esp_shared_stack: enable shared stack function for riscv and reenable the unit test

components/freertos/port/riscv/include/freertos/xtensa_api.h

@@ -0,0 +1,2 @@
+/* Just a placeholder since this file is exposed in some top-level apps */
+#pragma once

components/riscv/CMakeLists.txt

@@ -9,6 +9,8 @@ else()
     set(srcs
         "interrupt.c"
         "stdatomic.c"
+        "expression_with_stack_riscv.c"
+        "expression_with_stack_riscv_asm.S"
         "vectors.S")
 endif()
 

components/riscv/expression_with_stack_riscv.c

@@ -0,0 +1,79 @@
+// Copyright 2015-2019 Espressif Systems (Shanghai) PTE LTD
+//
+// 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
+//
+//     http://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.
+
+#include <esp_expression_with_stack.h>
+#include <riscv/rvruntime-frames.h>
+#include <string.h>
+
+static portMUX_TYPE shared_stack_spinlock = portMUX_INITIALIZER_UNLOCKED;
+static void *current_task_stack = NULL;
+
+extern void esp_shared_stack_invoke_function(shared_stack_function function, void *stack);
+
+static StackType_t *esp_switch_stack_setup(StackType_t *stack, size_t stack_size)
+{
+#if CONFIG_FREERTOS_WATCHPOINT_END_OF_STACK
+    // TODO ESP32-C3 IDF-2207
+    // esp_clear_watchpoint(1);
+    // uint32_t watchpoint_place = ((uint32_t)stack + 32) & ~0x1f ;
+#endif
+    //We need also to tweak current task stackpointer to avoid erroneous
+    //stack overflow indication, so fills the stack with freertos known pattern:
+    memset(stack, 0xa5U, stack_size * sizeof(StackType_t));
+
+    StaticTask_t *current = (StaticTask_t *)xTaskGetCurrentTaskHandle();
+    //Then put the fake stack inside of TCB:
+    current_task_stack = current->pxDummy6;
+    current->pxDummy6 = (void *)stack;
+
+    StackType_t *top_of_stack = stack + stack_size;
+
+    //Align stack to a 16byte boundary, as required by CPU specific:
+    top_of_stack =  (StackType_t *)(((UBaseType_t)(top_of_stack - 16) & ~0xf));
+    RvExcFrame *adjusted_top_of_stack = (RvExcFrame *) top_of_stack;
+    adjusted_top_of_stack--;
+
+#if CONFIG_FREERTOS_WATCHPOINT_END_OF_STACK
+    // TODO ESP32-C3 IDF-2207
+    //esp_set_watchpoint(1, (uint8_t *)watchpoint_place, 32, ESP_WATCHPOINT_STORE);
+#endif
+
+    return ((StackType_t *)adjusted_top_of_stack);
+}
+
+
+void esp_execute_shared_stack_function(SemaphoreHandle_t lock, void *stack, size_t stack_size, shared_stack_function function)
+{
+    assert(lock);
+    assert(stack);
+    assert(stack_size > 0 && stack_size >= CONFIG_ESP_MINIMAL_SHARED_STACK_SIZE);
+    assert(function);
+
+    xSemaphoreTake(lock, portMAX_DELAY);
+    portENTER_CRITICAL(&shared_stack_spinlock);
+    stack = esp_switch_stack_setup(stack, stack_size);
+    portEXIT_CRITICAL(&shared_stack_spinlock);
+
+    esp_shared_stack_invoke_function(function, stack);
+
+    portENTER_CRITICAL(&shared_stack_spinlock);
+    StaticTask_t *current = (StaticTask_t *)xTaskGetCurrentTaskHandle();
+
+    //Restore current task stack:
+    current->pxDummy6 = (StackType_t *)current_task_stack;
+    vPortSetStackWatchpoint(current->pxDummy6);
+    portEXIT_CRITICAL(&shared_stack_spinlock);
+
+    xSemaphoreGive(lock);
+}

components/riscv/expression_with_stack_riscv_asm.S

@@ -0,0 +1,43 @@
+// Copyright 2015-2020 Espressif Systems (Shanghai) PTE LTD
+//
+// 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
+
+//     http://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.
+
+    .section .text
+
+    .global esp_shared_stack_invoke_function
+    .type esp_shared_stack_invoke_function, @function
+esp_shared_stack_invoke_function:
+    /* save current stack and return address */
+    mv t0, sp
+    mv t1, ra
+
+    /* Set shared stack as new stack pointer */
+    mv sp, a1
+    
+    /* store the ra and previous stack pointer in a safe place */
+    addi sp,sp,-4
+    sw  t0, 0(sp)
+    sw  t1, 4(sp)
+
+    /* call the subroutine */
+    jalr a0, 0
+
+    /* gets the ra and stack pointer saved previously */
+    lw  t0, 0(sp)    
+    lw  t1, 4(sp)
+    addi sp, sp, 4
+    
+    /* restore both ra and real stack pointer of current task */
+    mv ra, t1    
+    mv sp, t0
+    ret