/* * FreeRTOS Kernel V10.1.1 * Copyright (C) 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a copy of * this software and associated documentation files (the "Software"), to deal in * the Software without restriction, including without limitation the rights to * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of * the Software, and t o permit persons to whom the Software is furnished to do so, * subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. * * http://www.FreeRTOS.org * http://aws.amazon.com/freertos * * 1 tab == 4 spaces! */ #if __riscv_xlen == 64 #error Not implemented yet - change lw to ld, and sw to sd. #define WORD_SIZE 8 #elif __riscv_xlen == 32 #define WORD_SIZE 4 #else #error Assembler has not defined __riscv_xlen #endif #define CONTEXT_SIZE ( 30 * WORD_SIZE ) .global xPortStartFirstTask .global vPortTrapHandler .extern pxCurrentTCB .extern ulPortTrapHandler .extern vTaskSwitchContext .extern Timer_IRQHandler .extern pullMachineTimerCompareRegister .extern pullNextTime .extern ulTimerIncrementsForOneTick .extern xISRStackTop .extern vPortHandleInterrupt /*-----------------------------------------------------------*/ .align 8 vPortTrapHandler: addi sp, sp, -CONTEXT_SIZE sw x1, 1 * WORD_SIZE( sp ) sw x5, 2 * WORD_SIZE( sp ) sw x6, 3 * WORD_SIZE( sp ) sw x7, 4 * WORD_SIZE( sp ) sw x8, 5 * WORD_SIZE( sp ) sw x9, 6 * WORD_SIZE( sp ) sw x10, 7 * WORD_SIZE( sp ) sw x11, 8 * WORD_SIZE( sp ) sw x12, 9 * WORD_SIZE( sp ) sw x13, 10 * WORD_SIZE( sp ) sw x14, 11 * WORD_SIZE( sp ) sw x15, 12 * WORD_SIZE( sp ) sw x16, 13 * WORD_SIZE( sp ) sw x17, 14 * WORD_SIZE( sp ) sw x18, 15 * WORD_SIZE( sp ) sw x19, 16 * WORD_SIZE( sp ) sw x20, 17 * WORD_SIZE( sp ) sw x21, 18 * WORD_SIZE( sp ) sw x22, 19 * WORD_SIZE( sp ) sw x23, 20 * WORD_SIZE( sp ) sw x24, 21 * WORD_SIZE( sp ) sw x25, 22 * WORD_SIZE( sp ) sw x26, 23 * WORD_SIZE( sp ) sw x27, 24 * WORD_SIZE( sp ) sw x28, 25 * WORD_SIZE( sp ) sw x29, 26 * WORD_SIZE( sp ) sw x30, 27 * WORD_SIZE( sp ) sw x31, 28 * WORD_SIZE( sp ) csrr t0, mstatus /* Required for MPIE bit. */ sw t0, 29 * WORD_SIZE( sp ) lw t0, pxCurrentTCB /* Load pxCurrentTCB. */ sw sp, 0( t0 ) /* Write sp to first TCB member. */ csrr a0, mcause csrr a1, mepc test_if_environment_call: li t0, 11 /* 11 == environment call when using qemu. */ bne a0, t0, test_if_timer addi a1, a1, 4 /* Synchronous so return to the instruction after the environment call. */ sw a1, 0( sp ) /* Save updated exception return address. */ lw sp, xISRStackTop /* Switch to ISR stack before function call. */ jal vTaskSwitchContext j processed_source test_if_timer: sw a1, 0( sp ) /* Asynch so save unmodified exception return address. */ lui t0, 0x80000 addi t1,t0, 7 /* 0x80000007 == machine timer interrupt. */ bne a0, t1, test_if_external_interrupt lw t0, pullMachineTimerCompareRegister /* Load address of compare register into t0. */ lw t1, pullNextTime /* Load the address of ullNextTime into t1. */ lw t2, 0(t1) /* Load the low word of ullNextTime into t2. */ lw t3, 4(t1) /* Load the high word of ullNextTime into t3. */ sw t2, 0(t0) /* Store low word of ullNextTime into compare register. */ sw t3, 4(t0) /* Store high word of ullNextTime into compare register. */ lw t0, ulTimerIncrementsForOneTick /* Load the value of ullTimerIncrementForOneTick into t0 (could this be optimized by storing in an array next to pullNextTime?). */ add t4, t0, t2 /* Add the low word of ullNextTime to the timer increments for one tick (assumes timer increment for one tick fits in 32-bits. */ sltu t5, t4, t2 /* See if the sum of low words overflowed (what about the zero case?). */ add t6, t3, t5 /* Add overflow to high word of ullNextTime. */ sw t4, 0(t1) /* Store new low word of ullNextTime. */ sw t6, 4(t1) /* Store new high word of ullNextTime. */ lw sp, xISRStackTop /* Switch to ISR stack before function call. */ jal xTaskIncrementTick beqz a0, processed_source /* Don't switch context if incrementing tick didn't unblock a task. */ jal vTaskSwitchContext j processed_source test_if_external_interrupt: addi t1, t1, 4 /* 0x80000007 + 4 = 0x8000000b == Machine external interrupt. */ bne a0, t1, is_exception /* Only thing left it can be. */ jal vPortHandleInterrupt j processed_source is_exception: ebreak j is_exception processed_source: lw sp, pxCurrentTCB /* Load pxCurrentTCB. */ lw sp, 0( sp ) /* Read sp from first TCB member. */ /* Load mret with the address of the next task. */ lw t0, 0( sp ) csrw mepc, t0 /* Load mstatus with the interrupt enable bits used by the task. */ lw t0, 29 * WORD_SIZE( sp ) csrw mstatus, t0 /* Required for MPIE bit. */ lw x1, 1 * WORD_SIZE( sp ) lw x5, 2 * WORD_SIZE( sp ) /* t0 */ lw x6, 3 * WORD_SIZE( sp ) /* t1 */ lw x7, 4 * WORD_SIZE( sp ) /* t2 */ lw x8, 5 * WORD_SIZE( sp ) /* s0/fp */ lw x9, 6 * WORD_SIZE( sp ) /* s1 */ lw x10, 7 * WORD_SIZE( sp ) /* a0 */ lw x11, 8 * WORD_SIZE( sp ) /* a1 */ lw x12, 9 * WORD_SIZE( sp ) /* a2 */ lw x13, 10 * WORD_SIZE( sp ) /* a3 */ lw x14, 11 * WORD_SIZE( sp ) /* a4 */ lw x15, 12 * WORD_SIZE( sp ) /* a5 */ lw x16, 13 * WORD_SIZE( sp ) /* a6 */ lw x17, 14 * WORD_SIZE( sp ) /* a7 */ lw x18, 15 * WORD_SIZE( sp ) /* s2 */ lw x19, 16 * WORD_SIZE( sp ) /* s3 */ lw x20, 17 * WORD_SIZE( sp ) /* s4 */ lw x21, 18 * WORD_SIZE( sp ) /* s5 */ lw x22, 19 * WORD_SIZE( sp ) /* s6 */ lw x23, 20 * WORD_SIZE( sp ) /* s7 */ lw x24, 21 * WORD_SIZE( sp ) /* s8 */ lw x25, 22 * WORD_SIZE( sp ) /* s9 */ lw x26, 23 * WORD_SIZE( sp ) /* s10 */ lw x27, 24 * WORD_SIZE( sp ) /* s11 */ lw x28, 25 * WORD_SIZE( sp ) /* t3 */ lw x29, 26 * WORD_SIZE( sp ) /* t4 */ lw x30, 27 * WORD_SIZE( sp ) /* t5 */ lw x31, 28 * WORD_SIZE( sp ) /* t6 */ addi sp, sp, CONTEXT_SIZE mret /*-----------------------------------------------------------*/ .align 8 xPortStartFirstTask: la t0, vPortTrapHandler csrw mtvec, t0 lw sp, pxCurrentTCB /* Load pxCurrentTCB. */ lw sp, 0( sp ) /* Read sp from first TCB member. */ lw x1, 0( sp ) /* Note for starting the scheduler the exception return address is used as the function return address. */ lw x5, 2 * WORD_SIZE( sp ) /* t0 */ lw x6, 3 * WORD_SIZE( sp ) /* t1 */ lw x7, 4 * WORD_SIZE( sp ) /* t2 */ lw x8, 5 * WORD_SIZE( sp ) /* s0/fp */ lw x9, 6 * WORD_SIZE( sp ) /* s1 */ lw x10, 7 * WORD_SIZE( sp ) /* a0 */ lw x11, 8 * WORD_SIZE( sp ) /* a1 */ lw x12, 9 * WORD_SIZE( sp ) /* a2 */ lw x13, 10 * WORD_SIZE( sp ) /* a3 */ lw x14, 11 * WORD_SIZE( sp ) /* a4 */ lw x15, 12 * WORD_SIZE( sp ) /* a5 */ lw x16, 13 * WORD_SIZE( sp ) /* a6 */ lw x17, 14 * WORD_SIZE( sp ) /* a7 */ lw x18, 15 * WORD_SIZE( sp ) /* s2 */ lw x19, 16 * WORD_SIZE( sp ) /* s3 */ lw x20, 17 * WORD_SIZE( sp ) /* s4 */ lw x21, 18 * WORD_SIZE( sp ) /* s5 */ lw x22, 19 * WORD_SIZE( sp ) /* s6 */ lw x23, 20 * WORD_SIZE( sp ) /* s7 */ lw x24, 21 * WORD_SIZE( sp ) /* s8 */ lw x25, 22 * WORD_SIZE( sp ) /* s9 */ lw x26, 23 * WORD_SIZE( sp ) /* s10 */ lw x27, 24 * WORD_SIZE( sp ) /* s11 */ lw x28, 25 * WORD_SIZE( sp ) /* t3 */ lw x29, 26 * WORD_SIZE( sp ) /* t4 */ lw x30, 27 * WORD_SIZE( sp ) /* t5 */ lw x31, 28 * WORD_SIZE( sp ) /* t6 */ addi sp, sp, CONTEXT_SIZE csrs mstatus, 8 /* Enable machine interrupts. */ ret 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