任务上下文保存
addi sp, sp, -portCONTEXT_SIZE
store_x x1, 1 * portWORD_SIZE( sp )
store_x x5, 2 * portWORD_SIZE( sp )
store_x x6, 3 * portWORD_SIZE( sp )
store_x x7, 4 * portWORD_SIZE( sp )
store_x x8, 5 * portWORD_SIZE( sp )
store_x x9, 6 * portWORD_SIZE( sp )
store_x x10, 7 * portWORD_SIZE( sp )
store_x x11, 8 * portWORD_SIZE( sp )
store_x x12, 9 * portWORD_SIZE( sp )
store_x x13, 10 * portWORD_SIZE( sp )
store_x x14, 11 * portWORD_SIZE( sp )
store_x x15, 12 * portWORD_SIZE( sp )
store_x x16, 13 * portWORD_SIZE( sp )
store_x x17, 14 * portWORD_SIZE( sp )
store_x x18, 15 * portWORD_SIZE( sp )
store_x x19, 16 * portWORD_SIZE( sp )
store_x x20, 17 * portWORD_SIZE( sp )
store_x x21, 18 * portWORD_SIZE( sp )
store_x x22, 19 * portWORD_SIZE( sp )
store_x x23, 20 * portWORD_SIZE( sp )
store_x x24, 21 * portWORD_SIZE( sp )
store_x x25, 22 * portWORD_SIZE( sp )
store_x x26, 23 * portWORD_SIZE( sp )
store_x x27, 24 * portWORD_SIZE( sp )
store_x x28, 25 * portWORD_SIZE( sp )
store_x x29, 26 * portWORD_SIZE( sp )
store_x x30, 27 * portWORD_SIZE( sp )
store_x x31, 28 * portWORD_SIZE( sp )
store_x x3, 31 * portWORD_SIZE( sp )
store_x x4, 32 * portWORD_SIZE( sp )
addi a0, sp, portCONTEXT_SIZE
store_x a0, 30 * portWORD_SIZE( sp )
csrr a0, mepc
store_x a0, 0 * portWORD_SIZE( sp ) ----中断返回执行的地址指令存储到栈中
csrr t0, mscratch
store_x t0, 33 * portWORD_SIZE( sp )
csrr t0, mstatus
store_x t0, 29 * portWORD_SIZE( sp )
lw t0, pxCurrentTCB /* Load pxCurrentTCB. */
sw sp, 0( t0 ) /* Write sp to first TCB member. */
检查是否为中断并跳转
load_x sp, xISRStackTop ----设置中断栈，中断与用户是不同栈
call enter_interrupt_handler
csrr a0, mcause
andi a0, a0, 0x7FF ---按位与，只取低11位，低11位也有2048个中断了
call irq_core_handle_root_ic_irq --跳转到中断处理，参数为a0
call exit_interrupt_handler
任务上下文恢复
lw t1, pxCurrentTCB /* Load pxCurrentTCB. */
lw sp, 0( t1 ) /* Read sp from first TCB member. */
中断函数处理完成后，准备恢复任务的上下文，需要先获取sp
中断用的是中断的栈
load_x t0, 0 * portWORD_SIZE( sp )
csrw mepc, t0 ----中断返回后，跳转执行的地址指令
/* Load mstatus with the interrupt enable bits used by the task. */
load_x t0, 29 * portWORD_SIZE( sp )
csrw mstatus, t0 ----恢复mstatus，使能中断
load_x t0, 33 * portWORD_SIZE( sp )
csrw mscratch, t0
load_x x1 , 1 * portWORD_SIZE( sp )
load_x x5 , 2 * portWORD_SIZE( sp ) /* t0 */
load_x x6 , 3 * portWORD_SIZE( sp ) /* t1 */
load_x x7 , 4 * portWORD_SIZE( sp ) /* t2 */
load_x x8 , 5 * portWORD_SIZE( sp ) /* s0/fp */
load_x x9 , 6 * portWORD_SIZE( sp ) /* s1 */
load_x x10, 7 * portWORD_SIZE( sp ) /* a0 */
load_x x11, 8 * portWORD_SIZE( sp ) /* a1 */
load_x x12, 9 * portWORD_SIZE( sp ) /* a2 */
load_x x13, 10 * portWORD_SIZE( sp ) /* a3 */
load_x x14, 11 * portWORD_SIZE( sp ) /* a4 */
load_x x15, 12 * portWORD_SIZE( sp ) /* a5 */
load_x x16, 13 * portWORD_SIZE( sp ) /* a6 */
load_x x17, 14 * portWORD_SIZE( sp ) /* a7 */
load_x x18, 15 * portWORD_SIZE( sp ) /* s2 */
load_x x19, 16 * portWORD_SIZE( sp ) /* s3 */
load_x x20, 17 * portWORD_SIZE( sp ) /* s4 */
load_x x21, 18 * portWORD_SIZE( sp ) /* s5 */
load_x x22, 19 * portWORD_SIZE( sp ) /* s6 */
load_x x23, 20 * portWORD_SIZE( sp ) /* s7 */
load_x x24, 21 * portWORD_SIZE( sp ) /* s8 */
load_x x25, 22 * portWORD_SIZE( sp ) /* s9 */
load_x x26, 23 * portWORD_SIZE( sp ) /* s10 */
load_x x27, 24 * portWORD_SIZE( sp ) /* s11 */
load_x x28, 25 * portWORD_SIZE( sp ) /* t3 */
load_x x29, 26 * portWORD_SIZE( sp ) /* t4 */
load_x x30, 27 * portWORD_SIZE( sp ) /* t5 */
load_x x31, 28 * portWORD_SIZE( sp ) /* t6 */
addi sp, sp, portCONTEXT_SIZE ----销毁栈空间
mret ---中断返回