Hi All,

In _stack_init function of crt0.S file, when the current mode is not user mode,
all the processor modes are parsed and the corresponding stack limit are set for
these modes for all A-profile and R-profile CPU's. But if a CPU implements EL2
as its highest exception level, then the core (or a model of it) will start in that
mode. For example, with Cortex-R52 the processor starts by default is hypervisor
mode (EL2), changing to any other mode using CPSR will result in an illegal
instruction as per Arm-arm.
This patch prevent the change of Hypervisor mode to any other EL1 modes in
_stack_init function in crt0.S files and does not set the stack limit for those
EL1 modes.

Regression tested on arm-none-eabi target for newlib and newlib-nano and found
no regressions.

Ok for newlib master?

Regards,
Srinath.

libgloss/ChangeLog:

2023-03-03  Srinath Parvathaneni<srinath.parvathaneni@arm.com>

         * arm/crt0.S (_stack_init): Add check for hypervisor mode.

newlib/ChangeLog:

2023-03-03  Srinath Parvathaneni<srinath.parvathaneni@arm.com>

         * libc/sys/arm/crt0.S (_stack_init): Add check for hypervisor mode.