d4674ed3b7
Implement functions to read from a memory location and indicate failure in case this is not possible. Since we do not have a MMU, intercept the data abort handler and simply return when the abort comes from the safe read routines. Change-Id: I08f2e59898dcac893319a8150d4cf626f3adabbd Reviewed-on: http://gerrit.rockbox.org/207 Reviewed-by: Marcin Bukat <marcin.bukat@gmail.com>
143 lines
3.7 KiB
ArmAsm
143 lines
3.7 KiB
ArmAsm
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2012 by Amaury Pouly
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "config.h"
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.data
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was_aborted:
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.word 0
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.section .text.safe_read8
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.type safe_read8, %function
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.global safe_read8
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@ bool safe_read8(uint8_t *addr, uint8_t *value)
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safe_read8:
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@ was_aborted = 0
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ldr r2, =was_aborted
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mov r3, #0
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str r3, [r2]
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@ r0=*addr
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safe_read8_faulty_addr:
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ldrb r0, [r0]
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@ if(was_aborted)
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ldr r2, [r2]
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cmp r2, #1
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@ return false;
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moveq r0, #0
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bxeq lr
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@ if(value != NULL)
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cmp r1, #0
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@ *value = r0
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strneb r0, [r1]
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@ return true;
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mov r0, #1
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bx lr
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.size safe_read8, . - safe_read8
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.section .text.safe_read16
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.type safe_read16, %function
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.global safe_read16
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@ bool safe_read16(uint16_t *addr, uint16_t *value)
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safe_read16:
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@ was_aborted = 0
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ldr r2, =was_aborted
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mov r3, #0
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str r3, [r2]
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@ r0=*addr
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safe_read16_faulty_addr:
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ldrh r0, [r0]
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@ if(was_aborted)
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ldr r2, [r2]
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cmp r2, #1
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@ return false;
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moveq r0, #0
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bxeq lr
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@ if(value != NULL)
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cmp r1, #0
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@ *value = r0
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strneh r0, [r1]
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@ return true;
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mov r0, #1
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bx lr
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.size safe_read16, . - safe_read16
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.section .text.safe_read32
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.type safe_read32, %function
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.global safe_read32
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@ bool safe_read32(uint32_t *addr, uint32_t *value)
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safe_read32:
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@ was_aborted = 0
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ldr r2, =was_aborted
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mov r3, #0
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str r3, [r2]
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@ r0=*addr
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safe_read32_faulty_addr:
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ldr r0, [r0]
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@ if(was_aborted)
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ldr r2, [r2]
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cmp r2, #1
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@ return false;
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moveq r0, #0
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bxeq lr
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@ if(value != NULL)
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cmp r1, #0
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@ *value = r0
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strne r0, [r1]
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@ return true;
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mov r0, #1
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bx lr
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.size safe_read32, . - safe_read32
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#if (CONFIG_PLATFORM & PLATFORM_NATIVE)
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.section .text.data_abort_handler
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.type data_abort_handler, %function
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.global data_abort_handler
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data_abort_handler:
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@ store minimal amount of registers
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stmfd sp!, {r0-r1}
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@ compute faulty address
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sub r0, lr, #8
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@ compare to safe_read8
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ldr r1, =safe_read8_faulty_addr
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cmp r0, r1
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beq 1f
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@ compare to safe_read16
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ldr r1, =safe_read16_faulty_addr
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cmp r0, r1
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beq 1f
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@ compare to safe_read32
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ldr r1, =safe_read32_faulty_addr
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cmp r0, r1
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beq 1f
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@ otherwise just normally to UIE
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mov r0, r1
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mov r1, #2
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b UIE
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1:
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@ set was_aborted
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ldr r1, =was_aborted
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mov r0, #1
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str r0, [r1]
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@ restore registers
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ldmfd sp!, {r0-r1}
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@ restore mode and jump back to the *next* instruction
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subs pc, lr, #-4
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.size data_abort_handler, . - data_abort_handler
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#endif
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