On 07/25/2018 11:48 PM, Shivaprasad G Bhat wrote:
Reference:
https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#REG
This document is for _CALL_ELF < 2. For ppc64le, the document is at
https://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf
In both cases, it appears that we can (ab)use SP+16 to save
the value of r14 across the syscall. This slot would normally
be used for saving our own return address (LR), but we have no
need to save that value because it *is* preserved across the syscall.