Hi On 2019-03-22 12:15 p.m., Gustavo Romero wrote:
Hi,
Please, could I get reviews for the following change?
bug : https://bugs.openjdk.java.net/browse/JDK-8221175 webrev: http://cr.openjdk.java.net/~gromero/8221175/v1/
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 [1].
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 [2].
Thank you.
Best regards, Gustavo
[1] http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html#FUNC-DES [2] https://bugs.openjdk.java.net/browse/JDK-8220794
Looks good, but not a reviewer. Chris