FreeRTOS + baremetal shell support for A class CPUs

docs/05 - Steps to work with FreeRTOS

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+1) clone the repository
+2) Inside /esh clone the freeRTOS kernel source code : https://github.com/FreeRTOS/FreeRTOS-Kernel
+3) Disable the configAssert of port.c in freeRTOS kernel Code (For the given example of GCC/ARM3/port.c Line 370)
+4) make
+5) make run
+
+This will start two tasks concurrently one to run shell and other to periodically print a statement

examples/emulation/freertos/FreeRTOSConfig.h

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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
+ *
+ */
+
+#ifndef FREERTOS_CONFIG_H
+#define FREERTOS_CONFIG_H
+
+/*-----------------------------------------------------------
+ * Application specific definitions.
+ *
+ * These definitions should be adjusted for your particular hardware and
+ * application requirements.
+ *
+ * THESE PARAMETERS ARE DESCRIBED WITHIN THE 'CONFIGURATION' SECTION OF THE
+ * FreeRTOS API DOCUMENTATION AVAILABLE ON THE FreeRTOS.org WEB SITE.
+ *
+ * See http://www.freertos.org/a00110.html
+ *----------------------------------------------------------*/
+
+#define configUSE_TRACE_FACILITY 0
+#define configGENERATE_RUN_TIME_STATS 0
+
+#define configUSE_TICKLESS_IDLE         0
+#define configUSE_PREEMPTION			1
+#define configUSE_IDLE_HOOK				0
+#define configUSE_TICK_HOOK				1
+#define configCPU_CLOCK_HZ				( ( unsigned long ) 25000000 )
+#define configTICK_RATE_HZ				( ( TickType_t ) 1000 )
+#define configMINIMAL_STACK_SIZE		( ( unsigned short ) 80 )
+#define configTOTAL_HEAP_SIZE			( ( size_t ) ( 60 * 1024 ) )
+#define configMAX_TASK_NAME_LEN			( 12 )
+#define configUSE_16_BIT_TICKS			0
+#define configIDLE_SHOULD_YIELD			0
+#define configUSE_MUTEXES				1
+#define configUSE_RECURSIVE_MUTEXES		1
+#define configCHECK_FOR_STACK_OVERFLOW	2
+#define configUSE_MALLOC_FAILED_HOOK	1
+#define configUSE_QUEUE_SETS			1
+#define configUSE_COUNTING_SEMAPHORES	1
+
+#define configMAX_PRIORITIES			( 9UL )
+#define configQUEUE_REGISTRY_SIZE		10
+#define configSUPPORT_STATIC_ALLOCATION	1
+
+/* Timer related defines. */
+#define configUSE_TIMERS				1
+#define configTIMER_TASK_PRIORITY		( configMAX_PRIORITIES - 4 )
+#define configTIMER_QUEUE_LENGTH		20
+#define configTIMER_TASK_STACK_DEPTH	( configMINIMAL_STACK_SIZE * 2 )
+
+#define configUSE_TASK_NOTIFICATIONS	1
+#define configTASK_NOTIFICATION_ARRAY_ENTRIES 3
+
+/* Set the following definitions to 1 to include the API function, or zero
+to exclude the API function. */
+
+#define INCLUDE_vTaskPrioritySet				1
+#define INCLUDE_uxTaskPriorityGet				1
+#define INCLUDE_vTaskDelete						1
+#define INCLUDE_vTaskCleanUpResources			0
+#define INCLUDE_vTaskSuspend					1
+#define INCLUDE_vTaskDelayUntil					1
+#define INCLUDE_vTaskDelay						1
+#define INCLUDE_uxTaskGetStackHighWaterMark		1
+#define INCLUDE_xTaskGetSchedulerState			1
+#define INCLUDE_xTimerGetTimerDaemonTaskHandle	1
+#define INCLUDE_xTaskGetIdleTaskHandle			1
+#define INCLUDE_xSemaphoreGetMutexHolder		1
+#define INCLUDE_eTaskGetState					1
+#define INCLUDE_xTimerPendFunctionCall			1
+#define INCLUDE_xTaskAbortDelay					1
+#define INCLUDE_xTaskGetHandle					1
+
+/* This demo makes use of one or more example stats formatting functions.  These
+format the raw data provided by the uxTaskGetSystemState() function in to human
+readable ASCII form.  See the notes in the implementation of vTaskList() within
+FreeRTOS/Source/tasks.c for limitations. */
+#define configUSE_STATS_FORMATTING_FUNCTIONS	0
+
+#define configKERNEL_INTERRUPT_PRIORITY 		( 255 )	/* All eight bits as QEMU doesn't model the priority bits. */
+/* !!!! configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to zero !!!!
+See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html. */
+#define configMAX_SYSCALL_INTERRUPT_PRIORITY 	( 191 )
+
+/* Use the Cortex-M3 optimised task selection rather than the generic C code
+version. */
+#define configUSE_PORT_OPTIMISED_TASK_SELECTION 1
+
+/* The Win32 target is capable of running all the tests tasks at the same
+ * time. */
+#define configRUN_ADDITIONAL_TESTS				1
+
+/* The test that checks the trigger level on stream buffers requires an
+allowable margin of error on slower processors (slower than the Win32
+machine on which the test is developed). */
+#define configSTREAM_BUFFER_TRIGGER_LEVEL_TEST_MARGIN   4
+
+#ifndef __IASMARM__ /* Prevent C code being included in IAR asm files. */
+	void vAssertCalled( const char *pcFileName, uint32_t ulLine );
+	#define configASSERT( x ) if( ( x ) == 0 ) vAssertCalled( __FILE__, __LINE__ );
+#endif
+
+#define intqHIGHER_PRIORITY		( configMAX_PRIORITIES - 5 )
+#define bktPRIMARY_PRIORITY		( configMAX_PRIORITIES - 3 )
+#define bktSECONDARY_PRIORITY	( configMAX_PRIORITIES - 4 )
+
+#endif /* FREERTOS_CONFIG_H */
+
+// #define configUSE_MALLOC_FAILED_HOOK              0
+// #define configUSE_MUTEXES                         1
+// #define configUSE_RECURSIVE_MUTEXES               1
+// #define configUSE_TIMERS                          1
+// #define configTIMER_TASK_STACK_DEPTH              ( configMINIMAL_STACK_SIZE * 2 )
+
+// #define INCLUDE_vTaskPrioritySet                  1
+// #define INCLUDE_uxTaskPriorityGet                 1
+// #define INCLUDE_vTaskDelete                       1
+// #define INCLUDE_vTaskCleanUpResources             0
+// #define INCLUDE_vTaskSuspend                      1
+// #define INCLUDE_vTaskDelayUntil                   1
+// #define INCLUDE_vTaskDelay                        1
+// #define INCLUDE_uxTaskGetStackHighWaterMark       1
+// #define INCLUDE_uxTaskGetStackHighWaterMark2      1
+// #define INCLUDE_xTaskGetSchedulerState            1
+// #define INCLUDE_xTimerGetTimerDaemonTaskHandle    1
+// #define INCLUDE_xTaskGetIdleTaskHandle            1
+// #define INCLUDE_xTaskGetHandle                    1
+// #define INCLUDE_eTaskGetState                     1
+// #define INCLUDE_xSemaphoreGetMutexHolder          1
+// #define INCLUDE_xTimerPendFunctionCall            1
+// #define INCLUDE_xTaskAbortDelay                   1
+
+// #define projCOVERAGE_TEST                         0
+// #define configKERNEL_INTERRUPT_PRIORITY           255
+// #define configMAX_SYSCALL_INTERRUPT_PRIORITY      191 /* equivalent to 0xa0, or priority 5. */
+// #define configMAC_INTERRUPT_PRIORITY              5
+
+
+// #define configASSERT_DEFINED                             1
+// extern void vAssertCalled( void );
+// #define configASSERT( x )    if( ( x ) == 0 ) vAssertCalled()
+// #define configQUEUE_REGISTRY_SIZE                        20
+
+// #define configUSE_PREEMPTION                             1
+// #define configUSE_TIME_SLICING                           0
+// #define configUSE_PORT_OPTIMISED_TASK_SELECTION          0
+
+// #define configUSE_IDLE_HOOK                              0
+// #define configUSE_TICK_HOOK                              0
+// #define configUSE_DAEMON_TASK_STARTUP_HOOK               0
+// #define configCPU_CLOCK_HZ                               ( ( unsigned long ) 25000000 )
+// #define configTICK_RATE_HZ                               ( ( TickType_t ) 10000 )
+// #define configMINIMAL_STACK_SIZE                         ( ( unsigned short ) 2000 )
+// #define configTOTAL_HEAP_SIZE                            ( ( size_t ) ( 80 * 1024 ) )
+// #define configMAX_TASK_NAME_LEN                          ( 10 )
+// #define configUSE_TRACE_FACILITY                         1
+// #define configUSE_16_BIT_TICKS                           0
+// #define configIDLE_SHOULD_YIELD                          1
+
+// #define configMAX_PRIORITIES                             ( 10 )
+// #define configTIMER_QUEUE_LENGTH                         20
+// #define configTIMER_TASK_PRIORITY                        ( configMAX_PRIORITIES - 1 )
+// #define configUSE_COUNTING_SEMAPHORES                    1
+// #define configSUPPORT_DYNAMIC_ALLOCATION                 1
+// #define configSUPPORT_STATIC_ALLOCATION                  0
+// #define configNUM_TX_DESCRIPTORS                         15
+// #define configSTREAM_BUFFER_TRIGGER_LEVEL_TEST_MARGIN    2

examples/emulation/freertos/Makefile

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+#
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# NOTE: the toolchain can be installed using -
+# sudo apt install -y gcc-arm-none-eabi
+
+TOOLCHAIN_PREFIX ?= arm-none-eabi-
+OPTIMIZATION     = g	
+
+EXTERN_SRC = ../../../../FreeRTOS-Kernel
+SRC_C += ../../../../FreeRTOS-Kernel/portable/GCC/ARM_CM3/port.c
+SRC_C += ../../../../FreeRTOS-Kernel/portable/MemMang/heap_4.c
+IGNORE_SRC_PATH += ../../../../FreeRTOS-Kernel/examples
+IGNORE_SRC_PATH += ../../../../FreeRTOS-Kernel/portable
+IGNORE_HEADER_PATH += ../../../../FreeRTOS-Kernel/portable
+IGNORE_HEADER_PATH += ../../../../FreeRTOS-Kernel/examples
+INCLUDES += -I../../../../FreeRTOS-Kernel/include
+INCLUDES += -I../../../../FreeRTOS-Kernel/portable/GCC/ARM_CM3/
+TOOLCHAIN_VERSION := $(shell $(TOOLCHAIN_PREFIX)gcc -dumpversion)
+LIB_GCC_PATH = /usr/lib/gcc/arm-none-eabi/$(TOOLCHAIN_VERSION)/thumb/v7-m/nofp/
+
+DEFINES = -mcpu=cortex-m3 -mthumb
+ASM_FLAGS = -march=armv7-m
+LD_FLAGS = -lgcc -L$(LIB_GCC_PATH)
+
+STARTUP = cortex-m
+
+# MANDATORY:
+#     These 3 parameters are needed for every port
+#     Provide all values in hex
+ROM_BASE_PHYSICAL  = 0x00000000
+ROM_SIZE           = 0x3FFFF
+
+RAM_BASE_PHYSICAL  = 0x20000000
+RAM_SIZE           = 0x7FFFFF
+
+# to reduce binary size, set to 1
+# SHELL_LITE = 0
+
+# setting the stack start manually for m class processors
+DEFINES += -DSTACK_START=0x0003FFFF
+DEFINES += -DSHELL_NO_PRINTF_LL
+
+# MANDATORY:
+#     Provide relative path to shell/ from current directory
+#     Only Variable should be set above this line
+SHELL_ROOT=../../../shell
+-include $(SHELL_ROOT)/Makefile
+# ^^ Do not move the above line. All user targets to be defined below this line!
+
+# ------------------------ User targets below this line ------------------------
+### run: Launches QEMU and loads the project binary on it
+run: $(PROJECT).elf
+	@echo "Use Ctrl+A X to exit Qemu"
+	@qemu-system-arm -M mps2-an385 -cpu cortex-m3 -nographic \
+	 -kernel $(PROJECT).elf
+### debug: Qemu with GDB server. To be executed before 'make gdb'
+debug:
+	@echo Please use \"make gdb\" in another terminal to attach gdb.
+	@echo Use \"cltr+a,x\" to quit qemu debug
+	@qemu-system-arm -S -M mps2-an385 -cpu cortex-m3 -nographic -kernel \
+	 $(PROJECT).elf -gdb tcp::1234
+
+### gdb: Launches GDB and connects to qemu. To be executed after 'make debug'
+gdb:
+	@gdb-multiarch shell.elf -ex "target remote localhost:1234"

examples/emulation/freertos/hello.c

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+/**
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+/*
+ * This is a mandatory include.
+ * This has the ADD_CMD() macro
+ */
+#include "shell.h"
+
+/*
+ * There can be one or many function with same prototype, exposed as
+ * a command on the shell. They can be in same or multiple files.
+ */
+int hello(int argc, char** argv) {
+  for (int i = 0; i < argc; i++) {
+    printf(argv[i]);
+    printf(" ");
+  }
+
+  printf("\nPress ctrl + a, x to exit !\n");
+  return 0;
+}
+
+/*
+ * One or many such can exist per file.
+ * Description: ADD_CMD(command, help string, function to be exposed)
+ */
+ADD_CMD(hello, "Echoes the commandline\n\tusage: hello <any string>", hello);