51 lines
1.4 KiB
C
51 lines
1.4 KiB
C
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/*
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* Copyright (c) 2017, Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <string.h>
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#include <xtensa-asm2.h>
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#include <kernel.h>
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#include <kernel_structs.h>
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void *xtensa_init_stack(int *stack_top,
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void (*entry)(void *, void *, void *),
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void *arg1, void *arg2, void *arg3)
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{
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/* We cheat and shave 16 bytes off, the top four words are the
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* A0-A3 spill area for the caller of the entry function,
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* which doesn't exist. It will never be touched, so we
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* arrange to enter the function with a CALLINC of 1 and a
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* stack pointer 16 bytes above the top, so its ENTRY at the
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* start will decrement the stack pointer by 16.
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*/
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const int bsasz = BASE_SAVE_AREA_SIZE - 16;
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void **bsa = (void **) (((char *) stack_top) - bsasz);
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memset(bsa, 0, bsasz);
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bsa[BSA_PC_OFF/4] = entry;
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bsa[BSA_PS_OFF/4] = (void *)(PS_WOE | PS_UM | PS_CALLINC(1));
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/* Arguments. Remember these start at A6, which will be
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* rotated into A2 by the ENTRY instruction that begins the
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* entry function. And A4-A7 and A8-A11 are optional quads
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* that live below the BSA!
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*/
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bsa[-1] = arg2; /* a7 */
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bsa[-2] = arg1; /* a6 */
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bsa[-3] = 0; /* a5 */
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bsa[-4] = 0; /* a4 */
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bsa[-5] = 0; /* a11 */
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bsa[-6] = 0; /* a10 */
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bsa[-7] = 0; /* a9 */
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bsa[-8] = arg3; /* a8 */
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/* Finally push the BSA pointer and return the stack pointer
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* as the handle
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*/
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bsa[-9] = bsa;
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return &bsa[-9];
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}
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