mirror of
https://github.com/Rockbox/rockbox.git
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e29780fe09
The "mov lr, pc" instruction doesn't link a proper return address in Thumb mode: bit 0 will be unset, leading to a UsageFault exception when returning from the thread's main function. Cortex-M has the "blx" instruction to automatically branch and link the correct return address, so use that. Change-Id: I4c0ca55b1b2204286343f906f0b53be0c0ddc392
87 lines
3.4 KiB
C
87 lines
3.4 KiB
C
/***************************************************************************
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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) 2005 by Thom Johansen
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* Copyright (C) 2026 by Aidan MacDonald
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*
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* Threading support for ARM Cortex-M targets
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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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/*---------------------------------------------------------------------------
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* Start the thread running and terminate it if it returns
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*---------------------------------------------------------------------------
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*/
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static void __attribute__((naked)) USED_ATTR start_thread(void)
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{
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/* r0 = context */
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asm volatile (
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"ldr sp, [r0, #36] \n" /* Load initial sp */
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"ldr r4, [r0, #40] \n" /* start in r4 since it's non-volatile */
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"mov r1, #0 \n" /* Mark thread as running */
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"str r1, [r0, #40] \n"
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"blx r4 \n" /* Call thread function */
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"b thread_exit \n"
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); /* No clobber list - new thread doesn't care */
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}
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/* For startup, place context pointer in r4 slot, start_thread pointer in r5
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* slot, and thread function pointer in context.start. See load_context for
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* what happens when thread is initially going to run. */
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#define THREAD_STARTUP_INIT(core, thread, function) \
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({ (thread)->context.r[0] = (uint32_t)&(thread)->context, \
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(thread)->context.r[1] = (uint32_t)start_thread, \
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(thread)->context.start = (uint32_t)function; })
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/*---------------------------------------------------------------------------
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* Store non-volatile context.
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*---------------------------------------------------------------------------
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*/
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static inline void store_context(void* addr)
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{
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asm volatile(
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"stmia %0, { r4-r11, lr } \n"
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"str sp, [%0, #36] \n"
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: : "r" (addr)
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);
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}
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/*---------------------------------------------------------------------------
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* Load non-volatile context.
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*---------------------------------------------------------------------------
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*/
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static inline void load_context(const void* addr)
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{
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asm volatile(
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BEGIN_ARM_ASM_SYNTAX_UNIFIED
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"ldr r0, [%0, #40] \n" /* Load start pointer */
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"cmp r0, #0 \n" /* Check for NULL */
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/* If not already running, jump to start */
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"ldmiane %0, { r0, pc } \n"
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/* Load regs r4 to r14 from context */
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"mov r0, %0 \n"
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"ldmia r0, { r4-r11, lr } \n"
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"ldr sp, [r0, #36] \n"
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END_ARM_ASM_SYNTAX_UNIFIED
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: : "r" (addr) : "r0" /* only! */
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);
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}
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