a
function descriptor is not use to call the bad function address the program
segfaults before effectively calling the function, when trying to load
the (bad) function pointer from offset 0 of base address 0xF, so before
branching to the function.
It does not affect PPC64 little-endian machines because by default ABI ELFv2
is used (instead of ABI ELFv1) and for that ABI no function descriptor is
defined / employed.
The fix consists in defining properly a function descriptor with a bad function
at offset 0 (the following offset are no important in that case) and using that
function descriptor to call the bad function, only on PPC64 big-endian machines.
That issue was found when investigating the JDK-8220794 issue .
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