[修改] 增加freeRTOS

1. 版本FreeRTOSv202212.01，命名为kernel；

kernel/FreeRTOS/Demo/RISC-V-Qemu-virt_GCC/main.c

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+/*
+ * FreeRTOS V202212.01
+ * Copyright (C) 2020 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 to 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.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
+ */
+
+/* FreeRTOS kernel includes. */
+#include <FreeRTOS.h>
+#include <task.h>
+
+/* Run a simple demo just prints 'Blink' */
+#define DEMO_BLINKY	1
+#define mainVECTOR_MODE_DIRECT	1
+
+extern void freertos_risc_v_trap_handler( void );
+extern void freertos_vector_table( void );
+
+void vApplicationMallocFailedHook( void );
+void vApplicationIdleHook( void );
+void vApplicationStackOverflowHook( TaskHandle_t pxTask, char *pcTaskName );
+void vApplicationTickHook( void );
+
+int main_blinky( void );
+
+/*-----------------------------------------------------------*/
+
+int main( void )
+{
+	int ret;
+	// trap handler initialization
+		#if( mainVECTOR_MODE_DIRECT == 1 )
+	{
+		__asm__ volatile( "csrw mtvec, %0" :: "r"( freertos_risc_v_trap_handler ) );
+	}
+	#else
+	{
+		__asm__ volatile( "csrw mtvec, %0" :: "r"( ( uintptr_t )freertos_vector_table | 0x1 ) );
+	}
+	#endif
+
+#if defined(DEMO_BLINKY)
+	ret = main_blinky();
+#else
+#error "Please add or select demo."
+#endif
+
+	return ret;
+}
+
+/*-----------------------------------------------------------*/
+
+void vApplicationMallocFailedHook( void )
+{
+	/* vApplicationMallocFailedHook() will only be called if
+	configUSE_MALLOC_FAILED_HOOK is set to 1 in FreeRTOSConfig.h.  It is a hook
+	function that will get called if a call to pvPortMalloc() fails.
+	pvPortMalloc() is called internally by the kernel whenever a task, queue,
+	timer or semaphore is created.  It is also called by various parts of the
+	demo application.  If heap_1.c or heap_2.c are used, then the size of the
+	heap available to pvPortMalloc() is defined by configTOTAL_HEAP_SIZE in
+	FreeRTOSConfig.h, and the xPortGetFreeHeapSize() API function can be used
+	to query the size of free heap space that remains (although it does not
+	provide information on how the remaining heap might be fragmented). */
+	taskDISABLE_INTERRUPTS();
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
+void vApplicationIdleHook( void )
+{
+	/* vApplicationIdleHook() will only be called if configUSE_IDLE_HOOK is set
+	to 1 in FreeRTOSConfig.h.  It will be called on each iteration of the idle
+	task.  It is essential that code added to this hook function never attempts
+	to block in any way (for example, call xQueueReceive() with a block time
+	specified, or call vTaskDelay()).  If the application makes use of the
+	vTaskDelete() API function (as this demo application does) then it is also
+	important that vApplicationIdleHook() is permitted to return to its calling
+	function, because it is the responsibility of the idle task to clean up
+	memory allocated by the kernel to any task that has since been deleted. */
+}
+/*-----------------------------------------------------------*/
+
+void vApplicationStackOverflowHook( TaskHandle_t pxTask, char *pcTaskName )
+{
+	( void ) pcTaskName;
+	( void ) pxTask;
+
+	/* Run time stack overflow checking is performed if
+	configCHECK_FOR_STACK_OVERFLOW is defined to 1 or 2.  This hook
+	function is called if a stack overflow is detected. */
+	taskDISABLE_INTERRUPTS();
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
+void vApplicationTickHook( void )
+{
+}
+/*-----------------------------------------------------------*/
+
+void vAssertCalled( void )
+{
+volatile uint32_t ulSetTo1ToExitFunction = 0;
+
+	taskDISABLE_INTERRUPTS();
+	while( ulSetTo1ToExitFunction != 1 )
+	{
+		__asm volatile( "NOP" );
+	}
+}