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.
AngelSWI_Reason_ReportException does not return accoring to the ARM
documentation, so it is valid to mark _kill() as noreturn. This way,
the compiler does not warn about _exit() returning a value despite
being noreturn.
2018-10-01 Christophe Lyon <christophe.lyon@linaro.org>
* libgloss/arm/_exit.c (_exit): Declare _kill() as noreturn.
* libgloss/arm/_exit.c (_kill): Likewise. Remove the return
statements.
* newlib/libc/sys/arm/syscalls.c (_kill): Likewise..
The current SYS_EXIT has a bug that when making the call it always uses
the v2 calling convention. This is undefined behavior according to the
semihosting specification:
https://developer.arm.com/docs/100863/latest/semihosting-operations/sys_exit-0x18
This patch fixes it by making sure v1 passes the argument directly in the register instead
of in a block. And for v2 it does the same if the v2 extension isn't supported.
The sequence generated now is
12424: ebfffecd bl 11f60 <_has_ext_exit_extended>
12428: e3500000 cmp r0, #0
1242c: 11a0500d movne r5, sp
12430: 059d5000 ldreq r5, [sp]
12434: e1a00004 mov r0, r4
12438: e1a01005 mov r1, r5
1243c: ef00f000 svc 0x0000f000
Signed-off-by: Tamar Christina <tamar.christina@arm.com>
Semihosting v2 changes are documented here:
https://developer.arm.com/docs/100863/latest/
The biggest change is the addition of an extensions mechanism
to add more extensions in the future.
Signed-off-by: Tamar Christina <tamar.christina@arm.com>
Matthew Malcomson
Christophe Lyon
Tamar Christina
Yaakov Selkowitz
Jeff Johnston