/* IBM_PROLOG_BEGIN_TAG                                                   */
/* This is an automatically generated prolog.                             */
/*                                                                        */
/* $Source: src/ssx/ssx/ssx_stack_init.c $                                */
/*                                                                        */
/* OpenPOWER OnChipController Project                                     */
/*                                                                        */
/* Contributors Listed Below - COPYRIGHT 2014,2016                        */
/* [+] International Business Machines Corp.                              */
/*                                                                        */
/*                                                                        */
/* Licensed under the Apache License, Version 2.0 (the "License");        */
/* you may not use this file except in compliance with the License.       */
/* You may obtain a copy of the License at                                */
/*                                                                        */
/*     http://www.apache.org/licenses/LICENSE-2.0                         */
/*                                                                        */
/* Unless required by applicable law or agreed to in writing, software    */
/* distributed under the License is distributed on an "AS IS" BASIS,      */
/* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or        */
/* implied. See the License for the specific language governing           */
/* permissions and limitations under the License.                         */
/*                                                                        */
/* IBM_PROLOG_END_TAG                                                     */

/// \file ssx_stack_init.c
/// \brief SSX stack initialization
///
/// The entry points in this file are initialization routines - they are never
/// needed after SSX initialization and their code space could be reclaimed by
/// the application after initialization if required.
///
/// This code was split out from "ssx_init.c" because it may be needed in a
/// thread configuration if threads are being created dynamically. in an
/// interrupt-only configuration it is not needed after \c ssx_initialize().

#include "ssx.h"

/// Initialize a stack area.
///
/// \param stack A pointer to the smallest legal address of the stack.  The
/// stack address is modified as the stack is aligned and initialized.
///
/// \param size A pointer to the size of the stack (in bytes).  The size is
/// modified as the stack is aligned and initialized.  At exit this is the
/// final usable stack area size aligned to the size of the SSX_STACK_TYPE.
///
/// SSX makes no assumptions about size or alignment of the area provided as a
/// stack, and carefully aligns and initializes the stack.  Regardless of how
/// the stack grows, the \a stack parameter is considered to be the lowest
/// legal address of the stack.

int
__ssx_stack_init(SsxAddress* stack,
                 size_t*     size)
{
    SsxAddress mask;
    size_t excess, i, count;
    SSX_STACK_TYPE* p;

    if (SSX_STACK_DIRECTION < 0)
    {

        // Stacks grow down.  The initial stack pointer is set to just above
        // the last allocated stack address.  This is legal for pre-decrement
        // stacks, otherwise the initial address is first brought into range
        // before alignment.  The stack is aligned downward, then the size is
        // adjusted to a multiple of the stack type.  Stacks are optionally
        // prepatterned. Alignment is assumed to be a power of 2.

        *stack += *size;

        if (!SSX_STACK_PRE_DECREMENT)
        {
            *stack -= sizeof(SSX_STACK_TYPE);
            *size -= sizeof(SSX_STACK_TYPE);
        }

        mask = SSX_STACK_ALIGNMENT - 1;
        excess = *stack & mask;
        *stack -= excess;
        *size -= excess;
        *size = (*size / sizeof(SSX_STACK_TYPE)) * sizeof(SSX_STACK_TYPE);

        if (SSX_STACK_CHECK)
        {
            p = (SSX_STACK_TYPE*)(*stack);
            count = *size / sizeof(SSX_STACK_TYPE);

            for (i = 0; i < count; i++)
            {
                if (SSX_STACK_PRE_DECREMENT)
                {
                    *(--p) = SSX_STACK_PATTERN;
                }
                else
                {
                    *(p--) = SSX_STACK_PATTERN;
                }
            }
        }

        __ssx_stack_create_initial_frame(stack, size);

    }
    else
    {

        SSX_PANIC(SSX_UNIMPLEMENTED);
    }

    return SSX_OK;
}