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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.
This file is part of ChibiOS/RT.
ChibiOS/RT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
ChibiOS/RT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file GCC/ARMCMx/chcore_v6m.c
* @brief ARMv6-M architecture port code.
*
* @addtogroup ARMCMx_V6M_CORE
* @{
*/
#include "ch.h"
/**
* @brief PC register temporary storage.
*/
regarm_t _port_saved_pc;
/**
* @brief IRQ nesting counter.
*/
unsigned _port_irq_nesting;
/**
* @brief System Timer vector.
* @details This interrupt is used as system tick.
* @note The timer must be initialized in the startup code.
*/
CH_IRQ_HANDLER(SysTickVector) {
CH_IRQ_PROLOGUE();
chSysLockFromIsr();
chSysTimerHandlerI();
chSysUnlockFromIsr();
CH_IRQ_EPILOGUE();
}
/**
* @brief Post-IRQ switch code.
* @details On entry the stack and the registers are restored by the exception
* return, the PC value is stored in @p _port_saved_pc, the interrupts
* are disabled.
*/
#if !defined(__DOXYGEN__)
__attribute__((naked))
#endif
void _port_switch_from_isr(void) {
/* Note, saves r4 to make space for the PC.*/
asm volatile ("push {r0, r1, r2, r3, r4} \n\t"
"mrs r0, APSR \n\t"
"mov r1, r12 \n\t"
"push {r0, r1, lr} \n\t"
"ldr r0, =_port_saved_pc \n\t"
"ldr r0, [r0] \n\t"
"add r0, r0, #1 \n\t"
"str r0, [sp, #28]" : : : "memory");
chSchDoRescheduleI();
/* Note, the last register is restored alone after re-enabling the
interrupts in order to minimize the (very remote and unlikely)
possibility that the stack is filled by continuous and saturating
interrupts that would not allow that last words to be pulled out of
the stack.*/
asm volatile ("pop {r0, r1, r2} \n\t"
"mov r12, r1 \n\t"
"msr APSR, r0 \n\t"
"mov lr, r2 \n\t"
"pop {r0, r1, r2, r3} \n\t"
"cpsie i \n\t"
"pop {pc}" : : : "memory");
}
#define PUSH_CONTEXT(sp) { \
asm volatile ("push {r4, r5, r6, r7, lr} \n\t" \
"mov r4, r8 \n\t" \
"mov r5, r9 \n\t" \
"mov r6, r10 \n\t" \
"mov r7, r11 \n\t" \
"push {r4, r5, r6, r7}" : : : "memory"); \
}
#define POP_CONTEXT(sp) { \
asm volatile ("pop {r4, r5, r6, r7} \n\t" \
"mov r8, r4 \n\t" \
"mov r9, r5 \n\t" \
"mov r10, r6 \n\t" \
"mov r11, r7 \n\t" \
"pop {r4, r5, r6, r7, pc}" : : "r" (sp) : "memory"); \
}
/**
* @brief Performs a context switch between two threads.
* @details This is the most critical code in any port, this function
* is responsible for the context switch between 2 threads.
* @note The implementation of this code affects <b>directly</b> the context
* switch performance so optimize here as much as you can.
*
* @param[in] ntp the thread to be switched in
* @param[in] otp the thread to be switched out
*/
#if !defined(__DOXYGEN__)
__attribute__((naked))
#endif
void port_switch(Thread *ntp, Thread *otp) {
register struct intctx *r13 asm ("r13");
/* Stack overflow check, if enabled.*/
#if CH_DBG_ENABLE_STACK_CHECK
if ((void *)(r13 - 1) < (void *)(otp + 1))
asm volatile ("movs r0, #0 \n\t"
"b chDbgPanic");
#endif /* CH_DBG_ENABLE_STACK_CHECK */
PUSH_CONTEXT(r13);
otp->p_ctx.r13 = r13;
r13 = ntp->p_ctx.r13;
POP_CONTEXT(r13);
}
/**
* @brief Start a thread by invoking its work function.
* @details If the work function returns @p chThdExit() is automatically
* invoked.
*/
void _port_thread_start(void) {
port_unlock();
asm volatile ("mov r0, r5 \n\t"
"blx r4 \n\t"
"bl chThdExit");
}
/** @} */
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