The _exit function currently passes -1 as a "sig" to the _kill function as an
invalid signal number so that _kill can distinguish between an abort and a
standard exit.
For boards using the SYS_EXIT_EXTENDED semi-hosting operation to return a
status code, this means that the "status" paramter to _exit is ignored and the
return code is always -1.
https://developer.arm.com/docs/100863/latest/semihosting-operations/sys_exit_extended-0x20
This patch puts shared code between _kill and _exit into a new function
_kill_shared that takes the semi-hosting "reason" to use (if semi-hosting is
available) as an argument.
For semi-hosting _kill_shared provides that "reason".
Without the "sig" argument being used to distinguish between a normal and
abnormal exit, the _exit function can provide the return code to be used if the
SYS_EXIT_EXTENDED operation is available.
Hence the exit code can be returned.
bfin - Analog Devices Blackfin processor.
sparc - Fujitsu Sparclite board. Works on the ex930, ex931, ex933
hp74x - Hewlett Packard HP742 board. Also some support for the hp743.
m68hc11 - Motorola 68HC11 or 68HC12 support.
m68k - Motorola MVME135 and IDP board. For CPU32 systems.
mep - Toshiba Media Processor.
pa - WinBond and Oki boards with a PA.
mips - R3000 support. Array Tech LSI33k based RAID disk controller.
lm32 - Lattice Mico32 simulator.
epiphany - Adapteva Epiphany multicore processor.
or1k - OpenRISC 1000 processor.
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