#### G.4.9 S/390 and System z Features

The ``org.gnu.gdb.s390.core`' feature is required for S/390 and System z targets. It should contain the PSW and the 16 general registers. In particular, System z targets should provide the 64-bit registers ``pswm`', ``pswa`', and ``r0`' through ``r15`'. S/390 targets should provide the 32-bit versions of these registers. A System z target that runs in 31-bit addressing mode should provide 32-bit versions of ``pswm`' and ``pswa`', as well as the general register's upper halves ``r0h`' through ``r15h`', and their lower halves ``r0l`' through ``r15l`'.

The ``org.gnu.gdb.s390.fpr`' feature is required. It should contain the 64-bit registers ``f0`' through ``f15`', and ``fpc`'.

The ``org.gnu.gdb.s390.acr`' feature is required. It should contain the 32-bit registers ``acr0`' through ``acr15`'.

The ``org.gnu.gdb.s390.linux`' feature is optional. It should contain the register ``orig_r2`', which is 64-bit wide on System z targets and 32-bit otherwise. In addition, the feature may contain the ``last_break`' register, whose width depends on the addressing mode, as well as the ``system_call`' register, which is always 32-bit wide.

The ``org.gnu.gdb.s390.tdb`' feature is optional. It should contain the 64-bit registers ``tdb0`', ``tac`', ``tct`', ``atia`', and ``tr0`' through ``tr15`'.

The ``org.gnu.gdb.s390.vx`' feature is optional. It should contain 64-bit wide registers ``v0l`' through ``v15l`', which will be combined by gdb with the floating point registers ``f0`' through ``f15`' to present the 128-bit wide vector registers ``v0`' through ``v15`'. In addition, this feature should contain the 128-bit wide vector registers ``v16`' through ``v31`'.